Welding Health and Safety: A Field Guide for OEHS Professionals [2 ed.] 9781950286102

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Welding

Health and Safety

A Field Guide for OEHS Professionals 2nd Edition

Learn to communicate more effectively with welding shop and plant personnel with this practical guide. By Michael K. Harris, PhD, CIH and Michael R. Phibbs, CIH, ROH

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

Michael K. Harris, PhD, CIH Michael R. Phibbs, CIH, ROH

Published by AIHA Falls Church, VA

Disclaimer This publication was developed by experts with background, training, and experience in various aspects of industrial hygiene (IH) and occupational and environmental health and safety (OEHS), working with information that was available at the time of publication. AIHA, as publisher, and the author(s) have been diligent in ensuring that the material and methods addressed in this book reflect prevailing IH and OEHS practices. It is possible, however, that certain policies or procedures discussed will require modification because of changing federal, state, local, or international regulations. AIHA® and the author(s) disclaim any liability, loss, or risk resulting directly or indirectly from use of the practices and/or theories presented in this publication. Moreover, it is the user’s responsibility to stay informed of any changing federal, state, local, or international regulations that might affect the material contained herein, as well as the policies adopted specifically in the user’s workplace. Specific mention of manufacturers and products in this book does not represent an endorsement by AIHA® or the author(s). Copyright © 2021 by AIHA® All rights reserved. No part of this publication may be reproduced in any form or by any other means—graphic, electronic, or mechanical, including photocopying, taping, or information storage or retrieval systems—without written permission from the publisher. Book design by Jim Myers Editorial support provided by Lisa Lyubomirsky Stock Number: SWEF21-490 ISBN: 978-1-950286-10-2 AIHA 3141 Fairview Park Drive, Suite 777 Falls Church, VA 22042 Tel: (703) 849-8888 Fax: (703) 207-3561 Email: [email protected] aiha.org

Dedication This volume is dedicated to my mother, Irma Sell Harris, who left her job in Iowa as a newspaper reporter and photographer to work as a welder in the shipyards in Long Beach, California during World War II. In so doing, she became one of the first ten women to be a U.S. Navy-certified stainless steel welder.

American Welding Society AIHA and the author express their appreciation to American Welding Society for granting permission to numerous figures from their Welding Handbook in this tion. Their figures have added greatly to the usefulness appearance of this field guide.

the use ediand

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

Table of Contents Preface..................................................................................................................ix Acknowledgments......................................................................................... xii About the Author.......................................................................................... xiii Chapter 1. Introduction to Welding Health and Safety................... 1 1. Introduction to Welding and Thermal Cutting.......................... 1 2. Anticipation and Recognition of Welding and Cutting Health and Safety Hazards.............................................. 3 3. Regulations............................................................................................ 6 4. Resource Materials.............................................................................. 7 5. Welding Health and Safety: Initial Evaluation Form............... 8 Chapter 2. Welding Processes: Health and Safety Considerations..........................................................................................19 1. Shielded Metal Arc Welding (SMAW or “Stick Welding”)...21 1.1 SMAW Health and Safety Hazards Summary............21 1.2 SMAW Common Metals......................................................21 1.3 SMAW Process Description...............................................22 1.4 SMAW Health and Safety Hazards Discussion..........24 1.5 Equipment Comments Specific to SMAW.....................27 2. Gas Tungsten Arc Welding (GTAW, “HeliArc,” or “TIG Welding”)...........................................27 2.1 GTAW Health and Safety Hazards Summary.............27 2.2 GTAW Common Metals.......................................................28 2.3 GTAW Process Description................................................28 2.4 GTAW Health and Safety Hazards Discussion...........31 2.5 Equipment Comments Specific to GTAW......................34 3. Gas Metal Arc Welding (GMAW or “MIG”)................................34 3.1 GMAW Health and Safety Hazards Summary...........34 3.2 GMAW Common Metals......................................................34 3.3 GMAW Process Description...............................................35 3.4 “MIG” vs. “Short-Arc”............................................................37 3.5 Tubular Filler Wire.................................................................37 3.6 GMAW Health and Safety Hazards Discussion.........38 3.7 Equipment Comments Specific to GMAW....................39 4. Flux Cored Arc Welding (FCAW)..................................................39 4.1 FCAW Health and Safety Hazards Summary.............39 4.2 FCAW Common Metals.......................................................39 Copyright AIHA® For personal use only. Do not distribute.

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4.3 FCAW Process Description.................................................40 4.4 FCAW Health and Safety Hazards Discussion...........42 4.5 Equipment Comments Specific to FCAW......................42 5. Submerged Arc Welding (SAW or “SubArc”)..........................43 5.1 SAW Health and Safety Hazards Summary................43 5.2 SAW Common Metals..........................................................43 5.3 SAW Process Description...................................................43 5.4 SAW Health and Safety Hazards Discussion..............45 5.5 Equipment Comments Specific to SAW.........................45 6. Electrogas Welding (EGW)............................................................46 6.1 EGW Health and Safety Hazards Summary...............46 6.2 EGW Common Metals..........................................................46 6.3 EGW Description....................................................................46 6.4 EGW Health and Safety Hazards Discussion.............48 6.5 Equipment Comments Specific to EGW.........................49 7. Electroslag Welding (ESW)............................................................49 7.1 ESW Health and Safety Hazards Summary................49 7.2 ESW Common Metals..........................................................50 7.3 ESW Description....................................................................50 7.4 ESW Health and Safety Hazards Discussion..............51 7.5 Equipment Comments Specific to ESW.........................52 8. Stud Welding (SW)...........................................................................52 8.1 SW Health and Safety Hazards Summary..................52 8.2 SW Common Metals.............................................................52 8.3 SW Process Description......................................................53 8.4 SW Health and Safety Discussion...................................54 8.5 Equipment Comments Specific to SW............................54 9. Plasma Arc Welding (PAW)...........................................................55 9.1 PAW Health and Safety Hazards Summary................55 9.2 PAW Common Metals..........................................................55 9.3 PAW Process Description...................................................56 9.4 PAW Health and Safety Hazards Discussion..............58 9.5 Equipment Comments Specific to PAW.........................59 10. Oxyfuel Gas Welding (OFW).........................................................59 10.1 OFW Health and Safety Hazards Summary...............59 10.2 OFW Common Metals..........................................................59 10.3 OFW Process Description...................................................60 10.4 OFW Health and Safety Hazards Discussion.............62 10.5 Equipment Comments Specific to OFW........................64

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11. Brazing..................................................................................................64 11.1 Brazing Health and Safety Hazards Summary..........64 11.2 Brazing: Common Metals....................................................65 11.3 Brazing Process Description..............................................66 11.4 Brazing Health and Safety Hazards Discussion........69 12. Soldering...............................................................................................72 12.1 Soldering Health and Safety Hazards Summary.......72 12.2 Soldering: Common Metals................................................73 12.3 Soldering Process Description...........................................74 12.4 Soldering Health and Safety Hazards Discussion.....77 13. Oxyfuel Gas Cutting (OFC “Torch Cutting”)..............................78 13.1 OFC Health and Safety Hazards Summary.................78 13.2 OFC Common Metals............................................................78 13.3 OFW Process Description...................................................78 13.4 OFC Health and Safety Hazards Discussion...............79 14. Oxygen Lance Cutting (LOC).........................................................80 14.1 LOC Process Description.....................................................80 14.2 LOC Health and Safety Hazards Discussion...............81 15. Arc Cutting and Arc Gouging........................................................82 15.1 Plasma Arc Cutting (PAC)...................................................82 15.2 Air Carbon Arc Cutting (CAC-A, “Air-Arc,” “Arc-Gouging”)...................................85 15.3 Shielded Metal Arc Cutting (SMAC)................................89 15.4 Oxygen Arc Cutting (AOC)..................................................90 15.5 Gas Tungsten Arc Cutting (GTAC)...................................90 15.6 Gas Metal Arc Cutting (GMAC).........................................92 16. Laser Beam Welding (LBW), Cutting (LBC), and Drilling (LBD)..............................................................................93 16.1 LBW, LBC, and LBD Health and Safety Hazards Summary...................................................................................93 16.2 LBW, LBC, and LBD Common Metals.............................93 16.3 Laser Beam Welding (LBW) Process Description......94 16.4 LBW, LBC, and LBD Health and Safety Hazards Discussion.................................................................................96 16.5 Shock and Electrocution......................................................98 17. Resistance Welding: Spot, Seam, and Projection Welding.................................................................................................99 17.1 Spot, Seam, and Projection Welding Health and Safety Hazards Summary..................................................99 17.2 Spot, Seam, and Projection Welding: Common Metals......................................................................99

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Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

17.3 Spot, Seam, and Projection Welding Process Descriptions.......................................................................... 100 17.4 Spot, Seam, and Projection Welding Health and Safety Hazards Discussion............................................. 100 18. Resistance Welding: Flash, Upset, and Percussion Welding.............................................................................................. 102 18.1 Flash, Upset, and Percussion Welding Health and Safety Hazards Summary............................................... 102 18.2 Flash, Upset, and Percussion Welding: Common Metals................................................................... 102 18.3 Flash, Upset, and Percussion Welding Process Descriptions.......................................................................... 102 18.4 Flash, Upset, and Percussion Welding Health and Safety Hazards Discussion............................................. 105 19. High-Frequency Welding............................................................. 106 19.1 High-Frequency Welding Health and Safety Hazards Summary............................................................. 106 19.2 High-Frequency Welding: Common Metals.............. 106 19.3 High-Frequency Welding Process Descriptions...... 106 19.4 High-Frequency Welding Health and Safety Hazards Discussion........................................................... 107 20. Electron Beam Welding (EBW).................................................. 108 20.1 Electron Beam Welding Health and Safety Hazards Summary............................................................. 108 20.2 Electron Beam Welding: Common Metals.................. 108 20.3 Electron Beam Welding Process Descriptions.......... 108 20.4 Electron Beam Welding Health and Safety Hazards Discussion............................................. 110 21. Friction Welding.............................................................................. 111 21.1 Friction Welding Health and Safety Hazards Summary................................................................................ 111 21.2 Friction Welding: Common Metals................................ 111 21.3 Friction Welding Process Descriptions........................ 111 21.4 Friction Welding Health and Safety Hazards Discussion.............................................................................. 111 22. Explosion Welding.......................................................................... 112 22.1 Explosion Welding Health and Safety Hazards Summary............................................................. 112 22.2 Explosion Welding: Common Metals........................... 112 22.3 Explosion Welding Process Descriptions................... 112 22.4 Explosion Welding Health and Safety Hazards Discussion........................................................... 114 iv

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23. Ultrasonic Welding (USW).......................................................... 114 23.1 USW Health and Safety Hazards Summary............ 114 23.2 USW: Common Metals...................................................... 115 23.3 USW Process Description................................................ 115 23.4 USW Health and Safety Hazards Discussion.......... 115 24. Thermal Spraying (THSP)............................................................ 118 24.1 THSP Health and Safety Hazards Summary............ 118 24.2 THSP Common Metals...................................................... 118 24.3 THSP Process Description............................................... 119 24.4 THSP Health and Safety Hazards Discussion.......... 120 25. Surfacing........................................................................................... 121 25.1 Surfacing Health and Safety Hazards Summary.... 121 25.2 Surfacing Common Metals.............................................. 122 25.3 Surfacing Process Description....................................... 122 25.4 Surfacing Health and Safety Hazards Discussion.. 123 Appendix: Case Studies............................................................................ 127 Chapter 3. Welding Equipment: Health and Safety Considerations....................................................................................... 131 1. Regulations (U.S.)........................................................................... 131 2. Guidelines and Regulations Specific to Oxyfuel Equipment......................................................................................... 132 3. Compressed Gases and Cryogenic Liquids........................... 135 3.1 Regulations Specific to Compressed Gases and Cryogenic Liquids........................................................................... 136 3.2 Compressed Gas Hazards........................................................... 136 3.3 Storage............................................................................................... 137 3.4 Handling Compressed Gas Cylinders...................................... 138 3.5 Using Compressed Gas Cylinders............................................. 139 3.6 Cryogenic Liquid Hazards........................................................... 140 4. Emergency Response Plan.......................................................... 142 5. Gas-Specific Remarks................................................................... 143 5.1 Acetylene............................................................................... 143 5.2 Methylacetylene-Propadiene (MAPP Gas)................ 145 5.3 Oxygen.................................................................................... 145 6. Electric Arc Equipment.................................................................. 146 Chapter 4. Welding and Cutting in Restricted, Enclosed, or Confined Spaces1.................................................................................. 153 1. Regulations....................................................................................... 153 2. Investigate Possible Hazards Before Starting Work......... 157 2.1 Fire............................................................................................ 157

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Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

2.2 Changes in Work Practices or Chemicals Since Last Entry............................................................................... 161 2.3 Make-Up Air Quality.......................................................... 161 2.4 Very Small Spaces.............................................................. 162 2.5 Carbon Monoxide (CO)...................................................... 162 2.6 Noise........................................................................................ 163 2.7 Nonionizing Radiation (Ultraviolet).............................. 163 2.8 Electrocution......................................................................... 164 3. Atmospheric Hazards—Engineering and Administrative Controls................................................................ 165 3.1 Ventilation.............................................................................. 165 3.2 Atmospheric Testing and Personal Air Monitoring.............................................................................. 167 Chapter 5. Construction, Maintenance, and Repair Welding: Health and Safety Considerations................................................ 171 1. Regulations (U.S.)........................................................................... 172 2. Investigate Possible Hazards Before Starting Work......... 173 2.1 Coatings................................................................................. 173 2.2 Base Metal............................................................................. 176 2.3 Filler Metal............................................................................. 177 2.4 Vessel Contents Residue.................................................. 178 2.5 Nearby Workers and Processes.................................... 180 3. Investigate Alternatives to Welding and Cutting................ 181 3.1 Water/Hydroabrasive Jet Cutting.................................. 181 Chapter 6. Health Effects of Metals, Gases, and Other Agents Commonly Encountered in Welding Processes........................ 185 Chapter 7. Personal Protective Equipment....................................... 193 1. Regulations (U.S.)........................................................................... 193 2. Eye Protection.................................................................................. 194 2.1 Welding Helmets (Hoods)................................................ 194 2.2 Filter Shade Selection........................................................ 195 2.3 Automatic Darkening Filters for UV............................. 197 2.4 Laser Protective Eyewear................................................ 197 3. Skin Protection................................................................................. 198 3.1 Welding Helmet/Hood...................................................... 198 3.2 Gloves...................................................................................... 198 3.3 Protective Clothing............................................................. 199 3.4 Foot Protection..................................................................... 200

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8 Air Monitoring........................................................................................ 201 1. Identifying Contaminants of Concern..................................... 202 2. Selecting Air Monitoring Sampling and Analysis Methods............................................................................................. 203 2.1 Gravimetric Methods.......................................................... 203 2.2 Substance-Specific Methods.......................................... 203 3. Collecting Air Samples.................................................................. 206 Chapter 9. Developing Similar Exposure Groups........................... 213 1. Summary........................................................................................... 218 Chapter 10. LEV Discussion.................................................................... 219 1. LEV Evaluation Critique................................................................ 224 2. LEV Evaluation Outcomes........................................................... 224 3. LEV Commentary............................................................................ 225 Chapter 11. Welding Fume as a Group 1 Carcinogen: A Discussion............................................................................................ 227 1. Segment 1: Welding Fume is a Group I Carcinogen with No OEL and No Method: Suggestions for a Path Forward................................................................................... 227 2. Segment 2: Near-Term Approaches to Dealing with Welding Fume as a Carcinogen................................................ 237 2.1 Mixtures Method.................................................................. 237 2.2 NIOSH-Suggested OEL of 0.01 mg/m3........................ 238 2.3 Exposure Control Banding............................................... 239 Chapter 12. Control Banding and Welding...................................... 243 1. Introduction....................................................................................... 243 2. Control Banding and Its Limitations........................................ 245 2.1 Control Banding and COSHH Essentials.................... 245 2.2 Exposure Predictor Bands for Dusts............................ 245 3. Grouping of Control Approaches.............................................. 248 3.1 Control Approach 1 (CA1) Low Risk/General Ventilation.............................................................................. 248 3.2 Control Approach 2 (CA2) Medium Risk, Local Exhaust Ventilation................................................. 249 3.3 Control Approach 3 (CA3) High Risk Level, Containment, or Isolation................................................. 250 3.4 Control Approach 4 (CA4) Extreme Risk, Expert Advice....................................................................... 250 3.5 Additional Resources for Exposure Control Guidance................................................................................ 250

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Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

4. Specific Metals and Applicability to Control Banding....... 252 5. Control Banding and RPE Selection......................................... 252 6. Online Control Banding Tools..................................................... 255 7. Summary........................................................................................... 255 Appendix A: Metals Data1....................................................................... 258 Appendix B: GHS Hazard Statements1,2............................................ 262 Chapter 12: Exercise – Welding Control Banding.......................... 264

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Preface One of the challenges faced by Health and Safety Professionals is communicating effectively with people working in a wide range of technical fields. The more we know about their work, the more effective we can be at providing our contributions in the workplace. Also, if we understand the process and the vocabulary, we may pick up useful clues about what’s actually happening at the jobsite. In that vein, this volume attempts to provide enough detail regarding welding processes to allow the Health and Safety Professional to anticipate, recognize, evaluate, and control the hazards associated with the work. This work stems from my interest in welding and allied processes that began when I was taught to weld while in the U.S. Army, later staying at the welding school as an instructor. After my stint in the military, I welded environmental test equipment for Ling Electronics, drop tanks for F-4 fighters at Royal Industries, and nuclear pressure vessels for Trident submarines at Aerojet General. Much of my work in industrial hygiene (IH) has been focused on petrochemical turnarounds that entail a great deal of welding and cutting work. My observations of welding, both as a welder and as an industrial hygienist, have suggested that there is room to improve the Health and (to a lesser extent) Safety awareness for these processes. Our appreciation of welding health hazards has changed significantly since the first edition of this book was published in 2002. Three examples are: • In 2003, the American Conference of Governmental Industrial Hygienists (ACGIH) withdrew the Threshold Limit Value (TLV-TWA®) for welding fume, noting that “…arc welding fumes frequently must be tested for individual constituents that are likely to be present to determine whether specific TLVs are exceeded.”1 • Promulgation of the Hexavalent Chromium Standard in 2006 focused our attention on the carcinogenic effects of hexavalent chromium and the likelihood of overexposures when performing welding or thermal cutting operations on chromium-containing metals. Copyright AIHA® For personal use only. Do not distribute.

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Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

• In 2018, the International Agency for Research on Cancer (IARC) published Monograph 118: Welding, Molybdenum Trioxide, and Indium Tin Oxide, classifying welding fume as a Group 1 Carcinogen. Note that the IARC does not differentiate welding fumes from various processes and metals: ALL welding fume is classified as a Group 1 carcinogen. This text makes a case for hexavalent chromium in aluminum alloys and iron oxide in ferrous alloys as the agents of concern. In order to successfully deal with welding fume as a carcinogen, we really should know something about the process generating the fume. The first eight chapters from the first edition provide this background. To assist the Health and Safety professional in addressing and controlling welding fume health hazards, four new chapters have been added to this second edition: • Chapter 9, Developing Similar Exposure Groups • Chapter 10 offers a discussion of the use of local exhaust ventilation (LEV) devices for control of welding fume exposures • Chapter 11 outlines the reasons for identifying iron oxide as having a role in carcinogenesis and provides suggestions for a path forward in developing an occupational exposure limit (OEL) for welding fume and/or iron oxide. Additionally, nearterm approaches to dealing with welding fume as a carcinogen are discussed. • At the request of the primary author, Chapter 12 has been developed by Mike Phibbs, CIH, ROH of Chemscape. This chapter offers a discussion of the application of exposure control banding to welding fume as a carcinogen. Given the absence of an OEL for welding fume, exposure control banding appears to be a reasonable approach to controlling welding fume exposures. Mike’s tables in Chapter 12 provide clear examples of how to apply exposure control banding to welding fume. Human enterprises are seldom without flaw, and this text is unlikely to be an exception to that condition. The reader is therefore most strongly encouraged to review the resources listed throughout the text. There is simply no substitute for doing one’s homework, and this volume is best viewed as a study guide rather than a definitive work. The responsibility for identification and implementation of best practices therefore remains with the on-site Health and Safety Professional. x

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Reference

1. American Conference of Governmental Industrial Hygienists (ACGIH). 2003 TLVs® and BEIs®: Based on the Documentation of the Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices. Cincinnati, OH: ACGIH, 2003, pg. 71.

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Acknowledgments I am deeply grateful to my peers who have provided me with a safety net by devoting their valuable professional time to reviewing and critiquing this volume. The first edition was reviewed in whole or in part by the following: Wendell Britnel, Stephanie Carter, Kim Froats, Don Garvey, Tim Hitchcock, Fran Kuecker, Linda Sullivan, Ralph Marshall, and Zandra Walton. Their efforts have most certainly resulted in a better product. The recent (2018) classification of welding fume as a Group 1 carcinogen identifies an airborne contaminant for which we do not have an occupational exposure limit (OEL). In the absence of an OEL, Exposure Control Banding is an obvious choice for addressing welding fume. This is not my strength. I therefore asked Mike Phibbs of Chemscape to craft Chapter 12, in which Mike addresses the background for developing Exposure Control Banding and provides a treatment of the topic that charts a useful path forward for controlling welding fume exposures. I remain indebted to Mike for this valuable contribution. I am especially grateful to my colleague, Heidi Oas, and my wife, Ludy, for their support and patience as I struggled to develop this edition. Responsibility for sins of omission and commission in this edition remains mine.

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About the Author Michael K. Harris, PhD, CIH Mike Harris received an earned research Doctorate from Louisiana State University in 1979 and is President of Hamlin & Harris, Incorporated in Baton Rouge, Louisiana. His welding experience includes: • Teaching aircraft welding at the U.S. Army Transportation School • Welding environmental test equipment for Ling Electronics • Welding aircraft drop tanks at Royal Industries • Welding pressure vessels for nuclear submarines at Aerojet General Mike is a Fellow of the AIHA and the 2014 recipient of the Donald E. Cummings award.

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1 Introduction to Welding Health and Safety 1. Introduction to Welding and Thermal Cutting This chapter is designed to acquaint the occupational and environmental health and safety (OEHS) Professional with basics of welding and thermal cutting, investigation procedures, regulations, and resource materials related to welding health and safety. Information presented in Chapter 2 of this book is intended to provide sufficient understanding of the details of the work to allow the OEHS Professional to communicate with shop and plant personnel and understand the jargon used by welders. However, no attempt has been made to offer an encyclopedic discussion of the numerous nuances of welding. The American Welding Society (AWS) produces a wide variety of welding publications that may be consulted for a comprehensive treatment of welding. The AWS may be contacted at 8669 NW 36 Street, #130 Miami, FL 33166 (800-443-9353) or www.aws.org. Many hazards such as noise, thermal burns, and crushing/pinch point injuries are generally self-evident during a walk-through. Other hazards, such as those associated with inhalation exposures to a variety of metal fumes, products of flux decomposition, products of cleaning solvent decomposition, handling of compressed gases, working with high-amperage electrical equipment, and the unique hazards associated with work in confined spaces, may be less obvious. Welding has often been regarded by our profession as a “task,” not unlike abrasive blasting or painting. It is more appropriate to regard welding and thermal cutting as an industry that is interdigitated with fabrication and repair processes. Welding is similar to painting and blasting tasks in that the worker is seldom more than an arm’s length from the source of the airborne contaminant(s). There, however, the similarity ends. In the case of blasting or painting, a relatively limited number of abrasives and coatings are found common use, constraining the number of airborne contaminants. By comparison, the AWS lists well over 30 welding and thermal Chapter 1: Introduction to Welding Health and Safety Copyright AIHA® For personal use only. Do not distribute.

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cutting processes, each with its own suite of health and safety hazards. Moreover, hundreds of ferrous and nonferrous alloys (each with its own distinct chemical composition) are subjected to the violence of electricity during construction, fabrication, and repair tasks. In addition to the variety of welding and thermal cutting processes, base metals, filler metals, and tasks, there is another source of variability that has proven to be a frequent cause of frustration when parsing out the sources of exposure data variability: the work environment. The size, configuration, dimensions, and ventilation (natural or mechanically assisted) of the work environment have a profound effect on the dispersion, or lack thereof, of the welding fume. Finally, individual variations in body position, eyesight, and personal habit can have a notable effect on exposure potential between workers performing essentially the same work. Several challenges are faced by welding engineers and welders as they develop processes and techniques for joining metal. Some are mechanical, such as controlling distortion caused by the cooling of the weld metal. Think about that for moment. Welding has been defined as “A joining process that produces coalescence of materials by heating them to the welding temperature, with or without the application of pressure alone and with or without the use of filler metal.”1 In the case of the most common manual welding processes, filler metal is added to the pool of molten metal to create weld. As this metal solidifies and cools, it contracts, and in doing so creates stresses in the welded assembly or “weldment.” These stresses due to contraction result in warpage or distortion of the weldment. This can be counteracted by preheating, postheating, joint design, and use of fixtures to limit component movement as it cools. That’s the easy part. The hard part is protecting the molten metal from exposure to atmospheric oxygen and nitrogen. Exposure of the molten pool of metal to the atmosphere can easily result in weakening of the weld due to voids in the weld (“Swiss cheesing”) and compromised metallurgical properties that may cause outright failures of the weld. When one considers that the weldment may be the hull of a ship, the chassis of a piece of earthmoving equipment, the housing of a jet engine, the body of a railroad passenger car, or the body of the car you drove to work, the need for ensuring weld quality by excluding the atmosphere from the weld pool is evident.a Not all welding processes create a pool of molten metal subject to exposure to the atmosphere. Exceptions include resistance welding, explosion welding, and stud welding. a

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A number of methods are used to exclude the atmosphere during the welding process. The shielding techniques for each process are described in Chapter 2. The shielding methods used for the various processes affect the quantity and makeup of the fume emitted by the processes. Welding and cutting operations can result in the generation of a hazardous atmosphere, especially in a confined space, even though that space may have been found safe for entry prior to beginning the work. For example, thermal cutting, welding, and arc gouging release metal fumes into the air. In steel fabrication and repair, the most common fume is iron oxide, which in recent literature has been associated with development of neoplastic disease. When hardfacing, corrosion-resistant, or high-strength alloys are subject to welding and cutting, other contaminants of concern such as hexavalent chromium and nickel (among others) are likely to be released. Metal fumes are not the only contaminants of concern. Welding and cutting also generate a number of gaseous contaminants. These include the following: • • • •

Ozone, particularly during aluminum welding. Carbon monoxide, particularly during arc gouging. Oxides of nitrogen. Argon or other inert gases used for gas-shielded arc processes. • Fluorides that might be released when shielded metal arc welding (SMAW) is used. • Thermal decomposition of paint coatings might release a wide variety of contaminants, and the material safety data sheet (MSDS) for coated metal should be consulted before commencing welding or cutting operations on those surfaces. Examples include the following: – Isocyanates from decomposition of paint coatings that require catalysts (e.g., urethane and polyurethane paints) – Aldehydes from decomposition of “weldable paints” and some degreasers.

2. Anticipation and Recognition of Welding and Cutting Health and Safety Hazards An evaluation of the following three sets of factors will very likely reveal the health and safety hazards associated with nearly all welding and cutting processes: Chapter 1: Introduction to Welding Health and Safety Copyright AIHA® For personal use only. Do not distribute.

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1) Materials in use: i) Metals being joined or cut ii) Filler metals in use (if any) iii) Fluxes in use (if any) iv) Shielding gases (if any) v) Coatings on the metals being joined or cut vi) Cleaning or degreasing solvents 2) Heat source for the process under investigation: i) Electric arc ii) Electrical resistance iii) Oxyfuel iv) Plasma v) Laser beam vi) Electron beam 3) Workplace environment: i) Open work areas ii) Confined spaces iii) Restricted spaces iv) Wet work areas v) Multiple welder worksites In this context, the answers to a few questions should direct the OEHS Professional’s attention to the most likely hazards. The following examples may be of use in this regard: • “What are you welding?” This question should initiate a discussion of the materials being welded. Generally, the answer will come in the form of some sort of shop shorthand. For example, chrome-molybdenum steel containing 1.25 percent chromium is frequently called “one-and-a-quarter-chrome.” Similarly, steel that contains a minimum of alloying ingredients is commonly referred to as “carbon steel” or “mild steel.” The process of investigation should now proceed to the facility’s Hazard Communication Manual (HazCom Manual) for review of the MSDSs to identify probable contaminants of concern. • A second question might be: “What kind of welding (or cutting) process are you using?” The answer to this question should direct the OEHS Professional to Chapter 2 of this edition. Chapter 2 outlines 25 common welding and thermal cutting processes and briefly describes the health and safety hazards associated with the various processes.

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The majority of Chapter 2 is for reference purposes in the event that the less common processes are in use at your facility. Rather than reading the entire chapter, focus your attention on the commonly used processes. Common high-fume emission processes are: • • • •

Shielded metal arc welding (SMAW), Section 1 Gas metal arc welding (GMAW), Section 3 Flux cored arc welding (FCAW), Section 4 Arc cutting and arc gouging, Section 15

Common low-fume emission processes are: • • •

Gas tungsten arc welding (GTAW), Section 2 Submerged arc welding (SAW), Section 5 Resistance welding (RW), Sections 17 and 18

Welding processes usually (but not always) use filler metal that is melted along with the parts being joined. If the joining process is brazing or soldering rather than welding, it will also be necessary to determine what filler metal is being used. Also, fluxes are in common use for many processes. In either event, it will likely be necessary to revisit the HazCom Manual to identify the possible contaminants of concern from filler metal and flux sources. • A third question might address the possibility of coatings on the metals being joined or cut. These coatings may include: – Process chemical residue, e.g., » Some halogenated cleaning chemicals decompose to form chlorine gas and/or phosgene. » Some petrochemical vessels may contain sulfur compounds that form sulfur dioxide (a profound upper respiratory tract irritant) upon heating. – Paints – Polymers – Primers – Claddings – Plated materials These possible sources of contaminants are deserving of particular consideration when executing repair and maintenance tasks. Pay attention to the “products of decomposition” section of the MSDS for the coatings. Cadmium, lead, strontium chromate, and isocyanates may evolve or outgas from some of these coatings when heated. Chapter 1: Introduction to Welding Health and Safety Copyright AIHA® For personal use only. Do not distribute.

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• A fourth question, or set of questions, should focus on characterizing the work environment. For example: – How many welders will be involved in the work? – How many helpers will be working with the welders? – What other activities are being conducted in the area? – Will this work be conducted in a confined space? – Will the work be carried out in a fairly open work area? – Will the work be executed in a “fabrication tent” at a construction site? These questions focus on identifying worksite characteristics that may mitigate or exacerbate exposure potentials, not only for the welder, but for other nearby workers as well. Recognizing that we all have our relative strengths and “growth areas,” the industrial hygienist is reminded to consider the potential for physical hazards when working with the high energy levels necessary to melt, weld, cut, and join metals. Similarly, the OEHS Professional is advised to look carefully at the potential for airborne hazards from welding and allied processes. A site-specific checklist for investigating welding and cutting processes may be of real value in this context. A draft or prototype checklist (Welding Health and Safety: Initial Evaluation Form) is provided at the end of this chapter. This evaluation form is by no means all-inclusive and very likely will not address all the probable hazards at all facilities. However, it may be useful as a starting place for development of a more appropriate site-specific evaluation form.

3. Regulations The Occupational Safety and Health General Industry Standards, Subpart Q – Welding, Cutting and Brazing includes the following sections pertinent to welding and other hotwork processes. These standards may be worth reviewing, particularly for OEHS Professionals working in the United States. • • • • •

6

29 CFR 1910.251: Definitions 29 CFR 1910.252: General Requirements 29 CFR 1910.253: Oxygen-Fuel Gas Welding and Cutting 29 CFR 1910.254: Arc Welding and Cutting 29 CFR 1910.255: Resistance Welding

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Applicable OSHA Shipyard standards include: • 29 CFR 1915.51: Ventilation • 29 CFR 1915.52: Fire Prevention • 29 CFR 1915.53: Welding, Cutting and Heating in Way of Preservative Coatings • 29 CFR 1915.54: Welding, Cutting and Heating in Hollow Metal Structures • 29 CFR 1915.55: Gas Welding and Cutting • 29 CFR 1915.56: Arc Welding and Cutting Construction industry standards promulgated by OSHA with provisions regulating use of welding equipment include: • • • •

29 CFR 1926.350: Gas Welding and Cutting 29 CFR 1926.351: Arc Welding and Cutting 29 CFR 1926.352: Fire Prevention 29 CFR 1926.353: Ventilation and Protection in Welding, Cutting and Heating • 29 CFR 1926.354: Welding and Cutting in Way of Preservative Coatings Other standards pertinent to specific welding and cutting operations are listed and, to some degree annotated, in subsequent chapters of this book.

4. Resource Materials Several documents have been the source of much of the welding-specific information summarized in this volume. Their use is recommended for those with welding OEHS responsibilities. • O’Brien A., ed. Welding Handbook, Ninth Edition, Volume 2: Welding Processes, Part 1. Miami, FL: American Welding Society, 2004. • American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:20129. Miami, FL: American Welding Society, 2012. • Hitchcock RT, Rockwell RJ. Laser Radiation: AIHA Nonionizing Radiation Guide Series. Fairfax, VA: AIHA Press, 1999. • Hitchcock RT. Ultraviolet Radiation: Nonionizing Radiation Guide Series. Fairfax, VA: AIHA Press, 2001.

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5. Welding Health and Safety: Initial Evaluation Form One must practice great care when using forms, as they rarely exhibit the precise focus one might desire (unless they are site specific). One size does not fit all. The reader is therefore cautioned that this sample welding health and safety evaluation form is neither all-inclusive nor designed to address all worksites. The intended use of this sample form is to offer a starting place for development of a site-specific evaluation form. For instance, many worksites may require additional emphasis and detail regarding fire prevention. Conversely, worksites that do not use compressed gases will have no need to include reference to compressed gas hazards. Cryogenic storage is not addressed here as it is not as common as gaseous state storage. Certainly, if the user has cryogenics on site, those hazards should be addressed in a site-specific evaluation form. This sample evaluation form uses a question-and-answer format. Some of these questions have added syntax to allow a consistent “Yes” answer if conditions meet the desired criteria. This approach merely reflects the author’s preference and is not the only way to develop an evaluation form. The layout of the reader’s site-specific form is a matter of personal preference, and the reader is encouraged to make his/her form fit his/her workplace and work habits. There is a certain amount of redundancy in the form offered here. For example, reference to correct filter lenses is made under nonionizing radiation and again under personal protective equipment (PPE). This reflects the dichotomy many of us face when evaluating hazards and PPE in the same breath: does the question go under the hazard itself [ultraviolet (UV) radiation] or under the PPE needed to address the hazard (filter lenses)? This author (M.K. Harris) elects to leave that editorial decision up to the developer of the site-specific evaluation form. Clearly, there is room for more detailed questions than those asked here. However, the following form is believed to be an adequate starting point for developing an initial evaluation form for the site under investigation.

Reference

1. O’Brien RL, ed. Jefferson’s Welding Encyclopedia, 18th Edition. Miami, FL: American Welding Society, 1997.

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Welding Health and Safety: Initial Evaluation Form Company:

Date:

Location/ Site:

Response

Comments

1. Basic Questions Has the investigator reviewed ANSI Z49.1:1999 and the appropriate regulations? (If working in the United States, see this book, Chapter 3, Section 1 for a list of U.S. federal regulations.)

Yes

No

Yes

No

Preliminary Hazard Identification What materials are being welded? (e.g., aluminum, carbon steel, Monel, stainless steel) What process is in use? (e.g., “Stick,” “MIG,” “TIG”)* What coatings are on the metal? (e.g., paint, cadmium plating, nickel plating) If this is repair work, what process residues may be present? (e.g., petroleum, adhesives, uncured polymers, sludge) How many welders will be involved in the work? How many helpers will be working with the welders? Is there a record of employee training regarding the specific hazards of welding and cutting?

* The familiar shop terms are shown here because they are more likely to be used than the formal AWS terms of SMAW (“Stick”), GMAW (“MIG”), or GTAW (“TIG”).

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Welding Health and Safety: Initial Evaluation Form (continued) Questions

Response

Comments

2. Environmental Considerations What is the work environment like? (e.g., open shop, fabrication tent, confined space) What protective measures are in use? (e.g., dilution ventilation, local exhaust ventilation, welding screens, PPE) Is the work environment configuration free of impediments to adequate ventilation?

Yes

No

If mechanical ventilation is in use, has the airflow been quantified?

Yes

No

Yes

No

3. Fire Prevention What fire prevention measures are in place? e.g.: • Fire watch • Fire hoses • Fire blankets • Fire screens Is the area free from accumulations of flammable solid materials? e.g.: • Unprotected wooden scaffold boards • Plywood barriers or partitions • Cardboard boxes containing parts or supplies • Workers’ clothing • Plastic ventilation ducts (if not fire-rated) • Residual sludge from incomplete cleaning of internal surfaces (especially pertinent in petrochemical process vessels) • Soil contamination (particularly when working trenches in petrochemical facilities)

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Welding Health and Safety: Initial Evaluation Form (continued) Questions

Response

Have possible sources of flammable gases or vapors been evaluated? e.g.: • Vessel contents that have not been adequately purged or cleaned • Leaking blinds or block valves • Painting operations • Paint removal • Solvent cleaning procedures

Yes

No

Has the work environment been evaluated for tasks associated with airborne combustibles (Rule of thumb: Vision obscured at 5 ft or less); e.g.: • Grain silos • Wood dust silos/cyclones • Aluminum dust • Magnesium dust • Coal dust

Yes

No

If compressed gases are in use, is appropriate signage posted at storage areas? FLAMMABLE GASES AND/OR OXIDIZERS. SMOKING AND/OR OPEN FLAMES PROHIBITED (Does not apply to individual use areas)

Yes

No

Comments

4. Compressed Gases (See Chapter 3, Section 3 for more details) What compressed gases are in use? • If acetylene is in use, see Chapter 3, Section 5.1 • If MAPP gas is in use, see Chapter 3, Section 5.2 • If oxygen is in use, see Chapter 3, Section 5.3 Does the site Emergency Response Plan address hazards associated with compressed gas cylinders? (Chapter 3, Section 4)

Yes

No

Are cylinders secured?

Yes

No

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Welding Health and Safety: Initial Evaluation Form (continued) Questions

Response

Are cylinders located away from probable falling object hazards?

Yes

No

Are valve protection caps in place on cylinders not in use?

Yes

No

Are cylinders placed so that sparks, slag, or flame do not come in contact with the cylinders?

Yes

No

Is appropriate signage posted at storage areas? FLAMMABLE GASES AND/OR OXIDIZERS. SMOKING AND/OR OPEN FLAMES PROHIBITED (Does not apply to individual use areas)

Yes

No

Are hoses correctly routed and in good repair?

Yes

No

Are hoses clear of stairways, ladders, and passageways?

Yes

No

Are hoses, cylinders, regulators, fittings, etc., clean and free from hydrocarbons?

Yes

No

Are cylinder, hose, and torch connections leak tested prior to use?

Yes

No

Have hoses carrying oxygen or fuel gases been inspected prior to the beginning of the shift?

Yes

No

Comments

5. Electric Arc Welding (See Chapter 3, Section 6 for more details) Are other employees and personnel working in the area of electric arc welding and cutting shielded from the arc and spatter by distance or noncombustible and flameproof screens?

Yes

No

Unattended electrode holders are not left with electrodes in them, correct?

Yes

No

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Welding Health and Safety: Initial Evaluation Form (continued) Unattended electrode holders are placed so that they do not come in contact with employees or conducting objects, correct?

Yes

No

Are welding machine frames grounded?

Yes

No

Have welding machines been de-energized (open the power supply switch) when the welder/cutter leaves the work for breaks, lunch, or at the end of shift?

Yes

No

Are cables correctly routed and in good repair?

Yes

No

Are cables clear of stairways, ladders, and passageways?

Yes

No

Are cables free from repairs or splices for a minimum of 10 ft from the electrode holder?

Yes

No

Are cables sized correctly? (See Chapter 3, Table 3.1)

Yes

No

Is the work area maintained as dry as possible?

Yes

No

6. Confined Spaces (See Chapter 4 for more information) Has the confined space been evaluated for possible asphyxiation hazards?

Yes

No

Has the confined space been evaluated for possible elevated concentration of toxic contaminants?

Yes

No

Has the confined space been evaluated for possible increased risk of fire or explosion?

Yes

No

Has the confined space been evaluated for possible entrapment and/or engulfment hazards?

Yes

No

Has the confined space been evaluated for other mechanical hazards such as crushing or electrocution?

Yes

No

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Welding Health and Safety: Initial Evaluation Form (continued) Questions

Response

Have possible sources of contaminated make-up air entering the confined space been identified and corrected? e.g.: • Carbon monoxide from generators, air compressors, and vehicles • Carbon monoxide and metal fumes from welding and cutting outside the vessel • Paint and cleaning solvent vapors • Silica from adjacent blasting operations (watch the plume) • Lead from paint removal work • Metal fumes from adjacent welding and cutting • Asbestos or insulation work • Nearby process sources

Yes

No

Are torches removed from the confined space or shut off at a point outside the confined space during breaks, lunch, and at change of shift?

Yes

No

Has adequate ventilation been verified (i.e., 2,000 cfm per welder dilution or 100 fpm at the arc/flame for source capture)?

Yes

No

If carbon arc cutting (CAC-A, air-arc, or arc-gouging) is employed, is supplied air respiratory protection employed?

Yes

No

Has atmosphere testing (“gas testing”) also included confined spaces within confined spaces (e.g., sumps, wells, internal cyclones, spaces behind vessel liners, or baffles)?

Yes

No

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Comments

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Welding Health and Safety: Initial Evaluation Form (continued) Questions

Response

Comments

7. Noise Have noise levels from the following potential sources been evaluated? • Welding machines and air compressors

Yes

No

• Air carbon arc cutting (CAC-A, arcair, arc-gouging)

Yes

No

• Electric arc welding

Yes

No

• Grinding and fitting prior to welding

Yes

No

• Chipping of concrete or refractory linings

Yes

No

• Ventilation equipment

Yes

No

• Use of air-powered equipment (e.g., impact wrenches, saws, drills)

Yes

No

• Hammering and impact of repair or construction materials against vessel walls

Yes

No

Have confined spaces received emphasis during the noise evaluation?

Yes

No

8. Nonionizing Radiation [Ultraviolet (UV)] Are personnel exposed to UV radiation protected against skin exposure by ensuring that all skin is covered completely (e.g., heavy long-sleeved shirts buttoned at the collar and gloves)?

Yes

No

Has the possibility of UV light entering the back of the hood, striking the lens inside the welder’s hood, and reflecting into the welder’s eyes been evaluated?

Yes

No

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Welding Health and Safety: Initial Evaluation Form (continued) Questions

Response

Has possible UV decomposition of chlorinated solvents to phosgene and other halogenated species been considered? • The use of chlorinated solvents is kept at least 200 feet from the exposed arc. • Surfaces cleaned with chlorinated solvents are thoroughly dried before welding is permitted on such surfaces.

Yes

No

Are filter lenses appropriate for process and amperage used? (See Chapter 7, Tables 7.1 and 7.2)

Yes

No

Has an assessment of the potential hazards in the workplace and PPE required to mitigate those hazards been performed? (29 CFR 1910.132)

Yes

No

Is there a record of training and demonstrated employee competency in the following topics? • When PPE is necessary. • What PPE is necessary. • How to properly don, doff, adjust, and wear PPE. • The limitations of the PPE. • The proper care, maintenance, useful life, and disposal of the PPE.

Yes

No

Are safety glasses or goggles worn behind the welding hood to provide impact protection when the hoods (or the filter plate holder) are lifted?

Yes

No

Comments

9. PPE and Clothing

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Welding Health and Safety: Initial Evaluation Form (continued) Questions

Response

Have hazards from spatter and flying slag been evaluated and compared with possible skin protection ensembles? (e.g., gloves, capes, jackets, and chaps)

Yes

No

Is dark clothing worn when working with electric arc processes to minimize reflections into the helmet?

Yes

No

Are filter lenses appropriate for process and amperage used? (See Chapter 7, Tables 7.1 and 7.2)

Yes

No

Has respirator selection been based on air monitoring data collected at the site under investigation? (See Chapter 8 for additional details.)

Yes

No

Is there a record of respirator wearers being trained in the use, care, and storage of respirators?

Yes

No

Are respirators being worn in accordance with site-specific criteria for respirator type and circumstances under which respirators should be worn?

Yes

No

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Comments

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2 Welding Processes: Health and Safety Considerations Many of the technical details of the welding processes described in this chapter are summarized from the American Welding Society (AWS) Welding Handbook, 8th Edition, Vol. 2, Welding Processes.1 The welding professional will note that the summaries offered here are not fully descriptive of the details of the various welding processes and many fascinating technical aspects have been omitted. This brevity is intentional as the focus of this volume is anticipation, recognition, evaluation, and control of occupational and environmental health and safety (OEHS) hazards associated with welding and cutting rather than on the processes themselves. The interested reader is encouraged to refer to the AWS Welding Handbook for additional information on welding processes. Although accepted AWS terminology for welding processes has been used throughout this volume, welders are often not as particular in their use of AWS terminology. Consequently, many common terms used in welding shops have also been included. The descriptions of welding processes offered in this section are intended to allow one to anticipate health and safety hazards associated with various welding processes before the work begins. If the work is underway when “discovered” by the OEHS Professional, this information should allow for rapid recognition of the hazards associated with the work. The descriptions become more succinct as one reads sequentially from one welding process to another, reflecting the similarity of many of the processes. The sequence or order of the health and safety hazards listed in the “Process Health and Safety Hazards Summary” for each welding process in Chapter 2 has been the subject of some discussion between the author and the reviewers. Some of the reviewers preferred that the health and safety hazards be listed in the same order for each process rather than different orders for the various processes. However, the health and safety hazards are listed for each process in the order of the most common or likely hazard to be encountered, followed by the next most likely, et cetera. The reader is advised that this ordering reflects a certain amount of discretion based on the au-

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thor’s experiences. Those experiences may not be strictly applicable to the reader’s worksite because the degree to which a hazard will be evident is, in part, a function of the process itself as well as the conditions under which the welding operation is conducted. Nonetheless, the sequences adopted are believed to be more beneficial than using the same sequence of hazards throughout. The general format outlined below has been standardized for each process.

n. Process AWS Name (and common terms when applicable) n.1 Process Health and Safety Hazards Summary Hazard

Sources

e.g., UV radiation burns to eyes and skin

e.g., Electric arc

n.2 Process Common Metals • A list of metals commonly welded via the process being described.

n.3 Welding Process Description These discussions (hopefully) provide enough information for the OEHS Professional to be able to: • Anticipate health and safety hazards that may arise from welding and cutting; • Recognize the welding processes that may be encountered in the field; • Identify potential hazards associated with these processes when encountered; and • Use appropriate vocabulary while engaging in meaningful conversations regarding potential hazards with affected personnel.

n.4 Process Health and Safety Hazards Discussion Subheadings are in bold and italics and numbered n.4.1, n.4.2, etc. Examples include: n.4.1 UV radiation burns to eyes and skin n.4.2 Thermal burns 20

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n.4.3 Metallic fume constituents n.4.4 Nonmetallic fume constituents n.4.5 Eye hazard: slag

n.5 Equipment Comments Specific to Processes This heading offers brief comments noting equipment concerns of interest to the OEHS Professional. References to other related chapters are also provided.

THE PROCESSES 1. Shielded Metal Arc Welding (SMAW or “Stick Welding”) 1.1 SMAW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin

• Electric arc

Photoretinitis or blue-light injury

• Electric arc

Thermal burns

• Spatter • Handling hot metal • Handling hot electrodes stubs

Metal fumes

• Parent metal • Welding rod

Products of flux decomposition, including carbon monoxide

• Flux coating on welding rod

Methylene chloride

• Some anti-spatter compounds

Particulate in eyes

• Spatter • Chipping cooled flux from weld • Pre- or postweld grinding operations

Noise

• Gasoline or diesel-driven generators • Arc

Electrocution

• Damaged high-amperage welding cables

1.2 SMAW Common Metals to:

Metals commonly welded via SMAW include but are not limited

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• • • • •

Carbon and low-alloy steels Stainless steels Cast iron Copper and its alloys Nickel and its alloys

The metal alloy cores of SMAW electrodes are usually similar to the metals being welded. However, this is not always the case, and the material safety data sheet (MSDS) for the electrodes should be consulted. Some examples of metals (other than the base metal) that may be included in SMAW electrodes are provided below. • Low-alloy steel electrodes may contain: – Iron – Molybdenum – Chromium – Nickel – Manganese • Electrodes for cast iron: – Nickel • Electrodes for hardfacing (see Section 25: Surfacing) may contain: – Chromium – Cobalt – Copper – Iron – Manganese – Molybdenum – Nickel – Vanadium

1.3 SMAW Process Description According to the AWS, shielded metal arc welding is the most common welding process presently in use.2 Because of the widespread use of the SMAW process in construction, as well as renovation and repair of industrial buildings and equipment, it is probable that this is the single process most likely to be encountered by the OEHS Professional. The heat necessary for this welding process is generated by establishing an arc between the base metal and an electrode (Figure 2.1).

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Figure 2.1: Shielded metal arc welding Figure 2.1. Shielded metal arc welding

The arc must overcome electrical resistance to bridge the gap between the base metal and the electrode. Electrical resistance The arc must overcome electrical resistance to bridge the gap between the generates heat in a conductor. Because both the base metal and base metal and the electrode. Electrical resistance generates heat in a the electrode are conductors in this process, they become heated. conductor. Because both the base metal and the electrode are conductors in The electrode, generally having less mass than the base metal, this process, they become heated. The electrode, generally having less mass heats and melts more quickly. No current flows through the SMAW than the base metal, heats and melts more quickly. No current flows through the circuit until the welder establishes an arc between the base metSMAW circuit until the welder establishes an arc between the base metal, or al, or “work,” and the electrode. The arc is established when the “work,” and the electrode. The arc is established when the welder brushes or welder brushes or taps the end of the electrode on the work. If this taps the end of the electrode on the work. If this act of “striking an arc” is not act of “striking an the arc”electrode is not performed correctly, theitself electrode will performed correctly, will instantaneously weld to the work, instantaneously weld itself to the work, requiring a certain amount requiring a certain amount of struggle on the part of the welder to rectify the of struggle on this the occurs, part of itthe welder to rectify situation. When situation. When is best to avoid beingthe overly inquisitive and this occurs, it is best to avoid being overly inquisitive and asking asking questions of the welder. questions of the welder. the surface of base metal will melt, creating the Once the arc is established, Once the arc is established, thetosurface of base metal will melt, puddle of molten metal often referred as the “weld pool” or simply, the creating the puddle of molten metal often referred to as the “weld “puddle.” This melting process begins almost immediately due to the extreme pool” or simply, the (> “puddle.” meltingThe process begins almost temperature of the arc 9000°F orThis > 5000°C). end of the electrode will immediately due to the extreme temperature of the arc (> 9000°F quickly melt as the electrode metal is deposited into weld via a stream of tiny or > 5000°C). of the electrode will quickly melt as the elecglobules in the The arc. end Consequently, the welder must constantly adjust for trode metal is deposited into weld via a stream of tiny globules in consumption of the electrode; otherwise, the arc will grow longer as the the arc. Consequently, the welder must constantly adjust for conelectrode gets shorter. Excessive arc length is undesirable, and welders are sumption of the electrode; otherwise, thethe arc will grow longer trained to constantly move the electrode toward puddle at the same rateasat the electrode getsisshorter. Excessive arc length is of undesirable, and which the electrode being melted or consumed. Some the molten metal weldersescape are trained movea the electrode the globules from thetoarcconstantly stream, creating fire and thermaltoward burn hazard. Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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puddle at the same rate at which the electrode is being melted or consumed. Some of the molten metal globules escape from the arc stream, creating a fire and thermal burn hazard. These flying globs of molten metal, called “spatter,” may also be deposited on the surface of the base metal. If it becomes necessary to remove the cooled spatter, a chipping hammer is frequently the tool of choice. The resulting flying debris may present an eye hazard. In the SMAW process, the electrode is a metal rod, usually from 9 to 18 inches in length. The terms “electrode,” “rod,” and “stick” are often used interchangeably on the jobsite. As the puddle of molten metal is moved along the joint, the electrode is melted, or “deposited” into the puddle, filling in gaps and reinforcing the weld. Rods are specified by, among other criteria, the diameter of the metallic core or rod. Larger diameters are used when possible because they can carry more electrical current and will therefore speed the welding process. Larger rods also facilitate more rapid deposition. However, rod diameter must also be matched to the thickness of the metal being welded. Thinner metals require smaller rods because large rods require more amperage (heat) to melt. If the rod is too large for the metal being welded, the excessive amperage will melt the base metal too quickly and rather than forming a puddle, the base metal will simply be melted away. This creates a hole rather than a weld. The amperage and voltage are adjusted by the welder to provide sufficient heat to melt the base metal and electrode at a rate appropriate for the metal thickness, type of joint, work position, and electrode used for the weld. Typical values range from 16 to 40 volts and from 20 to 550 amps. Increasing the amperage (and, usually concomitantly, the voltage) will result in increased rates of electrode consumption and increased rates of fume generation.

1.4 SMAW Health and Safety Hazards Discussion 1.4.1 UV radiation burns to eyes and skin Electrode diameter is an important consideration for OEHS Professionals because larger rods require more current if they are to melt at the correct rate. Current has a direct effect on the quantity of ultraviolet (UV) radiation produced by the arc. See Chapter 6: Health Effects and Chapter 7: PPE for further discussion of this health hazard and use of filter lenses to protect the eyes.

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1.4.2 Thermal burns The SMAW process creates “spatter,” which will produce painful burns if adequate personal protective equipment (PPE) is not worn. Generally, a leather welding jacket and leather gloves are worn to protect the welder from this hazard. When SMAW is conducted overhead, the potential for burn injuries is greatly increased because the spatter can fall directly onto the welder. In these circumstances, the welding jacket must fit snugly around the neck to prevent spatter from getting under the PPE. When an SMAW electrode has been consumed, the stub is released from the electrode holder (“stinger”) by squeezing the spring-loaded clamp handle and the stub is dropped or sometimes “flicked” to the floor. The curious and uninitiated will quickly learn that hot stubs can burn the skin through light gloves. Thermal burns from the welded assembly (“weldment”) are equally probable, and it is prudent to treat all weldments as hot. Leather gloves are consequently standard PPE in a welding area. 1.4.3 Fume constituents SMAW creates a substantial quantity of fume, and much of the health and safety literature addressing welding concentrates on quantifying the metallic fume exposure potentials associated with the generation of this fume. However, there are many variables that may affect employee exposures. These variables are often specific to the individual production or repair/maintenance operation, and it is difficult to identify, isolate, and compensate for their effects. This difficulty may make it inappropriate to apply the data in the literature to a specific site or operation. Consequently, exposure-monitoring data should be collected for the site and process under investigation. A review of the MSDS for the base metal and the SMAW electrode will provide an initial evaluation of the metals for which monitoring should be conducted during an initial characterization. It is important to bear in mind that much of the SMAW fume comes from decomposition of the flux coating on the electrode as well as the metals involved. SMAW electrodes are coated with materials that help stabilize the arc and create a gaseous shield to protect the molten metal from the atmosphere. As the coating and the rod are consumed during the welding process, some of the coating is vaporized, creating the gaseous shield. It is imperative to exclude the atmosphere from the molten metal in the puddle; otherChapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

wise, oxygen and nitrogen in the atmosphere will form nitrides and oxides of the metal being welded. These oxides and nitrides are typically brittle and exhibit low tensile strength, neither property being desirable in most applications. The OEHS Professional should also be aware that some electrode coatings contain metals that are intended to become incorporated in the weld metal. As these metals may be present in the breathing zone during welding, a review of the coating constituents on the rod MSDS is recommended. The gaseous shield created by heating the electrode coating also serendipitously acts to limit the emission of UV radiation from the arc, reducing the UV hazard when compared to the gas-shielded welding (GTAW and GMAW) process described below. Carbon monoxide may be a concern when working with SMAW corrosion-resistant steels (“stainless steels”). The electrode coatings for many corrosion-resistant steels may contain a high percentage of calcium carbonate. Heating this material in the presence of oxygen produces carbon monoxide (CO) and carbon dioxide (CO2). Accumulation of these gases, particularly CO, may present a hazard when welding in confined spaces. Finally, one should note that electrodes used with alternating current (AC) frequently contain potassium persulfate [threshold limit value (TLV®) = 0.1 mg/m3]. 1.4.4 Eye hazard: slag As the welding process moves along the joint, the liquid weld metal cools and solidifies. To avoid formation of unwanted nitrides and oxides due to contact with the atmosphere, the nonmetallic constituents of the rod coatings are designed to solidify over the surface of the pool of molten metal, forming a protective blanket over the hot, easily oxidized weld. This blanket is called “slag,” and it protects the metal while it cools. Depending on the coating type and welding conditions, the slag may require mechanical removal. Removal of slag is generally required when additional welding must be performed that overlaps the slag-covered weld. Generally, the tools of choice are either a chipping hammer or a needle gun. In some instances, the slag may “pop” off the weld as the workpiece cools. In either case, the potential for eye injury from flying slag has been amply demonstrated by a history of corneal injuries.

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1.5 Equipment Comments Specific to SMAW • Keeping electrode holder jaws clean is necessary to avoid elevated resistance between the electrode and the electrode holder. Elevated resistance can result in excessive holder temperatures and welder discomfort when continuing to weld with a hot electrode holder. • Cables: See Chapter 3: Welding Equipment. • Helmet: See Chapter 7: PPE. • Clothing: See Chapter 7: PPE.

2. Gas Tungsten Arc Welding (GTAW, “HeliArc,” or “TIG Welding”) 2.1 GTAW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin

• Reduced shielding* of electric arc

Photoretinitis or blue-light injury

• Electric arc

Ozone and nitrogen dioxide

• Ionization of atmospheric gases due to reduced shielding of electric arc

Thermal burns

• Handling hot metal • Mishandling hot electrodes

Metal fumes

• Parent metal • Filler metal

Particulate in eyes

• Grinding electrodes • Pre- or postweld grinding operations

Asphyxiation (in confined spaces)

• Inert shielding gases

Phosgene, chlorine, and other halogenated compounds

• Decomposition products from chemical cleaners/degreasers

Noise

• Gasoline or diesel-driven generators • Arc

Compressed gases

• Shielding gases

Electrocution

• Damaged high-amperage welding cables

* The term “reduced shielding” is used here to note the lack of fumes and other fine particulates in the immediate area of the arc during gas tungsten arc welding compared to shielded metal arc welding.

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2.2 GTAW Common Metals Nearly all metals can be welded via GTAW. Examples include but are not limited to: • • • • • • • • • • •

Aluminum alloys Beryllium (usually in an inert atmosphere chamber) Cast iron Carbon as well as nearly all alloy steels Chromium alloys Copper and its alloys, including bronze, brass, and copper-nickel Heat-resistant alloys with iron, nickel, and/or cobalt as primary metals Magnesium alloys Nickel and its alloys Stainless steels Titanium alloys

GTAW is generally considered unsuitable for metals whose liquid phases exhibit high vapor pressures, such as cadmium, tin, or zinc.

2.3 GTAW Process Description As is the case with SMAW, the heat necessary for gas tungsten arc welding is produced by an arc between the base metal and an electrode. There the similarity ends. The electrode is not considered a “consumable” in the GTAW process as it is made of tungsten and exists solely to provide a means of controlling the location and direction of the arc. The device used to hold the electrode, conduct electrical power to the electrode, and provide a means for directing a shielding gas onto the puddle is called a “Torch” and is often referred to as a “TIG torch” in the field (see Figure 2.2). GTAW torches cooled by the shielding gases passing through them may be rated for up to 200 amps, and water-cooled torches may be rated up to 500 amps. The shielding gas is directed onto the puddle via a nozzle or “cup,” which is concentric with the torch collet that holds the electrode. In low-amperage applications, the nozzles are often ceramic. However, metallic nozzles are commonly used for high-amperage welding applications. Shielding gas flow rates vary from 15 to 35 cubic feet per hour (cfh) for argon, whereas representative rates for helium are 30 to 50 cfh. 28

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The shielding gas is directed onto the puddle via a nozzle or “cup,” which is concentric with the torch collet that holds the electrode. In low-amperage applications, the nozzles are often ceramic. However, metallic nozzles are commonly used for high-amperage welding applications. gasSafety: flow WeldingShielding Health and rates vary from 15 to 35A Field cubic Guide feet per hour (cfh) for argon,2nd whereas for OEHS Professionals, edition representative rates for helium are 30 to 50 cfh.

Copyright AIHA®

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Figure 2.2: Gas tungsten arc welding arrangement

The tungsten electrode is generally from 0.010 to 0.250 inches in diameter and 6 inches or less in length. In the industrial setting, GTAW is often referred to as “TIG” (tungsten inert gas) welding because the primary defining aspects of this process are a tungsten electrode and an “inert” gas shield. However, the AWS has noted that although argon and helium are chemically inert, this cannot be said of all shielding gas used in this process. As an aside, the first shielding gas used for this arc welding process was helium (hence the trade name “HeliArc,” which remains a commonly used term for this process). The GTAW electrode is considered a nonconsumable item even if it does get “used up.” The GTAW process is therefore unlike SMAW, in which the filler metal is automatically added as the electrode is consumed. In the GTAW process, filler metal is added by the welder who holds the GTAW torch in one hand and a length of filler wire in the other hand. The arc melts the base metal and forms the weld pool or puddle. The filler wire is dipped into the puddle by the welder and melted by the heat of puddle as well as the heat of Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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the arc (Figure 2.3). Some joint designs (e.g., edge joints and corner joints) on thin metals may not require the use of filler wire for a satisfactory weld. In these instances, the joint design allows the base or parent metal to flow together without the need for adding more metal to the puddle. Shielding gases in the GTAW process are varied to match the requirements of the metals being joined and are usually one of the following: • Argon • Helium • Argon/helium mixture • Argon/hydrogen mixture The welding engineer or welder may use different types of current and different types of electrodes. Welding current used in the GTAW process may be direct current electrode positive (DCEP), direct current electrode negative (DCEN), or alternating current (AC).

Figure 2.3: Gas tungsten arc welding operation Figure 2.3. Gas tungsten arc welding operation

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Chapter 2: Welding Processes

® Copyright AIHA Forare personal only. not distribute. Shielding gases in the GTAW process varied touse match theDo requirements of the metals being joined and are usually one of the following:

 Argon

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

Electrodes may be pure tungsten or alloyed with a number of other metals, thorium and zirconium being the most common.

2.4 GTAW Health and Safety Hazards Discussion 2.4.1 UV Radiation burns to skin and eyes Holding voltage and amperage constant, the risk of UV radiation burns is increased with welding processes such as GTAW and GMAW (see Section 3 for GMAW) when compared to SMAW. The increased risk relative to SMAW is due to the transparency of the inert shielding gases used in GTAW and GMAWa to UV radiation. In contrast, the gaseous shield created by vaporizing the electrode coatings used in SMAW is relatively cloudy and provides some attenuation of the UV radiation emitting from the electric arc. Dark-colored upper-body clothing, buttoned to the neck, is recommended for GTAW welding to reduce reflections of UV radiation within the welding helmet that may result in skin and eye burns. The AWS recommends use of paints containing titanium dioxide or zinc oxide for walls in GTAW welding areas to minimize reflection of UV radiation and consequent eye injuries to unprotected personnel in the immediate vicinity of the GTAW welding operation (ANSI Z49.1 Ultraviolet Reflection of Paint). 2.4.2 Ozone and nitrogen dioxide The AWS notes that “welding with shielding gases high in argon will generate substantial ultraviolet radiation, which will react with oxygen in the vicinity of the arc to produce ozone.”3 Ultraviolet radiation can ionize and dissociate oxygen in the atmosphere, leading to the creation of ozone and nitrogen dioxide. Among the factors that can influence the generation rates of these irritant gases are: • Reflectivity of the metal being welded. Aluminum is particularly effective at reflecting UV radiation, and aluminum welding is associated with increased UV, ozone, and nitrogen dioxide exposures. a The OSHA Shipyard Employment Standard [29 CFR 1915.51(e)] notes that “. . .the inert gas metal arc welding process involves the production of ultraviolet radiation of intensities of 5 to 30 times that produced during shielded metal arc welding. . .”

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Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

• Arc intensity. • Humidity. • Amount of UV shielding provided by welding fume. Ozone and nitrogen dioxide are rarely concerns when welding in well-ventilated work areas. However, when welding in confined spaces, adequate ventilation must be provided to ensure that these gases do not accumulate (see Chapter 4: Confined Spaces). 2.4.3 Particulate in eyes: grinding electrodes The OEHS Professional should take note of how the GTAW electrodes are used and handled in the shop. When the GTAW electrodes are unintentionally touched to the puddle or filler wire, the electrode becomes contaminated. Best practice dictates removing the electrode from the torch, breaking off the contaminated portion of the electrode, and shaping the electrode tip. Thoriated and zirconiated tungsten electrodes are shaped by grinding a point on the end of the electrode, generally using a bench grinder. Welders will often perform the grinding operation while still wearing the welding hood, which is simply flipped up to allow them to see. Unless the welder habitually wears safety glasses under the hood, the possibility for eye injury during electrode grinding exists, even if the grinder is equipped with safety shields. The reason for this apparent dichotomy lies in the habit of swinging the safety shield aside to allow better access to the grinding wheel and unrestricted vision while grinding a fine point on the electrode. Because thorium (232Th) is slightly radioactive, some concern has been expressed regarding the possibility of overexposure during both the welding and shaping (or as it is more often called, “sharpening”) processes. However, several studies of exposure potentials have shown that radiation doses from welding with GTAW-thoriated electrodes and sharpening thoriated GTAW electrodes are below those associated with recognized health hazards.4–7 Pure tungsten electrodes are shaped by reinserting them in the torch, striking an arc on a copper plate, and increasing the current until a small hemispherical shape is produced by melting the tungsten. Consequently, grinding is usually not necessary when using pure tungsten GTAW electrodes.

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2.4.4 Asphyxiation If a welder is working in a small, confined space and argon is used as shielding gas, it is possible to displace the atmosphere with argon in a surprisingly short period of time. For example: • Assume a welder working in a cylinder with dimensions of 4-ft diameter and 8-ft height • Assume 40 cfh argon shielding gas and a breathing zone height of 5 ft • Area of cylinder = (4/2)2 × 3.1416 = 12.57 ft2 • Volume of cylinder to breathing zone height = 5 ft × 12.57 ft2 = 62.85 ft3 The simplest, and possibly most conservative, assumption is that no mixing takes place. Assuming no mixing, time to displace atmosphere at breathing zone height = 62.85 ft3/40 cfh = 1.6 hours. This period approximates the actual working time between normal working. Consequently, in an unventilated space, the normal flow of argon shielding gas could completely displace the atmosphere in a small, confined space in the time between the start of work and the first morning break. This author (M.K. Harris) is aware of at least one fatality that has occurred in this manner. 2.4.5 Phosgene, chlorine, and other halogenated compounds GTAW requires that both the parent metal and the filler wire be scrupulously clean. In order to achieve the necessary pre-weld cleanliness, parts are often solvent-cleaned in vapor degreasing tanks or cleaned on site by the welder using spray cans and wiping cloths. In many cases, the solvent selected will be a nonflammable halogenated hydrocarbon such as 1,1,1 trichloroethane, trichloroethylene, or perchloroethane. These solvents decompose under high heat or UV radiation to form phosgene, chlorine gas, and/or other chlorinated species. To minimize exposure potentials to these compounds, cleaning operations that may release the vapor phase of halogenated hydrocarbon cleaning agents should not be performed in areas where GTAW and GMAW are conducted. Additionally, welders and other workers should be instructed to avoid applying these degreasing compounds to hot metal.

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Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

2.5 Equipment Comments Specific to GTAW • • •

Compressed Gases: See Chapter 3: Welding Equipment Cables: See Chapter 3: Welding Equipment Helmet: See Chapter 7: PPE

3. Gas Metal Arc Welding (GMAW or “MIG”) 3.1 GMAW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin

• Reduced shielding of electric arc

Photoretinitis or blue-light injury

• Electric arc

Ozone and nitrogen dioxide

• Ionization of atmospheric gases due to reduced shielding of electric arc

Thermal burns

• Handling hot metal

Metal fumes

• Parent metal • Filler metal

Particulate in eyes

• Pre- or postweld grinding operations

Asphyxiation (in small, confined spaces)

• Inert shielding gases

Phosgene, chlorine, and other halogenated compounds

• Decomposition products from chemical cleaners/degreasers (particularly when welding aluminum)

Noise

• Gasoline or diesel-driven generators • Electric arc

Compressed gases

• Shielding gases

Electrocution

• Damaged high-amperage welding cables

3.2 GMAW Common Metals Nearly all commonly used commercial metals can be welded via GMAW. Examples include but are not limited to: • • • •

Aluminum alloys Carbon steel as well as nearly any alloy steels Chromium alloys Copper and its alloys, including bronze, brass, and copper-nickel • Heat-resistant alloys with iron, nickel, and/or cobalt as primary metals • Magnesium

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• Nickel and its alloys • Stainless steels • Titanium alloys

3.3 GMAW Process Description Gas metal arc welding employs a shielding gas in the same manner as does gas tungsten arc welding and for the same purpose. However, the electrode for GMAW is not tungsten. Rather, in this process, the electrode is consumed as the filler metal and is the reason for the “M” in GMAW. Referring to Figures 2.4 and 2.5, the similarity between GTAW and GMAW is evident in the use of shielding gas to exclude the atmosphere and an electrode to conduct current. However, the figures are static and do not adequately convey the differences in the dynamics of the two welding processes. TheProcesses GMAW electrode begins its journey to the weld pool as Welding 17 a spool of filler wire. That spool of wire may be small enough to be inwill be remotely mounted at the“gun” welding As thethe welder initiates therecorporated on the GMAW or, machine. more often, spool will be arc by squeezing on the GMAW gun, automatic circuitryinitiates energizesthe motely mountedtheattrigger the welding machine. As the welder an electric motor at the unitGMAW and the filler is fed to the gun arc by squeezing theelectrode trigger feed on the gun,wire automatic circuitry and the weld pool through a wire guide constructed of copper tubing. At energizes an electric motor at the electrode feed unit and thethe filler GMAW gun,tothe through a short sectionaof copper tubing wire is fed thefiller gunwire andpasses the weld pool through wire guide concalled the “contact tube” and is energized with the welding current. structed of copper tubing. At the GMAW gun, the filler wire passes through a short section of copper tubing called the “contact tube” and is energized with the welding current.

Figure 2.4: Diagram of gas metal arc welding equipment Figure 2.4: Diagram of gas metal arc welding equipment

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Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

Figure 2.5: metal arc welding process process Figure 2.5:Gas Gas metal arc welding

At this the filler the electrode in a mannerin similar to Atpoint, this point, thewire fillerbecomes wire becomes the electrode a manner SMAW. The rate of electrode feed is a function of welding current and wire similar to SMAW. The rate of electrode feed is a function of welding diameter, among other criteria, and may range from 100 inches per minute to current and wire diameter, among other criteria, and may range as much as 800 inches per minute. These values are one to two orders of from 100 inches per minute to as much as 800 inches per minmagnitude greater than those commonly used in hand-held GTAW welding ute. These The values areamperages one to two orders magnitude greater than applications. higher often used of with GMAW and the much those commonly used in hand-held GTAW welding applications. higher rates of filler wire application to the weld pool are the reasons for the The higher amperages often used with GMAW and the much highgreater productivity usually associated with GMAW compared to GTAW and er rates of filler wire application to the weld pool are the SMAW. In health and safety terms, this greater productivity results reasons in elevatedfor the greater usually associated with GMAW compared levels of fume productivity and nonionizing radiation compared to GTAW. In response to toincreased GTAW and SMAW. In health and safety terms, this greater prothe generation of fume, several manufacturers of welding equipment, ductivityair results in elevated levels ventilation of fume and nonionizing radiaindustrial cleaners, and industrial equipment offer fume extractors designedtotoGTAW. be concentric with theto GMAW gun nozzle. tion compared In response the increased generation of fume, several manufacturers of welding equipment, industrial air cleaners, industrial ventilation equipment offer fume extractors 3.4 “MIG” and vs. “Short-Arc” designed to be concentric with the GMAW gun nozzle. Copyright AIHA®

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3.4 “MIG” vs. “Short-Arc” Although the terms “MIG” and “Short-Arc” are rarely used in technical welding literature, they are in common use in welding shops; therefore, the OEHS Professional should be aware of the distinction implied by welders who use this terminology. “MIG” refers to GMAW processes that transfer molten filler metal from the end of the filler wire via a spray or stream of globules of molten metal. “Short-Arc” is used to identify GMAW welding wherein the transfer of metal takes place by contact between the filler wire and the base metal, resulting in a short circuit. The heat resulting from the short circuit immediately melts the end of the filler wire into the weld pool. This cycle is repeated several times per second and can often be identified by a sputtering sound as the weld progresses. The AWS uses the term “Short Circuiting Transfer” for this process. “Short-Arc” or “Short Circuiting Transfer” is commonly used for thin metal and is typically the process of choice for many automobile body shops. It is faster than GTAW or oxyfuel gas welding and minimizes distortion of sheet metal due to excessive localized heating and consequent expansion.

3.5 Tubular Filler Wire Some GMAW processes use tubular filler wire. Although the hollow wire contains small amounts of flux that perform some of the same functions as the flux coating used for SMAW, most of the material in the tubular wire is metal powder that contains alloying elements to enhance certain weld characteristics. In many shops, these tubular filler wires containing both flux and metal powder are commonly called “flux-core” wire. Bear in mind, however, that the AWS differentiates between GMAW using tubular filler wire (with flux and metal powder) and flux cored arc welding (FCAW). If the OEHS Professional has the opportunity to inspect a newly completed weld, an FCAW weld can be distinguished from a GMAW weld using tubular wire by inspecting the weld. GMAW with tubular filler wire leaves only small islands of slag on the weld surface, whereas FCAW “. . .leaves a substantial slag covering to protect the solidifying metal”8 as it cools. Another option involves reviewing the filler wire MSDS for the presence of fluxing agents. If neither of these methods is successful, and an interview of shop personnel leaves one unsure, it may be useful to contact the vendor of the filler wire for a more conclusive answer. Those of us working in larger facilities may, of course, contact the welding engineering or shop staff Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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responsible for the process under investigation. Shielding gases in the GMAW process are usually one of the following: • Argon • 98 percent Argon–2 percent Oxygen • Helium • 25 percent Argon–75 percent Helium mixture • Carbon dioxide (CO2): generally used only for carbon and low-alloy steels

3.6 GMAW Health and Safety Hazards Discussion 3.6.1 UV radiation burns to skin and eyes Comments in Section 2.4.1 under GTAW are applicable to GMAW. 3.6.2 Ozone and nitrogen dioxide Comments in Section 2.4.2 under GTAW are applicable to GMAW. 3.6.3 Thermal burns GMAW produces substantially less spatter than SMAW when working downhand. “Downhand” refers to the relative position of the welder, electrode holder (or GTAW torch, GMAW gun, etc.), and the workpiece. This position may be represented by a welder standing at work, which maintains the workpiece at a level about even with the welder’s belt. Generally, any horizontal weld made below shoulder height is considered “downhand.” When the welder is working overhead, there is an increased risk of thermal burns from spatter and a welding jacket and gauntlet-length welding gloves are recommended. 3.6.4 Fume constituents Comments in Section 1.4.3 under SMAW may be applicable to GMAW. The probability of overexposure to fume constituents is increased when: • •

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using tubular wire working in confined spaces

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A review of the MSDS for tubular GMAW electrodes may reveal small amounts of nickel, vanadium, chromium, copper, and/or other metals that warrant element-specific monitoring. 3.6.5 Phosgene, chlorine, and other halogenated compounds Comments in Section 2.4.5 under GTAW may be applicable when GMAW is used for joining aluminum.

3.7 Equipment Comments Specific to GMAW • • •

Compressed Gases: See Chapter 3: Welding Equipment Cables: See Chapter 3: Welding Equipment Helmet: See Chapter 7: PPE

4. Flux Cored Arc Welding (FCAW) 4.1 FCAW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin

• Electric arc

Thermal burns

• Handling hot metal

Metal fumes (usually more than SMAW or GMAW)

• Parent metal • Filler metal

Products of flux decomposition, including carbon monoxide and fluorides

• Flux contained in filler wire

Noise

• Gasoline or diesel-driven generators • Electric arc

Compressed gases

• Shielding gases

Electrocution

• Damaged high-amperage welding cables

4.2 FCAW Common Metals to:

Metals commonly welded via FCAW include but are not limited • • •

Carbon steel as well as many low-alloy steels Stainless steels Cast iron

FCAW is also widely used for surfacing applications (see Section 25).

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4.3 FCAW Process Description For both the welder and the OEHS Professional, FCAW exhibits characteristics of the three welding processes already discussed (see Figure 2.6). These similarities are briefly described below. • Like GMAW, FCAW employs a spool of filler wire driven by a wire feed unit and a “gun” manipulated by the welder to control the weld pool. Because of this similarity, some shops refer to FCAW as “flux core MIG.” • Like SMAW, FCAW uses the gases created by decomposition of fluxes to create a gaseous shield to protect the metal from the atmosphere. In the case of FCAW, the fluxes are contained within the filler wire rather than applied as an exterior coating. • In many applications, FCAW employs shielding gases to supplement the gaseous shield created by the decomposition of the fluxes (see Figure 2.7). In this respect, FCAW is than applied as an exterior coating.

Figure 2.6: Self-shielded flux arc arc welding Figure 2.6: Self-shielded fluxcored cored welding 40

Chapter 2: Welding Processes

In many applications, shielding gases supplement CopyrightFCAW AIHA® employs For personal use only. Dotonot distribute. the gaseous shield created by the decomposition of the fluxes (see Figure 2.7). In this respect, FCAW is similar to GMAW. When used, shielding gases in the GMAW process are usually one of the following:

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

similar to GMAW. When used, shielding gases in the GMAW process are usually one of the following: – Carbon dioxide (CO2) – Argon and CO2 FCAW is applicable to a wide range of metal thicknesses by varying the diameter of the filler wire, the extension of the filler wire past the contact tube and the welding current. FCAW is generally more productive, in terms of inches of weld per minute, than SMAW. This improved productivity is due to FCAW’s constant supply of filler wire from a spool rather than the segmented supply of filler metal offered by the individual welding electrodes used in SMAW. In health and safety terms, this greater productivity results in elevated levels of fume production compared to SMAW or Welding Processes 23 GMAW. In response to this consideration, several manufacturers of welding equipment, industrial air cleaners, and industrial vento be concentric with the FCAW nozzle. designed to be concentric tilation equipment offer fumegun extractors with the FCAW gun nozzle.

Figure Gas-shielded flux arc welding Figure 2.7:2.7: Gas-shielded fluxcored cored arc welding

Chapter 2: Welding Processes

4.4 FCAW Health and Safety Hazard Discussion Copyright AIHA® For personal use only. Do not distribute. 4.4.1 UV radiation burns to skin and eyes Comments in Section 1.4.1 under SMAW are applicable to FCAW.

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4.4 FCAW Health and Safety Hazards Discussion 4.4.1 UV radiation burns to skin and eyes Comments in Section 1.4.1 under SMAW are applicable to FCAW. 4.4.2 Thermal burns Comments offered in Section 1.4.2 under SMAW are applicable to FCAW. 4.4.3 Fume constituents Comments in Section 1.4.3 under SMAW are applicable to FCAW. One may also anticipate more flux-generated fume from FCAW than from GMAW. When reviewing the filler wire MSDS for FCAW, pay particular attention to the “Products of Decomposition” section. The probability of overexposure to fume constituents is increased when working in confined spaces. Fluorides may be a particular concern. 4.4.4 Ozone and nitrogen dioxide The AWS notes that “welding with shielding gases high in argon will generate substantial ultraviolet radiation, which will react with oxygen in the vicinity of the arc to produce ozone.”9 This may be a concern when using shielding gases with FCAW.

4.5 Equipment Comments Specific to FCAW • Compressed Gases: See Chapter 3: Welding Equipment • Cables: See Chapter 3: Welding Equipment • Helmet: See Chapter 7: PPE

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5. Submerged Arc Welding (SAW or “SubArc”) 5.1 SAW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin (in the event of a process upset)

• Electric arc. Note: SAW is generally conducted in level “D” (shirt sleeve) clothing, as the flux completely covers the weld zone.

Thermal burns

• Handling hot metal

Metal fumes (low probability of overexposure)

• Parent metal • Filler metal • Alloying elements in flux

Products of flux decomposition, including carbon monoxide

• Flux contained in filler wire

Particulate in eyes

• Airborne granular and powered fluxes

Noise

• Gasoline or diesel-driven generators

Electrocution

• Damaged high-amperage welding cables

5.2 SAW Common Metals Metals commonly welded via SAW include: • • • • •

Carbon steels Low-alloy steels Chromium-molybdenum steels Stainless steels Nickel-base alloys

5.3 SAW Process Description Submerged arc welding is used in fabrication of pressure vessels, ships, barges, railroad cars, pipes, and fabrication of structural members requiring long welds. SAW employs a wire feed and contact tube mechanism electrode similar to that used for GMAW (Figure 2.8). As is the case with GMAW, the resistance to the electrical current flowing between the filler wire and the base metal provides the heat necessary for melting the wire and metals to be welded. However, SAW does not use a shielding gas to exclude the atmosphere. Rather, a stream of granular flux is added in sufficient quantity to bury the weld pool as the weld progresses. The granular flux is melted by the heat of the arc, just as it is with SMAW (“stick” welding). The gases evolved during the melting of the flux Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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Figure 2.8: Schematic view of submerged arc welding process

Figure 2.8: Schematic view of submerged arc welding process SAWthe is atmosphere. often used forAs welding thick flux sections metal, and multiple exclude the molten coolsofand solidifies over electrodes may bethe used for very heavyassections. electrodes may also weld, it protects molten metal it also Multiple cools and solidifies. be employed to control at theofweld pooland and multhereby SAW is often usedthe forelectromagnetic welding thick field sections metal, provide better control of the arc under the flux. tiple electrodes may be used for very heavy sections. Multiple elecSubmerged arcbe welding may betoused manually, but it is much morefield common trodes may also employed control the electromagnetic at to find this welding process used automatically or semiautomatically. the weld pool and thereby provide better control of the arc under the Under flux. certain circumstances, an additional hopper and feed system may add metal powder to the The may MSDSbeforused thesemanually, powders should Submerged arc weld. welding but it be is reviewed much because these powders often contain chromium, nickel, and other metals more common to find this welding process used automatically or of toxicological interest. semiautomatically. Under certain circumstances, an additional hopper and feed system mayHealth add metal powderHazard to the weld. The MSDS for these 5.4 SAW and Safety Discussion powders should be reviewed because these powders often contain chromium, nickel, and other metals of toxicological interest. 5.4.1 Fume constituents Comments regarding fume constituents in Section 1.4.3 under SMAW are 44 Copyright AIHA®

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5.4 SAW Health and Safety Hazards Discussion 5.4.1 Fume constituents Comments regarding fume constituents in Section 1.4.3 under SMAW are applicable to SAW. When reviewing the flux MSDS for SAW, pay particular attention to the “Products of Decomposition” section. Fluxes may contain alloying elements and are often referred to as “active” fluxes. However, the thick blanket of flux provides an effective engineering control for the metallic and nonmetallic fumes. This blanket of flux and general shop dilution ventilation generally eliminates concerns regarding overexposure to fume constituents. The probability of overexposure to fume constituents is increased when working in confined spaces. 5.4.2 Eye hazards An increased likelihood of particulates entering the eyes arises from the presence of large quantities of granulated or powdered flux, along with the air currents present when comfort fans are used. Also, when the slag formed by the molten flux cools over the weld, it may fly off the surface spontaneously. Flying slag is a recurring safety hazard for SAW welding. 5.4.3 Thermal burns—preheated metal It is common practice to preheat thick sections of metal prior to welding. Preheating provides for more uniform thermal expansion of the parts to be welded. A correlate of more uniform expansion is more uniform contraction, reducing postweld stresses. The hot metal itself and the large burners used to heat the metal increase the likelihood of thermal burns.

5.5 Equipment Comments Specific to SAW Automatic welding equipment, such as that used in SAW, has an abundance of electrically energized motors, relays, switches, and connections. Any or all of these may be energized during the welding process. If the equipment is not turned off between weld passes, many of these electrical components may be energized even if welding is not taking place. Personnel working with automatic welding equipment should be initially trained by the equipment manufacturer’s representative regarding:

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• • • •

Potential electrical hazards; Items of equipment requiring particular care; Approved procedures for de-energizing equipment; and Approved maintenance procedures.

6. Electrogas Welding (EGW) 6.1 EGW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin

• Electric arc Note: EGW is typically used for joining thick plates and may employ high current densities (up to 1000 amps) with resulting high UV radiation output.

Thermal burns

• Handling hot metal

Metal fumes

• Parent metal • Filler metal • Alloying elements in flux

Products of flux decomposition, including carbon monoxide

• Flux contained in filler wire

Noise

• Gasoline or diesel-driven generators • Arc

Electrocution

• Damaged high-amperage welding cables

6.2 EGW Common Metals Metals commonly welded via EGW include: • • • • •

Carbon steels Low-alloy steels Chromium-molybdenum steels Stainless steels (less common) Aluminum (less common)

6.3 EGW Description Electrogas welding is an automatic process used in fabrication of pressure vessels, ships, storage tanks, pipes, and structural members requiring long vertical welds. EGW employs a wire feed and contact tube/electrode guide mechanism similar to that used for GMAW. As is the case with GMAW, the resistance to the electrical current flowing between the filler wire and the base metal 46

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provides the heat necessary for melting metals toofbe joints. Water-cooled copper plates, called “shoes,”the are wire placedand on either side welded. EGW may use either shielding gas or the gases generated the vertical gap between the two parts to be joined and the weld pool is by decomposing fluxes electrodes to exclude the atcaptured between the edges of in theflux partscored and sides of the copper shoes (Figure mosphere from the weld pool. 2.9). As the welding process moves up the joint, the water-cooled shoes move Unlike GMAW, is designed specifically for The welding up the joint along with theEGW electrode guide, exposing the weld. shoes long are vertical joints. Water-cooled copper plates, called “shoes,” are long enough to ensure that the weld has solidified before the shoes move past. placed on either side of the vertical gap between the two parts Once started, the EGW process may continue for tens of feet up the side of ato pool is captured between of the shipbeorjoined storageand tank,the andweld the welder must continually monitorthe theedges process. parts and sides of the copper shoes (Figure 2.9). As the welding Shielding gases in the EGW process are usually one of the following: process moves up the joint, the water-cooled shoes move up the joint along with the electrode guide, exposing the weld. The shoes � Argon are long enoughdioxide to ensure the weld has solidified before the � Argon-Carbon (CO2)that mixture

Figure 2.9: Electrogas welding with a self-shielded cored electrode Figure 2.9: Electrogas welding with a flux self-shielded flux cored

electrode

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shoes move past. Once started, the EGW process may continue for tens of feet up the side of a ship or storage tank, and the welder must continually monitor the process. Shielding gases in the EGW process are usually one of the following: • Argon • Argon-Carbon dioxide (CO2) mixture

6.4 EGW Health and Safety Hazards Discussion 6.4.1 UV radiation burns to skin and eyes When shielding gases (rather than fluxes) are used in conjunction with high welding current, the risk of UV radiation burns is increased. The EGW process typically employs high current densities along with fluxes and/or transparent inert shielding gases. Although EGW is usually an automatic process (as is SAW), the welder must continually observe the welding process to ensure adequate weld quality. In view of the high current densities associated with EGW, darker lens shades are recommended. The AWS recommends Shade 13 for aluminum, Shade 12 for ferrous metals, and Shade 11 for nonferrous metals other than aluminum.10 When flux cored electrodes are used with EGW, the gaseous shield created by vaporizing the flux contained in the electrode is relatively cloudy and provides some attenuation of the UV radiation emitting from the electric arc. Dark-colored upper-body clothing, buttoned to the neck, is recommended to reduce reflections of UV radiation within the welding helmet, which may result in skin and eye burns. 6.4.2 Fume constituents When flux cored electrodes are used with EGW, comments in Section 1.4.3 under SMAW are applicable to EGW. When reviewing the flux MSDS for EGW, pay particular attention to the “Products of Decomposition” section. The probability of overexposure to fume constituents is increased when working in confined spaces. When welding long seams in the sides of ships and storage tanks, it is common practice to isolate the welding area with long panels to shield the welding operation from air currents that would disperse the shielding gas. If flux cored EGW is in use, these panels may also increase the chance of overexposure to fumes and gases generated by the flux. 48

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6.5 Equipment Comments Specific to EGW Automatic welding equipment has an abundance of electrically energized motors, relays, switches, and connections. Any or all of these may be energized during the welding process. Many may be energized prior to beginning the weld if the equipment is not turned off. Personnel working with automatic welding equipment should be initially trained by the equipment manufacturer’s representative regarding: • • • •

Potential electrical hazards; Items of equipment requiring particular care; Procedures for de-energizing equipment; and Approved maintenance procedures.

Electrical hazards are particularly serious and may be deadly when working with the large welding currents usually associated with automatic equipment welding thick sections of metal.

7. Electroslag Welding (ESW) 7.1 ESW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin

• Electric arc (this hazard exists only when initiating the weld)

Thermal burns

• Hot shoes • Molten slag/metal leaking from poorly fitting shoes

Spatter in eyes or skin

• Molten slag bath

Glass-like slag in eyes

• Removing copper shoes

Metal fumes

• Parent metal • Filler metal • Alloying elements in flux

Products of flux decomposition, including carbon monoxide

• Flux contained in filler wire

Noise

• Gasoline or diesel-driven generators • Arc

Electrocution

• Damaged high-amperage welding cables

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7.2 ESW Common Metals Metals commonly welded via ESW include: • Carbon steels • Low-alloy steels • Stainless steels (less common)

7.3 ESW Description Electroslag welding is an automatic process used in fabrication of heavy structural members requiring long vertical welds. It is similar to EGW and employs a wire feed and contact tube/electrode guide mechanism along with copper shoes similar to that used for EGW (Figure 2.10). However, ESW differs from EGW in that the welding heat is provided by resistance to the electrical current flowing through electrically conductive molten slag between the filler wire and the base metal (see Figure 2.10). At the beginning of the weld, an arc is struck between a sacrificial plug of metal at the bottom of the weld (called a “sump”) and is an flux automatic process in fabrication heavy the Electroslag filler wire. welding Granulated is added viaused either flux coredoffiller structural members requiring long vertical welds. It is similar to EGW wire or a hopper. The flux is unique in that it is electrically conduc-and employs a wire feed and contact tube/electrode guide mechanism along with tive when molten and the arc is extinguished as the pool of flux fills copper shoes similar to that used for EGW (Figure 2.10). However, ESW the sump and comes in contact with the arc. Because the molten differs from EGW in that the welding heat is provided by resistance to the slag is electrically conductive, current continues to flow through the electrical current flowing through electrically conductive molten slag between molten slag to the base metal and the electrical resistance melts the filler wire and the base metal (see Figure 2.10).

Figure2.10: 2.10:Nonconsumable Nonconsumable guide of ofelectroslag welding (three Figure guidemethod method electroslag welding electrodes) (three electrodes) 50 Chapter 2: Welding Processes At the beginning of the weld, an® arc is struck between a sacrificial plug of Copyright AIHA For personal use only. Do not distribute.

metal at the bottom of the weld (called a “sump”) and the filler wire. Granulated flux is added via either flux cored filler wire or a hopper. The flux is unique in that it is electrically conductive when molten and the arc is

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

both. As the welding machine and shoes move upward, the water-cooled shoes move up the joint along with the electrode guide, exposing the weld. The shoes are long enough to ensure that the weld has solidified before the shoes move past. Once started, the ESW process may continue for tens of feet. It may be necessary for the welder to occasionally add flux to the bath. The molten slag bath contained between the shoe and the base metal may be 3500°F, and the surface of the molten slag bath may be 3000°F.

7.4 ESW Health and Safety Hazards Discussion Because the entire ESW process (after weld pool initiation) takes place under a bath of molten flux and is largely contained between the shoes and the edges of the base metal, exposures to UV radiation and fume are often low. However, in the event of a process upset such as a misfit or loose shoe, a stream of molten metal and slag may strike the welder with potentially dire results. It would be prudent to be prepared for this contingency by ensuring that the welder wears welding leathers and gloves. 7.4.1 UV radiation burns to skin and eyes Although ESW is usually an automatic process, the welder must frequently monitor the welding process to ensure adequate weld quality. Shade 4 lenses are recommended for safety glasses along with side shields when observing the bath of molten slag. 7.4.2 Electrocution See Section 7.5 below. 7.4.3 Crushing hazards Electroslag welding is typically used for large, heavy parts, and the copper shoes may also be large and heavy. The shoes are often held in place by massive braces, clamps, strong-backs, and/or other restraints and fixtures. Positioning and welding these fixtures in place requires careful planning to avoid crushing hazards. These hazards may be amplified when removing the fixtures. Avoid allowing fixtures to fall on hoses, cables, or personnel. 7.4.4 Fume constituents When flux cored electrodes are used in ESW, comments in SecChapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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tion 1.4.3 under SMAW are applicable to ESW. The probability of overexposure to fume constituents is increased when working in confined spaces.

7.5 Equipment Comments Specific to ESW Automatic welding equipment has an abundance of electrically energized motors, relays, switches, and connections. Any or all of these may be energized during the welding process. Many of these components may remain energized when not welding if the equipment is not turned off. Personnel working with automatic welding equipment should be trained by the equipment manufacturer’s representative regarding: • • • •

Potential electrical hazards; Items of equipment requiring particular care; Procedures for de-energizing equipment; and Approved maintenance procedures.

Electrical hazards are particularly serious and may be deadly when working with large welding currents usually associated with automatic equipment welding thick sections of metal.

8. Stud Welding (SW) 8.1 SW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin

• Electric arc

Spatter

• Stud plunging into weld pool

8.2 SW Common Metals Metals commonly welded via SW include but are not limited to: • • • • •

52

Carbon and low-alloy steels Heat-treated structural steel Stainless steel Aluminum (with shielding gas) Magnesium (with shielding gas)

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8.3 SW Process Description Stud welding (SW) is a technique used to weld fasteners and/ or fastener fittings onto sheet or plate base metal. Most studs are cylindrical threaded fasteners that are essentially bolts without the usual hex-head. The stud is held in a plunger built into a stud welding gun, and the gun is pressed against the plate to which the stud is to be welded (Figure 2.11). When the operator depresses the trigger, an arc is very briefly established between the stud and the plate. A preset timer maintains the arc just long enough to adequately melt the base plate and the stud. At the end of the preset time, the plunger pushes stud into the weld pool and the arc is extinguished (Fig- 35 Weldingthe Processes ure 2.12). The weld solidifies almost immediately, and the operator removes the discharge stud gunstud from the stud/plate Capacitor welding uses a powerweldment, supply that completing stores electrical the operation. energy in a bank of capacitors. When the trigger is pulled, a very brief (3 to 15 Arc stud welding uses direct current (DC)The and, according to process the milliseconds) burst of amperage current ensues. remainder of the AWS, weld times for arc stud welding vary from 0.13 seconds is, in health and safety terms, essentially similar to arc stud welding. to 0.92 seconds for most operations. Production rates may range from 6 to 15 studs per minute.11

Figure 2.11: Stud welding equipment with timing control integrated into power Figure 2.11: Stud welding equipment with timing control supply

integrated into power supply

Ferrous studs designed for stud welding are often manufactured with 53 small Chapter 2: Welding Processes amounts of flux coating the end of the stud. Studs for aluminum and ® Copyright AIHA For personal use only. Do not distribute.

magnesium rely on the application of shielding gas (as in GTAW) to eliminate the atmosphere from the molten weld pool. This process is referred to as “gasarc stud welding” and may also be used for ferrous metals.

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

Figure 2.12: Steps in arc stud welding

Figure 2.12: Steps in arc stud welding

8.4 SW Health and Safety Discussion

Capacitor discharge stud welding uses a power supply that stores energy in a to bank capacitors. 8.4.1 electrical UV radiation burns skinofand eyes When the trigger is pulled, a very brief (3 to 15 milliseconds) burst of amperage current A ferrule this case aofsmall, ceramic tube) placedand around the stud when ensues. The(in remainder the process is, in is health safety terms, it is manufactured to protect the threaded portions of the stud from spatter essentially similar to arc stud welding. during welding. The designed ferrule alsofor serves protect the most UV Ferrous studs studtowelding arewelder oftenfrom manufacradiation and spatter. However, the ferrule is not completely effective in this tured with small amounts of flux coating the end of the stud. Studs role, and eye and skin protection are required during stud welding. Goggles for aluminum and magnesium rely on the application of shielding or face(as shield Shadeto3 eliminate lenses are recommended duringfrom SW operations. gas in with GTAW) the atmosphere the molten weld pool. This process is referred to as “gas-arc stud welding” and 8.5 also Equipment Specific to SW may be usedComments for ferrous metals. that capacitors in capacitor discharge SW equipment are completely 8.4 Ensure SW Health and Safety Discussion discharged prior to performing repair or maintenance procedures. 8.4.1 UV radiation burns to skin and eyes

9. Plasma Welding A ferrule Arc (in this case a (PAW) small, ceramic tube) is placed around the stud when it is manufactured to protect the threaded portions of9.1 thePAW stud Health from spatter during Hazards welding. The ferrule also serves to and Safety Summary protect the welder from most UV radiation and spatter. However, the Hazard ferrule is not completely effective in this role, and eye and skin Sources protection are required during stud welding. shield UV radiation burns to eyes and skin � ReducedGoggles shielding*orofface electric arc with Shade 3 lenses are recommended during SW operations. Ozone and nitrogen dioxide

� Ionization of atmospheric gases due

reduced 8.5 Equipment Comments Specificto to SWshielding of electric arc

� Handling hot metal Thermal Ensureburns that capacitors in capacitor discharge SW equipment � Mishandling hot electrodes are completely discharged prior to performing repair or mainte� Parent metal Metal fumes nance procedures. � Filler metal

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9. Plasma Arc Welding (PAW) 9.1 PAW Health and Safety Hazards Summary Hazard

Sources

UV radiation burns to eyes and skin

• Reduced shielding* of electric arc

Ozone and nitrogen dioxide

• Ionization of atmospheric gases due to reduced shielding of electric arc

Thermal burns

• Handling hot metal • Mishandling hot electrodes

Metal fumes

• Parent metal • Filler metal

Asphyxiation (in small, confined spaces)

• Inert shielding gases

Phosgene, chlorine, and other halogenated compounds

• Decomposition products from chemical cleaners/degreasers

Noise

• Gasoline or diesel-driven generators • Arc

Compressed gases

• Shielding gases

Electrocution

• Damaged high-amperage welding cables

*The term “reduced shielding” is used here to note the lack of fumes and other fine particulates in the immediate area of the arc.

9.2 PAW Common Metals Metals welded via PAW include but are not limited to: • Aluminum alloys • Beryllium • Carbon as well as nearly any alloy steels • Chromium alloys • Copper and its alloys, including bronze, brass, and copper– nickel • Heat-resistant alloys with iron, nickel, and/or cobalt as primary metals • Magnesium alloys • Nickel and its alloys • Stainless steels • Titanium alloys

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9.3 PAW Process Description In several respects, PAW is quite similar to GTAW (Figures 2.3 and 2.13). In both cases an arc, shielded by an inert gas, creates the heat necessary for the welding process. Also, in both cases, the electrode is normally not consumed during the welding process. However, PAW differs significantly from GTAW in that the primary means of heat transfer to the workpiece is via a hot ionized gas defined as a “plasma.” The plasma is generated by use of an electric arc to heat and ionize the “orifice gas” shown in Figure 2.13. The ionized gas issues from the orifice at temperatures of approximately 30,000°F. This temperature is substantially hotter than that achieved from the arc-only transfer of heat offered by GTAW and allows for much higher productivity. Additionally, the plasma created in the PAW process is highly effective in constricting the arc to a narrow column, rather than the fan- or cone-shaped arc created by the GTAW process. This highly focused arc has a higher energy density and allows for deeper penetration and more precise control of the weld pool than is the case with GTAW. In some cases, the plasma itself (created from the “orifice gas” shown in Figure 2.14) provides adequate shielding from the atmosphere to allow for a sound weld. However, it is more common to find that additional shielding gases must be provided to ensure satisfactory weld quality. Orifice gas flow rates generally range from 0.5 to 10.0 ft3/hr (0.25 to 5.00 L/min), whereas shielding gas flow rates are often in the range from 20 to 60 ft3/hr (10 to 30 L/min). As is the case with GTAW, PAW employs a device called a “torch” to hold the electrode, conduct electrical power to the electrode, and provide a means for directing the orifice gas and (when used) additional shielding gas onto the weld pool. The PAW torch may be designed to allow the arc to be established between the electrode and the workpiece (“transferred arc”) or between the electrode and the constricting nozzle (“nontransferred arc”); see Figure 2.14. Given the same welding amperage, transferred arc PAW is more likely to create a UV hazard than nontransferred arc PAW. Amperages used for PAW may range from 0.1 to 500 amps. The high temperatures (particularly at the constricting nozzle) resulting from high-amperage applications require that PAW torches be water-cooled. Because of the high rates of productivity and arc control offered by PAW, this welding method is often applied as a fully automatic process. However, hand-held PAW is also widely used for fabricating procedures on small parts, for sheet metal work, and, in some 56

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Welding Processes Welding Processes

Welding Health and Safety:39 A Field Guide for OEHS Professionals, 2nd edition 39

Figure 2.13: Comparison of gas arc tungsten arcarc and plasma arc Figure 2.13: Comparison of gas tungsten and plasma welding processes welding processes Figure 2.13: Comparison of gas tungsten arc and plasma arc welding processes

Figure 2.14: Transferred and nontransferred plasma arc modes Figure 2.14: Transferred nontransferred plasma arc arc modes Figure 2.14: Transferred andand nontransferred plasma modes Copyright AIHA®

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cases, for autobody repairs. Filler metal may be added during PAW, in either manual or automatic modes, in much the same manner as for GTAW. Plasma and shielding gases in the PAW process are usually one of the following: • Argon • Argon/helium mixture • Argon/hydrogen mixture

9.4 PAW Health and Safety Hazards Discussion 9.4.1 UV radiation burns to skin and eyes The AWS recommends the following UV eye and face protection for transferred arc PAW: • Up to 5 amps: glasses with side shields and Shade 6 lenses • 5 to 15 amps: full-face plastic shield in addition to eye protection with Shade 6 lenses • Over 15 amps: standard welder’s helmet with filter plate appropriate for the amperage in use Dark-colored upper-body clothing, buttoned to the neck, is recommended to reduce reflections of UV radiation within the welding helmet, which may result in skin and eye burns. 9.4.2 Particulate in eyes: grinding electrodes As with GTAW, electrodes are shaped by grinding a point on the end of the electrode, generally using a bench grinder. Welders will often perform the grinding operation while still wearing the welding hood, which is simply flipped up to allow them to see. Unless the welder habitually wears safety glasses under the hood, the possibility for eye injury during electrode grinding exists. 9.4.3 Asphyxiation If a welder is working in a small, confined space and argon is used as shielding gas, it is possible to displace the atmosphere with argon in a surprisingly short period of time. See the discussion in 2.4.4 under GTAW. 9.4.4 Phosgene, chlorine, and other halogenated compounds See discussion in 2.4.5 under GTAW. 58

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9.5 Equipment Comments Specific to PAW • Compressed Gases: See Chapter 3: Welding Equipment • Cables: See Chapter 3: Welding Equipment • Helmet: See Chapter 7: PPE

10. Oxyfuel Gas Welding (OFW) 10.1 OFW Health and Safety Hazards Summary Hazard

Sources

Compressed gases

• Oxygen and fuel gases

Spontaneous combustion

• Misuse of oxygen for blowing off combustible cloth and clothing contaminated with hydrocarbons

“Flashback” (burning of fuel gases in the torch body and/or hoses)

• Incorrect lighting technique • Overheated torch tip

Spontaneous decomposition (explosion) of acetylene

• Using excessive acetylene pressure

Freeze “burns”

• Liquefied oxygen lines and equipment

Confined space hazards: • Asphyxiation from low-odor fuel gases • Fire hazards and health effects from elevated oxygen content

• Leaving unattended OFW torches in confined spaces

Products of flux decomposition, including carbon monoxide

• Flux coating on some filler wires • Fluxes added during some welding processes

Thermal burns

• Handling hot metal • Mishandling hot electrodes

Metal fumes

• Parent metal • Filler metal

10.2 OFW Common Metals Metals welded via OFW include but are not limited to: • Carbon and low-alloy steels • Aluminum alloys in specialized applications (fluxes required) • Stainless steels in specialized applications (fluxes required)

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10.3 OFW Process Description Unlike the previously described process, OFW does not use an electric arc as the source of heat for the welding process. Rather, heat is derived from impingement of hot gases on the parts to be welded. These hot gases are the product of combustion of a fuel gas in the presence of oxygen. Both the fuel gas and oxygen are contained in (separate) compressed gas cylinders (Figure 2.15A). Fuel gases in the OFW process are usually one of the following: • Acetylene • Methylacetylene-propadiene (MAPP gas) • Methylacetylene-propadiene stabilized (MPS). This is liquefied gas consisting of propadiene, propane, butane, butadiene, and methylacetylene. • Propylene • Propane • Natural gas (methane/ethane mixture) For welding purposes, acetylene is a nearly universal choice because of its “combustion intensity.” When OFW equipment is used for brazing, soldering, heating, or cutting purposes, the other gases are in common use. In most cases, the flame produced by the oxidation of the fuel gas is distinguished by two visible elements, the inner flame (or cone) and the outer flame (Figure 2.15B). The inner flame represents the zone of combustion supported solely by the oxygen supplied by the OFW equipment. The outer flame is the zone of combustion supported primarily by atmospheric oxygen. Most of 43 Welding Processes

Figure 2.15A: Basic oxyfuel gas welding equipment

Figure 2.15A: Basic oxyfuel gas welding equipment 60

2: Welding Processes For welding purposes, acetylene ®is a nearlyChapter universal choice because of its Copyright AIHA For personal use only. Do not distribute. “combustion intensity.” When OFW equipment is used for brazing, soldering, heating, or cutting purposes, the other gases are in common use. In most cases, the flame produced by the oxidation of the fuel gas is

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

the heat is derived from the inner flame. When acetylene is used as the fuel gas, at the tip of the inner flame, the temperature of the combustion gases will be approximately 5589°F. The outer flame is derived from combustion of residual carbon monoxide and hydrogen left over from incomplete combustion in the inner flame. By adjusting the valves on the welding torch, the flame may be adjusted to produce a flame that is carburizing (inadequate oxygen for complete combustion), neutral (no excess carbon or oxygen that will affect the weld quality), or oxidizing (excess oxygen). Filler metal may be added during OFW. This is nearly always done manually, in much the same manner as for GTAW.

Figure 2.15B: Vector representation of laminar velocity in avelocity welding tip Figure 2.15B: Vector representation of flow laminar flow in and a in thewelding formationtip of aand uniform flame cone in the formation of a uniform flame cone Chapter 2: Welding Processes 10.4.1 Spontaneous decomposition of acetylene Copyright AIHA® For personal use only. Do not distribute.

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Given an adequate volume of gas, gaseous acetylene is not stable under the following conditions:

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10.4 OFW Health and Safety Hazards Discussion Oxyfuel gas welding may be the most portable welding process in common use. Because the process is entirely independent of electrical power, OFW is widely used at sites where access to utilities is limited or nonexistent. The OEHS Professional should also note that these circumstances are often associated with minimal supervision and that OFW equipment is often subject to abuse and misuse by incompletely or inadequately trained personnel. 10.4.1 Spontaneous decomposition of acetylene Given an adequate volume of gas, gaseous acetylene is not stable under the following conditions: • Temperatures above 1435°F • Pressures greater than 15-psi gauge (15 psig or 103 kPa) or 30 psi absolute (30 psia or 207 kPa) When these values are exceeded, acetylene may decompose (explode) violently with little or no provocation. The slightest impact may be sufficient to cause explosive decomposition. Consequently, acetylene cylinders must be treated with greater caution than other common compressed gases (the hazards of which are described in Chapter 3). Fortunately, acetylene is soluble in acetone, and this characteristic is useful in storing acetylene. Acetylene cylinders are packed with a porous filler (which historically has included a combination of charcoal and asbestos), and acetone is then added to the filler. Because acetone can absorb up to 25 times its own weight in acetylene, this procedure allows the cylinder to contain acetylene in a solution with acetone. The upper portion of the cylinder contains a small void (less than the critical volume for spontaneous explosive decomposition) into which the dissolved acetylene is allowed to outgas from the acetone and enter the valve/regulator/ hose/torch equipment ensemble. Because of the limited free volume of acetylene in the cylinder, the gauge pressure for the cylinder side of an acetylene regulator may safely read up to 250 psig. However, the working side of the regulator must not be adjusted to values greater than 15 psig (30 psia). 10.4.2 Spontaneous combustion due to misuse of oxygen Unfortunately, some workers become so inured to the hazards of working with compressed gases that they ignore the risks asso62

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ciated with using oxygen as a convenient source of compressed gas for blowing off their clothing at the end of a shift or prior to breaks. This practice may result in the spontaneous combustion of many types of cloth, particularly cotton, the primary fiber in denim jeans. This hazard may be increased when clothing is contaminated with hydrocarbons such as oil or grease, which can easily occur when welders are performing maintenance tasks on used equipment. 10.4.3 Hazards in confined spaces from unattended OFW equipment Under no circumstances should OFW torches or hoses be left unattended in confined spaces. Slight leaks in the hoses, fittings, or torch valves may allow oxygen or fuel gases (or both!) to accumulate in the confined space. This accumulation may result in elevated concentrations of flammable gases or oxygen. In either case, the probability of fire or explosion is increased. 10.4.4 Flashback If the torch hoses are not purged prior to lighting the torch, or if the torch tip becomes overheated during operation, a phenomenon called “flashback” may occur. Flashback is burning of the oxygen and fuel gases in or behind the mixing chamber in the torch. This burning may continue down the fuel hoses to the fuel cylinder with explosive results. Because of this possibility, the AWS and ANSI recommend that acetylene cylinder valves be opened a maximum of 1½ turns with a preferred maximum opening of ¾ turn to facilitate quick closing of the fuel gas cylinder valve in the event of a flashback or other emergency.12 10.4.5 “Freeze burns” from liquefied oxygen lines and equipment Some large shops with multiple welding stations (e.g., welding schools) may use a central source of liquefied oxygen to obviate the need for frequent change-out of oxygen cylinders. Caution should be used when laying out the oxygen lines leaving the liquefied oxygen storage vessel, as skin contact with the cold lines can cause “freeze burns” even several tens of feet from the vessel. (See Chapter 3, Section 3.)

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10.4.6 Flux fumes and gases Oxyfuel welding is usually associated with welding ferrous metals that do not require the use of flux. However, repair or fabrication work on some metals may require the use of fluxes for the same reasons discussed in the SMAW section. Metals for which fluxes are employed when using the OFW process include: • Bronze • Cast iron • Brass • Silicon bronze • Stainless steel • Aluminum Decomposition of these fluxes may release noxious fumes containing chlorides and/or fluorides. The risk of overexposure to the fume constituents may be minimal in open areas. However, work in confined spaces may result in elevated fume concentrations.

10.5 Equipment Comments Specific to OFW • Compressed Gases: See Chapter 3: Welding Equipment • Goggles: See Chapter 7: PPE

11. Brazing 11.1 Brazing Health and Safety Hazards Summary Note: Brazing may be used for joining more materials than any other process. Any number of combinations of parent materials, filler metal alloys, fluxes, and stopping compounds may be employed. In view of this broad scope, a careful review of the MSDSs for these materials is particularly important in identifying potential health and safety hazards. Note that the AWS Welding Handbook provides a separate chapter for the process known as “Diffusion Welding and Brazing.” Although there are sound technical reasons for offering a separate chapter on the technical aspects of this process, from the health and safety perspective, “Diffusion Welding and Brazing” is essentially indistinguishable from furnace brazing (which is addressed in this section).

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Sources

Phosgene, chlorine, and other halogenated compounds (see Section 2.4.5)

• Decomposition products from chemical cleaners/degreasers

Eye irritation, possibly severe

• Fluxes

Particulate in eyes

• Grinding/sanding, blasting parts prior to and after brazing • Slag from mechanically removing cooled flux

Eye and skin hazard

• Laser radiation

Severe tissue damage (corrosion)

• Acids (sulfuric, hydrofluoric, nitric) used in flux removal

Severe tissue damage (corrosion)

• Bases (NaOH) used in stopoff removal

Compressed gases

• Oxygen and fuel gases

Spontaneous combustion (see Section 10.4.2)

• Misuse of oxygen for blowing off combustible cloth and clothing contaminated with hydrocarbons

Spontaneous decomposition (explosion) of acetylene (see Section 10.4.1)

• Using excessive acetylene pressure

Thermal burns

• Handling hot metal

Metal fumes

• Parent metal • Filler metal

Freeze “burns”

• Liquefied oxygen lines and equipment

11.2 Brazing: Common Metals Brazing may be used to join a wide variety of materials, not all of them metallic. Among these materials are: • Aluminum and aluminum alloys • Magnesium and magnesium alloys • Beryllium • Copper and copper alloys • Low-carbon and alloy steels • High-carbon and high-alloy steels • Cast iron • Stainless steels • Chromium irons and steels • Nickel and high-nickel alloys • Heat-resistant alloys (often cobalt-based) • Titanium and zirconium Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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• Carbides (tungsten, titanium, and/or tantalum bonded with cobalt) • Cermets (ceramic particles bonded with various metals) • Ceramics • Precious metals • Tungsten • Molybdenum • Dissimilar metals (may require plating one or both pieces to be joined with a ductile or easily brazed metal or alloy) Brazing filler metals, which have been designed to work with specific parent metals, are available. Brazing filler alloys include: • • • • • • • •

Aluminum–silicon alloys Magnesium alloys Copper and copper–zinc alloys Copper–phosphorous alloys Silver alloys Gold alloys Nickel alloys Cobalt alloys

Note: Also, it should be noted that cadmium is a common component of many brazing alloys. Review the MSDS for the brazing filler metal to verify or deny the presence of this metal.

11.3 Brazing Process Description The welding processes described up to this point involved melting the portions of the metal parts to be joined and allowing the molten metal to coalesce and cool to form a single unit, or weldment. Brazing differs from these welding processes in that the metal parts are heated but not melted. The filler metals used in brazing have melting points above 840°F (450°C) but below that of the metal(s) to be joined. Thus, brazing may be conveniently defined as high-temperature (> 840°F/450°C) joining of materials with a filler metal that has a lower melting point than that of the base metal. The AWS definition of brazing also notes that the filler metal “wets” the base metal and that the filler metal is drawn into the joint via capillary action. The AWS makes a distinction between brazing and “braze welding.” Although the term “brazing” applies to processes wherein the filler metal is drawn into the joint via capillary action, the term “braze welding” denotes a very similar process that does not 66

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depend on capillary action to create a successful joint. In braze welding, the filler metal is added manually in the same manner as GTAW and bonds with the parent metal. The appearance of the braze weld is very similar to an OFW or GTAW weld except that the filler metal is a different color. In contrast to braze welding, the brazing process does not produce a joint with a distinctive “bead” because nearly all the filler metal is drawn into the joint rather than deposited onto the joint. In the shop, brazing with silver alloy filler metals is often referred to as “silver soldering.” However, this term is technically inaccurate because the silver-based alloys have a melting point above 840°F (450°C) and the AWS defines soldering as a similar process wherein the filler metal melts below 840°F (450°C). It is worth noting that shop personnel might pay little attention to this technical nicety when discussing joining processes. In nearly all cases, brazing requires the parts being joined to be scrupulously clean. Cleaning may require use of mechanical methods (sanding, grinding, abrasive blasting), chemical cleaning (solvents, often halogenated), or both. Further chemical cleaning of the parts takes place when flux is applied to the areas to be joined and heated prior to applying the filler metal. Brazing processes may use several sources of heat and are generally named for the heat source. For example: • • • • • •

Torch brazing (OFW equipment) Furnace brazing Induction brazing Resistance brazing Dip brazing Laser brazing

Torch brazing involves use of OFW equipment to heat the parts to be joined. In addition to the gases described for OFW above, two other combinations are in common use for torch brazing: • Air–natural gas • Oxy-hydrogen Torch brazing is a common technique for repair of cast iron, ornamental work, joining of parts with unequal masses, and jewelry fabrication and repair. Flux is usually applied to the base metal prior to heating the part. When the filler is added manually during the joining process, flux is applied to the filler wire by dipping the Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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hot filler wire in a small container of dry powdered flux. The flux partially melts and adheres to the filler metal. During manual torch brazing, filler metal is normally applied to the joint in a manner very similar to that used for GTAW and OFW welding. Furnace brazing requires applying flux and filler metal (in granulated, powdered, or sheet form) in and/or around the joint areas. Then, the parts are usually placed in fixtures to hold them in position and the entire assembly is placed in a furnace. Furnaces may be small, simple affairs or large and elaborate items of equipment that allow brazing to take place in a controlled or nonreactive atmosphere or a low-pressure (“vacuum”) environment. Although furnaces may be gas or oil fired, the most common source of heat is electrical resistance heating elements. Controlled atmosphere furnaces may create toxic or explosive gases and must be vented accordingly. Retorts (sealed chambers containing the parts in a controlled atmosphere) may be used with furnaces that are vented to the atmosphere. The use of retorts may achieve the desired atmospheric conditions for brazing without the need for a controlled atmosphere within the entire furnace. When using a retort, the parts are fluxed, filler metal is applied, and the parts are placed in the fixture to keep them in the desired spatial relationship. The entire assembly (parts and fixture) is placed in the retort, and the retort is sealed. The retort is then placed in the furnace and heated to the appropriate temperature. After the brazing operation is completed, the retort is removed from the furnace and allowed to cool. The atmosphere is purged from the retort, and the retort is then opened. Venting of the retort may expose workers to toxic or combustible gases. Induction brazing is most commonly used in production processes requiring high rates of production. The components to be brazed are frequently handled by automated equipment. Brazing filler metal and flux (when used) are usually pre-applied in wire, shim, powder, or paste form. Heat for the brazing process is provided by inducing an electric current between the components and a water-cooled coil carrying electrical current. Electric current is not applied directly to the parts. The parts being heated are, in effect, the short-circuited secondary coil of a transformer and heat to brazing temperature within seconds. Frequencies may range from 10 kHz to 450 kHz, and output of the induction generators may range from one kilowatt to several hundred kilowatts. Induction brazing may be performed in a vacuum atmosphere, a controlled atmosphere, or in ambient air with use of an appropriate flux. 68

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Resistance brazing differs from induction brazing in that an electrical current is applied directly to the parts to be brazed. The heat for brazing is generated by electrical resistance of the parts, which are held between two electrodes while the electrical power and mechanical pressure are applied. Low voltages (2–25 V) are common, whereas amperage may be as low as 50 amps for small parts or up to thousands of amps for large parts. Brazing filler metal and flux (when used) are usually pre-applied in wire, shim, powder, or paste form. Resistance brazing may be performed in a vacuum atmosphere, a controlled atmosphere, or in air with use of an appropriate flux. Dip brazing involves immersing the parts in a bath of molten brazing metal or a bath of molten flux. Use of the bath of molten brazing metal is usually limited to smaller parts such as wire connectors. The surface of the molten metal bath is covered with flux, and the parts are pre-fluxed prior to immersion. When the molten flux method is employed, the filler metal is often pre-applied as a paste or cladding. Filler metal may also be applied as a ring, washers, or shim inserted into the joint prior to dipping. In either the molten metal or molten flux process, surface contamination may lead to sputtering and create an eye hazard. Laser brazing may utilize neodymium: YAG (Nd:YAG), carbon dioxide (CO2), or diode lasers. All generate invisible infrared radiation: diodes, 800 to 1000 nm; Nd:YAG, 1064 nm; and CO2, 10.6 µm. Beams are often unfocused, which decreases the irradiance or radiant exposure, reducing the heat input that minimizes distortion. Laser brazing is relatively new but has applications with steel, titanium, and dissimilar metals.

11.4 Brazing Health and Safety Hazards Discussion Many of the hazards associated with brazing arise from the work required to prepare components for brazing and to clean them after the brazing process. The most common of these brazing-related procedures are briefly described below. 11.4.1 Solvent cleaning Removal of oils or other lubricants is often required for successful brazing of components that have been machined prior to brazing. Solvent cleaning processes include: • Wet solvent cleaning with petroleum solvents or chlorinated hydrocarbons Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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• Vapor degreasing with stabilized trichloroethylene or stabilized perchloroethylene • Alkaline cleaning with silicates, phosphates, carbonates, detergents, soaps, or hydroxides • Emulsion cleaning • Electrolytic cleaning Because these chemicals are designed to remove oils and fats, they may be expected to, at a minimum, defat the skin, and overexposure may lead to dermatitis. Additionally, these chemicals may cause eye irritation (possibly severe). Some chemicals may cause corrosive tissue damage to the eyes. Chlorinated hydrocarbons may decompose when heated to form phosgene, free chlorine, and other halogenated species. Adequate ventilation must be provided when thermal decomposition is likely. 11.4.2 Acid cleaning/pickling Chemicals used for acid cleaning may include: • • • •

Phosphate acids Sulfuric acids Nitric acids Hydrochloric acids

Target organs are the eyes and skin. 11.4.3 Mechanical cleaning Surfaces to be brazed must be free from oxides and other contaminants. Mechanical processes such as sanding, grinding, and abrasive blasting are employed to this end. These processes may generate an eye hazard from flying particulates. Additionally, using mechanical processes that generate fine dust may create an inhalation hazard when the metals being cleaned contain alloys of toxic metals such as beryllium, cobalt, copper, chromium, nickel, or zinc. 11.4.4 Fluxes Fluxes consist of powders or, more commonly, pastes that chemically clean the metal when heated and exclude the atmosphere from the hot metal while the braze filler metal flows and adheres to the parent metal. Flux is frequently applied manually. Fluxes are often basic compounds and when used for copper, stainless steel, or for 70

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long heating cycles, they may be strong enough to cause severe eye irritation and/or dermatitis symptoms. A material called “stopoff” or “parting compound” may be applied to areas from which the flux (and consequently, brazing filler metal) must be excluded. Decomposition of fluxes may release fluorine, chlorine, and/or boron compounds. Adequate ventilation is necessary when heating these fluxes. 11.4.5 Flux and stopoff removal Upon completion of the brazing process, the flux will have combined with oxygen to create a slag. Usually, this slag can be removed with hot water, resulting in possible thermal burns. When saturated with oxygen, flux forms a glass-like material. Quenching the hot brazement in water may crack the oxidized flux from the brazement. However, if the brazement cannot be quenched, it may be necessary to remove the flux with warm dilute acid (often 10 percent sulfuric). Fluxes used for brazing aluminum require rinsing in very hot water (>180°F or 82°C) or immersion in nitric or hydrofluoric acid. In some circumstances, a combination of these acids may be used. Removal of stopoff compounds used for corrosion-resistant metals such as stainless steel may require pickling in hot nitric and/ or hydrofluoric acid. Caustic soda (NaOH) is used in many stopoff compounds for more common metals. 11.4.6 Use of OFW equipment for torch brazing/braze welding The precautions listed for OFW in Section 10 of this chapter apply equally to torch brazing/braze welding. A number 4 or 5 lens is recommended by the AWS for operators and helpers during torch brazing. 11.4.7 Furnace brazing When a specific atmosphere is employed for furnace brazing, the furnace atmosphere may include or consist of: • Fuel gas combustion products (sometimes incorrectly called “inert gas”) • Hydrogen • Dissociated ammonia • Nitrogen–hydrogen mixtures Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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Opening and purging these furnaces or retorts must be conducted in accordance with the furnace manufacturer’s instructions to prevent fire, explosion, and possible asphyxiation. 11.4.8 Dip brazing If the parts to be immersed in dip brazing vessels are moist, a steam explosion can be anticipated. It is vital to ensure that parts to be dip brazed are completely dry. Use of an oven to pre-dry parts may be necessary. Goggles, preferably with face shields, are recommended for resistance, induction, and dip brazing. 11.4.9 Laser brazing Laser hazards are discussed in Section 16. In brief, the target tissue or the output from diode and Nd:YAG lasers is the retina and the skin, whereas the CO2 radiation targets the cornea and superficial layers of the skin. Because high-power lasers are used, there is a potential hazard from exposure to the beam or scattered radiation.

12. Soldering 12.1 Soldering Health and Safety Hazards Summary Note: Soldering is used for joining many materials. A remarkably diverse mix of parent materials, filler metal alloys, and fluxes may be used. A careful review of the MSDSs for these materials is therefore necessary to identify potential health and safety hazards. Hazard

Sources

Skin and eye irritation

• Fluxes and pickling acids

Eye and skin hazard

• Laser radiation

Thermal burns

• Hot soldering irons; hot soldered parts • Molten solder baths

Metal fumes

• Overheated dip soldering and wave soldering operations

Chlorinated organic hydrocarbons

• Vapor phase soldering (condensation soldering)

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12.2 Soldering: Common Metals Soldering may be used to join a wide variety of materials, not all of them metallic. Among these materials are: • Aluminum and aluminum alloys • Beryllium and beryllium–copper • Brass • Cadmium (plated surfaces) • Cast iron • Copper and copper alloys • Chromium irons and steels • Chromium (plated surfaces) • Glass • Gold • High-carbon and high-alloy steels • Inconel • Lead • Low-carbon and alloy steels • Magnesium and magnesium alloys • Molybdenum • Monel • Nickel and high-nickel alloys • Nichrome • Tin (plated surfaces) • Zinc (galvanized surfaces) • Zinc-based die castings Solders are available that have been designed to work with specific parent metals. Solder alloys include: • Tin–lead • Tin–antimony • Tin–antimony–lead • Tin–silver • Tin–copper–silver • Tin–lead–silver • Tin–zinc • Cadmium–silver • Cadmium–zinc • Zinc-based alloys • Bismuth-based (fusible solders) • Indium

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12.3 Soldering Process Description Like brazing, soldering does not require that the base/parent metal be brought up to a molten state. Rather, the metal parts are heated but not melted. The filler metals used in soldering have melting points below 840°F (450°C) and below that of the metal(s) to be joined. In all cases, solder joints require a close fit between the parts to be joined, as the solder itself is often quite weak when compared to the strength of the joint between the solder and the base/parent metal. This characteristic arises from the metallurgical bond created as the solder “wets” the joint when heated and mixes with a small portion of the base metal, forming an intermetallic compound. Upon cooling, the solder joint is held together by the same interatomic forces that hold solid metal together. Soldering requires the parts to be joined to be scrupulously clean. Cleaning may require use of any combination of the following: • Mechanical methods (sanding, grinding, abrasive blasting) • Chemical cleaning (solvents, often halogenated) • Pickling (acid etching with hydrochloric, sulfuric, phosphoric, nitric, hydrofluoric, or a combination) Further chemical cleaning of the parts takes place when flux is applied to the areas to be joined and the flux is heated prior to applying the solder. Fluxes may be liquid (common), solid (less common), or gaseous (not common). Many commercially available solders contain a flux core. Fluxes generally fall into one of three categories and, to a greater or lesser extent, may pose eye and skin hazards: • Rosin – Nonactive rosin (acetic acid in an organic solvent: relatively noncorrosive) – Mildly activated rosin (more aggressive cleaning action) – Activated rosin (may release chlorides or halides) • Organic. These typically form relatively inert byproducts when heated and may be removed with water. However, large operations or operations in close quarters may require mechanical ventilation. – Acetic acid – Ethylene diamine – Glutamic acid – Hydrazine hydrobromide

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– Oleic acid – Stearic acid • Inorganic – Zinc chloride – Ammonium chloride – Tin chloride – Hydrochloric acid – Phosphoric acid – Bromides Soldering processes may use several sources of heat and are generally named for the heat source. These are briefly described below. Soldering irons. The “iron” is typically copper plated at the tip and may be heated electrically or via a burner or small coke oven. The iron is heated and applied to the base metal until the base metal is hot enough to melt the solder. Solder is then applied and flows into the joint. Torch soldering. This process is very much like torch brazing but takes place at lower temperatures. Dip soldering. A molten bath of solder (“solder pot”) is maintained at liquid temperature, and the parts to be soldered are immersed in the bath to heat the parts (Figure 2.16). Wave soldering. This process is similar to dip soldering. However, the parts are not immersed in the bath of molten solder. Instead, the solder is pumped through a slotted opening/fixture to form a “wave” of molten solder over which the parts to be joined are passed (Figure 2.16). The parts remain in contact long enough to ensure adequate heating, and the excess solder drains off back into the solder pot. See Section 12.4.1 for a brief note regarding cleaning of wave solder tanks. Vapor phase soldering (condensation soldering). The parts to be heated are held in place in a reservoir of saturated vapor over a boiling liquid (usually a fluorinated organic with a boiling point between 420°F/215°C and 490°F/253°C). As the vapor condenses on the parts, the latent heat of condensation is released and the parts become hot enough to melt solder, which is generally placed in the joint prior to the parts being placed in the vapor reservoir. Oven/furnace soldering. This process typically employs inorganic fluxes and a reducing atmosphere. Solder may be placed in the joint prior to securing the parts in fixtures that are then placed in the oven. Inert oven atmospheres may be used in some applications. Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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pumped through a slotted opening/fixture to form a “wave” of molten solder over which the parts to be joined are passed (Figure 2.16). The parts remain in contact long enough to ensure adequate heating, and the excess solder drains off back into the solder pot. See Section 12.4.1 for a brief note regarding Welding Health and Safety: cleaning of wave solder tanks. A Field Guide for OEHS Professionals, 2nd edition

Figure techniques used for large Figure 2.16: 2.16: SeveralSeveral solderingsoldering techniques used for large production runs

Vapor phase soldering (condensation soldering). The parts to be heated production runs are held in place in a reservoir of saturated vapor over a boiling liquid (usually

Resistance soldering. This process passes electrical current Copyright AIHA® For personal use only. Do not distribute. through the parts. The size and location of the electrodes, as well as the amperage, are selected to bring the portions of the parts to be soldered to appropriate temperature. Electrodes may be stationary or may move with the parts as they pass down the production line. Induction soldering. Parts are heated by an induced alternating current. The parts are not in contact with electrodes. Instead, they are placed in an electrical field and heated by their resistance to the flow of the induced current. Infrared soldering. This process heats the parts with focused infrared radiation. Lamps may range from 45 to 1500 watts. Laser soldering. Laser soldering uses diode or neodymium:YAG lasers. Both emit radiation in the IR-A spectral region. Laser soldering is a relatively new technology but has application in lead soldering and nickel-pad soldering. Hot gas soldering. Heated inert gas is the heat transfer medium for this process. A fine jet of gas is most often used for small parts. 76

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Ultrasonic soldering. The advantage of ultrasonic soldering is the ability of the high-frequency vibrations produced by the ultrasonic transducer to break up oxide films on base metals. This characteristic makes it much easier for the solder to flow into the joint and create a sound joint. A common application is soldering the elbows on aluminum air-conditioner coils. Spray gun soldering. Either gas-fired or electrically heated guns are used to melt wire solder, which is continuously fed through the gun and sprayed onto the surfaces to be joined. The surface is also heated by the flame, or in the case of electrically heated guns, a blast of hot air.

12.4 Soldering Health and Safety Hazards Discussion Many of the hazards associated with soldering are essentially similar to those for brazing processes. See Section 11.4, Brazing Health and Safety Hazards Discussion. Laser soldering may expose workers to direct or scattered IR-A radiation, which is invisible. This radiation may be a hazard to the retinal tissues of the eye or the superficial layers of the skin. 12.4.1 Cleaning wave soldering equipment Use care when performing operations that may result in airborne lead. Examples include: 1) cleaning out dross, 2) skimming cooled solder from the surface of the tank, and 3) cleaning the fountain head. Simple measures such as dilution ventilation and keeping the worker’s head outside the wave soldering cabinet during cleaning operations have been reported as effective in reducing worker exposure levels.13

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13. Oxyfuel Gas Cutting (OFC “Torch Cutting”) 13.1 OFC Health and Safety Hazards Summary Hazard

Sources

Compressed gases

• Oxygen and fuel gases

Spontaneous combustion

• Misuse of oxygen for blowing off combustible cloth and clothing contaminated with hydrocarbons

“Flashback”

• Incorrect lighting technique; overheating torch tip

Spontaneous decomposition (explosion) of acetylene

• Using excessive acetylene pressure

Freeze “burns”

• Liquefied oxygen lines and equipment

Elevated confined space hazards

• Leaving unattended OFC torches in confined spaces

Thermal burns

• Handling hot metal

Metal fumes

• Parent metal • Filler metal

13.2 OFC Common Metals Metals cut via OFC include but are not limited to: • • • •

Carbon and low-alloy steels Cast iron Aluminum alloys in specialized applications (fluxes required) Stainless steels in specialized applications (fluxes required)

13.3 OFW Process Description The tanks, hoses, and gases used for OFC are basically those used for oxyfuel welding. However, the torch has a third valve and a lever. The torch is lit in the normal manner by opening the fuel valve slightly and igniting the flame. This is followed by adding oxygen and, if necessary, additional fuel gas until the flame produces adequate heat for preheating the metal to be cut. When the metal reaches orange heat, the lever is depressed and a lance of pure oxygen strikes the metal, causing immediate and rapid oxidation. This process is also called burning, flame cutting, and, when used with mechanized equipment, flame machining. Fuel gases in the OFC process are usually one of the following:

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• Acetylene • Methylacetylene-propadiene (MAPP gas) • Methylacetylene-propadiene stabilized (MPS). This is liquefied gas consisting of propadiene, propane, butane, butadiene, and methylacetylene. • Propylene • Propane • Natural gas (methane/ethane mixture) The slag produced by OFC may contain as much as 30 percent of unoxidized metal. Depending on the metal being cut, this may include unoxidized chromium, cobalt, nickel, molybdenum, vanadium, or other alloying elements.

13.4 OFC Health and Safety Hazards Discussion The equipment and hazards associated with OFC are essentially the same as those for OFW. Consequently, the reader is referred to Section 10.4, “OFW Health and Safety Hazards Discussion.” A few additional comments are offered below. 13.4.1 Elevated fume concentrations It should be borne in mind that when cutting metal, the goal is to remove the metal rather than deposit it. Therefore, one may expect elevated concentrations of airborne contaminants with OFC compared to OFW. 13.4.2 Underwater work When OFC is used for underwater salvage/construction work, acetylene should not be used at depths exceeding 20 feet (6 m) because at greater depths the gauge pressure will necessarily be set above 15 psig to overcome the water pressure at that depth. At pressures above 15 psig, acetylene may spontaneously and explosively decompose. 13.4.3 Fumes and gases from surface coatings/ contaminants OFC is frequently used for demolition projects and modification of existing structures. In these cases, the metals being cut may be coated with paints containing lead or cadmium. If this is the case, and if the work is performed in the United States, the work may need to be conducted in accordance with the OSHA Lead and/or Cadmium standards.b b

29 CFR 1910.1025, 29 CFR 1926.62, and/or 29 CFR 1910.1027.

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In petrochemical industries, there is the potential for various internal components of vessels such as drums and towers to be coated with hydrocarbons containing sulfur compounds. When heated, these compounds may release sulfur dioxide in concentrations as much as two orders of magnitude above the short-term exposure limit (STEL). Author Mike Harris and reviewer Stephanie Carter have measured sulfur dioxide concentrations in excess of the 100 ppm immediately dangerous to life or health (IDLH) measurement (current as of 2001) for brief periods during OFC and CAC-A (“air-arc” or “arc-gouging”) in petrochemical process and storage vessels.

14. Oxygen Lance Cutting (LOC) 14.1 LOC Process Description Oxygen lance cutting (LOC) employs a consumable steel pipe (lance) that may or may not be filled with low-carbon steel wires. Lances are generally around 10 feet long when new. In operation, the end of the lance is heated with OFW equipment to a cherry red and oxygen is fed through the lance (Figure 2.17). The steel lance burns fiercely and is used as a tool to melt through metals, refractory brick, mortar, and slag. LOC is used to remove solidified material from ladles, molds, vessels, and furnace tap holes as well as in demolition and petrochemical plant renovations. LOC may also be used with electric arc starting. Small-scale (18 in.) lances may be used with arc-started LOC, and current from a 12-volt automotive battery is sufficient for small-scale jobs.

Figure 2.17: Schematic view of oxygen lance cutting

Figure 2.17: Schematic view of oxygen lance cutting

14.2 LOC Health and Safety Hazards Discussion 80 14.2.1 Elevated fume concentrations Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

When used for large projects, the LOC process produces phenomenal clouds of fume. However, if the operator is at one side of the operation and the lance is not burned too short, actual personal exposures may be lower than first

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14.2 LOC Health and Safety Hazards Discussion 14.2.1 Elevated fume concentrations When used for large projects, the LOC process produces phenomenal clouds of fume. However, if the operator is at one side of the operation and the lance is not burned too short, actual personal exposures may be lower than first observations would lead one to expect. Initially, the length of the lance tends to keep the operator away from the plume. As the lance is consumed, the effectiveness of this “engineering control” is diminished. In view of the dimensions and density of the plume emitting from LOC, factors such as operator position, wind direction, and confined space work may be expected to have a notable effect on personal exposure potentials. Self-contained breathing apparatus (SCBA) or airline supplied-air (SA) respiratory protection may be required if the operator cannot be kept away from the plume. 14.2.2 Fire hazard LOC produces substantial spatter and sparks and can create a fire hazard. The AWS recommends removing combustible material in an area at least 35 feet from the LOC operation. 14.2.3 PPE Tinted goggles or face shields of Shade 3 or 4 are recommended for light work and Shade 5 or 6 is recommended for heavy work. Aluminized gloves, pants, and jackets are commonly worn in view of the potential for unplanned sprays of molten material erupting forth from the process as different material thicknesses and configurations are encountered. 14.2.4 Equipment hazards It is essential that the collar-type clamp holding the lance to the handle is properly maintained and kept adequately tight. There has been at least one episode of a loose connection resulting in severe burns as the lance fell loose and flame shot out of the collar and up the sleeve of the welder’s aluminized jacket.14

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15. Arc Cutting and Arc Gouging This section outlines the health and safety hazards associated with the following common processes: • Section 15.1: Plasma arc cutting (PAC) • Section 15.2: Air carbon arc cutting (CAC-A) The following uncommon processes are also briefly addressed: • • • •

Section 15.3: Shielded metal arc cutting (SMAC) Section 15.4: Oxygen arc cutting (AOC) Section 15.5: Gas tungsten arc cutting (GTAC) Section 15.6: Gas metal arc cutting (GMAC)

In most cases, these processes share much of the equipment and hazards associated with welding processes having similar names. The cutting processes have been listed separately in this section rather than in the welding section(s) to facilitate access to the information specific to cutting processes. As was noted for OFC, when cutting metal, the goal is to remove the metal rather than deposit the metal. Therefore, one may expect elevated concentrations of airborne contaminants with cutting processes when compared to their welding process equivalents.

15.1 Plasma Arc Cutting (PAC) 15.1.1 PAC health and safety hazards summary See Section 9.1 for the PAW Health and Safety Hazards Summary table. These are essentially the same for PAC. 15.1.2 PAC common metals • See Section 9.2 for metals cut via PAC. 15.1.3 PAC process description Plasma arc cutting is very similar to plasma arc welding. Using the same process described for PAW, PAC heats the metal to be cut via a plasma arc with a temperature ranging from 18,000 to 25,000°F (10,000 to 14,000°C). In the PAC process, the orifice gas is provided at higher pressure and is constricted to form a high-velocity jet that removes the molten metal. Because of the higher energy density of PAC, it is much faster than OFC. PAC equipment may be hand-held or mechanized, and the equipment is commonly classified by current capacity: 82

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• • •

Low power: < 30 amps Medium power: 30–100 amps High power: 100–1000 amps

High current torches are water-cooled. Direct current operating voltages typically range from 50 volts to 200 volts. Open circuit voltages may range from 150 volts to greater than 400 volts. Plasma gases in the PAC process are usually one of the following: • Nitrogen • Argon • Air • Oxygen • Argon/hydrogen mixture • Nitrogen/hydrogen mixture 15.1.4 PAC health and safety hazards discussion From the health and safety point of view, the increase in cutting productivity offered by PAC is reflected in increased exposure to hazards such as electrocution, fire, heat, fumes and gases, and noise. Thus, the introduction of PAC into the workplace to supplement or supplant other cutting processes represents an increase in existing hazards rather than an introduction of entirely new hazards. This brief discussion emphasizes the increased exposure potential associated with PAC. 15.1.4.1 UV radiation burns to skin and eyes The AWS recommends the following UV eye and face protection for PAC: • Up to 300 amps: Welding helmet with Shade 9 lenses • 300–400 amps: Welding helmet with Shade 12 lenses • 400–800 amps: Welding helmet with Shade 14 lenses Dark-colored upper-body clothing, buttoned to the neck, is recommended to reduce reflections of UV radiation within the welding helmet that may result in skin and eye burns. The use of eye protection remains recommended even when using water tables with nozzles on the cutting head used to control fumes (see Section 15.1.4.3). This seemingly needless protection is recommended to guard the operator’s eyes when unanticipated interruptions in the water flow occur, unmasking the high energy arc. Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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15.1.4.2 Electrical shock In view of the high open circuit direct current voltages employed with PAC, observation of the following precautions is recommended: • Ensure that all electrical circuits are kept dry. The use of water for cooling high-power torches and water tables for fume control presents a possible source of water that may result in unanticipated current conduction to, and through, the operator. • Keep electrical connections tight. • Ensure that cables are sized correctly for the current in use by following the manufacturer’s recommendations. • Train operators to keep electrical cabinet access doors closed and avoid working with live electrical circuits. • Ensure that primary and control circuits are de-energized and/or disconnected when replacing torch parts. Otherwise, this becomes a high-risk task. • Train operators in recognizing and managing the increased hazards associated with the increased energies used by PAC. 15.1.4.3 Elevated fume and gas concentrations PAC can produce dense clouds of fumes/gases, particularly when high energy levels are used to cut thick materials. Because of the high energy of the plasma arc, airborne contaminants are likely to include ozone and oxides of nitrogen in addition to oxidized and nonoxidized fumes of the metal being cut. This operating characteristic has led to the widespread use of environmental controls such as high-capacity local exhaust (often connected to a cartridge-type dust collector) or the use of a water table. Water tables are shallow pansc with an egg-crate style grid of steel strips to support the metal being cut. The water level in the water table is adjusted to keep the bottom surface of the metal immersed. Additionally, the head of the plasma torch is often fitted with an annular water supply nozzle. During operation, the plasma/fume/gas mixture is blown into the water, minimizing exposure potentials to airborne concentrations for the operator and The use of the word “pan,” while technically correct, does not convey the size of these tables. In shipyard and steel fabrication facilities, these water tables may be 20 feet wide and 100 feet long. In smaller fabrication shops, water table dimensions may be 4 feet by 8 feet. c

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adjacent personnel. The water level in this system may be modified to completely submerge the entire plate being cut. This is called “underwater cutting” and obviates the need for the water nozzle on the torch head. Dyes are sometimes added to the water to better control UV emissions. 15.1.4.4 Noise Sound energy generated by PAC is largely a function of the amperage and environmental controls used. At 400 amps, noise levels of 100 dBA may be anticipated at 6 ft from the operation, and at 750 amps, 110 dBA is likely. Water tables and annular water shrouds may reduce these sound levels by 20 dBA. Sound frequencies are primarily in the range of 5000 to 20,000 Hz. 15.1.5 Equipment comments specific to PAC • Compressed Gases: See Chapter 3: Welding Equipment • Cables: See Chapter 3: Welding Equipment • Helmet: See Chapter 7: PPE

15.2 Air Carbon Arc Cutting (CAC-A, “Air-Arc,” “Arc-Gouging”) 15.2.1 CAC-A health and safety hazards summary Hazard

Sources

Fire-ignition of nearby combustibles

• Stream of molten metal and slag from cutting process

UV radiation burns to eyes and skin

• Electric arc

Thermal burns

• Stream of molten metal and slag from cutting process • Handling hot metal

Metal fumes

• Parent metal

Copper fumes

• Copper cladding on CAC-A electrodes

Lead fumes (confined spaces)

• Traces of lead in CAC-A electrodes

Particulate in eyes

• Spatter

Noise

• Gasoline or diesel-driven generators • Air/arc interaction

Electrocution

• Damaged high-amperage cables

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15.2.2 CAC-A common metals Metals commonly cut via CAC-A include but are not limited to: Welding Processes • Aluminum

67 alloys • Carbon and low-alloy steels • Cast iron � Aluminum alloys • Copper alloys � Carbon and low-alloy steels • Magnesium alloys � Cast iron • Nickel alloys � Copper alloys • Stainless steels � Magnesium alloys � Nickel alloys 15.2.3 CAC-A process description � Stainless steels Air carbon arc cutting utilizes the intense heat generated between (usually copper-coated) and the metal to 15.2.3a carbon CAC-A electrode process description be cut to melt a portion of the workpiece. A lance of compressed air Air directed carbon arcatcutting utilizesmetal the intense heat generated between carbon is then the molten to displace, or blow away,athat electrode copper-coated) the metal be cut to melt portion of portion of (usually the workpiece (Figureand 2.18). The to workpiece and aCAC-A the workpiece. A lance of compressed is then to directed at the moltenarc metal electrode holder are connected viaaircables a conventional to displace, or blow away, of the (Figure 2.18). The welding power supply of that the portion type used forworkpiece SMAW. The electrode workpiece andconnected CAC-A electrode holder areairconnected via lance cables of to a holder is also to a compressed supply. The conventionalair arciswelding of the used forbySMAW. compressed emittedpower from supply the torch andtype controlled the op-The electrode holder is also aconnected to a compressed supply. The lance of erator, who depresses button-controlled valveair in the torch. compressed air is emitted from the torch and controlled by the operator, who depresses a button-controlled valve in the torch.

Figure 2.18: operating procedures for air carbon arccarbon gouging arc Figure 2.18:Typical Typical operating procedures for air gouging 86

CAC-A equipment is commonly classified by current capacity:

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CAC-A equipment is commonly classified by current capacity: • Light duty: < 450 amps • General purpose: 450–1000 amps • Heavy duty: up to 1600 amps when air-cooled and up to 2000 amps when water-cooled The CAC-A process may be used to remove metal in order to accomplish one of three objectives: • Sever one portion of the workpiece from another portion. For instance, removing risers and sprues from castings. • Gouge out old welds or the oxidized portions from the back of new welds without severing the workpiece. This is a common use of the CAC-A process in many industrial construction, maintenance, and repair activities, and the term “arc-gouging” is often used as a generic synonym for air carbon arc cutting. The term “arc-gouging” is so widely used in the workplace that welders usually do not make a distinction between severing and gouging when referring to the equipment or process. When CAC-A is used to remove oxidized weld deposits from the backside of a weldment, the process is frequently called “back gouging.” • Washing unwanted metal from the surface of the workpiece. This procedure is conceptually similar to arc-gouging but does not necessarily address welds. “Washing” requires moving the electrode from side-to-side in an oscillating motion to remove a thin layer of metal over a wide area. Common uses include removing riser pads from castings and damaged metal from petrochemical reactor vessels. This process may also be referred to as “skim gouging.” 15.2.4 CAC-A health and safety hazards discussion Air carbon arc cutting is extremely productive, both in terms of work performed per unit time and airborne contaminants generated per unit time. CAC-A hazards include exposure to electrocution, fire, heat, fumes and gases, and noise. Many of the hazards described for SMAW are shared by CAC-A, and the reader is encouraged to review Section 1.3 of this chapter for SMAW hazards. This discussion emphasizes the hazards specifically associated with CAC-A. (See pages 127–130 for CAC-A work monitoring results in confined spaces.)

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15.2.4.1 Fire-ignition of nearby combustibles The stream of molten metal and slag generated by the CAC-A process is a source of ignition, and the AWS recommends removing all combustibles from an area within 35 horizontal feet of CAC-A work. Molten metal and hot slag can fall many tens of feet vertically and remain hot enough to act as a source of ignition. Consequently, the 35-foot horizontal guideline is not likely to be adequate for vertical distances between the CAC-A activity and combustibles. This potential fire hazard can be of particular concern when large numbers of people are working in a restricted area during industrial demolition or renovation operations. Clearly, it is best to avoid scheduling work that requires one group of people to work beneath another group conducting CAC-A tasks. When this is not possible, workers below CAC-A operations may require protection via scaffolding, scaffold boards, and fire blankets. 15.2.4.2 UV radiation burns to skin and eyes The AWS recommends Shade 12 lenses for people working in the immediate vicinity of CAC-A work. Also, dark-colored upper-body clothing, buttoned to the neck, is recommended to reduce reflections of UV radiation within the welding helmet that may result in skin and eye burns. 15.2.4.3 Electrical shock Damaged cables can lead to possible electrical shocks. 15.2.4.4 Elevated fume and gas concentrations CAC-A creates dense clouds of fumes/gases. Because the metal is being blown into the workplace atmosphere (rather than being deposited, as is the case when welding), metal and metal oxide fume concentrations can be expected to be much greater than when welding. The CAC-A process itself is responsible for three airborne contaminants in addition to those emitted from oxidizing and displacing the metal: • Carbon monoxide (CO) from incomplete combustion of the electrode; • Copper fume from the CAC-A electrode cladding; and • Lead, a trace contaminant in the carbon electrode (less than 1 percent). Emission of carbon monoxide (along with carbon dioxide) from the CAC-A process can be reasonably expected due to the incom88

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plete combustion or oxidation of the carbon electrode. Although CO has not been identified as an exposure concern when performing CAC-A work in open spaces, air monitoring has shown an elevated exposure potential to CO when using this process in confined spaces (see chapter Appendix). 15.2.4.5 Noise CAC-A is a noisy process and in open areas can produce an estimated average noise level of 115 dBA.15 In confined spaces, this sound pressure level is likely to be exceeded. Hearing protection should be considered a requirement for personnel in the immediate vicinity of CAC-A work. In confined spaces, both plugs and muffs may be required. 15.2.5 Equipment comments specific to CAC-A • Compressed Gases: See Chapter 3: Welding Equipment • Cables: See Chapter 3: Welding Equipment • Helmet: See Chapter 7: PPE

15.3 Shielded Metal Arc Cutting (SMAC) 15.3.1 SMAC health and safety hazards summary See Section 1.1, SMAW Health and Safety Hazards Summary. 15.3.2 SMAC common metals The AWS notes that SMAC is used primarily for cutting risers and gates from nonferrous castings and for cutting nonferrous scrap for remelting. 15.3.3 SMAC process description SMAC employs SMAW equipment with direct current straight polarity to melt the unwanted metal. The molten metal is removed from the cutting zone by gravity. As one might imagine, this is a crude process and creates a very irregular edge. Substantial rework of the edge would be required for subsequent welding on edges cut via SMAC. 15.3.4 SMAC health and safety hazards discussion See Section 1.4, SMAW Health and Safety Hazards Discussion.

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15.4 Oxygen Arc Cutting (AOC) 15.4.1 AOC health and safety hazards summary See Section 14.2, LOC Health and Safety Hazards Discussion. 15.4.2 AOC common metals Most ferrous and nonferrous alloys. 15.4.3 AOC process description From the point of view of the OEHS Professional, AOC (Figure 2.19) is conceptually identical to oxygen lance cutting (LOC). The primary differences lie in the intended applications and the length of the electrodes. Oxygen arc cutting was designed for use in underwater cutting applications using a fully insulated electrode holder. The AOC electrode is of conventional length (approximately 18 in. when new), whereas the LOC electrode may be up to 10 ft in length when new. 15.4.4 LOC health and safety hazards discussion • See Section 14.2, LOC Health and Safety Hazards Discussion. • Additionally, note that a fully insulated holder is mandatory when using SMAC for underwater work. • Exceptionally high standards of maintenance of electrical connections and cables when using arc processes in a marine environment are necessary to avoid electrocution.

15.5 Gas Tungsten Arc Cutting (GTAC) 15.5.1 GTAC health and safety hazards summary See Section 2.1, GTAW Health and Safety Hazards Summary. 15.5.2 GTAC common metals • Aluminum alloys • Magnesium alloys • Copper alloys • Silicon bronze • Nickel alloys • Copper–nickel • Stainless steels 90

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15.5.3 GTAC process description From the health and safety perspective, GTAC is conceptually identical to Gas tungsten arc welding (GTAW). However, higher currents and higher gas flows (up to 60 cfh) are commonly used to cut the metal more quickly. The metal is melted by the arc and displaced from the cutting zone by gravity and the excess flow of Welding Processes 71 shielding gas. 10 ft in length when new.

Figure 2.19: Schematic arc electrode in operation Figure 2.19: Schematicof of oxygen oxygen arc electrode in operation 15.4.42:LOC health and safety hazard discussion Chapter Welding Processes 91 ® Copyright AIHA For personal use only. Do not distribute. � See Section 14.2, “LOC Health and Safety Hazards Discussion.”

� Additionally, note that a fully insulated holder is mandatory when using SMAC for underwater work.

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15.5.4 GTAC health and safety hazards discussion • See Section 2.4, GTAW Health and Safety Hazards Discussion. • Additionally, elevated potential exposures to nonionizing radiation may be expected from the higher current used in GTAC compared to GTAW for the same metal thickness. For example, up to 600 amps may be used for cutting 0.5-inchthick stainless steel.

15.6 Gas Metal Arc Cutting (GMAC) 15.6.1 GMAC health and safety hazards summary See Section 3.1, GMAW Health and Safety Hazards Summary. 15.6.2 GMAC common metals • Aluminum alloys • Stainless steels 15.6.3 GMAC process description GMAC is conceptually identical to gas metal arc welding (GMAW). However, higher currents are used to cut the metal more quickly. The metal is melted by the arc and displaced from the cutting zone by gravity and the force of the arc. 15.6.4 GMAC OEHS hazards discussion • See Section 3.4, GMAW Health and Safety Hazards Discussion. • In addition, elevated potential exposures to nonionizing radiation may be expected from the higher current used in GMAC compared to GMAW for the same metal thickness. Up to 2000 amps may be used in some applications.

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16. Laser Beam Welding (LBW), Cutting (LBC), and Drilling (LBD) 16.1 LBW, LBC, and LBD Health and Safety Hazards Summary Hazard

Sources

Electrocution and/or shock

• High-voltage power supplies

Eye damage to cornea and/or retina; Skin damage

• Laser beam

Metal fumes

• Metal being cut/welded; may be directed by plasma suppression gas stream

Noise (particularly in enclosed areas)

• LBC and LBD cutting process

Solvent vapors and products of decomposition

• Degreasing solvents

16.2 LBW, LBC, and LBD Common Metals Metals commonly worked via laser processes include but are not limited to: • Aluminum alloys • Brass • Carbon and low-alloy steels • Copper alloys • Iron alloys • Nickel and its alloys • Stainless steels • Titanium Also, the following nonmetallic materials are cut by LBC: • Alumina • Quartz • Glass • Cloth • Plastics • Composites • Wood

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16.3 Laser Beam Welding (LBW) Process Description Laser beams are created by supplying an optical resonance cavity (a crystal rod or gas chamber with mirrors at each end) with pulses of intense light (Figure 2.20). This light may be supplied by krypton or xenon flash lamps. These lamps are the “pumps” that supply energy to the optical resonance cavity, hence the name “pumped lasers.” In the optical resonance cavity, the broad-spectrum light supplied by the flash lamps is organized into light of a single wavelength by excitation and reemission of energy from the molecules of material(s) of the crystal rod or gas. Because different crystal or gaseous materials have different excitation/reemission characteristics, different optical resonance cavities create different wavelengths (ruby, for example, emits red light). As the light photons move through the crystal or gas, they organize into light that is not only of the same wavelength but is in phase as well. This light is said to be “coherent.” The coherent light produced by laser equipment is therefore able to concentrate the broad-spectrum energy supplied by the flash lamps into single wavelength-single phase light whose power is amplified by the stimulation of the crystal rod or gas and subsequent additional photon emission. This process is described as light amplification by stimulated emission of radiation, or laser. Welding Processes 75

Figure 2.20:Schematic Schematic view of aofsolid-state laser laser Figure 2.20: view a solid-state 94

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Laser beam welding employs the energy from a laser beam to provide the heat Copyright AIHA® For personal use only. Do not distribute. necessary for joining metals. Depending on the wattage and wavelength, lasers for LBW may be operated in either continuous or pulsed modes. Inert gases are often used to shield the weld pool from the atmosphere. The most

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Laser beam welding uses the energy from a laser beam to provide the heat necessary for joining metals. Depending on the wattage and wavelength, lasers for LBW may be operated in either continuous or pulsed modes. Inert gases are often used to shield the weld pool from the atmosphere. The most commonly used wavelengths for LBW are 1.06 µ yttrium-aluminum-garnet (YAG) laser and the 10.6 µ CO2 laser. Industrial YAG lasers are solid-state devices that use traces of neodymium in the crystal rods. These are referred to as Nd:YAG lasers. Output from these solid-state lasers is limited by the ability of the rods to accept thermal loading. They are typically operated in a series of pulses that may range from 0.1 to 20 milliseconds. Average power output generally ranges from 1 kW to 2 kW. The following wavelengths are emitted by Nd:YAG lasers:16 • Wavelength: 1.064 µ: Spectral region: IR-A • Wavelength: 0.532 µ: Spectral region: green (second harmonic) • Wavelength: 0.355 µ: Spectral region: UV-A (third harmonic) CO2 lasers (Figure 2.21) that use a mixture of nitrogen and helium with traces of CO2 are capable of delivering up to 25 kW of power. This increased ability to deliver power is due largely to the cooling of the recirculating gas tothermal keep the laser CO equipment keep theability laser equipment from experiencing overload. 2 lasers emit from experiencing thermal overload. CO lasers emit the following 2 the following wavelength: wavelength: Wavelength: 10.6 µ: µ: Spectral region: IR-CIR-C • � Wavelength: 10.6 Spectral region:

Note: There no visible emitted from CO2 lasers. Note: There is noisvisible light light emitted from CO 2 lasers.

Figure 2.21: Schematic diagram diagram of of a slow axialaxial flow laser Figure 2.21: Schematic a slow flow laser Chapter Welding Processes 16.3.12:Laser beam cutting (LBC) process description Copyright AIHA® For personal use only. Do not distribute.

95

Laser beam cutting (LBC) uses the energy from the laser beam to locally melt or vaporize the workpiece. LBC usually assists gases (from a nozzle

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16.3.1 Laser beam cutting (LBC) process description Laser beam cutting (LBC) uses the energy from the laser beam to locally melt or vaporize the workpiece. LBC usually assists gases (from a nozzle concentric with the beam) and is used to aid in the removal of the molten metal. These gases include air, oxygen, nitrogen, and argon. Both pulsed Nd:YAG lasers and pulsed or continuous CO2 lasers are employed for LBC. Power levels for LBC processes are generally in the range of 400 to 1500 watts. In nearly all cases, LBC is an automated process. 16.3.2 Laser beam drilling (LBD) process description Laser beam drilling (LBD) is typically employed for very small diameter holes, in the range of 0.0001 to 0.060 inches in diameter and less than 1 inch depth. The focusing abilities of the shorter wavelengths produced by Nd:YAG lasers have made them the preferred laser for this operation. Again, in nearly all cases, LBD is an automated process.

16.4 LBW, LBC, and LBD Health and Safety Hazards Discussion The following resources are recommended reading for those working with laser processes: • Hitchcock RT and Rockwell RJ, Jr. Laser Radiation: Nonionizing Radiation Guide Series. Fairfax, VA: AIHA Press, 1999. • Hitchcock RT. LIA Guide to Non-Beam Hazards Associated with Laser Use. Orlando, FL: Laser Institute of America, 1999. • Laser Institute of America. Laser Safety Guide, 10th Ed. Orlando, FL: Laser Institute of America, 2000. • Ready JF. LIA Handbook of Laser Material Processing. Orlando, FL: Laser Institute of America, 2001. • Sliney DH. Guide for the Selection of Laser Eye Protection, 5th Ed. Orlando, FL: Laser Institute of America, 2000. • American National Standard Institute. American National Standard for the Safe Use of Lasers (ANSI Z136.1-2000). Orlando, FL: Laser Institute of America, 2000. 16.4.1 Laser beam damage to eyes and skin Among the topics addressed in Hitchcock and Rockwell’s 1999 “Laser Radiation,”17 the following provide meaningful and substan96

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tive discussions directly applicable to laser welding and cutting operations: • • • • • • •

Hazard evaluation Assignment of a laser safety officer Characteristics and effects of laser radiation Exposure guidelines for laser radiation Engineering controls for laser radiation Laser-controlled areas Administrative and procedural controls, including medical qualification and use of PPE • Alignment practices Readers are also encouraged to refer to: • Sliney’s “Guide for the Selection of Laser Eye Protection”18 • ANSI Z136.1–200019 Workers should be trained in the skin and eye hazards associated with laser radiation. Engineering controls must be selected as a control technique over PPE when possible. Circumventing safety devices provided by equipment manufacturers must be strictly prohibited. Appropriate signage must be posted. Long-sleeve shirts are considered prudent. Criteria for eye protection must include the effectiveness of the protection at the wavelength of the light being used for welding or cutting. The AWS also recommends frequent eye examinations to ensure that the selected eye protection is both adequate and correctly used.20 16.4.2 Metal fumes As the LBW process melts the metals being joined, the high heat of the laser beam vaporizes a portion of the liquid metal. Some of the vaporized metal becomes ionized by the laser beam, creating a plasma. The plasma can lead to beam attenuation with consequent loss of productivity, and many LBW machines are equipped with an orifice that directs a stream of gas across the weld zone to displace the plasma (Figure 2.22). In nonenclosed machines, this may lead to asymmetric distribution of metal fumes around the LBW equipment. Thus, worker exposure potentials may vary with their location relative to the gas stream. Gases commonly used for the purpose of displacing the fume in order to mitigate beam attenuation include nitrogen and carbon dioxide. At higher powers, helium is more often employed. Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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may lead to asymmetric distribution of metal fumes around the LBW equipment. Thus, worker exposure potentials may vary with their location relative to the gas stream. Gases commonly used for the purpose of displacing the fume in order to mitigate beam attenuation include nitrogen and carbon Welding Health and Safety: dioxide. At for higher powers, helium is2nd more often employed. A Field Guide OEHS Professionals, edition

Figure Plasma suppression a transverse jet of Figure 2.22: 2.22: Plasma suppression using ausing transverse jet of inert gas inert gas 16.4.3 Degreasing solvents 16.4.3 solvents LBWDegreasing joining requires contaminant-free surfaces. Parts cleaning systems may be incorporated into LBW automated or semiauLBW joining requires contaminant-free surfaces. Parts cleaning systems tomated production lines.21 As a consequence, the OEHS Professional may wish to investigate the degreasing processes used and Copyright AIHA® For by personal use only. Do not distribute. the products of decomposition released thermal degradation of these solvents.

16.5 Shock and Electrocution Laser equipment requires careful maintenance to ensure that lenses, mirrors, shutters, lamps, and filters are in good working order (Figure 2.23). Laser equipment includes high-voltage power supplies and large capacitive storage devices. According to the AWS, “All reported laser-related deaths have been associated with the high voltage present in the laser system.”22 As a consequence: • Appropriate Lockout/Tagout procedures should be developed with guidance from the equipment manufacturer. • Affected personnel should be trained in the hazards of high-voltage equipment and appropriate procedures for de-energizing that equipment. This precaution is specifically applicable to capacitors. • Grounding and interlocking devices should be applied and used for working with high-voltage equipment. 98

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equipment and appropriate procedures for de-energizing that equipment. This precaution is specifically applicable to capacitors. � Grounding and interlocking devices should be applied and used for working with high-voltage equipment. Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

Figure 2.23: Schematic representation of the elements of an Nd:YAG of laser Figure 2.23: Schematic representation of the elements an

Nd:YAG laser

17. Resistance Welding: Spot, Seam, and Projection

17. Resistance Welding: Spot, Seam, and Welding Projection Welding

17.1 Spot, Seam, and Projection Welding Health and Safety Hazards SummaryFor personal use only. Do not distribute. Copyright AIHA® Hazard

Sources

Eye hazards and skin burns

• Spatter/flying molten metal

Metal fumes

• Metal being welded

Hand injuries

• Hand in pinch point

Shock and/or electrocution

• High-voltage power supplies

17.2 Spot, Seam, and Projection Welding: Common Metals Metals commonly joined by resistance welding processes include but are not limited to: • Aluminum alloys • Carbon and low-alloy steels • Copper alloys • Nickel and its alloys • Stainless steels • Titanium

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17.3 Spot, Seam, and Projection Welding Process Descriptions All these resistance welding processes produce coalescence of metals at the faying surfaces.d These processes use electrodes to apply pressure to the joint before, during, and after application of sufficient electrical current to locally melt the parts via the heat generated by resistance to the electrical current. When cooled, the spot weld is called a “nugget.” Figure 2.24 illustrates the three common resistance welding techniques. Although seam welding and projection welding use different electrode arrangements, the equipment is conceptually similar to the schematic for spot welding. Welding Processes

81

Figure Simplified diagrams depicting the basic process of resistance Figure2.24: 2.24: Simplified diagrams depicting the basic processwelding of

resistance welding

17.4 Spot, Seam, and Projection Welding Health and Safety 17.4 Hazards Spot, Seam, and Projection Welding Health and Discussion Safety Hazards Discussion 17.4.1 Spatter/flying molten metal 17.4.1 Spatter/flying molten metal A spray of molten metal may emit from the weld site if welding conditions of molten metallikely may with emit spot fromwelding the weld if weldare A notspray correct. This is more thansite with seam or ing conditions are not correct. This is more likely with spot projection welding, but it can occur during the latter two processes asweldwell. If ing with are seam projection welding, it can occur duringof the than electrodes not or properly maintained or but aligned or if the timing the lattermovement two processes well. If theofelectrodes are not properly electrode relativeas to application current is not correct, the molten maintained or ifmay thebetiming of as electrode movement rela-to metal formedor byaligned the process expelled a spray. This is detrimental tive application of current is not correct, the molten metal formed bothto employee welfare and product quality. Face shields, in addition to safety by the process may be expelled a spray. This is detrimental to glasses, are recommended along withas nonflammable gloves. Clothing should both and quality. Face shields, in addihave aemployee minimum welfare of pockets, andproduct shirt pockets should have flap closures. Pant cuffs are to be avoided as they can retain hot and/or molten metal. Protective d “Faying surfaces” are surfaces that are made to fit closely together for the footwear is recommended.

purposes of making a joint.

17.4.2 Metal fumes

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Fume generation from resistance slight. Copyright AIHA® Forwelding personalprocesses use only. is Dogenerally not distribute. However, when alloys containing (or plated with) nickel, chromium, zinc, or other relatively toxic metals are being resistance welded, prudence may dictate evaluating toxic metal concentrations in the workers’ breathing zones.

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

tion to safety glasses, are recommended along with nonflammable gloves. Clothing should have a minimum of pockets, and shirt pockets should have flap closures. Pant cuffs are to be avoided as they can retain hot and/or molten metal. Protective footwear is recommended. 17.4.2 Metal fumes Fume generation from resistance welding processes is generally slight. However, when alloys containing (or plated with) nickel, chromium, zinc, or other relatively toxic metals are being resistance welded, prudence may dictate evaluating toxic metal concentrations in the workers’ breathing zones. 17.4.3 Hand injuries at pinch points Large resistance welding equipment may have adequate space in the material handling portion of the machine to allow operators to insert their hands into the area between the electrode/electrode holders and the workpiece. To avoid injuries due to this circumstance: • Train personnel in pinch point hazards • Ensure that adequate guards are in place • If guards are not feasible, other methods may be required, such as: – Photoelectric sensors – Pull-out devices attached to the operator’s hands/wrists – Sweep devices – Two-hand control devices 17.4.4 Shock and electrocution See Section 16.5, LBW, LBC, and LBD: Shock and Electrocution.

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18. Resistance Welding: Flash, Upset, and Percussion Welding 18.1 Flash, Upset, and Percussion Welding Health and Safety Hazards Summary Hazard

Sources

Fire hazard (flash welding)

• Spatter/flying molten metal

Eye hazards, skin burns

• Spatter/flying molten metal

Nonionizing radiation (eyes)

• Electric arc

Metal fumes

• Metal being welded

Hand injuries

• Hand in pinch point

Shock and/or electrocution

• High voltage power supplies

18.2 Flash, Upset, and Percussion Welding: Common Metals Metals commonly joined by resistance welding processes include but are not limited to: • • • • • • •

Aluminum alloys Carbon and low-alloy steels Copper alloys Nickel and its alloys Stainless steels Titanium (in an inert gas atmosphere) Dissimilar metals (e.g., aluminum to copper)

18.3 Flash, Upset, and Percussion Welding Process Descriptions Flash, upset, and percussion welding differ from spot, seam, and projection welding in that electrodes in contact with the weld zone are not used to apply pressure to parts during the welding process. Rather, the parts (usually of similar cross section, e.g., bar stock, tubing) are held in clamps that also act as conductors. The clamps move together to bring the parts into contact and provide the required positioning and pressure. Because these are resistance welding processes, electrical current is used to locally melt the parts via the heat generated by resistance to the electrical current. 102

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Flash welding (Figure 2.25) applies current as the parts come in contact. The consequent electric arc melts the ends of the parts, which are then brought together under pressure. Not surprisingly,

Figure 2.25: basic stepssteps in flashinwelding: (A) position(A) andposition clamp the and parts; (B) Figure 2.25:The The basic flash welding: apply flashing voltage and start platen motion; (C) flash; (D) upset and terminate clamp the parts; (B) apply flashing voltage and start platen current.motion; (C) flash; (D) upset and terminate current.

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this process generates quite a spray of molten metal as well as fumes, and the work is conducted behind shields/guards. Flash welding is usually an automatic process once the welding schedule has been determined during the set-up procedure. Set up can entail a certain amount of trial and error; during this phase of the work, considerable molten metal spray can be produced, elevating the safety concerns for fire and eye/skin burns. From the perspective of the OEHS Professional, upset welding is a much more benign process compared to flash welding. Upset welding differs from flash welding in that the parts to be welded are held firmly in contact before the electrical current is applied. Consequently, there is no arcing or associated spray of molten metal from the process. As the parts heat up (due to electrical resistance at their interface), the faying surfaces become plastic and the force applied by the clamps causes the parts to flow together in a plastic manner (Figure 2.26). Although there should be no arcing or molten metal flying about during upset welding, the potential for these hazards does exist during set-up and process disturbances. Like flash welding, percussion welding initiates an arc between Welding Processes the faying surfaces prior to applying force to drive the parts to- 85

Figure2.26: 2.26: General General arrangement for upset of bars, rods, pipes Figure arrangement forwelding upset welding of and bars, rods, and pipes 104

Chapter 2: Welding Processes

Like flash welding, percussion® welding initiates an arc between the faying Copyright AIHA For personal use only. Do not distribute. surfaces prior to applying force to drive the parts together. In the percussion welding process, however, the parts are allowed to arc for only a very brief period of time (measured in microseconds) and are then brought together very

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

gether. In the percussion welding process, however, the parts are allowed to arc for only a very brief period of time (measured in microseconds) and are then brought together very quickly and abruptly (“percussively”) by mechanical or electromagnetic means. Although flash welding may be used for joining fairly large parts, percussion welding is primarily used for joining small parts, most frequently in the manufacture of electrical components.

18.4 Flash, Upset, and Percussion Welding Health and Safety Hazards Discussion 18.4.1 Spatter/flying molten metal Flash welding creates a spray of molten metal from the weld. When at all possible, this process should be conducted in enclosures or behind shields. Face shields, in addition to safety glasses, are recommended along with nonflammable gloves. Clothing should have a minimum of pockets, and shirt pockets should have flap closures. Pant cuffs are to be avoided as they can retain hot and/or molten metal. Protective footwear is recommended. Upset welding presents a relatively low health and safety hazard. However, eye protection and nonflammable clothing are recommended to guard against flying molten metal in the event of process disturbances. Percussion welding presents a much smaller-scale health and safety hazard than flash welding, and eye protection and nonflammable clothing may be adequate protection for this process. 18.4.2 Metal fumes Fume generation from flash welding may require engineering controls and/or respiratory protection. Fume generation from upset and percussive welding processes is generally slight. However, when alloys containing (or plated with) nickel, chromium, zinc, or other relatively toxic metals are being resistance welded, prudence may dictate evaluating toxic metal concentrations in the workers’ breathing zones. 18.4.3 Hand injuries at pinch points See Section 17.4.3, Spot, Seam, and Projection Welding. Additionally, a pinch/crush hazard exists due to the moving clamps, platens, or heads that bring the parts together. Pins, blocks, Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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or latches are recommended by the AWS to immobilize these machine elements during maintenance and/or set up.23 18.4.4 Shock and electrocution See Section 16.5, LBW, LBC, and LBD: Shock and Electrocution. 18.4.5 Nonionizing radiation Flash welding requires shaded lenses or a shaded view glass in the enclosure. Percussion welding may require shaded lens, depending on the amperage used.

19. High-Frequency Welding 19.1 High-Frequency Welding Health and Safety Hazards Summary Hazard

Sources

Metal fumes (low risk)

• Metal being welded

Hand injuries

• Hand in pinch point (material feed rollers)

Shock and electrocution

• High-voltage power supplies

Communication radio interference

• High-frequency radiation “leakage” from power supplies

19.2 High-Frequency Welding: Common Metals Metals commonly joined by high-frequency welding processes include but are not limited to: • • • • • •

Aluminum alloys Carbon and low-alloy steels Copper alloys Nickel and its alloys Stainless steels Titanium (in an inert gas atmosphere)

19.3 High-Frequency Welding Process Descriptions High-frequency welding is an upset welding process that uses high-frequency alternating current rather than the direct current used in the processes described in Sections 17 and 18 above. Ac106

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cording to the AWS, “By far the greatest number of high frequency machines are used to make pipe and tube”24 (Figure 2.27). Typically, sheet or strip metal is fed to rollers that form the stock to the desired shape. Immediately adjacent to the seam are either electrodes (high-frequency resistance welding) or an induction coil (high-frequency induction welding) that transfers electrical current to the workpiece. The advantage of the high-frequency alternating current is that current is concentrated at the surface of the part and much more rapid heating of a small area can be achieved. In the case of high-frequency welding, the rapid temperature rise is coordinated with applying pressure to the faying surfaces to create an upset weld. This is a continuous process during manufacture of tube and pipe.

Figure 2.27: Joining a tube seam by high-frequency induction welding

Figure 2.27: Joining a tube seam by high-frequency induction welding

19.4 High-Frequency Welding Health and Safety Hazards Discussion 19.4.1 fumes 19.4 Metal High-Frequency Welding Health and Safety

Hazards Discussion

Fume generation from high-frequency welding processes is generally slight. 19.4.1 Metal fumes However, when alloys containing (or plated with) nickel, chromium, zinc, or otherFume relatively toxic metals are being resistance welded, prudence may dictate generation from high-frequency welding processes is evaluating toxic metal concentrations in the workers’ breathing zones. generally slight. However, when alloys containing (or plated with) nickel, chromium, zinc, or other relatively toxic metals are being re19.4.2 Hand injuries at pinch sistance welded, prudence maypoints dictate evaluating toxic metal concentrations in the workers’ breathing zones. handling equipment (e.g., A pinch/crush hazard exists due to the material

rollers) associated with continuous welding or processes. Lockout/Tagout procedures should beProcesses developed and enforced when working with the material Chapter 2: Welding 107 handling portion ® of the equipment. Copyright AIHA For personal use only. Do not distribute. 19.4.3 Shock and electrocution

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19.4.2 Hand injuries at pinch points A pinch/crush hazard exists due to the material handling equipment (e.g., rollers) associated with continuous welding or processes. Lockout/Tagout procedures should be developed and enforced when working with the material handling portion of the equipment. 19.4.3 Shock and electrocution See Section 16.5, LBW, LBC, and LBD: Shock and Electrocution.

20. Electron Beam Welding (EBW) 20.1 Electron Beam Welding Health and Safety Hazards Summary Hazard

Sources

X-radiation

• Electron beam interaction with matter

High-intensity visible light

• Electron beam excitation of gases

Metal fumes (low risk)

• Metal being welded

Ozone and nitrogen dioxide (nonvacuum applications)

• Ionization of atmosphere by electron beam

Hand injuries

• Hand in pinch point (material feed rollers)

Shock and electrocution

• High-voltage power supplies

20.2 Electron Beam Welding: Common Metals Nearly all metals that can be welded via other fusion welding processes can be welded by EBW.

20.3 Electron Beam Welding Process Descriptions Electron beam welding (Figure 2.28) employs the energy from high-velocity electrons (moving at 30 to 70 percent of the speed of light!) impinging on the workpiece to create the heat necessary for fusion welding. Electron beam welding can take place in high vacuum enclosures (1 × 10–6 to 10–3 torr), medium vacuum enclosures (1 × 10–2 to 2.5 torr), or nonvacuum enclosures. In all cases, these pressure distinctions apply to the workpiece environment as the electron beam gun pressure must be less than 10–4 torr. Consequently, there are usually a number of different low-pressure sections or zones within a single EBW machine, depending on the welding schedule and beam generation requirements. 108

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Figure 2.28: The basic modesbeam of electron beam welding, vacuum Figure 2.28: The basic modes of electron welding, with a corresponding scale. (Note: One torr is 1/760 atmospheres pressure, approximately equal to 1 with a corresponding vacuum scale. (Note:orOne torr is 1/760 mmHg at standard temperature and pressure.) atmospheres pressure, or approximately equal to 1 mmHg at standard temperature and pressure.)

When used in the high vacuum applications, EBW is generally employed for high-precision applications (nuclear, aerospace, aircraft, and electronics When used and in the high vacuum applications, is generally work). Medium nonvacuum applications of EBW EBW take advantage of the employed for high-precision applications (nuclear, aerospace, reliable and repeatable results of this automated process to achieveairhigh craft, and electronics work). Medium nonvacuum applications production rates on components that mayand otherwise be expensive or difficult oftoEBW take advantage of the reliable and repeatable results of manufacture. this Nonvacuum automatedEBW process achieve highasproduction rates onthe comoftento requires as much 150 kV to overcome effects ponents that may expensive or difficultrequire to manufacof atmospheric beamotherwise attenuation.be High vacuum applications less power ture. due to minimal beam attenuation. A distinction is made between high-voltage Nonvacuum EBW as voltage much as 150electron kV to gun) over-and equipment (greater than often 60 kV requires accelerating at the come the effects of atmospheric beam attenuation. vacuum low-voltage equipment (less than 60 kV). It should be noted High that every electron applications power due to minimal beam attenuation. beam weldingrequire systemless operates with a voltage level high enough to cause A fatal distinction is made between equipment (greater than injury, regardless of whether thehigh-voltage system is referred to as being a “low voltage” 25 60 accelerating at the electron gun) and low-voltage or kV “high voltage” unit.voltage equipment (less than 60 kV). It should be noted that every electron beam welding system operates with a voltage level high enough to Copyright For personal use only. Do not distribute. Chapter 2:AIHA® Welding Processes 109 Copyright AIHA® For personal use only. Do not distribute.

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cause fatal injury, regardless of whether the system is referred to as being a “low voltage” or “high voltage” unit.25

20.4 Electron Beam Welding Health and Safety Hazards Discussion 20.4.1 X-Radiation X-rays are produced when high-velocity electrons strike the workpiece and/or gas and vapor molecules in the work chamber. A radiation survey of the electron beam equipment should be performed when it is installed. This survey should be repeated annually and after removing and replacing shielding for maintenance operations. According to the AWS, the following shielding is commonly used for accelerating voltages up to 60 kV:26 • One-inch-thick steel for the work portion of the vacuum enclosure when beam generating voltages are less than 60 kV. • High beam accelerating voltages require much more steel or lead cladding. • Leaded glass viewing windows supplied by enclosure manufacturers are generally adequate. Nonvacuum units using higher voltages may require walls of high-density concrete to protect operators while the EBW equipment is in operation. Note: Personal dosimetry for ionizing radiation may be necessary to verify the adequacy of these measures. 20.4.2 Metal fumes and gases Fume, ozone, and nitrogen dioxide generation in nonvacuum and medium vacuum operations may require mechanical ventilation to control personal exposures. 20.4.3 Hand injuries at pinch points A pinch/crush hazard exists because of the material handling equipment (e.g., rollers) associated with continuous welding or processes. Lockout/Tagout procedures should be developed and enforced when working with the material handling portion of the equipment. 20.4.4 Shock and electrocution See Section 16.5, LBW, LBC, and LBD: Shock and Electrocution. 110

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21. Friction Welding 21.1 Friction Welding Health and Safety Hazards Summary Hazard

Sources

Hand/eye injuries

• Rotating parts

Noise

• Friction welding process

Hand injuries

• Hand in pinch point

21.2 Friction Welding: Common Metals 21. Friction Welding

Nearly all metals that are not self-lubricating when dry can be 21.1 Friction Welding Health Safety Hazards Summary welded by friction welding. Many and dissimilar metals can be joined by friction welding. Hazard Sources

21.3 Friction Descriptions Hand/eye injuriesWelding Process Rotating parts

Noise process Friction welding is used to joinFriction partswelding of similar size and cross Hand(at injuries in pinch section the faying surfaces) by Hand holding onepoint part stationary and

rotating the other part while applying pressure to the parts (Figure 2.29). Friction supplies to the parts, 21.2 Friction Welding:heat Common Metalsand they flow together plastically with the addition of pressure. Nearly all metals that are not self-lubricating when dry can be welded by friction Friction welding. Many dissimilar metals can Safety be joinedHazards by friction welding. 21.4 Welding Health and

Discussion 21.3 Friction Welding 21.4.1 Hand and eyeProcess injuries Descriptions

Friction welding used to join of similar size andacross sectionhaz(at the Rotating parts,is collets, andparts chucks represent potential faying surfaces) by holding one part stationary and rotating the other part while ard to operators. Mechanical guards and shields are recommendapplying pressure to the parts (Figure 2.29). Friction supplies heat to the ed. Two-handed switches and interlocks may also be required parts, to and they flow togetherworkers plastically withcontact the addition pressure.equipment adequately protect from withofmoving

Figure Basic arrangement ofof a direct-drive welding machinemachine Figure 2.29:2.29: Basic arrangement a direct-drive welding Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

111

21.4 Friction Welding Health and Safety Hazard Discussion 21.4.1 Hand and eye injuries

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

and parts. Lockout/Tagout procedures may be required for servicing friction welding equipment. 21.4.2 Noise The scream of hot metal being rubbed against itself and then being squeezed together is sufficiently loud to require hearing protection for personnel in the vicinity of friction welding devices.

22. Explosion Welding 22.1 Explosion Welding Health and Safety Hazards Summary Hazard

Sources

Hand/eye injuries and death

• Explosions

Noise

• Explosions

Fume

• Jet from faying interface

22.2 Explosion Welding: Common Metals • Aluminum alloys • Carbon and alloy steels • Copper alloys • Columbium • Cobalt alloys • Gold • Nickel alloys • Magnesium alloys • Platinum • Silver • Stainless steels • Titanium • Joining of dissimilar metals is a common use of explosion welding.

22.3 Explosion Welding Process Descriptions Solid-state welding of similar or dissimilar metals can be achieved by forcing them into intimate contact by controlled detonation of a rapid oxidizer, or explosive. Cladding of flat plate (e.g., stainless steel cladding of carbon steel petrochemical reactor ves112

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sel components) is a common use of explosion welding. The part to be clad is the base component. This is separated from the cladcladding (prime component) by an air gap (Figure 2.30). The explosive is ding (prime component) by an air gap (Figure 2.30). The explosive placed on top of the prime component and detonated in a manner that causes is placed on top of the prime component and detonated in a manthe shock wave to move linearly across the prime component (Figure 2.31). ner that causes the shock wave to move linearly across the prime cladding (prime component) an air gap (Figure 2.30). surface, The explosive The high-velocity shock waveby progresses across the faying causing isa component (Figure 2.31). The high-velocity shock wave progresses placed on top primefrom component and detonated manner causesa jet of fume to of bethe emitted the weld and forcing in thea two partsthat to form across the faying causing a jet of fume to be emitted from the shock wave tosurface, move solid-state metallic bond.linearly across the prime component (Figure 2.31). the weld and forcing two parts toacross form the a solid-state metallic The high-velocity shockthe wave progresses faying surface, causing a bond. jet of fume to be emitted from the weld and forcing the two parts to form a solid-state metallic bond.

Figure 2.30: Typical component arrangement for explosion welding

Figure 2.30: Typical component arrangement for explosion welding Figure 2.30: Typical component arrangement for explosion welding

Figure 2.31: Action among components during explosion welding Figure 2.31: Action among components during explosion welding

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22.4 Explosion Welding Health and Safety Hazards Discussion 22.4.1 Hand and eye injuries and death Handling explosives is an inherently dangerous activity. Each state has licensing requirements for purchasing, storing, and using explosives. It is probable that a state “Blaster’s License” will be required for employing this welding process and that state laws will regulate certain aspects of this operation. The OSHA standard for explosive and blasting agents (29 CFR 1910.109) offers guidance for use of explosives. The reader is well advised to refer to this standard. Some of the topics addressed include: • Storing explosives in a magazine. There are several pages describing how the magazine is to be constructed. • Specific requirements for vehicles to be used to transport explosives. • Specific procedures for use and storage of explosives. 22.4.2 Noise Explosions are noisy, and hearing protection devices adequate for brief intense sound pressures are prudent. 22.4.3 Fume It is probable that personnel will not be sufficiently close to the explosion welding process to be overexposed to fume from faying surface interface. Furthermore, this is a sporadic process with a lot of set-up time between welds, reducing the probable time-weighted average exposures. However, because the materials making up the prime component are often relatively toxic metals, it may be prudent to evaluate exposure potentials. If the welding process is being conducted in an area with restricted dilution ventilation, the presence of combustion gases such as NOx should be investigated prior to reentry after the weld is completed.

23. Ultrasonic Welding (USW) 23.1 USW Health and Safety Hazards Summary Hazard

Sources

Noise

• Welding equipment

Shock and electrocution

• High-voltage power supplies

114

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23.2 USW: Common Metals Metals joined via USW include: • Aluminum alloys • Carbon and alloy steels • Copper alloys • Columbium • Cobalt alloys • Gold • Nickel alloys • Magnesium alloys • Platinum • Silver • Stainless steels • Titanium • Joining of dissimilar metals is a common use of USW.

23.3 USW Process Description Ultrasonic welding simultaneously applies pressure and vibratory energy to thin-section workpieces to produce a solid-state weld. Although there are several types of USW equipment, the Wedge–Reed figure (Figure 2.32) illustrates the fundamentals of the technique. The parts to be joined are clamped between a “sonotrode” and an anvil. At the same time, vibratory force is applied. Oscillating shear forces are created at the interface of the faying surfaces that result in “elastoplastic deformation” and atomic diffusion across the interface. The material recrystallizes to form a metallic bond between the two parts. High-power equipment (1200 W to 8000 W) is generally operated at lower frequencies (10 kHz to 20 kHz). Lower power equipment more often produces higher frequencies of 40 kHz to 75 kHz.

23.4 USW Health and Safety Hazards Discussion 23.4.1 Noise The range of sound pressure frequencies to which the human ear is sensitive has been variously reported at 30 Hz to 15,000 Hz27 and 20 Hz to 20,000 Hz.28 Because the mechanical vibration imparted to the workpiece is in the range of 10,000 Hz to 75,000 Hz,29 there is some overlap between the range of human hearing and the sound frequencies generated by this process. Consequently, a sound level meter (SLM) survey, and possibly personal dosimetry, Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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FigureWedge–Reed 2.32: Wedge–Reed ultrasonicspot-welding spot-welding system Figure 2.32: ultrasonic system

23.4 Health and Safety Hazards Discussion exposure may beUSW prudent for affected personnel. The occupational limits listed in Table 2.1 are from Bruce, Bommer, and Moritz.30 23.4.1 Noise The OEHS Professional should be cautious in measuring and The rangethe of sound pressure frequencies to ultrasound which the human ear isofsensitive interpreting results of measuring the portion the 27 30 to 20,000 Hz.28 has been variously reported at 30 Hz to 15,000 Hz and 20 Hz sound pressure spectrum. Bruce, Bommer, and Moritz have proBecause the mechanical vibration imparted summary to the workpiece in the range vided a succinct and readily available of theis health ef- of 29 there is some overlap between the range of human 10,000 Hz to 75,000 Hz, fects of overexposure to ultrasound as well as a discussion of meahearing and the sound frequencies generatedcontrols by this process. surement techniques and engineering (TableConsequently, 2.1). They a sound level meter (SLM) survey, and possibly personal dosimetry, may be note the following: prudent for affected personnel. The occupational exposure limits listed in • The betweenand ultrasound Table 2.1 arerelationship from Bruce, Bommer, Moritz.30 overexposure and hearing impairment is not well defined. Copyright AIHA®

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Table 2.1: Various Occupational Exposure Limits (in dB)e Sound Pressure Levels in One-Third Octave Bands Proposed by (*) Frequency in kHz

1

2

3

4

5

6

7

8

8

90

75

—

—

—

—

—

—

10

90

75

—

—

—

80

—

—

12.5

90

75

75

85

—

80

—

—

16

90

75

85

85

—

80

—

75

20

110

75

110

85

105

105

75

75

25

110

110

110

85

110

110

110

100

*Legend:

31.5

110

110

110

85

115

115

110

110

40

110

110

110

85

115

115

110

110

50

110

—

110

—

115

115

110

110

1–Japan (1971) 2–Acton (1975) 3–USSR (1975) 4–USAF (1976)

5–Sweden (1971) 6–USA ACGIH (1988) 7–INTL IRPA (1984) 8–Canada (1989)

• Other health effects may include local tissue heating and headache, sore throat, dizziness, and nausea as well as annoyance, distraction, and stress. • Third-octave band analyzers are more appropriate than equipment designed for A-weighted data “since ultrasound exposure limits (whether for hearing conservation or psychologically related problems) are often given in one third octave bands. . .”31 • Microphones may need to be ¼ inch in diameter or less to achieve a flat frequency response. However, small microphones may exhibit lower sensitivities and higher noise-tosignal ratios than desirable. • SLMs and dosimeters that meet OSHA’s Type II criteria are not likely to be appropriate because the Type II criteria do not include tolerance limits above 10,000 Hz. • Ultrasound is more directional than audible sounds, requiring multiple measurements in terms of directionality as well as location. • Available risk-damage criteria (exposure limits) do not address the variable pulse length, pulse frequencies, and pulse repetition rates characteristic of ultrasound welding. From Table 21.16 in Chapter 21: Noise, Vibration, and Ultrasound (Ref. 30). Reprinted with permission.

e

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All is not lost, however, as these authors also note that specialized equipment, techniques, and calibration procedures can be employed to overcome these hurdles. The primary message for the OEHS Professional is to avoid assuming that conventional SLM data are useful for ultrasound exposure assessments. 23.4.2 Shock and electrocution See Section 16.5, LBW, LBC, and LBD: Shock and Electrocution.

24. Thermal Spraying (THSP) Also: “Metallizing,” “Metal Spraying,” or “Flame Spraying.”

24.1 THSP Health and Safety Hazards Summary Hazard

Sources

Compressed gases

• Oxygen and fuel gases

Electrical shock and electrocution

• Plasma equipment

Fire hazards

• Hot/molten metal spray

Eye and skin damage

• Nonionizing radiation

Freeze “burns”

• Liquefied oxygen lines and equipment

Noise

• THSP processes

Products of flux decomposition, including carbon monoxide

• Flux coatings and sprays

Thermal burns

• Handling hot metal

Metal fumes

• Parent metal • Sprayed metal

24.2 THSP Common Metals Metals applied by THSP include but are not limited to: • Aluminum alloys • Brazing filler metals • Carbides • Ceramics • Chromium • Cobalt • Columbium • Carbon and low-alloy steels • Molybdenum 118

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� Columbium Welding Health and Safety: � Carbon and low-alloyA Field steelsGuide for OEHS Professionals, 2nd edition � Molybdenum �• Nickel Nickel �• Soldering filler metals Soldering filler metals �• Stainless steels Stainless steels � Tantalum • Tantalum � Tungsten • Tungsten

2.3 THSP Process Description 24.3 THSP Process Description The term “Thermal Spraying” encompasses a number of proThe term “Thermal Spraying” encompasses a number of processes that cessesathat deposit a heated andmaterial finely divided a subdeposit heated and finely divided onto a material substrate onto or workpiece strate or workpiece (Figure Themay material to be to applied may (Figure 2.33). The material to be2.33). applied be delivered the torch (or “gun”) as a wire, or(or powder. Asas theasurfacing materials pass through be delivered torod, thecord, torch “gun”) wire, rod, cord, or powder. the they become heated bypass one ofthrough three methods: Astorch, the surfacing materials the torch, they become heated by one of three methods: � Oxyfuel flame �• Electric arcflame Oxyfuel �• Plasma gasarc Electric • Plasma gas

Figure Schematicview view of spray system Figure 2.33:2.33: Schematic of wire wireflame flame spray system

The hot and/or molten surfacing material is then impinged upon The and/or molten surfacing is then impinged the hot workpiece (Figure 2.34).material This process may be upon usedthe to workpiece build up (Figure 2.34). apply This process may be to build uplayer, worn or parts, apply worn parts, a corrosionor used wear-resistant apply sol-a corrosionwear-resistant layer, or apply or brazing filler metals dering oror brazing filler metals prior to soldering joining metals by those processes. In some cases, a flux may be applied, usually as a powder fed to the torch and transferred to the workpiece via the flame or arc.

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prior to joining metals by those processes. In some cases, a flux may be applied, usually as a powder fed to the torch and transferred to the workpiece via the flame or arc.

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

Figure 2.34: Cross-section ofwire, typical orspray cordgun flame Figure 2.34: Cross-section of typical rod, wire, or cordrod, flame spray gun

2.4 THSP Health and Safety Hazards Discussion 24.4 THSP Health and Safety Hazards Discussion 2.4.1 OFW THSP processes 24.4.1 OFW THSP processes

See Section 10.4, OFW Health and Safety Hazards Discussion. See Section 10.4, OFW Health and Safety Hazards Discussion. TheAWS AWSrecommends recommends protection with the following shade The eye eye protection with the following shade numbers: numbers: Operation Operation WireWire flameflame spraying spraying WireWire flameflame spraying molybdenum spraying molybdenum Flame spraying metalmetal powder Flame spraying powder Flame spraying exothermics Flame spraying exothermics

Filter Shade Number Filter Shade Number 5 5 5 to 6 5 to 6

5 to 6 5 to 8

5 to 6 5 to 8

24.4.2 Electric arc THSP processes 2.4.2 Electric arc THSP processes See Section 3.4, GMAW Health and Safety Hazards Discussion. See 3.4, GMAW Health and Safety Hazards TheSection AWS recommends eye protection with theDiscussion. following shade The AWS recommends eye protection with the following shade numbers: numbers: Operation Operation Plasma and arc spraying Plasma and arc spraying

Filter Shade Number Filter Shade Number 9 to 12 9 to 12

24.4.3 Plasma THSP processes See Section 9.4, PAW Health and Safety Hazards Discussion. The AWS recommends eye protection with the following shade numbers: Operation Plasma and arc spraying 120

Filter Shade Number 9 to 12

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24.4.4 Fire hazards The finely divided metallic powders most frequently used for THSP processes should be regarded as potential sources of fuel for dust explosions.32 The AWS recommends using booth-type capture hoods and wet-type dust collectors for controlling dust THSP concentrations. Other combustibles should be removed from the THSP work area, and sources of ignition other than those required for the THSP process should be removed or isolated. 24.4.5 Fumes Thermal spraying generates substantial fumes, and use of respiratory protection may be necessary in addition to the engineering controls noted above. 24.4.6 Noise Thermal spraying is often noisy, and hearing protection may be required during this process.

25. Surfacing Also, “Cladding” or “Hardfacing.”

25.1 Surfacing Health and Safety Hazards Summary Hazard

Sources

Compressed gases

• Oxygen and fuel gases

Electrical shock and electrocution

• Arc and plasma equipment

Fire hazards

• Hot/molten metal spray

Eye and skin damage

• Nonionizing radiation • Laser radiation

Freeze “burns”

• Liquefied oxygen lines and equipment

Noise

• Surfacing processes

Products of flux decomposition, including carbon monoxide

• Flux coatings and sprays

Thermal burns

• Handling hot metal

Metal fumes

• Parent metal • Surfacing metal

Ergonomic concerns

• Highly repetitive work in tight quarters

Confined space concerns

• Repairs in reactor/mixing vessels

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25.2 Surfacing Common Metals Metals applied for surfacing purposes include but are not limited to: • Aluminum alloys • Brazing filler metals • Carbides • Ceramics • Chromium • Cobalt • Copper • Carbon and low-alloy steels • Manganese (austenitic steels may contain 11 to 20 percent manganese) • Nickel • Stainless steels • Tantalum • Tungsten

25.3 Surfacing Process Description Although both “Surfacing” and “Thermal Spraying” describe processes that deposit material in layers on a parent metal substrate (workpiece), surfacing uses welding processes that melt the workpiece. Thermal spraying, by comparison, does not melt the workpiece. Surfacing operations may use almost any of the welding processes described in this volume. The vocabulary used in shop settings to describe the various surfacing operations is often abused. However, the AWS has categorized surfacing as follows: • Cladding is the application of a corrosion-resistant layer of weld deposit to the workpiece. This is typically performed via SMA or SAW, but GMAW and FCAW are also used. • Hardfacing applies wear- or abrasion-resistant metal to the workpiece. Hardfacing may use nearly any welding process. • Buildup refers to adding more metal of the same type as the workpiece. Differences in alloy are minimal or nonexistent. The intent of “buildup” is to alter or restore the shape of the workpiece. • Buttering is a surfacing operation performed for the purpose of altering the metallurgical properties of the workpiece. For example, a layer of low-carbon steel may be “buttered” onto high-carbon steel to reduce propensity for cracking. 122

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25.4 Surfacing Health and Safety Hazards Discussion 25.4.1 Process hazards Having identified the welding process to be used (e.g., SMA, SAW, GMAW, or FCAW), refer to the relevant section of this volume for a summary of the hazards associated with the process. Additionally, carbon dioxide (CO2) and neodymium:YAG (Nd:YAG) lasers may be used in cladding. Both emit invisible infrared radiation. Nd:YAG lasers at 1064 nm target the retina and skin, and the CO2 at 10.6 µm targets the cornea and superficial layers of skin. The beams may be used in a continuous mode (called continuous wave, CW), or they may be pulsed. Potential hazards are associated with exposure to the direct beam or scattered radiation above the applicable exposure limit. 25.4.2 Ergonomic concerns When feasible, surfacing of large areas is frequently performed by automatic or semiautomatic equipment. From the ergonomic perspective, this is a desirable trend because surfacing is very often highly repetitive work. Nevertheless, manual surfacing remains dominant for small parts and repair work. When repair work is carried out in confined spaces, this repetitive work can require awkward body/limb positions and lead to possible ergonomic concerns. 25.4.3 Confined space concerns During industrial repair and maintenance work, surfacing operations are frequently performed on site inside reactor and/or mixing vessels. Because many metals used for surfacing applications have been identified as fairly toxic (e.g., Ni, Cr, Co, Cd), surfacing work in confined spaces represents an elevated health hazard potential compared to the same work in open areas. Inert gases used for shielding in the GMAW process may introduce asphyxiation as a possible hazard when employing GMAW in this application.

References

1. O’Brien RL (ed.). Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991. 2. Amos DR, et al. Shielded Metal Arc Welding, Chapter 2 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 44. Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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3. Barnes GC. Flux Cored Arc Welding, Chapter 5 in R.L. O’Brien (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 190. 4. Breslin AJ and Harris WB. Use of thoriated tungsten electrodes in gas shielded arc welding. Am Ind Hyg Assoc Q 13(4): 191–195, 1952. doi: 10.1080/00968205209343889. 5. Crim EM and Bradley TD. Measurements of air concentrations of thorium during grinding and welding operations using thoriated tungsten electrodes. Health Phys 68(5): 719–722, 1995. doi: 10.1097/00004032-199505000-00014. 6. Vinzents P, Poulsen OM, Ligaard R, Simonsen H, et al. Cancer risk and thoriated welding electrodes. Occup Hyg 1(1): 27–33, 1994. 7. Jankovik JT, Underwood WS, and Goodwin GM. Exposures from thorium contained in thoriated tungsten welding electrodes. Ind Hyg Assoc J 60(3):3 83–389, 1999. doi: 10.1080/00028899908984457. 8. Amos DR, et al. Shielded Metal Arc Welding, Chapter 2 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 58. 9. Barnes GC. Flux Cored Arc Welding, Chapter 5 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 190. 10. Shultz BL, et al. Electrogas Welding, Chapter 7 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 268. 11. Kuehn DE, et al. Stud Welding, Chapter 9 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 302. 12. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:1999. Miami, FL: American Welding Society, 1999, p. 29. 13. Personal communication: Don Garvey, July 25, 2001. 14. Personal communication: Don Garvey, July 25, 2001. 15. Arc Welding and Your Health, A Handbook of Health Information for Welding. Fairfax, VA: AIHA, 1984, p. 10. 16. Hitchcock RT and Rockwell RJ, Jr. Laser Radiation: Nonionizing Radiation Guide Series. Fairfax, VA: AIHA Press, 1999, p. 4. 17. Hitchcock RT and Rockwell RJ, Jr. Laser Radiation: Nonionizing Radiation Guide Series. Fairfax, VA: AIHA Press, 1999. 18. Sliney DH. Guide for the Selection of Laser Eye Protection (5th Edition), Laser Institute of America, Orlando FL, 2000. 124

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19. American National Standard Institute. American National Standard for the Safe Use of Lasers (ANSI Z136.1-2000) Orlando, FL: Laser Institute of America, 2000. 20. Chennat JC, et al. Laser Beam and Water Jet Cutting, Chapter 16 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 523. 21. Powers DE, et al. Laser Beam Welding, Chapter 22 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 735. 22. Chennat JC, et al. Laser Beam and Water Jet Cutting, Chapter 16 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 523. 23. Dent P, et al: Resistance Welding Equipment, Chapter 19 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 648. 24. Udall HN, et al. High Frequency Welding, Chapter 20 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 663. 25. Powers DE, et al. Electron Beam Welding, Chapter 21 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 710. 26. Powers DE, et al. Electron Beam Welding, Chapter 21 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 710. 27. Dinardi SR (ed.). The Occupational Environment–Its Evaluation and Control. Fairfax, VA: AIHA Press, 1997, p. 428. 28. Plog BA, Niland J, and Quinland PJ (eds.). Fundamentals of Industrial Hygiene, 4th Ed. Itasca, IL: National Safety Council, 1996, p. 83. 29. O’Brien RL (ed.). Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, Miami, FL, 1991, p. 786. 30. Bruce RD, Bommer AS, and Moritz CT. Chapter 21: Noise, Vibration and Ultrasound. In The Occupational Environment–Its Evaluation and Control, DiNardi SR (ed.): Fairfax, VA: AIHA Press, 1997, pp. 479–483. 31. Bruce RD, Bommer AS, and Moritz CT. Chapter 21: Noise, Vibration and Ultrasound. In The Occupational Environment–Its Evaluation and Control, DiNardi SR (ed.): Fairfax, VA: AIHA Press, 1997, p. 481. Chapter 2: Welding Processes Copyright AIHA® For personal use only. Do not distribute.

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32. Sampson ER, et al. Thermal Spraying, Chapter 28 in O’Brien RL (ed.) Welding Handbook, 8th Ed., Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 888.

126

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Appendix: Case Studies Case Study #1: Carbon Monoxide in Confined Spaces During CAC-A Work Summarized below are personal monitoring results for carbon monoxide (CO) performed by Stephanie Carter during petrochemical turnarounds (maintenance and repair). CAC-A work in confined spaces indicates a progressive increase in probable CO exposures with increasing “blow-back” of the stream of air and fume from the CAC-A process into the workers’ breathing zones. This progression is illustrated in Tables A-2.1, A-2.2, and A-2.3. Table A-2.4 offers a qualitative summary of potential for exceeding the ACGIH TLVTWA of 25 ppm and the NIOSH Ceiling REL of 200 ppm.a Appendix Table A-2.1: CO Concentrations During CAC-A Severing in Confined Spaces Process

Sample Period

Sample Period TWA

Max STEL

Cut floor

296 min

9 ppm

17 ppm

46 ppm

Cut cyclone

600 min

9 ppm

39 ppm

143 ppm

Seam prep

120 min

2 ppm

6 ppm

27 ppm

Max Peak

Cut cyclone

120 min

9 ppm

9 ppm

139 ppm

Cut cyclone

195 ppm

14 ppm

N/A

98 ppm

Data set GM

N/A

7 ppm

14 ppm

75 ppm

CAC-A, air carbon arc cutting; GM, geometric mean; ppm, parts per million; STEL, short-term exposure limit; TWA, time-weighted average.

These data are summarized from Harris MK and Carter SR. Anticipating Exposure Concerns during Confined Space Welding Activities. AIHce, 1998. a

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Appendix Table A-2.2: CO Concentrations During CAC-A Gouging in Confined Spaces Process

Sample Period

Sample Period TWA

Max STEL

Max Peak

Cut liner

218 min

29 ppm

N/A

N/A

Back gouge Cut liner Data set GM

60 min

122 ppm

N/A

280 ppm

151 ppm

62 ppm

119 ppm

208 ppm

N/A

60 ppm

119 ppm

241 ppm

CAC-A, air carbon arc cutting; GM, geometric mean; ppm, parts per million; STEL, short-term exposure limit; TWA, time-weighted average. Appendix Table A-2.3: CO Concentrations During CAC-A Washing in Confined Spaces Process

Sample Period

Sample Period TWA

Max STEL

Max Peak

Prep wall

215 min

37 ppm

N/A

403 ppm

Prep wall

238 min

56 ppm

N/A

520 ppm

Prep wall

373 min

17 ppm

N/A

185 ppm

Area sample during wall prep

227 min

47 ppm

N/A

185 ppm

N/A

36 ppm

N/A

291 ppm

Data set GM

GM, geometric mean; ppm, parts per million; STEL, short-term exposure limit; TWA, time-weighted average. Note that for this data set, the area sample was taken as indicative of exposure potentials for other workers in the confined space who were not directly performing air carbon arc cutting (CAC-A) tasks (e.g., helpers). Appendix Table A-2.4: Potential for Exceeding CO Exposure Limits During CAC-A Tasks in Confined Spaces Process

> 25 ppm

> 200 ppm

Sever

Possibly

Rarely

Gouge

Frequently

Usually

Washing

Usually

Nearly always

CAC-A, air carbon arc cutting; ppm, parts per million.

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Case Study #2: Lead in Confined Spaces During CAC-A Work Personal monitoring results for lead are summarized in Table A-2.5 below for welders working in seven different vessels during five petrochemical turnarounds that yielded 47 air samples. Seventeen were collected during CAC-A only tasks. Ten of these samples were above the OSHA action level of 30 µg/m3, and nine exceeded the OSHA permissible exposure limit (PEL) of 50 µg/m3.a None of the 30 samples collected from welders working in the same vessels exceeded 50 µg/m3, and only one exceeded 30 µg/m3.b Appendix Table A-2.5: Lead Concentrations During Hotwork Tasks in Confined Spaces No. of Samples

Sample Periods

Sample Period TWA Concentration

# > AL

# > PEL

CAC-A only

17

90–519 min

2–620 µg/m

10

9

CAC-A and welding

14

31–425 min

< 6–25 µg/m

1

0

Welding only

16

250–575 min

< 5 to < 12 µg/m3

0

0

Task

3 3

AL, action level; PEL, permissible exposure limit; TWA, time-weighted average. The presence of lead in these air samples (analyzed by NIOSH Method 7300, ICAP scan for metals) was entirely unexpected. To determine the source of the lead, four probable sources were investigated: • Contaminated make-up air from mechanical ventilation; • Analytical errors; • Substrate contamination (e.g., tetraethyl lead residue, presence of lead in the steel, presence of lead in previous welds, and presence of lead in inspection markers); and • Air carbon arc cutting (CAC-A) electrodes.

29 CFR 1910.1025 and 29 CFR 1926.62. These data are summarized from Harris MK and Carter SR. Anticipating Exposure Concerns during Confined Space Welding Activities. AIHCE in 1998, and Harris MK and Carter SR. Investigative industrial hygiene: airborne lead concentrations during arc gouging in confined spaces. Am Ind Hyg Assoc J 55: 1188–1192, 1994. a b

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Investigation of the first three sources did not provide information, suggesting that they were likely sources of lead. However, analysis of samples of CAC-A electrodes used at the petrochemical facility furnished the information summarized in Table A-2.6. Appendix Table A-2.6: Lead Content of CAC-A Rod Components Source (Dia.)

Copper Coating (mg/kg)

Carbon Center (mg/kg)

USA (5/16)

< 0.050

40.1

USA (1/4)

< 0.050

48.0

Japan (5/16)

< 0.050

10.4

Japan (1/4)

< 0.050

9.8

Mexico (5/16)

< 0.050

22.5

Mexico (1/4)

< 0.050

20.7

Thailand (5/16)

< 0.050

11.5

It is worth noting that these concentrations are well below the 1 percent criterion established for listing noncarcinogenic chemical components on material safety data sheets.c The reader is also advised that subsequent air monitoring during CAC-A tasks in open areas did not indicate potential overexposures to lead. This phenomenon appears to be a function of the low PEL for lead and concentration of airborne contaminants even in ventilated confined spaces. In view of the presence of copper cladding on the electrode, and the low PEL for copper fume (0.1 mg/m3 as of 2001), one may also anticipate elevated exposure potentials for copper during CAC-A work in confined spaces.

c

29 CFR 1910.1200 (g).

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3 Welding Equipment: Health and Safety Considerations Incorrect use of welding equipment can lead to needless injuries. This section has been compiled to provide the Occupational and Environmental Health and Safety (OEHS) Professional with an outline of generally accepted and recommended procedures designed to mitigate the safety hazards associated with operation of welding equipment. It is strongly recommended that the literature provided by welding equipment manufacturers (owner’s manuals) be reviewed for procedures and practices pertinent to safe use of the equipment. In the event that the practices and principles described here do not agree with those provided by the manufacturer of the equipment in use, the equipment manufacturer’s recommendations will take precedence over the information offered here.

1. Regulations (U.S.) Portions of the following OSHA General Industry standards are applicable to welding equipment: • • • •

29 CFR 1910.252: General Requirements 29 CFR 1910.253: Oxygen-Fuel Gas Welding and Cutting 29 CFR 1910.254: Arc Welding and Cutting 29 CFR 1910.255: Resistance Welding

Applicable OSHA Shipyard standards include: • 29 CFR 1915.51: Ventilation • 29 CFR 1915.52: Fire Prevention • 29 CFR 1915.53: Welding, Cutting and Heating in Way of Preservative Coatings • 29 CFR 1915.54: Welding, Cutting and Heating in Hollow Metal Structures • 29 CFR 1915.55: Gas Welding and Cutting • 29 CFR 1915.56: Arc Welding and Cutting Construction Industry standards promulgated by OSHA with provisions regulating use of welding equipment include: Chapter 3: Welding Equipment: Health and Safety Considerations Copyright AIHA® For personal use only. Do not distribute.

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• • • •

29 CFR 1926.350: Gas Welding and Cutting 29 CFR 1926.351: Arc Welding and Cutting 29 CFR 1926.352: Fire Prevention 29 CFR 1926.353: Ventilation and Protection in Welding Cutting and Heating • 29 CFR 1926.354: Welding, Cutting and Heating in Way of Preservative Coatings • 29 CFR 1926.406: Electric Welding: Disconnecting Means Although many of the more conspicuous elements of these standards have been annotated below, this does not serve as a replacement for a thorough reading of these standards. The hazards of working with high voltages and amperages as well as concentrated oxidizers and fuels include shock, electrocution, fires, explosions, and death. In view of the seriousness of these hazards, a careful reading of the guidance offered in the federal standards and in ANSI Z49.1.2012 may be deemed prudent.

2. Guidelines and Regulations Specific to Oxyfuel Equipment Oxyfuel equipment has a long history of abuse in the welding environment. This equipment is in common use and has a “margin of built-in safety” that, in the opinion of some users, allows for a certain amount of abuse with minimal fear of repercussion. The well-worn phrase about familiarity breeding contempt comes to mind in this context. In order to correct this tendency to become blasé about the hazards associated with oxyfuel equipment, many welding supply houses offer safety posters that have been provided by welding equipment manufacturers and distributors. Often cartoon-like and amusing, these represent a low-cost way of focusing the employees’ attention on the hazards associated with their equipment. The literature (owner’s manuals) supplied with welding equipment usually provides the detailed information necessary for safe operation of the equipment. Unfortunately, this information is often discarded when the equipment is unpacked. Of course, one may contact the manufacturer for a new copy of the owner’s manual. Other hazards, which may or may not be addressed in the owner’s manual(s), are noted in this section. Sources include excerpts from: 1) the various OSHA welding standards, 2) the AWS Welding Handbook, and 3) ANSI Z49.1:1999. In many instances, the primary hazards associated with oxyfuel equipment 132

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are those associated with compressed gases, noted in Section 3 of this chapter. Among the equipment-specific requirements described in the OSHA standards (other than those relating to compressed gases) are the following: • Employers shall ensure that affected workers have been instructed in the correct use, maintenance, and operation of oxygen and fuel gas supply systems. Employers shall be responsible for judging the competency of these employees before assigning them responsibilities for this equipment. Rules and instructions for use of this equipment shall be readily available. • All hoses, cylinders, regulators, and fittings, etc., shall be kept clean and free from hydrocarbons. • 29 CFR 1926.350(f) emphasizes the following points (much of this material is spread throughout 29 CFR 1910.253, and some is incorporated by reference): – Fuel and oxygen hoses shall be distinguishable from each other. Either different surface textures or different colors are allowed under the OSHA standards. ANSI Z491.2012 10.6.2 requires color coding of the hoses.1 In the United States, these colors are: » Red for fuel gas » Green for oxygen » Black for inert gas or air hose – Hoses carrying oxygen or fuel gases or gases that may constitute other hazards to employees shall be inspected at the beginning of each shift. – When hoses are taped together, no more than 4 inches in each running foot shall be taped. This allows trapped gases escaping from leaks in damaged hoses to escape rather than build up (with consequent explosion possibility) under the tape.2 – Hoses that have been subjected to flashback or show evidence of wear and/or damage shall be tested to no less than 300 psi before being placed back in service. – Hose couplings shall require more than a simple pull to disconnect (e.g., twist and pull or threaded fittings). – Hoses shall be kept clear of stairways, ladders, and passageways.

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• 29 CFR 1926.350(g) offers the following guidance: – Torches shall be inspected at the beginning of each shift for: » Leaking shutoff valves » Leaking hose fittings » Leaking tip connections Leaking equipment shall not be used. • 29 CFR 1910.253(b)(5) and 29 CFR 1926.350(a), (b), (c), and (d) provide detailed lists of precautions and procedures specific to oxyfuel cylinder handling and use. • Paragraph 29 CFR 1910.253(c) describes OSHA’s requirements for manifolding multiple cylinders. 29 CFR 1926.350(e) describes very similar requirements. • Paragraphs (d) and (e) describe OSHA’s requirements for installation, maintenance, and protection of piping systems’ distribution oxygen and fuel gases. • Paragraph (f) addresses OSHA’s requirements for acetylene generators. ANSI Z49.1.2012 also provides a useful listing of oxyfuel practices and precautions. Among them: • Leak test cylinder, hose, and torch connections prior to use. Almost unbelievably, some welders will “flame test” connections with a match or cigarette lighter. The undesirable consequences that may accompany this technique are easily avoided by using leak test solutions (various renditions of soapy water). • Separately purge hoses at the beginning of each day and after changing cylinders. This is intended to remove flammable mixtures from the hoses. Flammable mixtures are to be limited to the torch mixing chamber and tip. • Do not use matches, cigarette lighters, or welding arcs for lighting torches. Friction lighters (“sparkers”) and pilot flames are acceptable. • When torches are used in confined spaces, they shall be shut off unless in use. • When torches are used in confined spaces, they shall be shut off at a point outside the confined space during breaks, lunch, and at change of shift. This activity is usually interpreted as shutting off the valve at the cylinder and purging the lines. 134

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One might note that removing the torches from the confined space altogether is an unequivocal means of ensuring that leaks do not create an unnecessary hazard. However, when the confined space is in the hold of a ship or deep within a petrochemical process tower, workers may be reluctant to drag the hoses in and out of the confined spaces every two hours; hence, the above discussion is offered to provide an alternative means of controlling the effects of unidentified leaks and fuel and oxygen leaks.

3. Compressed Gases and Cryogenic Liquids Note: In preparing this section, the author has made abundant use of the Handbook of Compressed Gases (the CGA Handbook), now in its fourth edition.3 Much of the information presented in this section is summarized from the CGA Handbook, and the reader is encouraged to refer to the CGA Handbook for additional details regarding the handling of compressed gases. Compressed gases are used for fuel, oxidizers, and shielding gases for many of the welding processes in common use. The transportation, storage, and use of these gases represents a set of health and safety hazards that is most conveniently addressed in a separate section rather than endlessly repeated throughout the text. It is believed that this section is likely to be scanned for the purposes of creating a checklist or audit specific for the facility for which the OEHS Professional has responsibility. Consequently, bulleted lists have been used whenever reasonable to facilitate review of this information. The reader is advised that this section does not completely address those precautions used by compressed gas suppliers. As an introductory note, the literature supplied by equipment manufacturers and health and safety organizations is rife with statements to the effect that smoking should be strictly prohibited in areas where compressed or cryogenically stored flammable gases or oxygen are present. These statements could be repeated in this volume innumerable times. In view of the audience for which this book has been compiled, it is thought sufficient to make that statement one time, here:

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FLAMMABLE GASES AND/OR OXIDIZERS SMOKING AND/OR OPEN FLAMES PROHIBITED 3.1 Regulations Specific to Compressed Gases and Cryogenic Liquids The following federal regulations are pertinent to compressed gases used in welding and other hotwork: • 29 CFR 1910.101 Compressed Gases (General Requirements): – Requires inspections and appropriate marking of compressed gas cylinders per USDOT regulations described in 49 CFR Parts 171–179 and 14 CFR Part 103 and CGA pamphlets C-6-1968 and C-8-1962. – Requires that in-plant storage be in accordance with CGA pamphlet P-1-1965. – Requires pressure relief devices per CGA pamphlet S-1.1-1963 and 1965 addenda as well as CGA pamphlet S-1.2-1963. • 29 CFR 1910.102 Acetylene: – Addresses cylinder requirements, piped system requirements, and procedures for acetylene generators and filling of cylinders. • 29 CFR 1910.103 Hydrogen, 28 CFR 1910.104 Oxygen, and 29 CFR 1910.110 Liquefied Petroleum Gases. These regulations all address the following topics with details specific to each gas: – Storage and piping requirements for both liquid and gaseous states. – Specific requirements are listed for distances from gas/ cryogenic liquid storage facilities to other buildings or equipment as a function of the gas/cryogenic liquid storage capacity. – Require pressure relief devices for both liquid and gaseous state equipment. – Describe requirements for equipment assembly and testing for both liquid and gaseous systems.

3.2 Compressed Gas Hazards Among the salient health and safety hazards associated with compressed gases and cryogenic liquids used for welding are: 136

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• High pressure • Extreme cold–cryogenic liquids • Flammability • Asphyxiation • Oxidizing properties • Toxic properties • Corrosive properties • Pyrophoric properties Employee training covering these hazards should be part of the HAZCOM program per 29 CFR 1910.1200.4

3.3 Storage The following practices and precautions are recommended by the CGA: • Cylinders must be secured when stored. (Note that the means of securing is not stringently specified.) Some facilities require metal chains or bands for this purpose because ropes, straps, and other fibrous material may be subject to environmental degradation when used outside for prolonged periods of time. • Do not store cylinders in locations where objects may fall on them or strike them. • Ensure that storage areas are well drained and ventilated. Rust can pit poorly maintained cylinders and compromise structural integrity. • Cylinders may be stored outside if prolonged exposure to dampness, salt-laden air, and excessive temperatures is avoided. • Concrete paving is preferred over asphalt paving for storing liquid oxygen. A leak in the liquid oxygen container could result in a violent exothermic reaction if it comes in contact with hydrocarbons (paving asphalt is a hydrocarbon/gravel aggregate). • Avoid allowing storage area temperatures to exceed 125°F. This may lead to over-pressuring of full cylinders. (Note that the AWS recommends storage temperature criteria of –20°F to 130°F).5 • Do not store fuel gases and oxidizers together. The AWS and ANSI recommend a separation distance between oxygen and fuel gas cylinders of at least 20 feet. When that Chapter 3: Welding Equipment: Health and Safety Considerations Copyright AIHA® For personal use only. Do not distribute.

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distance is not achievable, then a noncombustible firewall at least 5 feet high with a ½-hour fire rating is recommended (ANSI Z49.1:2012).6 • Do not expose compressed gas cylinders to corrosive chemical liquids, gases, or vapors.

3.4 Handling Compressed Gas Cylinders The following practices and precautions are recommended by the CGA in the Compressed Gas Handbook and by the AWS and ANSI in Z49.1:1999 to reduce incidences of mishandling of compressed gas cylinders and the potentially catastrophic outcomes that may result from damaging a compressed gas cylinder. • Close cylinder valves before moving cylinders. This caution also applies to moving an oxyfuel rig on a cart from one location in the shop to another location in the same shop. • When feasible, move cylinders with a hand truck or fork truck using restraining devices to prevent dropping the cylinders or allowing them to strike violently against each other. • Do not move cylinders that are either full or contain residual product by: – Lifting by the valve or valve protection cap – Rolling or dragging in a horizontal position – Using magnetic devices • Do not use ropes, chains, or slings to lift cylinders unless the cylinders have been manufactured with lifting lugs for that purpose. • Use cradles or platforms for lifting cylinders without lugs. • Do not drop or slide cylinders in a manner that may damage them. • Do not ship cylinders that are leaking or damaged unless authorized to do so by the gas supplier. • Maintenance, painting, relabeling, and repair of cylinders (including changing valves) should only be performed by properly trained personnel. • Do not allow compressed gas cylinders to come in contact with electric arcs or become part of an electrical circuit. This precaution applies specifically to welding circuits. If a cylinder comes in contact with an electric arc, notify the gas supplier and obtain authorization prior to returning it. • Do not expose cylinder to direct heat, flame, or temperature extremes. Excessive pressure may result, damaging the cyl138

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inder’s structural integrity. Avoid storing or using in temperatures over 125°F. Note that ANSI Z49.1.2012 recommends a maximum use temperature of 120°F.a • Cylinders exposed to very low temperatures may exhibit low ductility and impact resistance. Avoid exposure to very low temperatures. • When a cylinder has a provision for a valve protection cap, that cap must be in place except when the cylinder is in use and secured. • In addition to or in lieu of valve protection caps, some cylinders have gas-tight outlet plugs or caps that must be in place and secured prior to shipment.

3.5 Using Compressed Gas Cylinders Much of the following information is summarized from the AWS and ANSI recommendations in Z49.1.2012.7 Be aware that the following list is a partial summary of the more conspicuous points and that OEHS Professionals who find themselves working these compressed gas issues would be well advised to review ANSI Z49.1.2012 in its entirety. • Always ensure that cylinders are secured to a cylinder truck, chain, or another steadying device to prevent the cylinders from being knocked over during use. • Employ either adequate distance from welding operations or a shield between the cylinders and the welding operations to ensure that sparks, slag, or flame do not come in contact with the cylinders. • Always attach a regulator to a compressed gas cylinder before using the gas. Release of gases at unregulated pressures (except as noted immediately below) can result in eye injury, embolisms, and fire hazards. • When connecting a regulator to a cylinder, first wipe the threads and seating area clean and visually inspect for damage. Then, briefly “crack” the cylinder valve open to dislodge a Note that the AWS recommends a maximum storage temperature of 130°F in the Welding Handbook, the CGA recommends a maximum of 125°F in the Compressed Gas Handbook, and the AWS offers another recommendation of 120°F in Z49.1:1999. The author agrees with an opinion offered by Don Garvey that the most conservative approach (120°F in Z49.1.1999) is most likely to result in the most favorable outcome.

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vestiges of dust or dirt before connecting the regulator. Do not stand in the “line of fire” from the valve when cracking the valve. Flying dust or dirt represents an eye hazard. • When connecting oxygen cylinder regulators, there is a possibility of igniting regulator components and/or explosive failure of the regulator adjusting screw. To minimize this possibility, ANSI Z49.1.2012 recommends observing the following procedure after the regulator has been connected to the oxygen cylinder: – “Engage the adjusting screw and open the downstream line to drain the regulator of gas. – Disengage the adjusting screw and open the cylinder valve slightly so that the regulator cylinder pressure gauge pointer moves up slowly before opening the valve all the way. – Stand to one side of the regulator and not in front of the gauge faces when opening the valve cylinder.”8 • High-pressure cylinders such as oxygen, argon, or CO2 (not fuel gas cylinders) should be opened all the way to engage the “fully open” seat in the valve assembly. Otherwise, gases will escape past the packing gland surrounding the valve stem. • Keep cylinder valves closed when not in use.

3.6 Cryogenic Liquid Hazards The term “cryogenic liquid” applies to gases that have been subjected to a change of state to the liquid form. This requires lowering of the gas temperature (often below –130°F) as well as storing the gas at elevated pressure. Gases used for welding that may be transported and stored as cryogenic liquids include: • Argon • Helium • Hydrogen • Helium • Nitrogen • Oxygen • LNG (liquefied natural gas) 3.6.1 Hazards associated with cryogenic liquids include: • Human tissue damage due to contact with extremely cold surfaces (vessels, pipes, hoses, valves, etc.). 140

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• Embrittlement of carbon steel, plastics, and rubber and a consequent increased likelihood of failure. • Asphyxiation due to rapid release of cryogenically stored inert gases. • Fire or explosion due to escaping/leaking flammable gases. • Fire or explosion due to rapid oxidation caused by escaping/ leaking oxygen. 3.6.2 The following precautions are recommended for handling cryogenic liquids • Train personnel in the use of the specialized equipment designed for cryogenic liquids. • Personal protective equipment (PPE) is recommended to protect personnel from contact with pipes, containers, valves, hoses, etc., as well as contact with the cold liquid itself, particularly if spilled or splashed during product transfer tasks: – Heavy leather gloves – Long sleeves of heavy material – Face shields and safety glasses – Protective footwear – Heavy aprons • Storage containers and piping must be equipped with pressure release devices to avoid rupture due to vaporization of the cryogenic liquid. 3.6.3 Precautions specific for liquid oxygen Oxygen is highly reactive, and most of these precautions address limiting/controlling the substances with which liquid or gaseous oxygen comes in contact. • 29 CFR 1910.253(4)(iv) describes specific requirements for storage and use of bulk liquid oxygen. Review this standard if bulk liquid oxygen is in use. • All containers, piping, and equipment to be used with liquid oxygen must be scrupulously cleaned specifically for oxygen service. Refer to Compressed Gas Association publication CGA G-4.1, Cleaning Equipment for Oxygen Service.9 • Do not allow liquid oxygen to come in contact with organic materials or flammables of any kind. Examples include: – Oil Chapter 3: Welding Equipment: Health and Safety Considerations Copyright AIHA® For personal use only. Do not distribute.

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– Grease – Asphalt – Kerosene or other organic solvents – Tar – Cloth – Dirt contaminated with hydrocarbons • If liquid oxygen is spilled on oil-soaked asphalt or oil-soaked concrete or gravel or asphalt, do not walk on or roll equipment over that surface. The pressure or slight impact may initiate ignition.10 • If liquid oxygen is spilled on clothing or organic PPE (e.g., leather gloves), immediately remove the clothing to avoid the possibility of ignition or spontaneous combustion of the PPE while it is being worn.

4. Emergency Response Plan The Compressed Gas Association recommends developing a site-specific Emergency Response Plan to address the actions, roles, and responsibilities of affected personnel.11 The presence of compressed gases at a facility is a source of additional hazards that may arise in the event of: • Climatic or weather-related catastrophes; • Accidental release of cryogenic fluids or flammable/toxic gases; • Fires, power outages, explosions; and/or • Highway, rail, or other transportation incidents. Bearing these possibilities in mind, the Emergency Response Plan should include: • Maps/diagrams showing locations of: – Stored gases and cryogenic liquids – Other stored flammable materials – Personnel gathering points – Fire alarms – Emergency exits – Escape routes – Rescue and safety equipment – Hydrants – Fire equipment – Plant controls to be activated in the event of a release 142

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• Evacuation procedures • A list of emergency phone numbers • A list of types and quantities of compressed/liquefied gases on site • Material safety data sheets (MSDSs) for compressed/liquefied gases on site • Employee emergency response training plan • Schedule for discussing the Emergency Response Plan with affected government agencies (e.g., Fire, Police, Rescue) • Schedule for implementing periodic emergency response drills

5. Gas-Specific Remarks A few of the gases used with welding processes exhibit unusual hazards that are outlined below.

5.1 Acetylene Acetylene, when pure, has no odor. However, when produced commercially by combining calcium carbide with water, a distinct garlic-like odor is imparted to the gas. Given an adequate volume of gas, gaseous acetylene is not stable under the following conditions: • Temperatures above 1435°F • Pressures greater than 15-psi gauge (15 psig or 103 kPa) or 30 psi absolute (30 psia or 207 kPa) When these values are exceeded, acetylene may explode violently with little or no provocation. The slightest impact will be sufficient to cause explosive decomposition. Consequently, acetylene cylinders must be treated with greater caution than other common compressed gases. Fortunately, acetylene is soluble in acetone, and this characteristic is useful in storing acetylene. Acetylene cylinders are packed with a porous filler (which historically has included a combination of charcoal and asbestos), and acetone is then added to the filler. Because acetone can absorb up to 25 times its own weight in acetylene, this procedure allows the cylinder to contain acetylene in a solution with acetone. The upper portion of the cylinder contains a small void (less than the critical volume for spontaneous explosive decomposition) into which the dissolved acetylene is allowed to outgas from the acetone and enter the valve/regulator/hose/torch equipment ensemble. Chapter 3: Welding Equipment: Health and Safety Considerations Copyright AIHA® For personal use only. Do not distribute.

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Because of the limited free volume of acetylene in the cylinder, the gauge pressure for the cylinder side of an acetylene regulator may safely read up to 250 psig. However, the working side of the regulator must not be adjusted to values greater than 15 psig (30 psia). Although acetylene may spontaneously decompose under pressures as low as 6 psig under the right conditions of volume and container shape, 15 psig has been shown to be a very low-risk working pressure for welding equipment using this gas.12 Other noteworthy characteristics and precautions regarding acetylene in the welding environment include the following: • Because of the possibility of flashback in the fuel hoses, the AWS and ANSI recommend that acetylene cylinder valves be opened a maximum of 1½ and preferably only ¾ turn. This precaution is intended to facilitate quick closing of the fuel gas cylinder valve in the event of a flashback or other emergency.13 Always open acetylene cylinders the minimum necessary to allow for adequate gas flow. • Pipes/tubing for distribution of acetylene must be made only of steel or wrought iron pipe. • Fittings must be welded or made with flanged or threaded fittings. • Cast iron fittings are not allowed. • Do not use copper for acetylene lines. Acetylene reacts with copper to form explosive acetylide compounds. • Brass with less than 65 percent copper is acceptable for acetylene service. • Acetylene pipes and lines should be installed in accordance with: – ANSI/ASME B13.3 Chemical Plant and Petroleum Refinery Piping.14 – NFPA 51 Standard for the Design and Installation of Oxygen-Fuel Gas Systems for Welding, Cutting, and Allied Processes.15 • Store acetylene cylinders at least 20 feet from oxygen cylinders or separate acetylene cylinders from oxygen cylinders by a noncombustible wall at least 5 feet high with a fire-resistance rating of ½ hour. • In the United States, acetylene storage must be limited to 2500 ft3 per building. • Storage in a horizontal position may result in solvent loss and will expose the fuse plug on the cylinder base to poten144

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tial damage. The General Industry standard requires storing acetylene cylinders with the “valve end up.”16 • Chapter 11 of the Compressed Gas Handbook provides additional information regarding acetylene safety and health issues.

5.2 Methylacetylene-Propadiene (MAPP Gas) MAPP gas is a mixture of methylacetylene and propadiene stabilized with alkane and alkene hydrocarbons. These alkane and alkene stabilizers render the methylacetylene and propadiene mixture shock insensitive, and stabilized MAPP gas is consequently less hazardous to work with than acetylene. MAPP gas has a strong odor above 100 ppm and is associated with central nervous system (CNS) symptoms at 5000 ppm.

5.3 Oxygen The two primary uses of oxygen in the welding environment are 1) as an oxidizer for fuel gases and 2) as a “hangover cure.” Although oxygen has been demonstrated to be an effective oxidizer, its efficacy in overcoming the effects of ethanol over-dosage has not been proven. Because welding shop folklore continues to mistakenly attribute curative prowess to oxygen, it may be worthwhile to train/remind welders that: • Inhalation of high concentrations of pure oxygen may lead to biological conversions of ordinary molecular oxygen (O2) into free oxygen radicals, which are highly reactive in the body. These can combine to form: – Hydrogen peroxide (H2O2) and/or – The hydroxyl free radical (OH°) • Hydrogen peroxide and the hydroxyl free radical combine with fatty tissues (lipids) and can damage cell membranes and other vital cell structures. • This damage is often expressed as local irritation of the mucous membranes. Extended overexposure (usually measured in hours, not just a few minutes) may lead to lung damage.17 Unfortunately, some workers become so inured to the hazards of working with compressed gases that they ignore the risks associated with using oxygen as a convenient source of compressed gas for blowing off their clothing at the end of a shift or prior to breaks. This practice may result in the spontaneous combustion of Chapter 3: Welding Equipment: Health and Safety Considerations Copyright AIHA® For personal use only. Do not distribute.

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many types of cloth, particularly cotton, the primary fiber in denim jeans. This hazard may be increased when clothing is contaminated with hydrocarbons such as oil or grease. This contamination can easily occur when welders are performing maintenance tasks on used equipment.

6. Electric Arc Equipment Electric arc equipment is used for the following common welding processes: • Shielded metal arc welding (SMAW or “Stick Welding”) • Gas tungsten arc welding (GTAW, “HeliArc” or “TIG Welding”) • Gas metal arc welding (GMAW or “MIG”) • Flux cored arc welding (FCAW) • Submerged arc welding (SAW or “SubArc”) • Electrogas welding (EGW) • Electroslag welding (ESW) • Stud welding (SW) • Plasma arc welding (PAW) Electrical hazards are caused by contact with energized electrical conductors and can cause: • Burns and death from shock; • Involuntary muscular contractions and possible injuries from violent contact with the surroundings or falling from a ladder or scaffold; • Respiratory paralysis and death; • Ventricular fibrillation and death; and • Cardiac arrest and death. These effects occur when current passes through the body, completing an electrical circuit. The extent and type of electrical injury is a function of voltage and amperage of the current, the electrical path through the body, and the duration of the exposure. Low voltages (< 600–1000 volts) are most often associated with muscular contractions and cardiovascular/pulmonary effects, whereas high-voltage current is more often associated with burns. Even a 110-volt electrical current can be fatal. These exposures can occur when light bulbs break, insulation on power cords to electrical equipment is damaged, welding cables are not properly insulated, or energized conductors are present in electrical vaults. 146

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The hazards specific to each of the electric arc process are annotated in the relevant sections of Chapter 2, Welding Processes. As noted above for oxyfuel processes, owner’s manuals provided with welding equipment usually contain the detailed information necessary for safe operation of the equipment. Other hazards that may or may not be addressed in the owner’s manual(s) are noted in this section. These include excerpts from: 1) the various OSHA Welding Standards, 2) the AWS Welding Handbook, and 3) ANSI Z49.1.2012. Most of the electric arc welding health and safety guidance in these sources addresses SMAW welding. This emphasis may be due to the following factors: • SMAW is the most common welding process with the greatest number of welders at risk. • SMAW equipment is most often used in the manual mode rather than the automatic mode with consequently greater opportunities for personnel to be exposed to the welding hazards due to their proximity to the process. • SMAW equipment is widely used in shipyard work, construction work, and industrial maintenance and repair. Compared to the automatic and semiautomatic welding environments becoming more common in manufacturing, these workplaces may be associated with increased chances of equipment damage by nonusers and misuse by partially trained individuals. Among the electric arc equipment-specific requirements described in the OSHA standards are the following: • Whenever practicable, other employees and personnel working in the area of electric arc welding and cutting shall be shielded from the arc and spatter by noncombustible and flameproof screens. • Workmen assigned to operate or maintain arc welding equipment shall be acquainted with the requirements of this section (29 CFR 1910.254) and with 29 CFR 1910.255(a), (b), and (c). • Employers shall ensure that affected employees receive training covering the following topics [29 CFR 1926.352(d) and 29 CFR 1910.254(d)]: – Unattended electrode holders shall not be left with electrodes in them.

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– Unattended electrode holders shall be placed so that they do not come in contact with employees or conducting objects. – Do not dip hot electrode holders in water.b – Welding machine frames shall be grounded. – Cooling water leaks are not allowed. – Operators shall report any defective equipment to their supervisor, and the equipment shall not be used until repairs have been made by qualified personnel. – Welding machines that have become wet shall be thoroughly dried and tested before being used. – Welding machines shall be de-energized (open the power supply switch) when the welder/cutter has occasion to leave the work for an appreciable period of time (e.g., breaks, lunch, and end of shift). The specifics for this directive are provided in 29 CFR 1926.406(c), which requires that a “disconnecting means shall be provided in the supply circuit for each motor-generator arc welder and for each AC transformer and DC rectifier arc welder which is not equipped with a disconnect mounted as an integral part of the welder.” • Use only electrode holders designed for the purpose and ensure that they are maintained per manufacturer’s directions.c • Note that 29 CFR 1910.254(c) lists several specific requirements for grounding electric arc welding circuits. Review of this regulation is recommended. • Cables shall be free from repairs or splices for a minimum of 10 ft from the electrode holder. Exceptions are made for standard insulating cable connectors and for splices whose insulating qualities are equal to that of the cable. Field repairs with electrician’s tape seldom meet the requirement for use within 10 ft of the electrode holder. Rubber or friction SMAW electrode holders can become uncomfortably hot when used in a high production rate setting. Dipping the hot electrode holder in water with the intent of cooling the holder may cause a shock or electrocution. Water-cooled electrode holders or changing to the GMAW processes may be a reasonable alternative to electrocuting welders. C Although it may seem beyond credulity, while serving in the U.S. Army, this author has observed a welder using a pair of Vice-Grip pliers connected to a welding cable via a C-clamp in lieu of an SMAW “stinger.” In defense of that practice, one may note that creativity and a “can-do” attitude are to be admired when working under extraordinary circumstances. b

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tape repairs are allowed for covering bare cable exposed when insulation is damaged and the site is more than 10 ft from the electrode holder. Any repairs should be inspected frequently to ensure that they have not become compromised in service. • Electrical conduits or pipes and pipelines carrying flammable gases or liquids may not be used as ground return portions of welding circuits. • Welding cables shall be completely insulated, flexible, and capable of carrying the required current. Note that the recommendations in Table 3.1 are not from OSHA but from the AWS.18 Table 3.1: Recommended Copper Welding Cable Sizes AWG Cable Size of Combined Length of Electrode and Ground Cables

Power Source Size (Amps)

Duty Cycle (%)

0–50 ft 0–15 m

50–100 ft 15–30 m

100

20

6

4

100–150 ft 150–200 ft 30–46 m 46–61 m 3

200–250 ft 61–76 m

2

1

180

20–30

4

4

3

2

1

200

60

2

2

2

1

1/0

200

50

3

3

2

1

1/0

250

30

3

3

2

1

1/0

300

60

1/0

1/0

1/0

2/0

3/0

400

60

2/0

2/0

2/0

3/0

4/0

500

60

2/0

2/0

2/0

3/0

4/0

600

60

2/0

2/0

2/0

4/0

Two 3/0 cables in parallel

AWG, American wire gauge

In addition to the requirements listed in the CFRs, the AWS offers the following precautions and preventive measures in ANSI Z49.1.2012: • Unusual work conditions may require specific steps to protect the welder. Examples of unusual work conditions include: Chapter 3: Welding Equipment: Health and Safety Considerations Copyright AIHA® For personal use only. Do not distribute.

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– Water in the work area (rain, coolant leaks, maritime work) and excessive perspiration in hot climates. » Maintain gloves and clothing in a dry condition to minimize conductivity. This may require multiple changes of gloves and some items of clothing. » Protect the welder from electrically conductive surfaces with rubber-soled shoes (at a minimum). Use of a rubber mat or dry boards is recommended.19 – Locations requiring restricted freedom of movement (kneeling, sitting, lying) with physical contact with conductive parts. » Insulate conductive parts in the vicinity of the operator per wet work, above. Refer to ANSI/NEMA EW1, Electric Arc Welding Power Sources for other examples of unusual service conditions.20 • Portable control devices shall not be connected to voltages greater than 110 volts. • Do not operate welding equipment at amperages or duty cycles above their rated capabilities. This precaution is to avoid overheating and possible fire. • “Installation including grounding, necessary disconnects, fuses, and types of incoming power lines shall be in accordance with ANSI/NFPA 70 and NFPA’s National Electrical Code, and all local codes.”21,22 • Do not use chains, elevators, and wire ropes to conduct electrical current. • Section 11.3.6 provides specific instructions regarding minimizing shock hazards for multiple welders working closely together on one structure. • Welding machine output shall be de-energized when changing electrodes or contact tips. An exception is made for SMAW, where it is a common and accepted practice to remove electrodes by squeezing the electrode holder clamp to release the electrode and then insert a new electrode without de-energizing the machine.

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References

1. Rubber Manufacturers Association. IP-7: Specifications for Rubber Welding Hose. Eighth Edition. Philadelphia, PA: Rubber Manufacturers Association, 1999. 2. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:1999. Miami, FL: American Welding Society, 1999, p. 24. 3. Compressed Gas Association, Inc. Handbook of Compressed Gases, 4th Ed. Arlington, VA: Compressed Gas Association, Inc., 1991. 4. “Occupational Safety and Health Standards,” Code of Federal Regulations, Subpart Z–Toxic and Hazardous Substances, Hazard Communication Standard (29 CFR 1910.,1200(e) and (h). 5. Spies GR, et al. Safe Practices, In Conner LP (ed.), Welding Handbook, 8th Ed., Volume 1, Welding Technology. Miami, FL: American Welding Society, 1991, p. 536. 6. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:1999. Miami, FL: American Welding Society, 1999, p. 27. 7. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:1999. Miami, FL: American Welding Society, 1999, pp. 28–30. 8. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:1999. Miami, FL: American Welding Society, 1999, pp. 28–29. 9. Compressed Gas Association, Inc. CGA G-4.1 Cleaning Equipment for Oxygen Service, 4th Ed. Arlington, VA: Compressed Gas Association, 1991. 10. Compressed Gas Association, Inc. Handbook of Compressed Gases, 4th Ed. Arlington, VA: Compressed Gas Association, Inc., 1991, p. 25. 11. Compressed Gas Association, Inc. Handbook of Compressed Gases, 4th Ed. Arlington, VA: Compressed Gas Association, Inc., 1991, p. 33. 12. Compressed Gas Association, Inc. Handbook of Compressed Gases, 4th Ed. Arlington, VA: Compressed Gas Association, Inc., 1991, p. 226. 13. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:2012. Miami, FL: American Welding Society, 2012, p. 29.

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14. American Society of Mechanical Engineers. ASME/ANSI B31.3–1999 Chemical Plant and Petroleum Refinery Piping. New York: American Society of Mechanical Engineers, 1999. 15. National Fire Protection Association. NFPA 51B: Five Prevention During Welding, Cutting and Other Hotwork. Quincy, MA: National Fire Protection Association, 1999. 16. Occupational Safety and Health Administration (OSHA). 29 CFR 1910.253(b)(3)(ii). 17. Compressed Gas Association, Inc. Handbook of Compressed Gases, 4th Ed. Arlington, VA: Compressed Gas Association, Inc., 1991, p. 558. 18. Amos, DR, et al. Shielded Metal Arc Welding, Chapter 2 in O’Brien RL (ed.) Welding Handbook, 8th Edition, Vol. 2, Welding Processes. Miami, FL: American Welding Society, 1991, p. 51. 19. Spies GR, et al. Chapter 16, Safe Practices. In Conner LP (ed.), Welding Handbook, 8th Ed., Vol. 1, Welding Technology, Miami, FL: American Welding Society, 1991, p. 540. 20. National Electrical Manufacturers Association. ANSI/NEMA EW1–1988, Electric Arc-Welding Power Sources. Washington, DC: National Electrical Manufacturers Association, 1988. 21. National Fire Protection Association. ANSI/NFPA 70B, Electrical Equipment Maintenance. Quincy, MA: National Fire Protection Association, 2019. 22. National Fire Protection Association. 2020 NEC National Electrical Code. Quincy, MA, National Fire Protection Association, 2020.

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4 Welding and Cutting in Restricted, Enclosed, or Confined Spaces1 This chapter emphasizes the health hazards associated with welding and cutting in environments that impede the dispersion of atmospheric contaminants. For the sake of brevity, the term “confined spaces” is used throughout this chapter. However, it should be borne in mind that not all workspaces that restrict dispersion of welding and cutting fumes and gases meet the definition of a permit-required confined space in 29 CFR 1910.146. An example would be a “fire box,” which controls the dispersion of welding sparks and spatter by means of a temporary scaffold structure surrounded by fire blankets. These are common in petrochemical repair and maintenance scenarios. Fire boxes may be as small as 6 ft by 6 ft and effective at limiting fume dispersion as well as limiting dispersion of the sources of ignition created by sparks and spatter. Occupational and Environmental Health and Safety (OEHS) Professionals planning welding and cutting tasks in confined spaces are also encouraged to review Chapter 5, Construction, Maintenance, and Repair Welding: Health and Safety Considerations. Chapter 5, plus this chapter, focus on anticipating and identifying the health and safety hazards peculiar to these work environments. Much of the welding and cutting work conducted in confined spaces is construction, maintenance, or repair welding. Consequently, the information provided in Chapter 5 may be applicable for confined space welding and cutting. Also, Confined Space Entry: An AIHA Protocol Guide, Second Edition2 is a valuable source of information for practices and procedures that help protect employees during confined space entries.

1. Regulations Welding and cutting activities include torch cutting, all forms of welding, brazing, and soldering, and arc gouging. Welding and cutting in confined spaces frequently amplify the hazards associated Chapter 4: Welding and Cutting in Confined Spaces Copyright AIHA® For personal use only. Do not distribute.

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with these tasks when performed in the open. NIOSH and OSHA have noted that the primary hazards associated with confined space entries can be grouped into five categories: 1) Asphyxiation; 2) Elevated concentration of toxic contaminants; 3) Increased risk of fire or explosion; 4) Entrapment and/or engulfment; and 5) Other mechanical hazards such as crushing or electrocution.3,4 Among these, welding and cutting in confined spaces could reasonably be expected to increase the expectation of 1, 2, 3, and 5. Improper rigging/slinging and cutting sequences in a confined space could also increase the opportunities for 4 to occur as well. Intending to mitigate or minimize these risks, OSHA has promulgated and enforces several federal regulations that dictate confined space entry procedures. Of course, these regulations carry the force of law only in the United States. However, OEHS Professionals working in other nations may find the OSHA standards useful as references. Thus, they are annotated here to provide a framework for discussion of welding and cutting in confined spaces. The usual presumption is that work conducted in compliance with the OSHA regulations will likely meet most of the minimum requirements for healthful and safe working conditions in confined spaces. However, prudent practice would be best served by developing and applying procedures that combine the best guidance available from industry practice and OSHA standards, whether one has a regulatory responsibility for compliance with a particular standard or not. Federal regulations addressing welding and cutting in confined spaces include: • 29 CFR 1910.146: Permit-Required Confined Spaces • 29 CFR 1910.252: Welding, Cutting, and Brazing (General Industry) • 29 CFR 1926.353: Ventilation and Protection in Welding, Cutting, and Heating • 29 CFR 1910.134: Respiratory Protection Many of the above standards work hand-in-glove with the OSHA standard for Control of Hazardous Energy (Lockout/Tagout), 29 CFR 1910.147. Although this chapter addresses Lockout/Tagout only in passing, 29 CFR 1910.147 provides information and guidance fundamental to safe entry into many confined spaces. 154

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According to 29 CFR 1910.146, a confined space meets all the following three criteria: 1) It is large enough and so configured that an employee can bodily enter the space and perform her/his assigned work; 2) It has limited or restricted means for entry or exit; and 3) It is not designed for continuous human occupancy. Examples include but are by no means limited to the followinga: • Storage tanks • Pits beneath equipment • Truck tanker trailers • Process vessels • Storm drains • Manholes • Silos • Storm water separators • Cooking vessels • Hoppers • Storage drums • Boilers • Boilers/fire boxes • Subgrade pipe chases • Furnaces • Ash pits • Pits and excavations • Railroad tank cars • Open surface tanks In addition to these criteria, the Construction Industry Excavation Standard identifies any excavation more than four feet deep as a worksite requiring atmosphere testing. Because of several similarities between excavation entries and confined space entries, it is common (but not universal) practice to include entries into any subgrade worksite in a facility’s confined space entry program for the sake of administrative convenience. Also, one should be aware that the states of California, Kentucky, Maryland, Michigan, Minnesota, Oregon, Virginia, and Washington all have their own definitions of confined spaces. People working in these states should refer to the state standards as well as the federal standards. Although these spaces may exhibit the characteristics of a confined space as defined by 29 CFR 1910.146: Permit-Required Confined Spaces, compliance with this OSHA Standard is not the focus of this chapter. a

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Also, the following OSHA Shipyard Employment standards offer useful guidance for welding and cutting in confined spaces regardless of whether the spaces are regulated by 29 CFR 1915: • 29 CFR 1915: Subpart D – Welding, Cutting, and Heating • 29 CFR 1915.53: Welding, Cutting, and Heating in Way of Preservative Coatings • 29 CFR 1915.54: Welding, Cutting, and Heating in Hollow Metal Structures Bear in mind that this chapter is not a guideline for guaranteed OSHA compliance. Read the standards carefully; while not all-inclusive, they offer valuable information. The reader should take note that there is more than one OSHA confined space entry standard and that more than one standard might apply in the same workplace. The reader is encouraged to review these standards and Confined Space Entry: An AIHA Protocol Guide, Second Edition2 before planning or commencing work in any confined space. The Mine Safety and Health Administration (MSHA) provides these specific regulations for welding in TITLE III—INTERIM MANDATORY SAFETY STANDARDS FOR UNDERGROUND COAL MINES Sec. 311 [30 USC 871] FIRE PROTECTION (d): All welding, cutting, or soldering with arc or flame in all underground areas of a coal mine shall, whenever practicable, be conducted in fireproof enclosures. Welding, cutting, or soldering with arc or flame in other than a fireproof enclosure shall be done under the supervision of a qualified person who shall make a diligent search for fire during and after such operations and shall, immediately before and during such operations, continuously test for methane with means approved by the Secretary for detecting methane. Welding, cutting, or soldering shall not be conducted in air that contains 1.0 volume per centum or more of methane. Rock dust or suitable fire extinguishers shall be immediately available during such welding, cutting, or soldering.

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2. Investigate Possible Hazards Before Starting Work A few topics worthy of investigation include: • Investigating possible “confined spaces within confined spaces.” Examples may include: – Cyclones in catalyst regenerators – Sumps and areas behind baffles in ship cargo tanks • Reviewing drawings for process vessels, construction projects, ships, barges, bridge beams, tunnels, sewers, and other complex structures. • Are there baffles, substructures, or internal structures that can affect airflow? • Could areas of restricted movement allow atmospheric contaminants to accumulate? • Could workers become wedged in some out-of-the-way corner? • Projects involving construction, demolition, renovation, petrochemical turnarounds, and similar operations frequently create new confined spaces as the projects evolve. Confined space concerns may include: – Unscheduled work in confined spaces as a result of discoveries unearthed during the project – Creation of new confined spaces (in the context of 29 CFR 1910.252 rather than 29 CFR 1910.146) by putting up welding curtains that restrict airflow • Personnel who are not trained in health and safety might, in good faith, offer assurances that these factors are not a concern. These assurances may or may not be credible.

2.1 Fire The possible consequences of being trapped in a confined space with an out-of-control fire are beyond verbal description. It suffices to say that the risk of this scenario being played out is increased with the introduction of welding and cutting processes into the confined space. Chapter 3, Welding Equipment: Health and Safety Considerations, enumerates the most widely recognized fire risks associated with common welding processes. The relevant sections of Chapter 3 are recommended reading for OEHS Professionals planning work in confined spaces.

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2.1.1 Sources of ignition Sources of ignition generated by work procedures must be investigated. The following list is clearly not all-inclusive. Rather, the list provides examples intended to spark the reader’s interest in controlling sources of ignition and elimination of combustible materials from confined space welding areas. Possible sources of ignition include: • Processes that produce noise and UV radiation (see following sections) • Sparks from grinding or welding • Slag and hot metal from thermal cutting processes • Electric arcs from the commutators of electric hand tools 2.1.2 Flammable solids and liquids Inspect the site for flammable materials such as: • • • • • •

Unprotected wooden scaffold boards Plywood barriers or partitions Cardboard boxes containing parts or supplies Worker’s clothing Plastic ventilation ducts (if not fire-rated) Residual sludge from incomplete cleaning of internal surfaces, especially pertinent in petrochemical process vessels • Soil contamination, particularly when working trenches in petrochemical facilities 2.1.3 Flammable gases and/or vapors Consider the possibility that the work generates flammable gases or vapors in excess of 10 percent of the lower explosive limit (LEL)/ lower flammable limit (LFL). Causes of this condition may include: • • • • •

Vessel contents that have not been adequately purged Leaking blinds or block valves Painting operations Paint removal Solvent cleaning procedures

2.1.4 Combustible dust Consider the possibility that welders will be working in an environment that either exhibits or may generate airborne combustible 158

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dust in excess of 10 percent of the LEL/LFL. (Rule of thumb: Vision obscured at 5 ft or less.) • • • • •

Grain silos Wood dust silos/cyclones Aluminum dust Magnesium dust Coal dust

In situations where the specific work activity will generate or increase the level of flammable materials, continuous monitoring may be required. Combustible dusts may include organic materials such as grain or wood dust. Combustible dusts may be generated by grinding of aluminum or magnesium. If dusts of combustible materials obscure vision at a distance of 5 ft or less, the atmosphere may be considered flammable. 2.1.5 Other fire-hazard-related notes: • Leaking oxygen hoses, valves, and/or fittings may increase the fire hazards by enriching the confined space atmosphere’s oxygen content. Oxygen-enriched atmosphere means an atmosphere containing more than 23.5 percent oxygen by volume. • Compressed gas cylinders and electric arc/plasma/laser power sources must not be allowed in the confined space.5 • Do not leave unattended oxyfuel equipment in confined spaces. Remove torches and hoses from confined spaces during breaks, lunch, and at the end of the shift. Unnoticed leaks may have developed during the period of use immediately preceding the break. Leaking fuel or oxygen may create fire/explosion hazard during the unattended period. • Igniting an oxyfuel torch in a confined space can be a risky procedure and should be avoided whenever feasible. It is possible for the igniter to malfunction several times before creating a spark (just like it does on your barbecue at home). If that happens in a small space, the potential for a conflagration cannot be ignored. The geography of the worksite can exacerbate this problem when the work area is some distance from the entrance manway (as in the hold of a ship). Consequently, the OEHS Professional may be challenged to find adequate means of educating welders about the possible consequences of lighting a torch in a small, Chapter 4: Welding and Cutting in Confined Spaces Copyright AIHA® For personal use only. Do not distribute.

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confined space. One engineering control option may be to direct welders to ignite torches within the capture distance of local exhaust ventilation equipment (see Section 3.1). Additional insights regarding mitigation of fire hazards come from Finkel’s work, published by the ASSE.6 Written by a Certified Marine Chemist (CMC), Finkel’s volume offers a CMC’s perspective on identifying and addressing potential fire and explosion hazards that may be encountered when performing welding, cutting, and associated tasks in storage tanks and tank ships. This information is widely applicable in nonmarine work environments as well. For those of us not trained in fire science, Finkel offers this distinction between a fire and an explosion: In a fire, the flame front moves (propagates) from the source of ignition at subsonic speed, whereas an explosion is characterized by a supersonic flame (or reaction) front. One should take note that because sound travels at approximately 1100 feet per second at sea level, “subsonic” should not be equated with “slow.” Guidance offered by Finkel for reducing fire hazards includes: • Plastic ducts should have no more than 100,000-ohm resistance to ensure adequate conductivity to prevent accumulation of static electricity charges. • Less than 10 percent LEL is a common value for confined space entry. However, 0 percent LEL is much more prudent and is considered a requirement for hotwork in a confined space. • When performing atmosphere testing for LEL: – Check low spots if the space contained flammables with vapor density >1 – Check high spots if the space contained flammables with vapor density 8/32 in.

< 60 60–160 160–250 250–550

7 8 10 11

Not specified

< 60 60–160 160–250 250–500

7 10 10 10

Gas tungsten arc welding

Not specified

< 50 50–150 150–500

8 8 10

Air carbon arc cutting

Light work Heavy work

< 500 > 500

10 11

Not specified

< 20 20–100 100–400 400–800

6 8 10 11

Light** Medium** Heavy**

< 300 300–400 400–800

8 9 10

Oxyfuel torch brazing

Not specified

Not specified

Oxyfuel torch soldering

Not specified

Not specified

Carbon arc welding

Not specified

Not specified

14

Oxyfuel gas welding

< 1/8 in. plate 1/8–1/2 in. > 1/2 in.

Not specified

4 5 6

Oxyfuel gas cutting

< 1 in. plate 1–6 in. > 6 in.

Not specified

3 4 5

Operations Shielded metal arc welding

Gas metal arc welding

Plasma arc welding

Plasma arc cutting

3 2

Edited from 29 CFR 1910.132 * As a rule of thumb, start with a shade that is too dark to see the weld zone. Then go to a lighter shade that gives sufficient view of the weld zone without going below the minimum. In oxyfuel gas welding or cutting where the torch produces a high yellow light, it is desirable to use a filter lens that absorbs the yellow or sodium line in the visible light of the (spectrum) operation. ** These values apply where the actual arc is clearly seen. Experience has shown that lighter filters may be used when the arc is hidden by the workpiece.

1

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2.3 Automatic Darkening Filters for UV Welders (or more accurately, their employers who provide the PPE) now have an option that may reduce the frequency of this apparent cumulative trauma disorder. That option is the “automatic darkening filter,” or ADF. Like ordinary filter plates, the ADF offers UV protection and visible light protection. However, unlike the ordinary filter plate, the ADF has two operating conditions. In the nonenergized state, the ADF allows transmission of visible light approximately equivalent to that offered by a Shade 3 or 4 filter. A Shade 3 or 4 filter is used most often for oxyfuel processes, and the welder can see the work area reasonably well through this filter. This level of vision allows the welder to ensure that the parts to be joined and the electrode are in their correct spatial relationship. When the arc is initiated, the ADF UV sensors (there may be 2 or 4 sensors, depending on the welding hood manufacturer and mode) send a signal to the built-in circuitry, which then energizes the liquid crystal element that darkens the filter. Some ADFs are adjustable with a 2 to 3 Shade range (e.g., Shade 9 to 11); however, due to cost considerations, most are single shade. Whether they are energized or not, ADFs are constructed of materials that offer the same infrared and UV protection as equivalent conventional filters. Hence, an ADF malfunction does not present a UV hazard to the eyes.a To a greater or lesser extent, ADFs tend to “flicker” when used in a multi-welder workplace. This phenomenon is a function of the location, number, and sensitivity of the sensors that trigger the automatic darkening feature. If use of ADFs is contemplated, it may be worthwhile to try hoods from several different manufacturers because each manufacturer uses their own layout for the sensors.

2.4 Laser Protective Eyewear Applications that utilize lasers such as welding, cutting, or drilling of metals may require protection from scattered laser radiation and from nonlaser wavelengths, called plasma radiation, that are generated during interaction of the laser beam with the metal. Laser protective eyewear may utilize absorbing dyes or reflective coatings on glass or plastic lenses in a variety of frames or in goggles. Dyes add color to the lenses while coatings are typically transparent. a Information on ADFs provided by Mr. James Twigg of Fibre-Metal Products, P.O. Box 248, Concordville, PA 193311.

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Both provide wavelength-specific attenuation and are therefore prescribed for a specific laser or laser application. Laser protective eyewear must be marked with the optical density (measure of attenuation) at the wavelength or wavelengths for which it is designed. Optical density is expressed as OD = log10 [E/OEL], where E is the incident irradiance and OEL is the applicable exposure limit (units must be the same as E). The two lasers most often used in material processing applications are the Nd:YAG and CO2 lasers. Nd:YAG lasers, which produce near-infrared (IR-A) radiation, are used for absorbing dyes. CO2 laser radiation, in the far infrared (IR-C) spectral region, is absorbed well by polycarbonate. When energetic beams from either type of laser are used with metals, the interaction may generate ultraviolet and visible radiation. Hence, it may be necessary to use eyewear that will absorb the scattered laser radiation, UV radiation, and visible wavelengths, especially in the blue-green spectral region.

3. Skin Protection The primary means of skin protection are the welding hood or helmet, gloves, and work clothes. This PPE serves to protect the welder’s skin from heat and UV radiation. While it is presumed that the occupational and environmental health and safety (OEHS) Professional will have reasonable familiarity with skin protection, some comments specific to protecting against welding and cutting hazards are offered here.

3.1 Welding Helmet/Hood • Caps are commonly worn under welding helmets to protect the scalp against flying sparks, slag, and molten metal. • Welding helmets should be kept clean and replaced when damaged. • The ratchets on the helmet that connect the helmet suspension to the helmet proper should be well maintained to ensure smooth function and reduce ergonomic stress from “nodding” the helmet down with needless force.

3.2 Gloves • Welder, cutters, and, where appropriate, helpers should wear flame-resistant gloves. • Gloves should be kept dry and in good repair. 198

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• Leather gloves are conventional, but Nomex®/leather combinations and treated cotton are also used. • If electric arc processes are used, criteria for glove selection should include protection against electrical shock. Inner linings may be necessary to meet this requirement. • Gloves for work in high-heat applications may require outer reflective layers and/or insulated inner layers.

3.3 Protective Clothing • Clothing requirements vary with: – The amount of spatter produced by the electric arc welding process [shielded metal arc welding (SMAW) and gas metal arc welding (GMAW) being worse than gas tungsten arc welding (GTAW)]. – Whether the work is being performed downhand, vertical, or overhead (overhead being more hazardous). – Presence or absence of potential for electrical shock. – Whether the process involves metal removal [air carbon arc cutting (CAC-A) being worse than oxyfuel cutting (OFC)] or metal deposition. – Amperage (high-amperage applications may produce more UV radiation than can be stopped by thin shirts). • For electric arc processes, dark clothing is preferred to light colors to reduce the amount of UV radiation reflected up into the welding hood. The goal is to minimize eye exposures to UV radiation. • For all welding and cutting processes, clothing materials such as heavy wool or heavy cotton are preferred over synthetic materials, which may melt. • If cotton clothing is used for protection, treated cotton is preferred. Note that clothing may require retreating after repeated laundering or washing. • Leather capes and sleeves, aprons, and/or chaps may be required for processes that generate flying molten metal or slag. In some cases, leather shirts and trousers may be required, particularly in restricted spaces when performing overhead work. • When capes and sleeves have high collars, the collars should be fastened closely around the throat to avoid creating a crevice-like site where slag, molten metal, or sparks may lodge against the neck.

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• Avoid pant cuffs, pants tucked inside boots, rolled-up sleeves, and garments with pockets that do not have flaps. Sparks, slag, and/or molten metal may become lodged in the cervices and burn through the clothing. • In some cases, the welders may be working overhead in awkward positions, exposing the earcanals to possible entry by slag or molten metal. This author (M.K. Harris) has personal experience with hot sparks in the earcanal, and the reader may rest assured that the sensation is every bit as uncomfortable as it sounds. In such cases, flame-resistant earplugs should be provided to the welder.4

3.4 Foot Protection • Heavy leather boots are accepted as adequate footwear for most welding and cutting operations. • Ankle-length boots provide more protection against entry by sparks, slag, and molten metal than low-cut shoes do. • Leggings/chaps, when worn, should overlap over the tops of boots.

References

1. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:2012. Miami, FL: American Welding Society, 2012, p. 6. 2. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:2012. Miami, FL: American Welding Society, 2012, p. 8. 3. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:2012. Miami, FL: American Welding Society, 2012, p. 8. 4. American Welding Society. Safety in Welding, Cutting and Allied Processes, American National Standard Z49.1:2012. Miami, FL: American Welding Society, 2012, p. 9.

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8 Air Monitoring When involved in the process of educating management, one of the first questions heard by the occupational and environmental health and safety (OEHS) Professional is: “Do we have to do air monitoring?” One answer to that question can be found in 29 CFR 1910.134(d)(1)(iii): The employer shall identify and evaluate the respiratory hazard(s) in the workplace; this evaluation shall include a reasonable estimate of employee exposures to respiratory hazard(s) and an identification of the contaminant’s chemical state and physical form. Where the employer cannot identify or reasonably estimate the employee exposure, the employer shall consider the atmosphere to be IDLH. Work in an immediately dangerous to life and health (IDLH) atmosphere requires supplied-air respiratory protection.1 In the absence of data, but in the presence of reasonable suspicion, a work atmosphere that has not been evaluated would, per this standard, be assumed to be an IDLH atmosphere. Although some welding processes present virtually no inhalation hazard [e.g., gas tungsten arc welding (GTAW) and submerged arc welding (SAW)], in most cases the visible plume fume and smoke makes it difficult to deny the possibility of an inhalation hazard. Respirators with protection factors of 10 or 50 are often adequate for many welding and cutting operations, and supplied air is truly necessary only in specific circumstances. Consequently, air monitoring to determine the required protection factor is generally considered a cost-effective option compared to working in supplied air. This chapter does not purport to provide a comprehensive guide to air monitoring. The intent is to focus only on those aspects of air monitoring that are more or less peculiar to quantifying exposure potentials associated with welding and allied processes.

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Topics addressed here include: • Identifying Contaminants of Concern • Selecting Air Monitoring Sampling and Analysis Methods • Collecting Air Samples

1. Identifying Contaminants of Concern If the reader has read this volume sequentially, the following list will be familiar: • Review the material safety data sheets (MSDSs) for: – Metals being joined or cut – Filler metals in use (if any) – Fluxes in use (if any) – Shielding gases (if any) – Coatings on the metals being joined or cut – Electrodes • In addition to the constituents listed for the materials, look for the hazardous products of decomposition. This may be especially appropriate when investigating possible contaminants of concern generated by the use of fluxes. • A thorough analysis of the MSDS may be necessary to identify possible contaminants of concern. For example, hexavalent chromium (CrVI) is a component of stainless steel welding fume.2 Hexavalent chromium is an IARC–1 Human Carcinogen.3 However, CrVI is not often listed as a component of stainless steel on the MSDSs for stainless steel because chromium in the hexavalent state is not present when the stainless steel is in the solid state. (As an aside, one may note that stainless steel is often described as a “solid-state solution” of iron, chromium, nickel, and carbon.) • Also, ensure that the presence or absence of coatings has been confirmed. These coatings may include: – Process chemical residue, e.g., » some halogenated cleaning chemicals decompose to form chlorine gas and/or phosgene » some petrochemical vessels may contain sulfur compounds that form sulfur dioxide (a profound upper respiratory tract irritant) upon heating – Paints – Polymers 202

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– Primers – Claddings – Plated materials These possible sources of contaminants deserve particular consideration when executing repair and maintenance tasks. Pay attention to the “products of decomposition” section of the MSDS for the coatings. Cadmium, lead, strontium chromate, and isocyanates may outgas from some of these coatings when heated.

2. Selecting Air Monitoring Sampling and Analysis Methods The NIOSH Manual of Analytical Methods (NMAM)4 is generally considered to be the most comprehensive document describing air sampling and analytical techniques available to the OEHS Professional. Before embarking on an air monitoring campaign, the reader is encouraged to review the section titled “Using NMAM” to ensure that the field scientist’s assumptions regarding use of the methods agree with the assumptions employed by NIOSH in developing the methods.

2.1 Gravimetric Methods Simply sampling for total particulate with gravimetric analysis and interpreting the result as total welding fume has been historically regarded as a reasonable first step in evaluating welding fume exposures. However, the variety of airborne contaminants associated with welding and cutting processes appears to limit the applicability of this technique to relatively benign contaminants such as dust and iron oxide. Consequently, a more detailed initial evaluation focusing on the contaminants of concern identified during the MSDS review process would seem more appropriate.

2.2 Substance-Specific Methods For certain contaminants, federal or local regulations may dictate the methods used. For example: • The OSHA Cadmium Standard (29 CFR 1910.1027, Appendix E) specifies use of 0.8µ mixed cellulose ester filters (MCE) and analysis by either flame atomic absorption spectroscopy (AAS) or flameless atomic absorption spectroscopy using a heated graphite furnace atomizer (AAS-HGA). Chapter 8: Air Monitoring Copyright AIHA® For personal use only. Do not distribute.

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• The OSHA Lead Standard [29 CFR 1910.1025(d)(9)] requires that the results be reported with a confidence level of 95 percent. If the work is to take place in an environment that may reasonably be expected to equal or exceed the action level of 30 µg/m3, then sampling and analysis in accordance with NIOSH Sampling and Analytical Method 7300 by inductively coupled plasma (ICP) for elements may be somewhat problematic because NIOSH 7300 does not list a coefficient of variation (CV). In the absence of a CV or some other appropriate measure of precision, calculating a confidence limit is not possible. Consequently, one is more likely to use NIOSH Method 7082 (flame AAS), which offers a measure of precision (as Srt ) for lead fume of 0.068. NIOSH Method 7300 for elements by ICP is, however, entirely suitable for broad spectrum sampling and analysis for welding and cutting environments. Among the elements listed among the analytes for Method 7300 are the following metals commonly encountered in hotwork: • Aluminum (also NIOSH 7013) • Beryllium (also NIOSH 7102) • Cadmium (also NIOSH 7048) • Chromium (also NIOSH 7024) • Cobalt (also NIOSH 7027) • Copper (also NIOSH 7029) • Iron • Lead (also NIOSH 7082) • Magnesium • Manganese • Nickel • Silver • Vanadium (also NIOSH 7504 for vanadium oxides) • Zinc (also NIOSH 7030 and 7502 for zinc oxides) Based on the above list, Method 7300 is a worthy candidate for consideration for performing cost-effective initial air monitoring during hotwork. Most of the metals listed above have occupational exposure limits less than the 2001 threshold limit value (TLV)® of 5 mg/m3 for total welding fume as “particulates not otherwise specified.” Method 7300 will allow the OEHS Professional to characterize exposure potentials to a wide variety of metals with a minimum of field time. 204

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It may be prudent to be familiar with other methods, such as: • NIOSH Method (7600) for hexavalent chromium (CrVI). This method specifies a polyvinyl chloride (PVC) filter to reduce the rapidity with which the CrVI reduces. Analysis within 2 weeks is recommended to mitigate against loss of analyte due to reduction.5 (Note that the filter must be removed from the cassette within an hour of sampling and placed in a sealed vial, again to minimize reduction prior to analysis.) • NIOSH Methods 5506 and 5515 for PNAs in petrochemical process residue that may become disturbed and made airborne during turnarounds. • NIOSH Methods 7902 and 7906 for fluorides that may outgas during shielded metal arc welding (SMAW) welding. It is also prudent to evaluate the possibility of overexposure to coatings that may be present on the materials being joined or cut. • Process chemical residue, e.g., – some halogenated cleaning chemicals decompose to form chlorine gas (NIOSH 6011) and/or phosgene (OSHA 61). – some petrochemical vessels may contain sulfur compounds that form sulfur dioxide (a profound upper respiratory tract irritant) upon heating (NIOSH 6004). • Paints will decompose upon heating and release the metals used for the pigments or as biocides, e.g., – lead – cadmium – copper naphthanate (NIOSH 7300 for copper) and mercury compounds (NIOSH 6009). These compounds are found in antifouling paint used on hulls of ships. • Polymer coatings that may be encountered during hotwork include: – polyurethane; upon decomposition, it may release CN (NIOSH 7904) and NOx. – acrylates; upon decomposition, they may release acrid smoke and fumes. • Primers – chromium compounds (NIOSH 7300 and, possibly, NIOSH 7600) – lead compounds (NIOSH 7082) – zinc compounds (NIOSH 7300, 7030, and, for zinc oxides, 7502) Chapter 8: Air Monitoring Copyright AIHA® For personal use only. Do not distribute.

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This brief discussion is not intended to be exhaustive. Rather, it is intended to stimulate a more careful and thorough approach to evaluating the welding and cutting workplace atmosphere. The reader is encouraged to work closely with an AIHA-accredited laboratory to select sampling and analytical methods that are appropriate for all suspected contaminants of concern. Table 8.1 was developed by Stephanie Carter to summarize major contaminants of concern, along with occupational exposure limits and basic sampling criteria for NMAM 7300.

3. Collecting Air Samples There is one aspect of air monitoring for welding and cutting that is out of the ordinary. That aspect is the influence of the welding hood (when used) on contaminant concentrations in the breathing zone. The welding hood affects airflow patterns around the face and may deflect some of the contaminant plume away from the breathing zone. The research reported in the literature does not, however, agree on the extent to which this phenomenon takes place. Goller and Paik described the results of simultaneous air monitoring with collection sites at four locations on the welder’s body: • • • •

Left front shoulder Right front shoulder Front chest Inside the helmet6

Figure 8.1 illustrates these locations. Goller and Paik’s work involved collection of 40 sets of 4 samples each, or 160 samples. The welders were monitored while engaged in flux cored arc welding (FCAW) production work involving building railroad locomotives. The results of this monitoring are summarized below: • Left front shoulder mean concentrations were 2.8 times those measured inside the helmet. • Right front shoulder mean concentrations were 1.7 times those measured inside the helmet. • Chest mean concentrations were 1.8 times those measured inside the helmet. These data support the “inside the helmet” protocol recommended by the AWS.7 However, the cassette dangling in the work206

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Chapter 8: Air Monitoring Copyright AIHA® For personal use only. Do not distribute. 0.00005 I

0.0005*

0.02 R 0.1 I*

0.2 I 0.02 R

C

5 5

Manganese

Molybdenum: soluble

0.5 R

10 I

10

5R

0.2

0.5 I 0.5 0.000 2I

0.02 I

15

5

0.1

0.5 0.5 0.0002

0.05

0.01* 0.002 R*

0.01*

0.002 *

LFC*

0.5 C

1

ACGIH TLV®–TWA (mg/m3)

0.5

10 5

NIOSH REL–TWA (mg/m3)

Magnesium oxide fume

10 (as Fe)

0.1

Cobalt

Iron oxide fume

0.005

Cadmium fume: total respirable

0.1

0.0002, 0.005C, 0.025P

Beryllium

Copper fume

0.01 0.005A

Arsenic

0.003 I 1 0.005C

0.5

Antimony

Chromium   Cr, III  Metal   Cr, VI

15 5

Aluminum: total respirable

Substance

OSHA PEL–TWA (mg/m3)



8+++

+++ 0.05 µg/sample

0.8

0.2

3.9

3.8

5

5

5

5

5

5

2.7

25 0.8

13

1250++

5

50

5

Minimum Air Volume (L) NMAM 7300

0.5

0.3

0.2

5.6

7.7

4.6

LOD (ng/mL)

Table 8.1: Summary of Occupational Exposure Limits and Air Sampling Criteria for Metals Important in Welding/Hotwork

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207

208 0.1 1 5

Titanium dioxide

Vanadium pentoxide fume: respirable

Yttrium

Zinc oxide fume

Chapter 8: Air Monitoring Copyright AIHA® For personal use only. Do not distribute. LFC*

5

1

0.05

5, 10

S

2 R, 10 RS

1

0.05 I

10

0.1 0.02 Isk

0.1 0.1sk

0.1

0.2

1 0.002

0.1

0.05

5 5 5

12.4 0.9

5

5

25

25

250

13

25

50++

5

0.5

1.1

2.0

3.7

3.1

1.7

5.4

3.7

2.5

0.8

LOD (ng/mL)

Minimum Air Volume (L) NMAM 7300

A, action level; C, ceiling level; P, maximum peak, 30 min; S, STEL value; LFC, lowest feasible concentration; * cancer designation; ( ), proposed changes; sk, Skin; – usually 10 mL dilution; ++ AA method more sensitive (Pb–7082/7105; Be–7102); +++ NMAM 7600

Welding fumes

Zirconium

15

Thallium c

0.1 0.1sk

Tellurium

0.01

0.01

1 0.002

Silver metal

0.002

Platinum metal: soluble

0.1

0.05

0.2

0.1

Phosphorus

Selenium

0.05

Lead

0.2 I

0.1 I

0.015

0.015 *

1 1

Nickel: soluble

Nickel: insoluble

ACGIH TLV®– TWA (mg/m3) 10 I 3R

NIOSH REL– TWA (mg/m3)

15

Substance

Molybdenum: insoluble

OSHA PEL–TWA (mg/m3)

Table 8.1 (continued): Summary of Occupational Exposure Limits and Air Sampling Criteria for Metals Important in Welding/Hotwork

Welding Health and Safety: A Field Guide for OEHS Professionals, 2nd edition

Air Monitoring

Welding Health and 1Safety: A Field Guide for OEHS Professionals, 2nd edition

Figure Locations filter cassettes—helmet Figure 8.1:8.1: Locations of filterof cassettes—helmet in up position.in up position. Goller and Paik described the results of simultaneous air monitoring with er’ssites faceat(shown in Figure is onebody: of the reasons that sampling collection four locations on the8.1) welder’s inside the helmet generates a certain amount of reticence on the � Left front shoulder part of the welder who is asked to wear this device for one or more � Right front shoulder shifts. � Front chest Later work reported by Liu et al. suggests that the relationship � Inside the helmet6 between sample location and measured contaminant may not be as clear-cut as earlier believed.8 These researchers conducted air Figure 8.1 illustrates these locations. Goller and Paik’s work involved monitoring volunteers SMAW in a concollection of 40 setsofof20 4 samples each,performing or 160 samples. Thewelding welders were trolled laboratory environment. Twenty-three samples were monitored while engaged in flux cored arc welding (FCAW) production work collected from railroad both the breathing The zones inside and involving building locomotives. results of the this helmets monitoring areat the shoulders of these volunteers. The results of this monitoring indisummarized below: cated that there was generally little difference between fume con� Left front shoulder mean concentrations were 2.8 times those measured centrations inside the helmet and those outside the helmet. inside the helmet. Whether the results reported by Goller and Paik or those re� Right front shoulder mean concentrations were 1.7 times those ported by Liu et al. are considered, there is little disagreement that measured inside the helmet. the traditional welding helmet an inconsistent respiratory � Chest mean concentrations were 1.8istimes those measured inside theprotection device, at best. Indeed, the work reported by Liu et al. suggests helmet. that at low fume concentrations, the contaminant concentrations inside the hood may be greater than those outside the hood. This Copyright AIHA® in results may be a function For personal variation of:use only. Do not distribute. Chapter 8: Air Monitoring Copyright AIHA® For personal use only. Do not distribute.

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• Minor differences in hood aerodynamics • Relationship of the hood and welder to local airflow patterns • Relationship of the welder to the work (e.g., overhead vs. downhand) • Rate of fume generation • Propensity of fume to agglomerate • Size and shape of the welder’s head relative to the hood • Location and size of the welding cape/sleeve collar and whether the collar is fastened Given these sources of variation and the variation in results reported in the literature, it is prudent to perform air monitoring inside the hood, even in the face of some resistance by the welders being monitored. Note: Both the OSHA Technical Manual and ANSI Z49.1:2012 require placing the sample medium under the welding hood. If the cassette is placed at the throat (attached to the fully buttoned-up collar), the cassette will be under the welding hood when lowered. In this author’s (M.K. Harris’) experience, this is the least intrusive and most effective sample medium location for welding fume (See Figures 8.2 and 8.3).

Figure 8.2

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Figure 8.3 If resistance to wearing the cassette within the hood is excessive, then collecting data from outside the hood remains the only choice. However, the data collected from outside the hood may result in either underestimation or overestimation of actual exposure in the breathing zone.

References

1. Occupational Safety and Health Administration (OSHA). 29 CFR 1910.134(d)(2). 2. American Conference of Governmental Industrial Hygienists. Documentation of the Threshold Limit Values and Biological Exposure Indices, 7th Ed. Cincinnati, OH: ACGIH, 2002. 3. American Conference of Governmental Industrial Hygienists. Guide to Occupational Exposure Values. Cincinnati, OH: ACGIH, 2020. 4. U.S. Department of Health and Human Service, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. NIOSH Manual of Analytical Methods, 2003 5. U.S. Department of Health and Human Service, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. NIOSH Manual of Analytical Methods, 2003 and American Welding Society. Methods for Analysis of Airborne Particulates Generated by Welding and Allied Processes. Miami, FL: American Welding Society, 1997, p. 8. Chapter 8: Air Monitoring Copyright AIHA® For personal use only. Do not distribute.

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6. Goller JW and Paik NW. A Comparison of Iron Oxide Fume Inside and Outside of Welding Helmets. Am Ind Hyg Assoc J 46(2): 89–93, 1985. 7. American Welding Society. Method for Sampling Airborne Particulates Generated by Welding and Allied Processes American National Standard F1.1. Miami, FL: American Welding Society, 1997. 8. Liu D, Wong H, Quinlan P, and Blanc PD. Welding Helmet Airborne Fume Concentrations Compared to Personal Breathing Zone Sampling. Am Ind Hyg Assoc J (56): 280–293, 1995.

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9 Developing Similar Exposure Groups This Chapter provides three examples of the level of detail that may be used in defining similar exposure groups (SEGs): • Moderate detail (six factors) • High level of detail (spreadsheet) • Minimal level of detail (high- or low-fume emission process) Similar exposure groups (SEGs) have been defined as a: “Group of workers having the same general exposure profile for the agents(s) being studied because of the similarity and frequency of the tasks they perform, the materials and processes with which they work and the similarity of the way they perform the tasks.”1 Because welding and thermal cutting are convenient means of shaping and joining metals, these processes are ubiquitous throughout most industrial settings. Although these thermal processes may not be used in the actual manufacturing processes at many facilities, they are frequently used in maintenance and repair work. Consequently, the application of welding and thermal cutting processes can be differentiated into two broad categories: 1) production welding and 2) maintenance and repair welding and thermal cutting. Production welding is much easier to characterize because the work tends to be repetitive—the work is conducted at the same workstation on the same kind of parts using the same process day after day. In contrast, maintenance and repair work may be conducted at any number of different locations in the facility and on any number of items of equipment, potentially using a variety of processes in the execution of the work. In either case, there are fundamental factors that drive worker exposure to welding and thermal cutting fumes. A condensed list of these factors would include: 1) Welding or thermal cutting process 2) Filler wire or electrode is in use 3) The extent to which the work environment promotes or restricts the dispersion of the fume from the worker’s breathing zone Chapter 9: Developing Similar Exposure Groups Copyright AIHA® For personal use only. Do not distribute.

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4) Task description 5) The metal being welded or cut 6) Allied processes (e.g., grinding, sanding) The above six factors may define a minimum level of information necessary to define SEGs for welding and thermal cutting. However, the level of detail provided by this six-factor list may not be adequate to determine why any given sample is outside the range of expected values for the work being monitored. An example of a more detailed description of the work is offered here as an The above six factors may define a minimum level of information necessary Excel spreadsheet entitled “Welding Fume Data Entry Sheet.” This to define SEGs for welding and thermal cutting. However, the level of detail Data Entry Sheet is designed to be used as a “front end” for accuprovided by this six-factor list may not be adequate to determine why any mulating welding exposure information in a database. None of the given sample is outside range of that expected values forhygienist the work(IH) being cells are locked, as it the is presumed the industrial monitored. An example of a more detailed description of the work is offered will need to edit the spreadsheet to correspond with the worksite here as aninvestigation. Excel spreadsheet entitled “Welding Entry Sheet.” is This under A screenshot of pageFume 1 of Data the spreadsheet Data Entry Sheet is designed to be used as a “front end” for accumulating shown in Figure 9.1, and the full spreadsheet is available at bit.ly/ welding exposure information in a database. None of the cells are locked, as it welding_health_and_safety. is presumed that the industrial hygienist (IH) will(all need edit the The spreadsheet includes dropdowns of to which canspreadsheet be edto correspond with the worksite under investigation. A screenshot of page ited by the IH) to oblige the person entering the data to use pre-1 of thedefined spreadsheet is shown in Figure 9.1. descriptors. This rigor allows the database to be queried using terms that have been determined to be useful in defining the

Figure 9.1: Page 1 of the “Welding Fume Data Entry Sheet.”

Figure 9.1

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The spreadsheet includes dropdowns (all of which can be edited by the IH) to oblige the person entering the data to use predefined descriptors. This rigor allows the database to be queried using terms that have been determined to be

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exposure circumstances. These dropdowns have been populated on page 2 of the spreadsheet and are listed below. • Sample type – Personal – Area • Job Classification – Welder – Helper – QA/QC inspector – Roustabout • Sample medium – MCE – Pre-tared PVC • Welding/Cutting Process – SMAW (Stick) – GTAW (TIG) – GMAW (MIG) – FCAW (Flux Core) – PAC (Plasma Arc Cutting) – CAC (Carbon Arc Cutting) – OFC (Oxyfuel Cutting) • Base Metal – Carbon steel – 1¼ chrome (4130 chrome-moly steel) – 2¼ chrome steel – Stainless steel – Galvanized steel – Aluminum • Consumable type – E6011 – E7018 – E8018 – Stainless – Specialty (Stellite, Hastalloy, etc.) – E70S – E70T

• Consumable diameter – 0.035 – 0.045 – 1/16 in. – 3/32 in. – 1/8 in. – 5/32 in. • Worksite – Open air – Inside non-shop building with no obstructions to fume dispersion – Inside non-shop building with nearby obstructions to fume dispersion – Inside shop building – Horizontal drum – Vertical drum – Skirt – Conventional storage tank – PRC Confined Space – Sphere • Number of welders in space – 1 – 2 – 3 – 4 – 5 – 6 – 7 – 8 – 9 – 10

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• Weld Position – Flat – Horizontal – Vertical – Overhead – All positions (e.g., circumferential pipe welding) • Welder Position – Standing – Kneeling – Sitting – Prone/Supine – All positions (e.g., circumferential pipe welding)

• Engineering Control – LEV = 1000 fpm at face and 1 to 1½ hood diameter criteria not met – LEV ≥ 1000 fpm at face and 1 to 1½ hood diameter from arc criteria are met – Dilution Ventilation at 2000 cfm per welder criterion is NOT met – Dilution Ventilation at 2000 cfm per welder criterion IS met • RPD – None required – HFAPR – PAPR without Cape – PAPR with Cape – SA

Most of the cells in the spreadsheet are self-explanatory; however, a few cells require some brief discussion. • The Work Site cell dropdowns reflect the writer’s experience in the petrochemical industry. If the reader elects to use this spreadsheet, these dropdown options will require revision to match the worksites at the facility under investigation. The primary significance of the worksite description is whether the worksite encourages or discourages dispersion of the welding fume from the worker’s breathing zone. • Welding/Cutting Process: Be aware that some welding tasks use more than one welding process. For example, in pipe welding, a “root pass” is often run with GTAW for enhanced weld quality. The root pass is then followed by “filler passes” and “cap pass” using SMAW. When beginning a monitoring session, it is prudent to ask whether the welder will be using the same process for the entire task or if there will be multiple processes used. • Weld Position describes the orientation of the weld bead.

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• Welder Position describes the posture of the welder, not the orientation of the weld bead. • Engineering Control criteria noted here are discussed at length in Chapter 11, Ventilation Controls. The level of information that can be captured via the spreadsheet may exceed the level of information desired by the IH. The determination of the desired level of detail is governed by the professional judgment of the IH. The “Detailed Description of the operation monitored” block is large enough to encourage the field IH to capture as much detailed information as practical. If the analytical results for a given sample are either higher or lower than anticipated, the details recorded in this block may provide insight as to why that is the case. When circumstances permit, a photograph of the operation monitored is often useful for interpreting the results. “Allied processes” such as fitting, tacking, grinding, and activities of adjacent workers that would affect sample results should be recorded in the “Detailed Description of the operation monitored” block. At the opposite extreme of the level of detail captured in the “Welding Fume Data Entry Sheet” are the broad categories based solely on whether the process being monitored is a “high fume” or “low fume” process noted in Chapter 1. Characteristics of common high-fume emission processes are: • No physical barrier between the arc and the welder • Welding process uses the consumable as the electrode • Thermal cutting processes are default high emitters Examples are: • • • •

Shielded metal arc welding (SMAW or MMA) Flux cored arc welding (FCAW) Gas metal arc welding (GMAW) Arc cutting and arc gouging

Characteristics of low-fume emission processes: • Case 1: Gas tungsten arc welding (GTAW or “TIG”) – Process does NOT use consumable as electrode. Therefore, the consumable is not vaporized in the arc.

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• Case 2: Submerged arc welding (SAW) – Physical barrier (mound of flux) between the arc and the welder. • Case 3: Resistance welding (RW) “Spot welding” – Physical barrier (parts being welded) between the arc and the welder.

1. Summary In many cases, there is only one process, one consumable, and one welder involved—that being ordinary plant maintenance and repairs at small facilities. At the other extreme, this writer has found SMAW, FCAW, CAC-A, multiple consumables, over a dozen welders, multiple worksites, and a half dozen contractors all working the same petrochemical turnaround on the same day. The amount of information, or level of detail, required for evaluating SEGs can be expected to be driven by work undertaken at the facility under investigation. There is ample room for professional judgment when determining how much information is adequate for determination and evaluation of SEGs for welding and thermal cutting.

Reference

1. Jahn SD, Bullock, WH, Ignacio JS (eds.). A Strategy for Assessing and Managing Occupational Exposures. Falls Church, VA: AIHA, 2015, p.545. 2002.

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10 LEV Discussion This chapter focuses on use of local exhaust ventilation (LEV) to reduce worker exposures to welding fume. When asked to use LEVs, welders often express concerns about the LEV displacing or removing the shield protecting the weld pool from the atmosphere provided by the shielding gas and/or the vaporization of the flux. The American Welding Society (AWS) provides a guideline for MAXIMUM airflow velocity in ANSI Z49.1:2012: Ventilation should not produce more than approximately 100 feet per minute (0.5 meters per second) air velocity at the work (welding or cutting) zone. This is to prevent disturbance of the arc or flame. It should be recognized that approximately 100 feet per minute (0.5 meters per second) air velocity is a recommended maximum value for quality control purposes in welding and cutting. It is not intended to imply adequacy in contaminant control for worker health protection. The Occupational Safety and Health Administration (OSHA) has published the following MINIMUM airflow velocity in 1910.252(c)(3)(i): Hoods. Freely movable hoods intended to be placed by the welder as near as practicable to the work being welded and provided with a rate of air-flow sufficient to maintain a velocity in the direction of the hood of 100 linear feet (30 m) per minute in the zone of welding when the hood is at its most remote distance from the point of welding. One might comment that maintaining precisely 100 feet per minute (fpm) at the arc is an unobtainable performance standard due to the turbulent airflow at the arc. Nonetheless, 100 fpm is a useful guideline and should assuage welder concerns about removing the gaseous shield produced by the vaporization of flux in the shielded metal arc welding (SMAW) and flux cored arc welding (FCAW) processes. However, LEVs are less suitable for the gas metal arc welding (GMAW) process, wherein the gaseous shield is produced by the gentle flow of the shielding gas from the GMAW gun nozzle. Weld quality concerns may be anticipated when Chapter 10: LEV Discussion Copyright AIHA® For personal use only. Do not distribute.

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using 100 fpm at the arc. Consequently, LEVs may be best suited to SMAW and FCAW processes. Ventilation controls are generally regarded as “engineering controls.” However, in this application it is more appropriate to regard LEVs as “work practice controls” because, unlike a traditional engineering control, LEVs used for welding fume require near-constant attention on the part of the worker to be effective. Results of two LEV evaluations below illustrate that point. Meeker et al. have demonstrated that a small LEV (2-inch diameter duct) can be useful in reducing fume exposures. In a lab setting, these researchers reported breathing zone total particulate fume reductions of 60%. Using the same LEV equipment, fume reductions of 10% were achieved in a field demonstration. The difference in the lab data and the field data is due to positioning of the LEV. Note that in either case, fume concentrations in the breathing zone were reduced but not eliminated. This paper illustrates the importance of LEV location when used for control of welding fume exposures and the relatively small effective capture zone created by a 2-inch duct with bell-shaped LEV hood. The following evaluation of an LEV with filtration illustrates how critical the proper location of an LEV is in producing effective fume capture. An evaluation of an LEV with filtration employing an 8-inch diameter duct was conducted by this writer (M.K. Harris), the results of which are summarized in the following table.a,b The air cleaner evaluated was an Air Quality Engineering (AQE) Model M66V portable air cleaner. Relevant specifications include: • • • • •

2HP 220/240-volt motor Backwards inclined (B.I.) blower 35% ASHRAE prefilter (4 inches thick) 95% ASHRAE primary filter 8-inch diameter, 10-foot-long flexible intake equipped with a 13-inch diameter conical hood • Face velocity was approximately 1100 fpm. • Unit was evaluated both with and without a high-efficiency particulate air (HEPA) filter (99.97% effective at 0.3 µ). Full Disclosure: M.K. Harris has a business relationship with Air Quality Engineering, the manufacturer of the LEV evaluated. It should be noted that physics is not brand sensitive and similar equipment from other manufacturers would provide similar results. b A web search for “air cleaners for welding” will bring up multiple manufacturers of similar equipment. a

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• This unit was a “shop unit” in everyday use at AQE and was equipped with new filters for this evaluation. • The HEPA installation was not DOP tested for leakage after the filter was installed.c Welder exposures, area concentrations, and airflow at the arc were measured under the following conditions: • No air cleaner. This was the baseline or “control” condition. • Air cleaner WITH HEPA: – Hood suspended 1.0 diameter from the arc. – Hood suspended 1.5 diameters from the arc. – Hood suspended 2.0 diameters from the arc. • Air cleaner WITHOUT HEPA: – Hood suspended 1.0 diameter from the arc. – Hood suspended 1.5 diameters from the arc. – Hood suspended 2.0 diameters from the arc. – Hood 2.0 diameters from the arc with hood on table. The work area exhibited the following characteristics: • Welding area dimensions: – 38 ft × 30 ft = 1140 ft2 – 24-ft height – Work area volume = 27,360 ft3 • Walls to ceiling on two sides • Screens to ceiling on two sides • One 6.5 ft × 7 ft walk-through opening on west side of welding area • No ventilation (e.g., shop fans, overhead fans, or open doors) other than the LEV equipment being evaluated The welding consisted of running stringer beads under the following conditions: • • • •

1/8-inch diameter 308L stainless steel electrodes 125 amps current Flat position 20 to 26 electrodes consumed during a 30-minute exposure period

The decision to evaluate the unit without seal testing was based on the assumption that end users do not perform leak tests after filter replacement. c

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221

222

30.29 µg/m3

25.34 µg/m3

29.44 µg/m3

N/A

Area sample 5 ft from arc

Area sample 10 ft from arc

Area sample 15 ft from arc

Airflow at arc

32 to 34 fpm

7.46 µg/m3

8.45 µg/m3

8.985 µg/m3

30.83 µg/m3

61 to 62 fpm

3.96 µg/m3

5.64 µg/m3

5.57 µg/m3

6.12 µg/m3

2.10 µg/m3

E

96 to 97 fpm

5.72 µg/m3

6.89 µg/m3

5.035 µg/m3

9.01 µg/m3

0.44 µg/m3

32 to 34 fpm

0.55 µg/m3

1.09 µg/m3

1.08 µg/m3

2.74 µg/m3

6.21 µg/m3

95% 95% ASHRAE. ASHRAE. NO HEPA PLUS HEPA Hood 1 Diam- Hood 2 Diameter Away eters Away

D

61 to 62 fpm

1.66 µg/m3

2.27 µg/m3

2.20 µg/m3

0.54 µg/m3

4.06 µg/m3

95% ASHRAE. PLUS HEPA. Hood 1.5 Diameters Away

F

96 to 97 fpm

1.63 µg/m3

0.55 µg/m3

1.08 µg/m3

9.98 µg/m3

1.83 µg/m3

95% ASHRAE. PLUS HEPA. Hood 1 Diameter Away

G

95 fpm

3.542 µg/m3

2.633 µg/m3

2.453 µg/m3

N/A

2.195 µg/m3

95% ASHRAE. Upgraded Seal Hood 2 Diameters Away ON TABLE

Values in bold exceed permissible exposure limit (PEL) of 5 µg/m3. fpm, feet per minute; HEPA, high-efficiency particulate air; HFAPR, half-facepiece, air-purifying respirators; LEV, local exhaust ventilation.

453.51 µg/m3

Welder’s Right Shoulder

49.77 µg/m3

95% ASHRAE. NO HEPA Hood 2 Diameters Away

HFAPR w/ P100. NO Air Cleaner.

658.24 µg/m3

95% ASHRAE. NO HEPA Hood 1.5 Diameters Away

Inside Welder’s Hood

Sample Location

C

B

A

Table 10.1 LEV Evaluation Data

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Figures 10.1 through 10.5 show the location of the LEV hood during the evaluation.

Figure 10.1: No local exhaust ventilation (LEV)

Figure 10.2: Two diameters from arc

Figure 10.3: One and a half (1½) diameters from arc

Figure 10.4: One diameter from arc

Figure 10.5: Local exhaust ventilation (LEV) on table Chapter 10: LEV Discussion Copyright AIHA® For personal use only. Do not distribute.

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1. LEV Evaluation Critique It should be emphasized that the information in Table 10.1 is best regarded as indicative of LEV performance potential rather than definitive. Note that there is only one data point in each cell of the table. A more robust and reliable evaluation would include multiple runs for each cell with the geometric mean being recorded in each cell. The writer (M.K. Harris) was the welder during this evaluation, and great care was taken to weld within the LEV’s effective capture zone. It is often the case that welders do not take care to move the LEV hood as the welding work progresses. Unless the hood is frequently relocated to maintain the appropriate distance from the weld, the arc gradually moves away from the LEV hood with resultant loss of capture efficiency. Each electrode produces a weld bead approximately 9 to 10 inches in length, and that distance is sufficient to require relocating the LEV hood every one or two electrodes. Variations in shop air movement (e.g., from comfort fans and passing fork trucks) can negatively impact the effectiveness of LEV equipment. Those variations in shop conditions were NOT duplicated during this effort. The suspended location of the LEV hood is far from optimal. This location tends to move welding fume toward the breathing zone. Placing the LEV hood on the table (or part being welded) is a superior location. However, the suspended location is driven by the configuration of the LEV intake “arm,” which, regardless of manufacturer, rises up from the blower/filter cabinet before descending to the work area. LEVs connected to overhead ventilation systems exhibit the same limitation on LEV hood placement. This industrial hygienist has seen successful applications of LEVs that have been freed from the restrictions of a rigid “arm” by replacing the arm with a length of flex duct with either (or both) a bracket or strong magnet placed at the hood entry (see Figure 10.6).

2. LEV Evaluation Outcomes • Suspended LEV hood locations 1.0 to 1.5 diameters from the arc were effective at keeping welder exposures to less than 5 µg/m3. • Suspended LEV hood locations 2 diameters were not shown to be effective.

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Figure 10.6: Flex duct rather than rigid arm • Placing the LEV hood on the table 2 diameters from the arc was effective at keeping welder exposures to less than 5 µg/m3. • All nine area samples using HEPA filtration indicated hexavalent chromium exposures less than 5 µg/m3, eliminating the need for a “regulated area.”d • Eight of the nine area samples collected when not using a HEPA post-filter exceeded 5 µg/m3, indicating a need for a regulated area. • In no case was the 100-fpm capture velocity criterion specified by the AWS in ANSI Z49.2:2012 exceeded.

3. LEV Commentary LEVs require frequent worker involvement to ensure that the LEV hood is correctly placed relative to the arc. This IH’s observations of LEVs in use are that they are seldom used correctly and A “regulated area” as defined by the OSHA Standard is an area where workers may expect to be exposed to 5 µg/m3 hexavalent chromium, or more, while working in the area. d

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are more often to be found suspended 2 diameters from the arc or more rather than 1.0 to 1.5 diameters from the arc. At the 2-diameter suspended distance breathing zone, exposures exceeded the permissible exposure limit (PEL) for hexavalent chromium, requiring the use of respiratory protection even when using the LEV. Increased effectiveness can be gained by placing the LEV hood on the table or on the part to be welded. A little-recognized potential benefit of using LEVs, even when sub-optimally used with the hood 2 diameters away from the arc, is that a HEPA-equipped LEV (or an LEV that exhausts to the atmosphere outside the shop) can potentially eliminate the need for a regulated area when welding on stainless steel. Note that all nine of the area samples collected during the evaluation with HEPA filtration were below the PEL of 5 µg/m3, thereby eliminating the need for a regulated area. Because of the need for worker involvement when using LEVs, these exposure control measures are more accurately described as work practice controls rather than engineering controls even when using the larger 8-inch duct with conical hood.

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11 Welding Fume as a Group 1 Carcinogen: A Discussion This chapter is in two segments. The first segment was originally published in the Journal of Occupational and Environmental Hygiene (JOEH 2019, Vol. 16, No. 6, 367–371)1 and is reprinted here with permission from that journal’s publisher, Taylor & Francis. This article outlines the reasons for identifying iron oxide as having a role in carcinogenesis and provides suggestions for a path forward in developing an occupational exposure limit (OEL) for welding fume and/or iron oxide. Recognizing that the process of developing an OEL takes time, and that basic science needs to be done to allow development of an OEL, the second segment offers some suggestions for what can be done in the near term (like right now) to address welding fume as a Group 1 human carcinogen.

1. Segment 1: Welding Fume is a Group I Carcinogen with No OEL and No Method: Suggestions for a Path Forward Introduction The International Association for Research on Cancer (IARC) has classified “welding fume” as Group 1 carcinogen[1]. While there are OELs for some of the components of welding fume, there is no Occupational Exposure Limit (OEL) for undifferentiated welding fume (aggregate welding fume without regard to individual constituents). It must be noted that IARC’s classification does not address possible differences in carcinogenicity that may arise from the substantial differences in the makeup of fumes produced by differing combinations of the metals and welding processes involved in different production and repair welding processes. The situation is further complicated by new information that illuminates the role of iron in development of neuroplastic disease. In short, we do not yet know enough about the health effects of welding fume in its various combinations or the health effects of iron to establish an OEL, or more likely, a set of OELs for welding fumes. This commentary Chapter 11: Welding Fume as a Group 1 Carcinogen Copyright AIHA® For personal use only. Do not distribute.

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is meant to initiate professional discussions focusing on concerns regarding welding fume exposures. These include the role of iron in promoting neoplastic disease, potential synergistic and/or additive health effects of the various components of common welding fumes and the development of welding fume OELs.

History of Welding Fume and Iron Hazards In 2003, the ACGIH®, recognizing the need for addressing the individual fume constituents, withdrew the welding fume TLV-TWA® as Total Particulate[2]. This made perfect sense because “the composition and quantity (of the fume) are both dependent on the alloy being welded and the process and electrodes used.” Consequently, individual fume constituents (e.g., hexavalent chromium (Cr(VI)), nickel (Ni) and respirable manganese) have been viewed as the primary contaminants of concern with much of the focus being on stainless steel and Cr (VI) exposures. However, Cr (VI) exposure concerns are not limited to stainless steel. As an example, recent work by McMannus and Haddad has shown that Cr (VI) exposures in excess of 5 µg/ m3 may be anticipated during gas metal arc welding (GMAW) on 5000 and 6000 series aluminum.[3] It should also be noted that Cr (VI) is far from the only carcinogen of concern; beryllium, cadmium, and nickel oxides are among IARC-1 carcinogens that are found in welding fume. One would expect that welders frequently exposed to fume from alloys containing these known carcinogens would exhibit a markedly higher incidence of lung cancer than those who are exposed only to mild steel/carbon steel fumes. This does not seem to be the case. Ambrose, Wild and Moulin[4] performed a meta-analysis on lung cancer and welding, using 60 studies that concluded that the CRR [Combined Relative Risk] values were similar for mild steel and stainless steel welders. These results did not support the hypothesis that stainless steel welders are at higher lung cancer risk than mild steel welders, despite their probable exposure to chromium and nickel compounds in welding fumes. For decades we have been unable to parse out the differences in lung cancer incidence among stainless steel welders vs. carbon steel welders.[5,6] In the opinion of this IH, that inability may be because the literature has been inconsistent in identifying a number of variables than can affect welding fume exposures (e.g., welder mobility, ventilation, workplace configuration and variation in metals being welded) and we have not been uniformly successful in

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separating out data reflecting exposures to known carcinogens from exposure data that do not include those carcinogens. As a consequence of that mixing of exposure scenarios, we really do not know who is exposed to the known carcinogens in welding fume and who is not. This results in an inability to parse out the carcinogen-exposed workers from those who are not. That opinion, however, was not informed by the possibility that there is a neoplastic agent in nearly all welding fume (aluminum excepted) for which there is epidemiological data and animal data associating exposure with increased neoplastic disease.

The Role of Iron If not Cr(VI), Ni and the others, what would be a common factor associated with elevated lung cancer risk among welders? The common substance to be found in nearly all welding fume (aluminum excepted) is iron. Although the profession has recognized that the health effects of iron fumes included siderosis, the literature indicates that iron fumes may also play a role in neoplastic disease.[7] In 1994, Knekt et al.[8] postulated that iron in lung tissue may “increase the risk of cancer through its contribution to the production of free oxygen radicals.” Fonseca-Nunes et al.[9] detected redox-active iron in the epithelial lining fluid of the normal lung. Torti and Torti[10] summarized that iron has a role in tumor irritation and growth. Siew et al.[10] identified the relationship between iron and welding fume exposure to an increased lung cancer risk, namely squamaous cell carcinoma. The case for iron as a neoplastic agent was recently further reinforced by animal data from NIOSH[7], where their work demonstrated that fumes from gas metal arc welding on mild steel, without the presence of metals known to be carcinogens, promoted lung tumors in mice. It must also be noted that the specific role of iron in development of neoplastic disease is not yet well understood. Falcone et. al.[7] provide a discussion of possible mechanisms by which iron may be involved. These include but are not limited to: the production of reactive oxygen species, altered iron homeostasis, and the ability of Fe to act as a micronutrient for bacteria, inhibition of the immune system, and enhanced binding of Streptococcus pneumoniae to lung epithelial cells. In view of the near ubiquity of iron fume during welding and the evident role of iron in neoplastic disease, there seems little reason to disagree with IARC’s classification of “welding fume,” without

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specifying the presence of Cr and Ni, as a Group 1 carcinogen with lung being the target organ.[12] However, there is no current OEL for an aggregate classification of “welding fume.” Resolving this conundrum requires addressing two questions: 1), Are all welding fume equally carcinogenic? and 2), What constitutes an appropriate OEL or set of OELs for welding fume?

Are All Welding Fumes Equally Carcinogenic? Recent work by Zeidler-Erdely et al.[12] indicates that there is a need for further investigation to evaluate welding fume carcinogenicity. Describing the results of animal responses to GMAW fume from stainless steel (GMA-SS), the authors noted that the total GMA-SS Welding Fume (WF) was more cytotoxic than the sum of the component metals. They also noted that the individual metal oxide components of the fume are likely to exhibit a synergistic influence on lung toxicity and inflammation. In another paper Falcone et al noted that in nasopharengeal doses of metals in ratios that approximate the makeup of stainless steel welding fume, iron was more effective at producing long-lasting inflammation (and concomitant elevated cancer risk) than either Cr(VI) or nickel.(Add new reference). The constituents of welding fume vary with the welding process as well as with the welding consumable. As an example, Shielded Metal Arc Welding (SMAW) and Flux Core Arc Welding (FCAW) are the two common welding processes employed in maintenance and repair work on the US Gulf Coast. The metal being welded is nearly always carbon steel. These welding processes use a flux to promote wled quality. However, the fluxes are not identical and the fumes from the two processes are not identical. Are these differences reflected in different cancer risks for these two fumes? As another example, a shipyard welder producing aluminum boats is not likely to experience an iron exposure but Cr(VI) exposure can be anticipated. In contrast, a shipyard welder producing steel ships will experience iron exposures but exposures to Cr(VI) are less likely. Are these fumes from these diverse welding consumables (aluminum vs carbon steel) likely to exhibit equivalent carcinogenicity? We do not yet know. It seems probable that animal studies would be required to address these questions. In view of the variable constituents of welding fume emitted from numerous combinations of processes and metals, and the need for further work elucidating the possible synergistic effects of these

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constituents, the perceived inference that all welding fume is equally carcinogenic may or may not be correct. When sufficient data has been collected to allow for control banding, the control banding approach may be useful for welding applications. Ranking of welding fume hazards would also inform development of an occupational exposure limit (OEL) or a set of OELs for various welding fumes.

What OEL Should We Use? Establishing an OEL ought to be informed by both the health effect data (noted above) and our technical abilities to reliably measure exposures at that OEL. In that vein, at least two OEL approaches seem worth investigation. Approach 1: Additive formula model. This constitutes a welding fume OEL analogous to the working OELs developed from the additive formula used, as an example, for solvent vapors. Employing such an approach would require simultaneous monitoring for the above noted IARC-1 substances plus iron. Using Approach 1 with current widely used monitoring techniques, we find that Cr(VI) requires a PVC filter while the other metals require an MCE filter. Consequently, simultaneous monitoring to characterize fume constituents for a given combination of process and consumable requires placing two sample media under the helmet. Multiple sample media under the welding helmet places an undesirable burden on the welder. Unresolved questions include: (1) Do we know enough about the effects and interactions of the various fume constituents to use an additive formula? (2) If an additive formula is used, which fume components do we include? (3) Regarding lung carcinogenesis, the additive, synergistic and potentiating aspects of the above fume constituents are not yet well studied. Their relative importance in development of neoplastic disease has yet to be established. (4) If we use an additive model, should the recognized IARC-1 fume constituents be equally weighted? (5) Recognizing the role of iron, how should iron exposures be weighted? Furthermore the current TLV-TWA® for iron oxide is 5 mg/m3 as a respirable sample. The links between neoplastic disease and iron exposure described in the literature suggest that it may be appropriate to revisit this OEL. The above additive formula model is something of a quagmire. There may be simply too many sample media and avoidable calculations involved.

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Approach 2: Aggregate undifferentiated fume model. Because of the above difficulties, Dr. Martin Harper proposed a much more elegant and practical approach: “We need to think outside of the box when it comes to complex mixtures such as welding fume and keep in mind that there are simple and cheap alternatives to measuring each and every component, which still can be used to help ensure worker protection.[15]” This approach would constitute a group of a few OELs that assign different risks, and concomitant OELs, to the fumes from different common combinations of process and consumable. This may be amenable to control banding via or aggregate fume could be monitored gravimetric analysis. Implementation will require two kinds of additional information: a dose-risk relationship for each type of fume and a determination of acceptable risk. Part 1: The dose-risk relationship for each type of fume. The “type of fume” refers to the combination of welding consumable and the welding process. This approach presumes that the fume from chromium and nickel containing alloys may exhibit different carcinogenic effects than carbon steel; a presumption that likely would require laboratory animal work comparing the effects of these fumes. “Type of fume” ought to also address Shielded Metal Arc Welding (SMAW) and FCAW as well as the GMAW processes evaluated in animal studies to date. While the GMAW and FCAW processes are amenable to fully automatic operation that facilitates replication of fume generation variables, the completely manual SMAW process is more challenging in that respect and developing techniques for producing consistently repeatable results from this manual process may be challenging. Nonetheless, since SMAW is the dominant process in the welding industry, that challenge will need to be met. Comparing GMAW with FCAW allows for evaluating if there is a difference in effects that can be attributed to the non-metallic fume products associated with the fluxes used in FCAW. Comparing stainless steel with carbon steel allows for investigation of synergism or potentiation by various species of chromium and nickel with iron. One is not attempting to offer a definitive scope of work for the research necessary to develop a dose-risk relationship. Rather, the intent is to suggest a possible path forward for that work. One would note that common thermal cutting processes such as Carbon Arc Cutting (CAC). And Plasma Arc Cutting (PAC) ought to be included in this investigation. The total undifferentiated or aggregate fume model has much to recommend it, not least of which are: 1) a single sample medium 232

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and 2) a single OEL for each common combination of consumable and process. Using the total fume approach also obviates the need for determining how to weight the carcinogenic effects of each of the fume constituents as would be necessary if using the additive approach. A pre-tared PVC can be analyzed gravimetrically for total fume and subsequently analyzed for CrVI. If that PVC sample medium is placed in a IOM sampler for the inhalable fraction, one can get results for total undifferentiated inhalable fume and inhalable Cr(VI) on a single sample medium. Part 2: A determination of “acceptable risk” for each type of fume. The determination of “acceptable risk” has not been consistent from one carcinogen to the next. As an example, the listing below is taken from an OSHA training materials presentation[16]: Asbestos: 6.7 deaths per 1000 workers Benzene: 10 deaths per 1000 workers Cr(VI): 10 to 45 deaths per 1000 workers. Consensus regarding the definition of acceptable risk for a carcinogen remains elusive and is not addressed further here.

Welding Fume Exposure Control While the science needed to establish a set of health-based gravimetric OELs is substantial and will not take place overnight, those tasks may pale in comparison to the culture change we face when it comes to controlling worker exposures to welding fume. With the exception of GTAW (or “TIG”) and Submerged Arc Welding (SAW) nearly every other welding and thermal cutting process is likely to require some level of respiratory protection device (RPD) for the welder. We will not know what protection factor is required until we have the set of OELs promoted above.

Summary The following paths forward are offered for discussion: • IARC’s classification implicates all welding fumes as being carcinogenic: It is feasible to determine if they are, or are not, equally carcinogenic? • Identify a No Observed Adverse Effect Level for iron or for aggregate or undifferentiated welding fume. • Laboratory work to date has utilized Gas Metal Arc Welding (GMAW) fume. It is worth investigating the more common Chapter 11: Welding Fume as a Group 1 Carcinogen Copyright AIHA® For personal use only. Do not distribute.

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• • • •

•

•

Shielded Metal Arc Welding (SMAW or “stick welding”) fume in lab work Develop a set of OELs that encompasses undifferentiated welding fume from common processes and consumables. Revise existing OELs for iron to address recent information regarding the role of iron in development of neoplastic disease. Investigate the possible synergistic and/or potentiating roles of the various fume constituents as they affect lung carcinogenesis It is suggested that an appropriate monitoring method for welding fume would employ a pre-tarred PVC filter in an IOM for inhalable aggregate or undifferentiated welding fume with subsequent analysis for Cr(VI). Effective and consistent control of welding fume exposures will require all of the tools at our disposal and, even more challenging, we are faced with substantial culture change in order to control those exposures. Safety Data Sheets for welding consumables should incorporate appropriate warnings regarding the carcinogenicity of welding fume.

There are a lot of unanswered questions here and I look forward to reading your thoughts in the pages of our Journal.

Acknowledgements I am indebted to Cathy Hovde for encouraging this IH to develop this commentary. Dr. Jim Antonini and Dr. Patti Zeidler-Erdely brought the neoplastic role of iron to my attention. Dr. Martin Harper’s perspectives were invaluable.

References 1. International Association for Research on Cancer, World Health Organization: Welding, Molybdenum Trioxide, and Indium Tin Oxide, Volume 118, Lyon France 2018, pg. 33. 2. ACGIH “TLVs and BEIs” 2003, pg. 71. 3. McMannus, T. N. and A. N. Haddad: Chromium emissions During Welding in an Aluminum Shipbuilding Environment. Welding Journal, American Welding Society, Vol. 95 86S --92S (2016). 4. Ambrose D., P. Wild, and J.-J. Moulin: Update of a meta-analysis on lung cancer and welding. Scand J Work Environ Health. 32(1):22-31 (2006).

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5. Hansen, K.S., J.M. Lauritsen, and A. Skytthe: Cancer incidence among mild steel and stainless steel welders and other metal workers. Am. J. Ind. Med. 30, 373–382 (1996). 6. Lauritsen, J.M., K.S. Hansen: . Lung cancer mortality in stainless steel and mild steel welders: a nested case-referent study. Am. J. Ind. Med. 30, 383–391 (1996). 7. Falcone LM, A. Erdely, V. Kodali, et al. “Inhalation of iron-abundant gas metal arc welding-mild steel fume promotes lung tumors in mice” Toxicology 409: 24-32. (2018). 8. Knekt, P., A. Reunanen, H. Takkunen, A. Aromaa, M. Heliövaara, and T. Hakuunen. Body iron stores and risk of cancer. Int. J. Cancer, 56: 379-382 (1994). 9. Fonseca-Nunes, A., P. Jakszyn, and A. Agudo. Iron and Cancer Risk—A Systematic Review and Meta-analysis of the Epidemiological Evidence. Cancer Epidemiol Biomarkers. Prev; 23(1): 12-31 (2014). 10. Torti, S. and F. Torti. Iron and cancer: more ore to be mined. Nature Reviews Cancer 13: 342–355 (2013). 11. Siew, S., T. Kauppinen, P. Kyyronen, P. Heikkila, and E. Pukkala: “Exposure to iron and welding fumes and the risk of lung cancer.” Scand J Work Environ Health 34(6): 444 – 450 (2008). 12. International Association for Research on Cancer, World Health Organization: Welding, Molybdenum Trioxide, and Indium Tin Oxide, Volume 118, Lyon France 2018, pg. 265 13. Jenkins, N. T. and T.W. Eagar: “Chemical Analysis and Welding Fume Particles.” Welding Journal, 84: 87S-93-S (2005). 14. Zeidler-Erdely PC, R. Salmen, A. Erdely, M. Keane, V.K. Kodali, J. Antonini, L.M. Falcone: Pulmonary toxicity of gas metal arc-stainless steel welding fume and its component metals. In The Toxicologist: Supplement to Toxicological Sciences, 150 Abstract #2125, 56th Annual Meeting and ToxExpo, Baltimore, MD, March 12-16, 2017. 15. Personal Communication, Dr. Martin Harper, June 14, 2018 16 “Hexavalent Chromium, Hazards of Hexavalent Chromium in the Workplace.” produced under grant number SH-22248-1160-F-54 from the Occupational Safety and Health Administration, U.S. Department of Labor. To the above, one must add a description of a possible mechanism for iron oxide’s role in carcinogenesis. Kornberg et al in 2017 offered the following description for intentionally created iron oxide nanoparticles. While Kornberg et al did not specifically address the Chapter 11: Welding Fume as a Group 1 Carcinogen Copyright AIHA® For personal use only. Do not distribute.

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iron oxide nanoparticles in welding fume, there seem to be little reason to believe that welding fume iron oxide nanoparticles would be processed any differently. “Proposed mechanism behind IONP-induced iron homeostasis disruption and subsequent adverse outcomes. If IONPs are engulfed by the cell via phagocytosis and end up in a phagosome, this membrane bound vesicle will then fuse with the lysosome, creating an acidic environment for degradation. However, once in this acidic environment, IONPs will instead dissolve, releasing free iron ions into the cell’s catalytically active labile iron pool. This may ultimately result in increased and excessive ROS generation, and subsequent adverse outcomes. Dissolved particle may also affect iron stores in mitochondria and other organelles. Maintenance of iron homeostasis via iron import proteins, iron storage proteins, and iron export proteins. In order to maintain appropriate iron levels within a cell, a complex network of iron-related proteins are involved in iron import, storage, and export. Example proteins for these processes (DMT1, CD71; ferritin; SLC40A1, respectively) are shown). Free Fe2+ in the labile iron pool is necessary for cellular function, but too much can cause an excess of reactive oxygen species generation via participation in the Fenton reaction. The labile iron pool is carefully maintained using iron storage mechanisms via ferritin. In pathologic conditions, increased iron in LIP will generate an excess of free hydroxyl radicals and induce adverse outcomes within the cell.”i To summarize: • There are epidemiological data linking welding fume to lung cancer. • There are lab animal studies linking welding fume, and specifically iron oxide, to lung cancer. • There is at least one suggested mechanism for the role of iron oxide in lung cancer. Potential Toxicity and Underlying Mechanisms Associated with Pulmonary Exposure to Iron Oxide Nanoparticles: Conflicting Literature and Unclear Risk. Kornberg et al, Nanomaterials 2017, 7, 307; doi:10.3390/ nano7100307

i

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2. Segment 2: Near-Term Approaches to Dealing with Welding Fume as a Carcinogen Recognizing that welding or thermal cutting fume is likely to contain either iron oxide or hexavalent chromium (or both), there are at least three approaches to recommending exposure controls: • Mixtures method • NIOSH-suggested OEL of 0.10 mg/m3 • Exposure control banding

2.1 Mixtures Method Regarding the use of the threshold limit values (TLV-TWAs®) for simultaneous exposures to a mixture of chemicals, the American Conference of Governmental Industrial Hygienists (ACGIH) states: When two or more hazardous substances have a similar toxicological effect on the same target organ or system, their combined effect, rather than that of either individually, should be given primary consideration. In the absence of information to the contrary, different substances should be considered as additive where the health effect and target organ or system is the same. That is, if the sum exceeds unity as per the following formula:

C1 C2 Cn —— + —— + ... —— T1 T2 Tn

then the threshold limit of the mixture should be considered as being exceeded (where C1 indicates the observed atmospheric concentration and T1 is the corresponding threshold limit).2 If the additive mixtures method is used, one would suggest that it is appropriate to limit the substances of interest to those associated with carcinogenesis: • Beryllium (IARC-1 Carcinogenic to Humans. See also 29 CFR 1920.1024)

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• Cadmium (IARC-1 Carcinogenic to Humans. See also 29 CFR 1910.1027) • Chromium VI (IARC-1 Carcinogenic to Humans. See also 29 CFR 1910.1026) • Cobalt (IARC-2B Possibly Carcinogenic to Humans) • Iron Oxide (Not yet recognized by any authoritative body as carcinogenic but should be included for reasons noted in the commentary paper above) • Lead (IARC-2B Possibly Carcinogenic to Humans. See also 29 CFR 1910.1025) • Nickel – Elemental (IARC-2B Possibly Carcinogenic to Humans) • Vanadium Pentoxide (IARC-2B Possibly Carcinogenic to Humans) The Excel spreadsheet accompanying this volume may be used for the mixtures method. 2.1.1 Critique of Mixtures Method • Not all the above substances are associated with the lung as the target organ (e.g., cobalt). • Although an MCE filter is used for most metals, a separate PVC filter is required for CrVI. This increases the burden on the workers being monitored. • If the TLV-TWA for iron oxide of 5 mg/m3R is used when employing the mixtures method, it should be recognized that this OEL does not take into account the role of iron oxide in carcinogenesis. • Development of welding SEGs and personal breathing zone monitoring for the welder and area monitoring to establish exposures for passersby and other workers in the area are required to utilize this tool. While this exercise in Occupational Hygiene is being conducted, workers are being exposed to a carcinogen.

2.2 NIOSH-Suggested OEL of 0.01 mg/m3 In Publication No. 2019-132, NIOSH suggests an occupational exposure band (OEB) of 0.01 mg/m3 for Group 1 carcinogens.3 Figure 1-2 of 2019-132 notes that the chemical substances with the highest health hazard potentials are categorized as Group E. Table 1-1, “Airborne concentration ranges associated with occupational exposure bands,” lists an “Airborne target range for dust or particle 238

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concentrations” for Group E as ≤ 0.01 mg/m3. Although this value is certainly useful for many applications, there is something of a dilemma in applying it to welding fume. 2.2.1 Critique of Using ≤ 0.01 mg/m3 OEL Taking into consideration that IARC does not differentiate between the various types of welding fume from various combinations of processes and consumables, unanswered questions and concerns include the following: • Should the ≤ 0.01 mg/m3 OEB be compared to aggregate undifferentiated or “total” welding fume collected as a gravimetric sample? • Should the ≤ 0.01 mg/m3 OEB be compared to either respirable or inhalable undifferentiated welding fume collected as a gravimetric sample? • Should the ≤ 0.01 mg/m3 OEB be compared to the aggregate concentrations of the fume constituents known to have respiratory effects or only those associated with lung cancer? • Development of welding SEGs and personal breathing zone monitoring for the welder and area monitoring to establish exposures for passersby and other workers in the area are required to utilize this tool. While this exercise in Occupational Hygiene is being conducted, workers are being exposed to a carcinogen. • On the positive side, it should be noted that one of the advantages of comparing the ≤ 0.01 mg/m3 OEB to any gravimetric exposure estimate is that the present conundrum concerning the status of iron oxide as a carcinogenic agent is circumvented; iron oxide is simply included as a component of the fume without having to refer to a substance-specific OEL for iron oxide. • Also, as a positive for using the ≤ 0.01 mg/m3 OEL, a simple gravimetric analysis of a pre-tared PVC is all that is required.

2.3 Exposure Control Banding Exposure control banding (ECB) is not new. Examples dictating work practice and respiratory protection requirements include: • The OSHA Construction Industry Standard (29 CFR 1926.1101 for the four Classes of work defined in this standard [1926.1101(h)(1)]. Chapter 11: Welding Fume as a Group 1 Carcinogen Copyright AIHA® For personal use only. Do not distribute.

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• The OSHA Respirable Crystalline Silica Construction Standard in Table 1 at 1926.1153(c)(1). • The U.S. Army Corps of Engineers Safety and Health Requirements Manual (Revised 2014, EM 385-1-1) Section 10, Welding and Cutting, offers examples of ECB for this work.4 However, in view of the 2014 publication date, the categorization of welding fume as a Group 1 carcinogen is not addressed in this Corps of Engineers document. Also, some sections require exposure assessments. In this chapter, two bands are offered for your consideration: one for high-fume emitters and one for low-fume emitters. These two bands are described below: • Assumptions: – Because steel and 5000- and 6000-series aluminum are among the most commonly welded metals, welding fume can be expected to contain either iron oxide (in steel fume) or CrVI (in aluminum fume). – Welding and thermal cutting processes can be classified as “high-fume emitters” or “low-fume emitters” based on the mechanics of the welding process. – Mechanics of the welding process will drive the control measures. – Although local exhaust ventilation (LEV) can substantially reduce fume exposures, LEVs are seldom used correctly (by which it is meant that they are usually placed more than 1 to 1½ hood diameters from the arc). Consequently, LEVs mitigate rather than eliminate fume exposures. Even so, LEVs can greatly reduce fume exposures for coworkers. 2.3.1 High-Fume Emitter Processes • High-Fume Emitter Process Characteristics: – Thermal cutting processes are default high emitters. – No physical barrier between the arc and the welder. – Welding process uses the consumable as the electrode: – Shielded metal arc welding (SMAW or MMA) – Flux cored arc welding (FCAW) – Gas metal arc welding • High-Fume Emitter Process personal protective equipment (PPE) for welders and helpers: powered air-purifying respi240

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rator (PAPR) with cape: assigned protection factor (APF) = 1,000 with data from manufacturer. This high level of PPE is in response to the lack of knowledge of what constitutes an “acceptable” level of exposure. • High-Fume Emitter Process PPE for other workers in the immediate area (working outdoors) or in the shop (working indoors): HFAPR/P100. This PPE is in response to 1) the lack of knowledge of what constitutes an “acceptable” level of exposure and 2) the “optics” of working in an area with a visible haze of a Group 1 carcinogen are not good and working in such an area without protection is likely difficult to defend. 2.3.2 Low-Fume Emitter Processes • Low-Fume Emitter Process Characteristics: – Case 1: Gas tungsten arc welding (GTAW or “TIG”) » Process does NOT use consumable as electrode. Therefore, the consumable is not vaporized in the arc. – Case 2: Submerged arc welding (SAW) » Physical barrier (mound of flux) between the arc and the welder. – Case 3: Resistance welding (RW or “Spot welding”) » Physical barrier (parts being welded) between the arc and the welder. • Low-Fume Emitter Process PPE for welders and helpers: half-facepiece, air-purifying respirators (HFAPR)/P100. Even though fume levels can be expected to be low [often barely above the limit of detection (LOD)], the lack of knowledge of what constitutes an “acceptable” level of exposure suggests that working without some level of respiratory protection may be imprudent. • Low-Fume Emitter Process PPE for other workers in the immediate area (working outdoors) or in the shop (working indoors): HFAPR/P11. Again, even though fume levels can be expected to be low (often barely above the LOD), the lack of knowledge of what constitutes an “acceptable” level of exposure suggests that working without some level of respiratory protection may be imprudent. The two ECBs offered above are based on this author’s 5 years of experience as a welder and more than 30 years as an occupational hygienist (OH). By necessity, these ECBs are painted with a broad brush and should be used as a rational approach for Chapter 11: Welding Fume as a Group 1 Carcinogen Copyright AIHA® For personal use only. Do not distribute.

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discussion at your facility but not as a definitive set of rules. The advantages of these ECBs are: • Workers are NOT left unprotected while we, as a profession, conduct the science and debate the fine points needed to generate welding fume OEL. • No air monitoring needs to be done prior to assigning respiratory protection. • The ECBs are presumed to be at least as protective as that required by a future OEL for welding fume (or iron oxide if the science should so dictate). 2.3.3 Critique of Two ECB Approaches The disadvantage of using these two ECBs is that they are not based on quantitative data in the sense that we are accustomed to. They depend on recognition of the mechanics of the processes as they affect fume generation (described above), recognition of the carcinogenicity of welding fume, and the professional judgment of the OH. A more discerning ECB approach is described in Chapter 12.

References

1. Harris M. Welding fume as a Group 1 carcinogen with no OEL and no method — Suggestions for a path forward. J Occup Environ Hyg 16(6): 367–371, 2019. doi: 10.1080/ 15459624.2019.1600703. 2. American Conference of Governmental Industrial Hygienists (ACGIH). Appendix E: Threshold Limit Values for Mixtures, Additive Mixture Formula. Ontario, Canada: CASSEN Group Inc., 2021. http://www.cassen.ca/acgih-appendix-e/. 3. Lentz TJ, Seaton M, Rane P, Gilbert SJ, McKernan LT, Whittaker C. NIOSH: Technical Report: The NIOSH Occupational Exposure Banding Process for Chemical Risk Management. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH), 2019. Publication No. 2019-132. 4. U.S. Army Corps of Engineers. Safety and Health Requirements Manual (EM 385-1-1). Washington, D.C.: Department of the Army, 2014. https://www.publications.usace.army.mil/ portals/76/publications/engineermanuals/em_385-1-1.pdf

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12 Control Banding and Welding 1. Introduction Welding occurs in large, medium, and small businesses. Large businesses might have industrial hygiene (IH) programs and processes where worker exposures are measured and known, particularly in production manufacturing situations. Production welding may occur in heavily controlled environments, with similar pieces being welded and specifically engineered ventilation systems, supervision, training, and other programs in place. Construction and maintenance welding operations are often conducted in less controlled environments, outside in heat or cold, at heights or depths, in restricted and confined spaces, etc. The ability of an industrial hygienist to capture and define multiple hazards occurring simultaneously has always been challenging. Small- and medium-sized businesses employ most welders who have no access to guidance from IH resources. Employers at small- and medium-sized businesses need timely, practical guidance, and control banding offers a pragmatic approach to assess risks and recommend controls. Control banding allows for control recommendations when no measurement methods or occupational exposure limits (OELs) are available. With over 100,000 chemical substances in commerce and less than 1000 OELs, control banding is a practical method to protect workers’ health. Control banding (CB) is a technique used to assess hazards and manage exposure risk to protect workers’ health—the ultimate goal of IH. Traditional IH uses Anticipation, Recognition, Evaluation, Control, and Confirm as the approach to worker protection, which is heavily weighted toward evaluating or measuring potential exposures to hazardous substances. Control banding provides an alternative approach to traditional methods by emphasizing controlling the hazard first with necessary controls before measuring or quantifying the hazard. Control banding was designed for small and medium enterprises to be easy, transparent, and understandable by a lay person using available information (e.g., safety data sheets, user task inputs), predicted exposure bands, and hazard groups. The result is a Control Approach for each task and associated actionable conChapter 12: Control Banding and Welding Copyright AIHA® For personal use only. Do not distribute.

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trol strategies typically 3-4 pages long with images and concise advice on how to protect workers from inhaling airborne contaminants. These control guidance sheets typically explain the process with a brief description of hazards, equipment needed (often with a sketch), respiratory protective equipment (RPE), personal protective equipment (PPE), maintenance of controls, housekeeping, exposure monitoring, health surveillance, training, and supervision. Control banding does not replace traditional IH assessment methods for welding. The IH gold standard is measuring discreet inhalation exposures with a pump and filter and then interpreting results to determine corrective measures that adhere to a regulated OEL. Challenges of traditional assessment methods include delays incurred waiting for sampling results while workers continue to be overexposed. The continuous cycle of sampling and study adds extra costs and uncertainty as to the day(s) and conditions when the measurements occurred and frequently results in further study by IH professionals that have varied interpretations of results. Control banding is considered a qualitative or a semiquantitative risk assessment that has a defined method of ranking hazards directly linked to safety data sheets (SDSs) now prepared to GHS (Globally Harmonized System for Classification and Labelling) standards. The mapping of hazard bands to GHS Classifications is based on the International Labor Organization’s (ILO’s) Chemical Control Toolkit and is consistent with the U.K. Control of Substances Hazardous to Health (COSHH) Essentials online tool.1,2 Initial versions of these control banding processes were designed prior to worldwide implementation of GHS and used Risk Phrases that were only common on material safety data sheets (MSDSs) in Europe. GHS offers worldwide consistency of hazard classification and communication of health and safety information on labels and SDS.3 The ILO ranking still applies, and the recent version of COSHH Technical Basis will give industrial hygienists a deeper understanding of chemical hazards and provide a process that fits the traditional IH approach. Proof of concept for control banding model validation is well-described in the literature. The COSHH Essentials core model was validated with a comparison to measured data and an extensive peer review of the logic and content by experts.4,5 The most extensive external validation of COSHH Essentials was completed by the German BAuA (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin – Federal Institute for Occupational Safety and Health) with close to 1000 data points for liquids and solids. The 95th per244

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centile of data fit within the ranges predicted by the COSHH Essentials. The BAuA study admittedly had limited data on milliliter or ton quantities of low or high volatility or dustiness substances. Another comprehensive study evaluated COSHH Essentials that calculated controls for vapor degreasing and bagging operations; this study predated GHS implementation and found issues that would no longer be relevant.

2. Control Banding and Its Limitations The COSHH Essentials Control Banding Approach is not applicable to tasks that are less than 15 minutes in duration. The COSHH Essentials does not include additive effects from multiple chemicals in an exposure and is not applicable to gases. COSHH Essentials does assess liquids and vapors, but they have been excluded from this discussion to maintain the focus on welding and solids.

2.1 Control Banding and COSHH Essentials The control banding approach of focus here is adapted from the COSHH Essentials Technical Basis.6 Workplace exposure factors, dustiness, and quantity are used to determine an exposure predictor (EP). The international implementation of GHS enables the user to systematically review SDSs for workplace chemicals. Hazard Groups A through E have been mapped to GHS Hazard (H) Statements. There is some United Kingdom and European Union terminology that is inconsistent and has been adapted to North American terminology; for example, the use of EU Hazard Statements and assigned protection factors (APFs). COSHH Essentials Solids pairs the size of dust particles and relative quantity of solids used per day with the relative toxicity gathered from the SDS. First, we will discuss the process and then the applicability to welding. Many of the following principals are similar for liquids but will not be covered.

2.2 Exposure Predictor Bands for Dusts 2.2.1 Dustiness definitions The following definitions of dustiness are used in Table 12.1 to designate the appropriate EP band: • Low: pellet-like, unlikely crushable powders with little indication of any dust during use. Chapter 12: Control Banding and Welding Copyright AIHA® For personal use only. Do not distribute.

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• Medium: crystalline granular solids with some dust evident during use. Dust is seen on surfaces after use. • High: fine light powders. Particles are suspended in air for several minutes after use. Table 12.1: Exposure Predictor Bands Exposure Predictor (EP) Band by Dustiness and Quantity Used Quantity of Powder Used Per Day

Low Dustiness (Coarse)

Medium Dustiness (Granular)

High Dustiness (Fine)

Grams

EP1 Solid

EP1 Solid

EP2 Solid

Kilograms

EP2 Solid

EP3 Solid

EP3 Solid

Tons

EP2 Solid

EP4 Solid

EP4 Solid

SDSs provide Hazard (H) Statements based on the GHS (Globally Harmonized System for Classification and Labelling). In accordance with many regulatory jurisdictions, SDSs are readily available in the workplace. See Appendix B for a list of H-Statements and corresponding Hazard Groups. Grouping hazards by H-statements and applying the appropriate Exposure Predictor Band results in a risk assessment and a relevant control approach. Control banding control approaches for dusts of different hazard groups and exposure profile can be found in Table 12.2. Table 12.2: Hazard Groups vs. Exposure Predictor Bands7 Hazard Group A Solid

Exposure Predictor Band EP1

EP2

EP3

EP4

H304, H315, H319, H336

H-Statements

CA1

CA1

CA1

CA2

B Solid

H302, H312, H332, H371

CA1

CA1

CA2

CA3

C Solid

H301, H311, H314, H317, H318, H331, H335, H370, H373

CA1

CA2

CA3

CA4

D Solid

H300, H310, H330, H351, H360, H361, H361d, H361f, H362, H372

CA2

CA3

CA4

CA4

E Solid

H334, H340, H341, H350

CA4

CA4

CA4

CA4

CA, control banding approach; EP, exposure predictor.

Control banding control approaches are directly related to risk levels and can be easily determined and communicated (see Table 12.3). 246

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Table 12.3: Control Approach and Risk Levels Control Approach

Risk Level

CA1

Low

General ventilation

1

CA2

Medium

Engineering controls (LEV)

10-fold reduction

Local exhaust ventilation (LEV) including effective capture of emissions and enclosing hoods

CA3

High

Containment

100-fold reduction

Isolation or containment of contaminant or worker, small leakages are anticipated

CA4

Extreme

Expert Advice

*

Type

Relative efficacy

General description Significant general or natural ventilation and good work practices

Expert advice is required to choose effective controls

Because of the validation done for control banding, the suitability of the control approach selected can be verified by air monitoring. Table 12.4 provides a prediction of concentrations of dust in air. Table 12.4: Predicted Concentrations and Control Approaches (CA1, CA2, and CA3) Predicted Concentrations of Dust in Air (mg/m3) by Exposure Predictor (EP) and Control Approach (CA) Exposure Predictor Band (quantity/day Control Approach 1 Control Approach 2 Control Approach 3 dustiness General Local Exhaust Containment or category) Ventilation Ventilation (LEV) Isolation EP1 Solid (Grams: medium or low dustiness)

0.01 to 0.1

0.001 to 0.01

< 0.001

EP2 Solid (Grams high dusty, kg & tons: low dusty)

0.1 to 1

0.01 to 0.1

0.001 to 0.01

EP3 Solid (Kg: medium & high dusty)

1 to 10

0.1 to 1

0.01 to 0.1

> 10

1 to 10

0.1 to 1

EP4 Solid (Tons: medium & high dusty)

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These predicted concentrations were validated for solids (not specifically welding). These predictions were validated and refined either by comparison with published exposure data, or where this has not been available, by extensive peer review. Independent validation of some general ventilation and engineering control scenarios was undertaken, based on BAuA. Validation of containment scenarios continues.8

3. Grouping of Control Approaches 3.1 Control Approach 1 (CA1) Low Risk/General Ventilation

• Involves good industrial practices that recognize inhalation hazards. • Chemical hazards are understood. • Fumes are hot and tend to rise. Provide air vents or extraction fans at high levels and openings at lower levels. Inlet air may require heating in winter. • Ensure extraction vents are well maintained and not blocked. • Welding fume should not accumulate in the air during the day. • Fans are checked visually at least weekly for damage and to ensure operationality. • If extraction vents are powered, train workers are to check that they are operating. • Make SDSs available and verify that workplace labels are in place and understood. • Position welding screens/curtains/blinds to protect other workers from arc flash yet still enable ventilation to remove fumes. • Schedule regular housekeeping to restrict dust accumulation. Use a vacuum fitted with HEPA filters. • Check that general ventilation is maintained and that natural ventilation is not blocked. • Train workers to change their position so that they do not directly inhale emissions. • Clean up spills promptly. 248

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Control Banding and Welding

Figure 12.1: General ventilation when welding indoors. [Reprinted with permission. Contains public sector information Figure 12.1: General ventilation when welding indoors. [Contains public published by the Health and Safety Executive and licensed under sector information licensed under the Open Government Licence v3.0.] the Open Government Licence (https://www.nationalarchives.gov.uk/ 3.1.2 Control Approach 2 (CA2) Medium Risk, Local Exhaust doc/open-government-licence/version/3/)]. Ventilation

More detail is provided in the control guidance sheets or direct advice sheets distributed by COSHH Essentials. Figure 12.1 was   reprinted from the COSHH Essentials Direct Advice Sheet WL3 This approach includes 9 all the controls listed in CA1 plus the following: Welding �fume control. Local exhaust ventilation (LEV) positioned to capture emissions generated and designed for the welding processes. Hood design and

positioning are crucial 2 for (CA2) effective removal of fumeRisk, from theLocal breathing 3.2 Control Approach Medium zone of welders. Exhaust � LEV isVentilation maintained and tested according to manufacturer’s specifications.

This approach includes all the controls listed in CA1 plus the following: • Local exhaust ventilation (LEV) positioned to capture emissions generated and designed for the welding processes. Hood design and positioning are crucial for effective removal of fume from the breathing zone of welders. • LEV is maintained and tested according to manufacturer’s specifications. Chapter 12: Control Banding and Welding Copyright AIHA® For personal use only. Do not distribute.

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• LEV has indicators to easily check whether it is on and working. • LEV draws fumes away from the welder’s breathing zone. Enclose the task as much as possible to encourage fumes to be drawn away from the welder. • Extracted air is filtered and vented outside. • Workers know how to use LEV, and its proper use is confirmed and enforced. • Bolt-on extraction tools are available to remove fumes close to the source. More detail is provided in the control guidance sheets or direct advice sheets distributed by COSHH Essentials.

3.3 Control Approach 3 (CA3) High Risk Level, Containment, or Isolation This approach includes all the controls listed in CA1 plus the following: • Emissions are captured at the source with the containment under negative pressure so that clean air leaks into the contaminated zone. OR • Workers are isolated in a clean room, which has a positive pressure so that clean air leaks out to the contaminated zone. More detail is provided in the control guidance sheets or direct advice sheets distributed by COSHH Essentials.

3.4 Control Approach 4 (CA4) Extreme Risk, Expert Advice This approach includes all the controls listed in CA1 plus guidance from a qualified industrial hygienist. This is where the industrial hygienist’s expertise is needed most. There is also value in identifying when industrial hygienists are not needed so they can prioritize the high-risk situations.

3.5 Additional Resources for Exposure Control Guidance There are hundreds of direct advice sheets (DASs) and control guidance sheets (CGSs) from COSHH, and more are being added regularly. At the time of writing, there were 20,000 downloads per month of these DASs and CGSs from the COSHH Essentials website. This is a measure of the control banding acceptance globally.

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These COSHH documents have a common format that generally includes: • Design and equipment • Maintenance • Examination and testing • Cleaning and housekeeping • PPE (personal protective equipment) • RPE (respiratory protective equipment) • Training • Supervision • Sample schematic (see above) of an engineering control • Employee checklist for proper utilization of controls Tools are quickly being developed with simple processes that small and medium enterprises and industrial hygienists can use to protect the health of welders. Many welding processes are a starting point for exposure control but need to be paired with exposure duration, metal types, and guiding principles. The following is an example of a tool developed by COSHH for welding since the IARC carcinogen classification of welding fumes. Table 12.5: Welding Frequency & Controls9 Frequency and Duration of Welding

Type of Welding

Good Control Practice

Infrequent or occasional low-intensity welding < 1 hour of arc time/welder/day

OFW, SMAW, FCAW, GMAW

LEV (CA2) where practical or good general ventilation (CA2) plus RPE

Infrequent or occasional low-intensity welding < 1 hour of arc time/welder/day

TIG and Resistance Spot Welding

General ventilation (CA2)

Regular high-intensity welding > 1 hour of arc time/welder/day indoors

OFW, SMAW, FCAW, GMAW

LEV (CA2) plus supplementary RPE

Regular high-intensity welding >1 hour per day of arc time outdoors

OFW, SMAW, FCAW, GMAW, TIG

RPE where LEV (CA2) is not practical

Regular high-intensity welding < 1 hour of arc time/welder/day indoors

TIG and Resistance Spot Welding

LEV (CA2)

CA, control approach; FCAW, flux core arc welding (high-fume emitter); GMAW, gas metal arc welding (high-fume emitter); LEV, local exhaust ventilation; OFW, oxyfuel welding; RPE, respiratory protective equipment; SMAW, shielded metal arc welding; (high-fume emitter); TIG, tungsten inert gas.

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The Welding Fume Control table (Table 12.5) links the frequency and the amount of “Arc time” per welder with welding process and controls considered as “good practice.” The one hour of arc time per welder per day is consistent with the online resource Breathe Freely. Significant details are provided to enable a small or medium enterprise or industrial hygienist to identify controls and issues around controls.

4. Specific Metals and Applicability to Control Banding Appendix A lists the metals discussed previously in this publication. Additional columns have been added for consideration. The recent Type 1 Carcinogen determination by IARC as discussed in Chapter 11 of this book of Welding Fumes would automatically rank these substances as a Hazard Group E. The corresponding H-Statement for proven carcinogens is H350: May cause cancer. Columns 5-8 are not typically part of control banding but do add to the assessment. The Melting Point and Boiling Point indicate which metals are likely to become fumes in a welding process. The Exposure Predictor Bands are determined by relative quantities of use and relative dustiness; comparing this data from “Appendix A” to the ingredients of welding consumables and metals welded should guide controls, priorities, and further evaluation. The NIOSH PG (Pocket Guide) Target Organs begs the consideration of additive effects. Appendix A also provides a quick comparison of different metals according to the ACGIH threshold limit value (TLV®) (or relevant OEL) to adjust TLVs appropriately.

5. Control Banding and RPE Selection Much of this control banding discussion is based on the COSHH Essentials Technical Guidance document. The next two tables (Tables 12.6 and 12.7) will identify RPE with control bands based on the Technical Guidance document. There are some differences between U.K. terminology and the U.S. NIOSH-based terminology, the most prevalent of which is the use of assigned protection factors (APFs) for respirators. There is no indication of which is right or better; rather, the intent is to provide a general description and ensure the reader has the U.S. NIOSH-based APF values. Given the scientific curiosity of the industrial hygiene profession, some readers

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may check the references and will see different APF values. Filtering facepieces are provided a much lower APF (4), and there is a difference between an N95 or P95 and N100 or P100 that are not in the U.S. NIOSH system. Table 12.7 (RPE Selection) identifies the respirator, facepiece, filter type (P, N, O), and efficiency rating (95 or 100) to protect against particulate like welding fume. Appendix A will link the Hazard Group to the metals being welded or consumables used. Appendix A and the Table of Hazards and Exposure Prediction guide show how to identify the Hazard Group from SDS. Table 12.6: Respiratory Protective Equipment and Assigned Protection Factors (United States and United Kingdom) RPE Code

Detail

Image

—

Not anticipated with other CA1 controls

HFP95

Half Facepiece with N, O, P 95 filter or filtering facepiece

95

HFP95

Half Facepiece with N, O, P 95 filter or filtering facepiece

95

100

HFP100

Half Facepiece with N, O, P 99 or 100 filter or filtering facepiece

FFP100

Full Facepiece with N, O, P 99 or 100 filters

100

100

PAPR100

Powered Air-Purifying Respirator with P 99 or 100 filters (APF40UK-100)

SAR-ve demand

Supplied Air with full facepiece and positive demand pressure

ve

ve

SCBA-ve demand

Self-Contained Breathing Apparatus with full facepiece and negative demand pressure

US APF

UK APF Code

APF10(US)

APF4(UK)

APF10(US)

APF10(UK)

APF10(US)

APF20(UK)

APF50(US)

APF40(UK)

APF25(US) APF100 (US) with hood

APF20(UK) APF30(UK) APF40(UK)

APF50(US)

APF40(UK)

APF50(US)

APF40(UK)

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Table 12.6 (continued): Respiratory Protective Equipment and Assigned Protection Factors (United States and United Kingdom) RPE Code

Detail

Image

SAR+ve demand

Supplied Air with full facepiece and negative demand pressure

+ve

+ve

SCBA+ve demand

Self-Contained Breathing Apparatus with full facepiece and positive demand pressure

US APF

UK APF Code

APF1000(US)

APF2000(UK)

APF10000(US)

APF2000(UK)

Table 12.7: Respiratory Protective Equipment Selection Dustiness Hazard Group A

B

C

D

E

254

Quantity used per day

Coarse (Low)

Granular (Medium)

Fine (High)

Grams (Low)

—

—

—

Kg (Medium)

—

HFP95

HFP100

Tons (High)

HFP95

HFP100

HFP100

Grams (Low)

—

HFP95

HFP100

Kg (Medium)

—

HFP95

HFP100

Tons (High)

HFP100

HFP100

PAPR100

Grams (Low)

—

HFP95

HFP95

Kg (Medium)

HFP100

HFP100

AFP20

Tons (High)

HFP100

HFP100

FFP100, PAPR100

Grams (Low)

HFP100

HFP100

FFP100, PAPR100

Kg (Medium)

HFP100

FFP100, PAPR100

FFP100, PAPR100

Tons (High)

HFP100

FFP100, PAPR100

SAR+, SCBA+

Grams (Low)

HFP100

HFP100

FFP100, PAPR100

Kg (Medium)

HFP100

FFP100, PAPR100

FFP100, PAPR100

Tons (High)

HFP100

FFP100, PAPR100

SAR+, SCBA+

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6. Online Control Banding Tools There are several online control banding tools that will assist both small and medium enterprises and industrial hygienists with calculating and selecting appropriate controls. Readers are encouraged to review the ones that apply to their workplace processes. The author has listed the tools in order of preference for welding, but they all have merit. • Breathe Freely (UK) has an online e-tool specific to welding. It uses timeframes similar to Table Welding Fume Control and provides straightforward advice (https://www.breathe freely.org.uk/WST/). • COSHH Essentials (UK) e-tool is always growing and expanding with hundreds of direct advice sheets (specific to an industry) and control guidance sheets (general control) to help small and medium enterprises mitigate workplace hazards (http://coshh-tool.hse.gov.uk/). • Stoffenmanager® (Dutch) is a well-developed tool using similar COSHH Essentials hazard scoring and exposure scenarios to identify potential exposures. Considerable work has been done to validate results with over 1000 measurements as an initial attempt to verify its usefulness for EU REACH legislation (https://stoffenmanager.com/what-isstoffenmanager/). • ILO Chemical Control Toolkit is based on COSHH Essentials for worldwide use. Its simplicity is its advantage, but there are fewer guidance sheets offered (https://www.ilo.org/legacy/ english/protection/safework/ctrl_banding/toolkit/icct/). • BAuA EMKG (Germany) also has a mobile app that conducts control banding and generates guidance documents.

7. Summary Control banding is an effective model to anticipate, recognize, assess, and define controls for inhalation hazards in the workplace. The implementation of GHS increases the viability of control banding methods with direct inputs on quantities of dust generated, relative dustiness, and hazard statements from SDSs. Because control banding was designed for small and medium enterprises, it is simple, impartial, transparent, and repeatable. The inputs for control banding are readily available, and the output Chapter 12: Control Banding and Welding Copyright AIHA® For personal use only. Do not distribute.

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is understandable and practicable. The need for RPE and related documented programs that include medical clearance to wear RPE and fit testing is calculated using toxicity, dustiness, quantities of contaminant generated, and engineering controls in place. Whatever can be done to simplify exposure control for the welding community must be viewed as beneficial. The ability to use a consistent system to identify the engineering and administrative controls is valuable. PPE is obviously the last line of defense and the least effective when a job can be characterized; however, it may be needed in the meantime to protect workers. The RPE tables included in this chapter identify when and what RPE to use in the absence of industrial hygiene monitoring results. There are occasions when exposure measurement does not make sense: when controls cost less than measurement, when time to measure and report is excessively long, and when an activity that would not be considered immediately dangerous to life and health occurs infrequently. Control banding can be a time- and cost-effective part of an industrial hygiene program. The unbiased hazard ranking and predicted controls can be used to prioritize. The content in the various control banding guidance documents should be part of the solution for any industrial hygiene control activity. We need to change the role of the industrial hygienist from measurement of health hazards to evaluation of controls and mitigation of risks. All information and diagrams are used in accordance with the COSHH Essentials License as posted at the time of writing.

References

1. Health and Safety Executive (HSE). Control of Substances Hazardous to Health (COSHH) Essentials: COSHH e-tool. http:// coshh-tool.hse.gov.uk/. 2. International Labor Organization (ILO). International Chemical Control Toolkit. https://www.ilo.org/legacy/english/protection/ safework/ctrl_banding/toolkit/icct/. 3. Globally Harmonized System of Classification and Labelling of Chemicals (GHS). Geneva, Switzerland: United Nations, 2003. United Nations Economic Commission for Europe (UNECE). 4. Rose VE, Cohrssen B (eds.). Patty’s Industrial Hygiene, 6th Ed, Vol 1: Hazard Recognition. Hoboken, NJ: John Wiley & Sons, Inc., 2011. 256

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5. Maidment SC. Occupational hygiene considerations in the development of a structured approach to select chemical control strategies. Ann Occup Hyg 42(6): 391–400, 1998. 6. Health and Safety Executive (HSE). Control of Substances Hazardous to Health (COSHH) Essentials Technical Basis. COSHH essentials: Controlling exposure to chemicals – a simple control banding approach. https://www.hse.gov.uk/pubns/ guidance/coshh-technical-basis.pdf. 7. United Nations. Globally Harmonized System for Classification and Labelling, Seventh revised edition. New York, NY: United Nations, 2017. https://unece.org/DAM/trans/danger/publi/ghs/ ghs_rev07/English/ST_SG_AC10_30_Rev7e.pdf. 8. Tischer M, Bredendiek-Kämper S, Poppek U. Evaluation of the HSE COSHH essentials exposure predictive model on the basis of BAuA field studies and existing substances exposure data. Ann Occup Hyg 47(7): 557–569, 2003. doi: 10.1093/annhyg/ meg086. 9. Health and Safety Executive (HSE). WL3: COSHH essentials for welding, hot work and allied processes. Welding fume control. April 2021. https://www.hse.gov.uk/pubns/guidance/wl3. pdf.

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257

258

CAS No.

Constituent

1344-28-1

7440-36-0

7440-41-7

Aluminum

Antimony

Beryllium

Total Dust – Welding Fume

2

1

3

H301: Toxic if swallowed. H315: Causes skin irritation. H317: May cause an allergic skin reaction. H319: Causes serious eye irritation. H330: Fatal if inhaled H335: May cause respiratory irritation. H350: May cause cancer. H372: Causes damage to organs through prolonged or repeated exposure.

H302: Harmful if swallowed. H332: Harmful if inhaled. H351: Suspected of causing cancer. H373: May cause damage to organs through repeated or prolonged exposure.

NAp

H350: May cause cancer**

Health-Based H-Statements

Appendix A: Metals Data1

630

1287

E

660

D

NAp

NAv

Melting Pt °C

Hazard Group E

5

4

2468

1635

2327

NAv

Boiling Pt °C

6

Eyes, skin respiratory system, cardiovascular system

Eyes, skin, respiratory system

0.00005 mg/m3 (I)

Eyes, skin respiratory system

0.5 mg/m3

1 mg/m3 (R)

NIOSH Target Organs

2021 ACGIH TLV – TWA

Eyes, skin respiratory system, central nervous system

8 ®

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2

CAS No.

7440-43-9

7440-47-3

7440-48-4

1

Constituent

Cadmium

Chromium

Cobalt

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H317: May cause an allergic skin reaction. H334: May cause allergy or asthma symptoms or breathing difficulties if inhaled.

H317: May cause an allergic skin reaction. H319: Causes serious eye irritation. H334: May cause allergy or asthma symptoms or breathing difficulties if inhaled.

H330: Fatal if inhaled. H341: Suspected of causing genetic defects. H350 May cause cancer. H361f: Suspected of damaging fertility. H361d: Suspected of damaging the unborn child. H372: Causes damage to organs through prolonged or repeated exposure.

Health-Based H-Statements

3

Appendix A (continued): Metals Data1

321

1907

E

E

1495

Melting Pt °C

Hazard Group

E

5

4

2927

2642

765

Boiling Pt °C

6

0.02 mg/m3 (I)

Cr(III) 0.003 mg/m3 (I)

Skin, respiratory system

Eyes, skin, respiratory system 0.5 mg/m3 (I)

NIOSH Target Organs Respiratory system, kidneys, prostrate blood

2021 ACGIH TLV – TWA 0.01 mg/m3 0.002 mg/m3 (R)

8 ®

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259

260

7439-92-1

7439-96-5

7439-98-7

7440-02-0

Lead

Manganese

Molybdenum

Nickel

7440-50-8

Copper

7439-89-6

CAS No.

Constituent

Iron

2

1

H317: May cause an allergic skin reaction. H351: Suspected of causing cancer. H372: Causes damage to organs through prolonged or repeated exposure.

H361: Suspected of damaging fertility or the unborn child.

H319: Causes serious eye irritation.

H360d: Suspected of damaging the unborn child. H360f: Suspected of damaging fertility. H362: May cause harm to breast-fed children.

H319: Causes serious eye irritation.

H302: Harmful if swallowed. H319: Causes serious eye irritation. H331: Toxic if inhaled.

Health-Based H-Statements

3

Appendix A (continued): Metals Data1

D

D

A

E

A

C

1455

2622

1246

327.4

1538

1083

5 Melting Pt °C

4 Hazard Group

6

2730

4639

2061

1740

2861

2595

Boiling Pt °C

Respiratory system (iron oxide)

5 mg/m3 (iron oxide)

Respiratory system, central nervous system, blood, kidneys Eyes, respiratory system, liver, kidneys Nasal cavities, lungs, skin

0.02 mg/m3 0.1 mg/m3 (inorganic compounds) 0.5 mg/m3(R) as Mo 1.5 mg/m3 (I)

0.05 mg/m3

1 mg/m3 (dusts)

Eyes, gastrointestinal tract, central nervous system, kidneys, blood, gingival tissue

Eyes respiratory system, liver, kidneys

NIOSH Target Organs

3

0.2 mg/m (fume)

8

7 2021 ACGIH TLV® – TWA

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13463-67-7 H351: Suspected of causing cancer**

1314-62-1

1314-13-2

630-08-0

18540-29-9 H317: May cause an allergic skin reaction. H350: May cause cancer.

TiO2 IARC 2b ACGIH A4

V2O5

ZnO

CO CB does not assess gases

Hex Chrome

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261

E

D

691

D

*1907

–205

1974

1855

Melting Pt °C

Hazard Group D

5

4

*2671

–191

2360

1750

2500– 3000

Boiling Pt °C

6

** Based on IARC Classification. (I), Inhalable; NAp, not applicable; NAv, not available; (R), respirable.

H331: Toxic if inhaled. H360d: Suspected of damaging the unborn child. H372: Causes damage to organs through prolonged or repeated exposure.

NAp

H302: Harmful if swallowed. H332: Harmful if inhaled. H335: May cause respiratory irritation. H341: Suspected of causing genetic effects. H361d: Suspected of damaging the unborn child. H372: Causes damage to organs through prolonged or repeated exposure.

Health-Based H-Statements

CAS No.

Constituent

3

2

1

Appendix A (continued): Metals Data1

Inhalation

Respiratory system (*OSHA)

0.0002 mg/m3 (I)

Respiratory system

Eyes, skin, respiratory system

Respiratory system

NIOSH Target Organs

8

25 ppm

2 mg/m3

0.05 mg/m3 (I)

10 mg/m 3

2021 ACGIH TLV® – TWA

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Appendix B: GHS Hazard Statements1,2 Hazard Group (inhalation)

H300: Fatal if swallowed

C

H301: Toxic if swallowed

B

H302: Harmful if swallowed

not included A not included

H303: May be harmful if swallowed H304: May be fatal if swallowed and enters airways H305: May be harmful if swallowed and enters airways

D

H310: Fatal in contact with skin

C

H311: Toxic in contact with skin

B

H312: Harmful in contact with skin

not included

H313: May be harmful in contact with skin

C

H314: Causes severe skin burns and eye damage

A

H315: Causes skin irritation

not included

H316: Causes mild skin irritation

C

H317: May cause an allergic skin reaction

C

H318: Causes serious eye damage

A

H319: Causes serious eye irritation

not included

H320: Causes eye irritation

D

H330: Fatal if inhaled

C

H331: Toxic if inhaled

B

H332: Harmful if inhaled

not included

262

Hazard Statement with number

D

H333: May be harmful if inhaled

E

H334: May cause allergy or asthma symptoms or breathing difficulties if inhaled

C

H335: May cause respiratory irritation

A

H336: May cause drowsiness or dizziness

E

H340: May cause genetic defects

E

H341: Suspected of causing genetic defects

E

H350: May cause cancer

D

H351: Suspected of causing cancer

D

H360: May damage fertility or the unborn child

D

H361: Suspected of damaging fertility or the unborn child

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Appendix B: GHS Hazard Statements1,2 Hazard Group (inhalation)

Hazard Statement with number

D

H361d: Suspected of damaging the unborn child

D

H361f: Suspected of damaging fertility

D

H362: May cause harm to breast-fed children

C

H370: Causes damage to organs

B

H371: May cause damage to organs

D

H372: Causes damage to organs through prolonged or repeated exposure

C

H373: Causes damage to organs through prolonged or repeated exposure

D

H300+H310: Fatal if swallowed or in contact with skin

D

H300+H330: Fatal if swallowed or if inhaled

D

H310+H330: Fatal in contact with skin or if inhaled

D

H300+H310+H330: Fatal if swallowed, in contact with skin, or if inhaled

C

H301+H311: Toxic if swallowed or in contact with skin

C

H301+H331: Toxic if swallowed or if inhaled

C

H311+H331: Toxic in contact with skin or if inhaled

C

H301+H311+H331: Toxic if swallowed, in contact with skin, or if inhaled

B

H302+H312: Harmful if swallowed or in contact with skin

B

H302+H332: Harmful if swallowed or if inhaled

B

H312+H332: Harmful in contact with skin or if inhaled

B

H302+H312+H332: Harmful if swallowed, in contact with skin, or if inhaled

References

1. Globally Harmonized System of Classification and Labelling of Chemicals (GHS). GHS Classification. United Nations, 2019. https://pubchem.ncbi.nlm.nih.gov/ghs/. 2. Health and Safety Executive (HSE). Control of Substances Hazardous to Health (COSHH) Essentials Technical Basis. COSHH essentials: Controlling exposure to chemicals – a simple control banding approach. https://www.hse.gov.uk/pubns/ guidance/coshh-technical-basis.pdf.

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Chapter 12: Exercise — Welding Control Banding Scenario: Welding is completed on small parts intermittently 2-3 times per week using a SMAW process. There are small brackets made of mild steel that are breaking and need repair. The preferred welding rods contain chromium and cadmium, according to the safety data sheets (SDSs). Is the worker’s health being compromised by this welding process? Note that for the purposes of this exercise, only Cr and Cd are addressed

Step 1: GATHER DATA 1) Gather data that contributes to worker exposures • Nature of task and type of welding. • Duration of task. • Determine what metals will be welded. See SDS. • What quantities are likely to be generated: grams, kilograms, tons? • What level of dustiness is being generated? (see Table 12.1) • Determine predicted concentrations (see Table 12.4) • What questions regarding Control Approaches need to be asked? – Is there general ventilation? Is it adequate? Are there any issues with airflow? – Is local exhaust ventilation (LEV) present? Is it adequate for the task? Is it used? Is it used properly and every time? • Is respiratory protective equipment (RPE) worn? Is the wearer clean shaven? • What procedures, maintenance, training, and supervision practices are in place for the task? • How many workers are affected directly and indirectly?

Step 2: FILTER DATA 2) What do you have? What can you find? What do you need to protect the worker? The quality of SDSs from welding rod manufacturers is inconsistent. Some classify the product as an article that does not give off hazardous fumes and some classify the product knowing it will generate fumes when used. • Type of welding: SMAW • Intermittent welding: < 1 hour/day

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• Determine fume concentrations from Table 1 • Review SDS and Appendix A: Metals Data for contaminants of concern: Chromium and Cadmium • Consider melting points, boiling points, target organs, and TLV of each contaminant – What do the H-Statements identify? – Which contaminant has the lower melting point and boiling point? – Consider the target organs and at least their additive effects. • Record the controls in place. – How effective is the general ventilation? How long does it take for visible fume to dissipate? – Do workers know how to use it and is this reinforced by supervision? – Are windows open or closed, aiding airflow and extraction or hindering it? – If local exhaust ventilation (LEV) is available, how effective is it? Is the LEV used regularly? – Is the LEV positioned properly? – Is the LEV maintained per manufacturer’s instructions? – Does the welder position his head (breathing zone) to encourage fumes to dissipate and are there screens to protect against arc flash? Do these inhibit fume from dissipating? – Does draft affect fume dispersion? (Can you record this with a video?) • Download COSHH Essentials direct advice sheets applicable to the task described. Other sources of control guidance sheets are also available from ILO Chemical Control Toolkit, BAuA, and others. • Is RPE being used? – Does the company have an RPE program? – Is the RPE cleaned and maintained properly? – Are workers clean shaven on the contact area for the RPE? – Are workers trained to don and doff the RPE properly?

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Step 3: CALCULATE DATA / CREATE INFORMATION 3) Exposure predictions of fume from Tables 12.1 and 12.4 identify there could be a concentration range for general ventilation of 0.1 to 1 mg/m3 or a concentration range of 0.01 to 0.1 mg/m3 for LEV. • What information can be added from the SDS data? • Appendix A: Metals Data identifies the following: – Cadmium has a melting point of 321°C and boiling point of 765°C – Chromium has a melting point of 1907°C and boiling point of 2671°C – Welding Fume total particulate has no TLV (currently being evaluated). Target organs are eyes, skin, respiratory system, and central nervous system. – Cadmium, TLV-TWA of 0.01 mg/m3 with target organs, respiratory system, kidneys, prostrate, and blood. – Chromium (metallic), TLV-TWA of 0.5 mg/m3 with target organs eyes, skin, respiratory system. – Does your company introduce controls at the TLV or at the Action Level (50% of TLV)? • Is respiratory protective equipment (RPE) used? – What type of RPE and filters are used? Is it the correct RPE and filter for the contaminant and concentration? – Is the welder medically cleared to wear RPE and fit tested for that specific respirator? – Is the worker trained on the RPE use, cleaning and maintaining as per manufacturer’s instructions? – Compare the Exposure Prediction (EP) to RPE APF (Assigned Protection Factor) You find that Cadmium has a much lower melting point and boiling point and will volatilize first. What RPE is needed to protect against Cadmium to the TLV-TWA? What RPE is needed to protect against Cadmium to 50% of the TLV-TWA with general ventilation? The most conservative EP is 1 mg/m3 Cadmium. The Cadmium TLV-TWA is 0.01 mg/m3. If a minimum APF of 100 is needed to meet the TLV-TWA, which RPE is indicated? Refer to Table 12.6 (RPE APF) and Table 12.7 (RPE Selection). What other controls may further reduce worker exposure?

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Step 4: CONTROL CALCULATIONS 4) A calculation to determine whether RPE is needed before exposure monitoring is conducted is shown. Assumptions are general ventilation control approach. Assuming only Cadmium volatilized for 1 hour, with a predicted concentration range of 0.1 to 1 mg/m3. Using the maximum value of the range, 1 mg/m3 for 1 hour of that task: 1 mg/m3 ÷ 0.01 mg/m3 (TLV) = APF of 100 needed for that 1 hour of welding. Assuming only Cadmium volatilized for 1 hour, with a predicted concentration range of 0.1 to 1 mg/m3. Using the minimum value of the range, 0.1 mg/m3 for 1 hour of that task: 0.1 mg/m3 ÷ 0.01 mg/m3 (TLV) = APF of 10 needed for that 1 hour of welding. If the welding task is longer, then RPE is protective for the length of the task. The calculation to determine if effective use of LEV will be adequate to reduce concentrations to TLV-TWA is shown. Refer to Table 12.4 (Control Approaches) to see that LEV can be calculated to have a tenfold reduction in concentrations provided it is used and maintained correctly. Assuming only Cadmium volatilized for 1 hour, with a predicted concentration range of 0.1 to 1 mg/m3. Using the maximum value of the range, 1 mg/m3 for 1 hour of that task: LEV reduction is 1 mg/m3 ÷ 10 = 0.1 mg/m3 0.1 mg/m3 ÷ 0.01 mg/m3 (TLV) = APF of 10 needed for RPE needed for that 1 hour of welding. Assuming only Cadmium volatilized for 1 hour, with a predicted concentration range of 0.1 to 1 mg/m3. Using the minimum value of the range, 0.1 mg/m3 for 1 hour of that task: LEV reduction is 0.1 mg/m3 ÷ 10 = 0.01 mg/m3 0.01 mg/m3 ÷ 0.01 mg/m3 (TLV) = APF of 1 RPE is not warranted. Answer: LEV used as designed and a half mask will protect the welder. Exposure measurements can be used for confirmation. Chapter 12: Control Banding and Welding Copyright AIHA® For personal use only. Do not distribute.

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The assumption that only Cadmium fumes will be emitted may be considered for a calculation like this. Of course, there will be some Chromium in the exposure, as well as total welding fume. The additive formula model was discussed in Chapter 11 of this book. At the time of writing, the ACGIH listed Welding Fume as a substance that is being studied. This calculation can be used to show the effect of LEV before actually performing measurements and possibly if measurements are needed. Although recommendations are to first protect the worker, evaluating costs of such controls and alternatives is a greater value purpose for the industrial hygienist. For instance, is substitution of a different welding rod possible? Will this result in greater or less harm to workers’ health? If LEV is added, recognize that there is an initial cost and ongoing costs, as well as training, maintenance, tracking, and supervision requirements. The required APF provides a wide variety of potential RPE. RPE also has an initial cost and ongoing costs. These costs and time to manage these controls must be understood. RPE has medical implications, too. Consult the DASs or CGSs to guide desired controls, maintenance, training, and supervision and engineering specifications. What controls are in place now? Define optimal/acceptable controls and the gaps needed between these. Any control recommendation must address PPE, RPE, training, supervision, maintenance, examination, testing, cleaning, housekeeping, decontamination, and potential health surveillance.

Step 5: AUDIT CHECK 5) Do you need to measure? What do you need to measure? Which methods (revisit PubChem for NIOSH and OSHA methods)? • Measurements are to be completed to determine the effectiveness of controls. • Consider that measuring exposures is not the same as controlling exposures. Do the costs of measuring take away from the budget of controls?

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Chapter 12: Control Banding and Welding Copyright AIHA® For personal use only. Do not distribute.

SAFETY

Welding Health and Safety – A Field Guide for OEHS Professionals, 2nd edition By Michael K. Harris, PhD, CIH and Michael R. Phibbs, CIH, ROH Learn to communicate more effectively with welding shop and plant personnel with this practical guide, written for those who have little actual “hands on” shop experience. Topics include health and safety considerations, welding terminology, equipment, welding and cutting in confined spaces, construction, maintenance, and repair welding, plus the health effects of metals, gases, and other agents commonly encountered in welding processes.

STOCK NUMBER: SWEF21-490