AWS C4.2/C4.2M:2009

An American National Standard

Recommended Practices for Safe Oxyfuel Gas Cutting Torch Operation

AWS C4.2/C4.2M:2009

An American National Standard

Approved by the American National Standards Institute

May 4, 2009

Recommended Practices for Safe Oxyfuel Gas Cutting Torch Operation

2nd Edition

Supersedes AWS C4.2/C4.2M:2006

Prepared by the American Welding Society (AWS) C4 Committee on Oxyfuel Gas Welding and Cutting

Under the Direction of the AWS Technical Activities Committee

Approved by the AWS Board of Directors

Abstract

These recommended practices for oxyfuel gas cutting include the latest procedures to be used in conjunction with oxyfuel gas cutting equipment and the latest safety recommendations. Complete lists of equipment are available from individual manufacturers.

International Standard Book Number: 978-0-87171-750-4

American Welding Society 550 N.W. LeJeune Road, Miami, FL 33126

© 2009 by American Welding Society

All rights reserved Printed in the United States of America

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All standards (codes, specifications, recommended practices, methods, classifications, and guides) of the American Welding Society (AWS) are voluntary consensus standards that have been developed in accordance with the rules of the American National Standards Institute (ANSI). When AWS American National Standards are either incorporated in, or made part of, documents that are included in federal or state laws and regulations, or the regulations of other governmen- tal bodies, their provisions carry the full legal authority of the statute. In such cases, any changes in those AWS standards must be approved by the governmental body having statutory jurisdiction before they can become a part of those laws and regulations. In all cases, these standards carry the full legal authority of the contract or other document that invokes the AWS standards. When this contractual relationship exists, changes in or deviations from requirements of an AWS standard must be by agreement between the contracting parties.

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On occasion, text, tables, or figures are printed incorrectly, constituting errata. Such errata, when discovered, are posted on the AWS web page (www.aws.org).

Official interpretations of any of the technical requirements of this standard may only be obtained by sending a request, in writing, to the appropriate technical committee. Such requests should be addressed to the American Welding Society, Attention: Managing Director, Technical Services Division, 550 N.W. LeJeune Road, Miami, FL 33126 (see Annex D). With regard to technical inquiries made concerning AWS standards, oral opinions on AWS standards may be rendered. These opinions are offered solely as a convenience to users of this standard, and they do not constitute professional ad- vice. Such opinions represent only the personal opinions of the particular individuals giving them. These individuals do not speak on behalf of AWS, nor do these oral opinions constitute official or unofficial opinions or interpretations of AWS. In addition, oral opinions are informal and should not be used as a substitute for an official interpretation.

This standard is subject to revision at any time by the AWS C4 Committee on Oxyfuel Gas Welding and Cutting. It must be reviewed every five years, and if not revised, it must be either reaffirmed or withdrawn. Comments (recommenda- tions, additions, or deletions) and any pertinent data that may be of use in improving this standard are required and should be addressed to AWS Headquarters. Such comments will receive careful consideration by the AWS C4 Commit- tee on Oxyfuel Gas Welding and Cutting and the author of the comments will be informed of the Committee’s response to the comments. Guests are invited to attend all meetings of the AWS C4 Committee on Oxyfuel Gas Welding and Cut- ting to express their comments verbally. Procedures for appeal of an adverse decision concerning all such comments are provided in the Rules of Operation of the Technical Activities Committee. A copy of these Rules can be obtained from the American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.

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Personnel

AWS C4 Committee on Oxyfuel Gas Welding and Cutting

A. T. Sheppard, Chair The DuRoss Group

M. J. Hogan, 1st Vice Chair The Harris Products Group, A Lincoln Electric

Company

1. B. Overvaag, 2nd Vice Chair Smith Equipment Manufacturing, Division of ITW

   1. M. Alonso, Secretary American Welding Society

J. D. Compton J. D. & Associates

D. E. Durkin Thermadyne Industries, Incorporated

L. L. Liston Consultant

C. R. McGowan McGowan Technical Services

R. A. Smith Compressed Gas Association

D. S. Werner Breakthrough Business Solutions

Advisors to the AWS C4 Committee on Oxyfuel Gas Welding and Cutting

J. G. Dawson, Jr. Consultant

J. D. Karow American General Corporation

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Foreword

This foreword is not part of AWS C4.2/C4.2M:2009, Recommended Practices for Safe Oxyfuel Gas Cutting Torch Operation, but is included for informational purposes only.

This Recommended Practices standard is intended for use by the oxyfuel gas cutter (operator). It describes the oxyfuel gas cutting process, including information relating to equipment, safety, and operating procedures. Although many references are made to safe practice throughout this standard, it is strongly recommended that all operators become thoroughly familiar with all aspects of safe operation. A suggested standard is ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes, available from the American Welding Society. Much of the information in this standard is necessarily general in nature due to the large number of variations in equipment produced by various manufacturers. The manufacturer’s manual should be consulted for details on safe installation and use of all equipment. When equipment or parts of equipment need repair, the work shall be performed by skilled mechanics who have been properly instructed.

Revisions to the 2006 edition have been editorial and are identified by a vertical line in the margin next to the text.

Comments and suggestions for the improvement of this standard are welcome. They should be sent to the Secretary, AWS C4 Committee on Oxyfuel Gas Welding and Cutting, American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.

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Table of Contents

Page No.

Personnel v

Foreword vii

List of Tables xi

List of Figures xi

1. Scope 1

2. Normative References 1

3. Terms and Definitions 1

4. Process and Operation 2

   1. Oxyfuel Gas Cutting Process 2

   2. Principles of Operation 3

5. Equipment and Supplies 3

   1. Oxygen Supply 3

   2. Fuel Supply 4

   3. Maximum Acetylene Pressure 4

   4. Pressure Regulators 5

   5. Hoses and Fittings 6

   6. Cutting Torches 7

   7. Cutting Tips 9

   8. Personal Protective Equipment (PPE) 11

   9. Cutting Machines 12

   10. Safe Use, Handling, and Storage of Gas Cylinders 12

   11. Safe Working Environment 13

6. Startup and Shutdown Procedure 13

   1. Setting Up Equipment 13

   2. Lighting the Torch 15

   3. Equipment Shutdown 16

7. Flame Adjustment 16

   1. Types of Flames 17

   2. Backfire and Sustained Backfire Safety Note 18

8. Cutting Procedures—Hand Torches 18

   1. Starting Methods 18

   2. Torch Position and Motion 18

   3. Piercing 19

   4. Oxygen Lancing 20

   5. Gouging, Washing, and Special Applications 21

      Page No.

9. Machine Oxygen Cutting 22

   1. Cutting Charts 22

   2. Operating Techniques 22

   3. Bevel Cutting 23

10. Hints for Best Selection of Tips, Speeds, and Pressures 23

    1. Correct Cutting Techniques 24

    2. Common Cutting Faults 24

    3. Tip Distance 24

    4. Gas Adjustment 24

    5. Bevel Cutting 24

11. Flashback Arrestors and Check Valves 25

    1. Flashback Arrestors 25

    2. Check Valves 25

    3. What to Do in the Event of a Flashback 25

    4. Flashback Prevention 25

Annex A (Informative)—Reference Documents 27

Annex B (Informative)—Fuel Gas Withdrawal Rates 29

Annex C (Informative)—Fuel Gases 31

Annex D (Informative)—Guidelines for the Preparation of Technical Inquiries 33

List of AWS Documents on Oxyfuel Gas Welding and Cutting 35

List of Tables

Table Page No.

1. Acetylene Withdrawal 29

2. Methylacetylene-Propadiene Stabilized (MPS) Withdrawal 29

3. Propylene Withdrawal 30

4. Propane Withdrawal 30

List of Figures

Figure Page No.

1. Description of Oxyfuel Gas Cutting 2

2. Oxygen Cylinder 4

3. Typical Fuel Gas Cylinders 5

4. Pressure Regulators 6

5. Hoses and Fittings 7

6. Manual Oxygen Cutting Torch 8

7. Combination Torch 8

8. Three Hose Machine Torch 8

9. Torches Classified According to Method of Mixing 9

10. Oxyfuel Gas Cutting Tips 10

11. Oxyfuel Gas Cutting Tips—One and Two Piece Designs 10

12. Carburizing Flame 17

13. Neutral Flame 17

14. Oxidizing Flame 17

15. Cutting Torch Starting a Cut and in Action 18

16. Lead Torch Angle for Straight Line Cutting 19

17. Oxygen Lance 20

18. Special Application Tips 21

19. Oxygen Orifice Design for Washing Tips 21

20. Bevel Cutting 23

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Recommended Practices for Safe Oxyfuel Gas Cutting Torch Operation

1. Scope

   This standard describes the equipment, procedures and safe practices for the oxyfuel cutting of steel. It is for the operators of both hand and machine torches and is recommended for management personnel associated with the oxyfuel cutting process.

   Oxyfuel gas cutting is a process whereby a metal (usually an iron base alloy) is heated to its kindling temperature (well below the melting point) by an oxyfuel gas flame and then burned rapidly by a regulated jet of oxygen. A cutting torch is used for this operation.

   This standard makes use of both U.S. Customary Units and the International System of Units (SI). The latter are shown within brackets ([ ]) or in appropriate columns in tables and figures. The measurements may not be exact equivalents; therefore, each system must be used independently.

   Although many references are made to safe practices throughout this standard, it is strongly recommended that operators become thoroughly familiar with all aspects of safe operation. Safety and health information is available from various sources, including, but not limited to, ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes, and applicable federal, state, and local regulations.

   
   

2. Normative References

   The following standards contain provisions which, through reference in this text, constitute provisions of this AWS standard. For undated references, the latest edition of the referenced standard shall apply. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply.

   ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes, 1

   AWS F4.1, Recommended Safe Practices for Preparation for Welding and Cutting of Containers and Piping; 2 and

   AWS A3.0, Standard Welding Terms and Definitions, Including Terms for Adhesive Bonding, Brazing, Soldering, Thermal Cutting, and Thermal Spraying.2

   
   

3. Terms and Definitions

AWS A3.0, Standard Welding Terms and Definitions, Including Terms for Adhesive Bonding, Brazing, Soldering, Thermal Cutting, and Thermal Spraying, provides the basis for terms and definitions used herein. However, the following terms and definitions are included to accommodate usage specific to this document.

backfire. The momentary return of the flame into the torch that is usually signaled by a popping sound. The flame may either extinguish or reignite at the end of the tip.

flashback. The return of the flame through the torch and into the hose and/or regulator. It may also reach the cylinder. This event is caused by the oxygen and fuel mixing in one side of the oxyfuel system and subsequently being ignited

1 ANSI Z49.1 is published by the American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.

2 AWS documents are published by the American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.