ANSI AWS C4.2 C4.2M-2009 Recommended Practices for Safe Oxyfuel Gas Cutting Torch Operation (Second Edition).pdf

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1、RecommendedPractices forSafe OxyfuelGas CuttingTorch OperationAWS C4.2/C4.2M:2009An American National StandardAWS C4.2/C4.2M:2009An American National StandardApproved by theAmerican National Standards InstituteMay 4, 2009Recommended Practicesfor Safe Oxyfuel GasCutting Torch Operation2nd EditionSupe

2、rsedes AWS C4.2/C4.2M:2006Prepared by theAmerican Welding Society (AWS) C4 Committee on Oxyfuel Gas Welding and CuttingUnder the Direction of theAWS Technical Activities CommitteeApproved by theAWS Board of DirectorsAbstractThese recommended practices for oxyfuel gas cutting include the latest proce

3、dures to be used in conjunction withoxyfuel gas cutting equipment and the latest safety recommendations. Complete lists of equipment are available fromindividual manufacturers.iiAWS C4.2/C4.2M:2009International Standard Book Number: 978-0-87171-750-4American Welding Society550 N.W. LeJeune Road, Mia

4、mi, FL 33126 2009 by American Welding SocietyAll rights reservedPrinted in the United States of AmericaPhotocopy Rights. No portion of this standard may be reproduced, stored in a retrieval system, or transmitted in anyform, including mechanical, photocopying, recording, or otherwise, without the pr

5、ior written permission of the copy-right owner.Authorization to photocopy items for internal, personal, or educational classroom use only or the internal, personal, oreducational classroom use only of specific clients is granted by the American Welding Society provided that the appropriatefee is pai

6、d to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, tel: (978) 750-8400; Internet:.iiiAWS C4.2/C4.2M:2009Statement on the Use of American Welding Society StandardsAll standards (codes, specifications, recommended practices, methods, classifications, and guides) of the America

7、nWelding Society (AWS) are voluntary consensus standards that have been developed in accordance with the rules of theAmerican National Standards Institute (ANSI). When AWS American National Standards are either incorporated in, ormade part of, documents that are included in federal or state laws and

8、 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 standardsmust be approved by the governmental body having statutory jurisdiction before they can become a part of those lawsand regu

9、lations. In all cases, these standards carry the full legal authority of the contract or other document that invokesthe AWS standards. When this contractual relationship exists, changes in or deviations from requirements of an AWSstandard must be by agreement between the contracting parties.AWS Amer

10、ican National Standards are developed through a consensus standards development process that brings to-gether volunteers representing varied viewpoints and interests to achieve consensus. While the AWS administers the pro-cess and establishes rules to promote fairness in the development of consensus

11、, it does not independently test, evaluate,or verify the accuracy of any information or the soundness of any judgments contained in its standards.AWS disclaims liability for any injury to persons or to property, or other damages of any nature whatsoever, whetherspecial, indirect, consequential, or c

12、ompensatory, directly or indirectly resulting from the publication, use of, or relianceon this standard. AWS also makes no guarantee or warranty as to the accuracy or completeness of any information pub-lished herein.In issuing and making this standard available, AWS is neither undertaking to render

13、 professional or other services for oron behalf of any person or entity, nor is AWS undertaking to perform any duty owed by any person or entity to someoneelse. Anyone using these documents should rely on his or her own independent judgment or, as appropriate, seek the ad-vice of a competent profess

14、ional in determining the exercise of reasonable care in any given circumstances. It is assumedthat the use of this standard and its provisions are entrusted to appropriately qualified and competent personnel.This standard may be superseded by the issuance of new editions. Users should ensure that th

15、ey have the latest edition.Publication of this standard does not authorize infringement of any patent or trade name. Users of this standard acceptany and all liabilities for infringement of any patent or trade name items. AWS disclaims liability for the infringement ofany patent or product trade nam

16、e resulting from the use of this standard.Finally, the AWS does not monitor, police, or enforce compliance with this standard, nor does it have the power to do so.On occasion, text, tables, or figures are printed incorrectly, constituting errata. Such errata, when discovered, are postedon the AWS we

17、b 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

18、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 profession

19、al ad-vice. Such opinions represent only the personal opinions of the particular individuals giving them. These individuals donot speak on behalf of AWS, nor do these oral opinions constitute official or unofficial opinions or interpretations ofAWS. In addition, oral opinions are informal and should

20、 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 mustbe reviewed every five years, and if not revised, it must be either reaffirmed or withdrawn. Comments (recommenda-tions, add

21、itions, or deletions) and any pertinent data that may be of use in improving this standard are required andshould 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 info

22、rmed of the Committees responseto 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 areprovided in the Rules of Operation of

23、 the Technical Activities Committee. A copy of these Rules can be obtained fromthe American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.This page is intentionally blank.ivAWS C4.2/C4.2M:2009vAWS C4.2/C4.2M:2009PersonnelAWS C4 Committee on Oxyfuel Gas Welding and CuttingA. T. Sheppard, Ch

24、air The DuRoss GroupM. J. Hogan, 1st Vice Chair The Harris Products Group, A Lincoln Electric CompanyD. B. Overvaag, 2nd Vice Chair Smith Equipment Manufacturing, Division of ITWA. M. Alonso, Secretary American Welding SocietyJ. D. Compton J. D. therefore, each system must be used independently. Alt

25、hough many references are made to safe practices throughout this standard, it is strongly recommended that operatorsbecome thoroughly familiar with all aspects of safe operation. Safety and health information is available from varioussources, including, but not limited to, ANSI Z49.1, Safety in Weld

26、ing, Cutting, and Allied Processes, and applicablefederal, state, and local regulations.2. Normative ReferencesThe following standards contain provisions which, through reference in this text, constitute provisions of this AWSstandard. For undated references, the latest edition of the referenced sta

27、ndard 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,1AWS F4.1, Recommended Safe Practices for Preparation for Welding and Cutting of Containers and Piping;2andAWS A3.0,

28、 Standard Welding Terms and Definitions, Including Terms for Adhesive Bonding, Brazing, Soldering,Thermal Cutting, and Thermal Spraying.23. Terms and DefinitionsAWS A3.0, Standard Welding Terms and Definitions, Including Terms for Adhesive Bonding, Brazing, Soldering,Thermal Cutting, and Thermal Spr

29、aying, provides the basis for terms and definitions used herein. However, thefollowing 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 mayeither extingu

30、ish 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 ignited1ANSI Z49.1 is published by

31、 the American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.2AWS documents are published by the American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.2AWS C4.2/C4.2M:2009at the tip. This condition is generally caused by the reverse flow of one gas into the other side of the syst

32、em.Flashback is considered a hazardous condition that could lead to an explosion.sustained backfire. The return of the flame into the torch with continued burning inside the torch. This event can beidentified by an initial popping sound followed by a squealing or hissing sound caused by the continue

33、d burninginside the torch.These terms describe potentially hazardous events that can occur when using oxyfuel gas equipment. It is important forthe operator to understand these events and the terms that are associated with them.4. Process and Operation4.1 Oxyfuel Gas Cutting Process. The process is

34、a series of chemical reactions between iron and oxygen. It is based onthe ability of high-purity oxygen to combine rapidly with iron when the iron is heated to its ignition temperature, above1600F 870C. The iron is quickly oxidized by the high-purity oxygen, and heat is liberated in several stages.

35、As theiron oxidizes (burns), it produces a mixture of molten oxides called slag. During the cutting, a narrow slot called a kerf isformed as a result of the removal of some of the metal by the stream of cutting oxygen (see Figure 1).Oxyfuel gas cutting of steel has been used on material ranging in t

36、hickness from 1/32 in 0.8 mm to thicknesses inexcess of 100 in 2500 mm. The majority of cutting is done on steel from 1/4 in to 2 in 6 mm to 50 mm in thickness. Askilled oxyfuel gas cutting torch operator using a mechanically guided torch can easily maintain tolerances as close as1/32 in 0.8 mm on m

37、aterials up to 2 in 50 mm thick.Oxyfuel cutting offers advantages over machining methods in terms of speed, versatility, and cost. Cutting speeds of20 in/min 500 mm/min on 1 in 25 mm steel are not uncommon. Almost any two-dimensional shape can be producedby oxyfuel gas cutting. Much of the versatili

38、ty is due to the nature of the oxygen cutting jet, as it will operate in any axiswith equal facility.Figure 1Description of Oxyfuel Gas Cutting3AWS C4.2/C4.2M:20094.2 Principles of Operation. “The oxyfuel gas cutting process employs a torch with a tip (nozzle). The torch cutting tipis designed with

39、a number of preheating flame ports and a center passage for the cutting oxygen. The functions of thetorch and tip are to mix the fuel gas and the oxygen in the correct proportions, to produce preheat flames, and to supplya concentrated stream of high-purity oxygen to the reaction zone. The oxygen ox

40、idizes the hot metal and blows themolten reaction products away from the cut.The preheat flames serve to heat the metal to a temperature at which the metal will react with the cutting oxygen. Theoxygen jet rapidly oxidizes most of the metal in a narrow section to make the cut. Metal oxides and molte

41、n metal areexpelled from the cut by the kinetic energy of the oxygen stream. Moving the torch across the workpiece at the properrate produces a continuous cutting action. The torch may be moved manually or by means of a mechanism or automatedcarriage.The accuracy of a manual operation depends largel

42、y on the skill of the operator. The accuracy and speed of the cut andthe finish of the cut surface are usually improved when mechanized or automated cutting operations are used. Severaltorches may be used on one machine. Automated operations can be programmed to perform a series of complex cutswith

43、a high level of accuracy.”35. Equipment and SuppliesTo perform oxyfuel gas cutting, some or all of the following are needed:4(1) Oxygen(2) Fuel gas(3) Cylinder or line pressure regulators(4) Oxyfuel hoses(5) Cutting torch(6) Cutting tips(7) Spark lighters(8) Tip cleaners(9) Safety equipment and prot

44、ective clothing5.1 Oxygen Supply. Oxygen of high purity (99.5% minimum) is supplied in individual cylinders of various sizes(see Figure 2) or may be distributed by pipeline from manifold cylinders or bulk liquid tanks. Oxygen from on-siteoxygen generators, while of a lesser purity, may be used for f

45、lame cutting in some applications. Always call oxygen byits proper name, “OXYGEN.” It should never be called “AIR.” Regardless of the source, be sure that sufficient pressureand flow capabilities are available for the work to be done. Consult cutting apparatus manufacturers literature forpressure an

46、d volume requirements.3Welding Handbook, (WBH) 9th Edition, Volume 2, Chapter 14, page 601, Principles of Operation, Welding Handbook, Miami, FL:American Welding Society.4To meet federal OSHA requirements, all gas apparatus must comply with CFR 1910, Subparagraph 251.CAUTION: Check valves or flashba

47、ck arrestors can be used. However, before using these devices, the user mustdetermine that they will allow adequate flow for the equipment being used.NOTE: These devices restrict flow which could result in a backfire or sustained backfire. See Clause 9 for moreinformation on these devices.4AWS C4.2/

48、C4.2M:2009Figure 2Oxygen Cylinder5.2 Fuel Supply. Many different fuel gases are utilized in oxyfuel gas cutting (see Annex C). They include acetylene,propane, natural gas, methylacetylene-propadiene stabilized (MPS), propylene, hydrogen, and several propane orpropylene base mixtures. The different f

49、uel gases vary in flame characteristics. The oxyfuel gas cutter should becomefamiliar with the proper flame adjustments for the fuel being used. A sufficient supply of fuel should always beavailable. Fuel gases are supplied in individual cylinders (see Figure 3), or distributed by pipeline from manifoldedcylinders or bulk sources. Never completely drain any cylinder or leave the valve open on “empty” cylinders. This couldresult in contamination of the cylinder.5.3 Maximum Acetylene Pressure. Acetylene shall not be generated, piped (except in approved cylinder manifolds),