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1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 2971 : 1991 Including
2、Amendment No. 1, not issued separately ICS 25.160.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Specification for Class II arc welding of carbon steel pipework for carrying fluids Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:53:02 GMT+00:00 2006, Uncontrolled
3、 Copy, (c) BSI BS 2971 : 1991Issue 2, February 1998 This British Standard, having been prepared under the direction of the Welding Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 28 June 1991 BSI 1998 First published April 1961 Second edi
4、tion October 1977 Third edition June 1991 The following BSI references relate to the work on this standard: Committee reference WEE/21 Draft for comment 90/71692 DC ISBN 0 580 19384 5 Amendments issued since publication Amd. No.DateText affected 9773February 1998 Indicated by a sideline in the margi
5、n Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Welding Standards Policy Committee (WEE/-) to Technical Committee WEE/21, upon which the following bodies were represented: Associated Offices Technical Committee British Gas plc British
6、Non-ferrous Metals Federation British Nuclear Fuels Ltd. Electricity Association Engineering Equipment and Materials Users Association Health and Safety Executive Heating and Ventilating Contractors Association Institute of Refrigeration Institution of Gas Engineers Institution of Mechanical Enginee
7、rs Joint Industry Board for Plumbing Mechanical Engineering Services in England and Wales National Association of Plumbing, Heating and Mechanical Services Contractors Power Generation Contractors Association (BEAMA Ltd.) Stainless Steel Fabricators Association of Great Britain United Kingdom Atomic
8、 Energy Authority Welding Institute Welding Manufacturers Association (BEAMA Ltd.) Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:53:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Issue 1, February 1998BS 2971 : 1991 BSI 1998a Summary of pages The following table identifies the current iss
9、ue of each page. Issue 1 indicates that a page has been introduced for the first time by amendment. Subsequent issue numbers indicate an updated page. Vertical sidelining on replacement pages indicates the most recent changes (amendment, addition, deletion). PageIssuePageIssue Front cover Inside fro
10、nt cover a b 1 2 3 4 5 6 7 8 to 18 19 20 2 2 1 blank original 2 2 original 2 original 2 original 2 2 21 22 23 24 25 26 27 28 29 30 31 32 Inside back cover Back cover original 2 original original original original original original original original original 2 2 2 Licensed Copy: sheffieldun sheffield
11、un, na, Tue Nov 28 13:53:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI bblank Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:53:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2971 : 1991 1 Contents Page Committees responsibleInside front cover Foreword3 Section 1. General 1Scope4 2Infor
12、mation and requirements to be agreed and to be documented4 3Parent metal4 4Weld metal5 5Gases for shielding and purging5 6Equipment5 7Welding processes6 8Backing rings6 9Joint preparations6 10Proximity of welds6 11Fusion faces6 12Assembly for welding7 13Purging7 14Damage to parent metal by arc strik
13、es7 15Inter-run cleaning7 16Cold pull7 17Preheating for cutting and welding7 18Heat treatment after welding8 Section 2. Butt joints 19General9 20All types of butt joint9 21Gusseted bends9 Section 3. Branches and small bore connections 22General12 23Branches12 Section 4. Sleeve joints and socket-weld
14、ing fittings 24General13 25Sleeve joint details13 26Socket joint details13 Section 5. Structural attachments 27General14 28Welding procedure14 Section 6. Flanges 29General15 30Welding neck flanges15 31Welded-on flanges15 Section 7. Inspection 32Requirements for visual examination of completed welds1
15、6 33Testing of completed welds16 34Non-destructive testing16 35Flaw limitations17 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:53:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2971 : 1991Issue 2, February 1998 2 BSI 1998 | Page Section 8. Rectification of unacceptable welds 36Removal
16、 of flaws18 37Preparation for rewelding18 38Rewelding18 Section 9. Welding procedures 39General19 40Attachments to thin pipes and branch welds19 Section 10. Welder approval 41General20 42Attachments to thin pipes20 Appendices AClasses of operating conditions21 BGrades of steel in British Standards a
17、nd similar grades for pipe in ASTM and DIN standards22 CTypical joint preparations23 Tables 1Methods of making initial root runs in butt joints6 2Typical limits for bore difference and alignment for manual welding9 3Classes of operating conditions21 4Grades of steel in British Standards22 5Grades in
18、 ASTM and DIN standards of similar weldability to British Standard grades of pipe22 Figures 1Segmental bends10 2Cut-and-shut bend11 3Sleeve joints13 4Fillet welds for sleeve joints13 5Socket joint details13 6Welding neck flange15 7Typical butt joint preparations for use with backing rings23 8Typical
19、 butt joint preparations for use without backing rings24 9Typical set-on branch without weld preparation25 10Typical preparation and assembly of set-on branches without backing26 11Typical preparation and assembly of set-on right-angle branches with temporary backing27 12Typical set-in branch withou
20、t weld preparation28 13Typical curved or easy sweep branch joint29 14Typical set-on (shaped) small bore connections30 15Typical set-in small bore connection30 16Typical small bore connections for pressures over 10 bar or for refrigerants or corrosive fluids31 17Typical slip-on welded-on flange31 18T
21、ypical slip-on hubbed welded-on flange31 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:53:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Issue 2, February 1998BS 2971 : 1991 BSI 19983 | | | Foreword This revision of this British Standard has been prepared under the direction of the Weldin
22、g Standards Policy Committee. It embodies the technical developments that have taken place since the 1977 edition, which is superseded and withdrawn. On common aspects the standard has generally been aligned with BS 2633. The relevant application standard, where it exists, should specify whether cla
23、ss II welding of pipework is required, but the factors to be taken into account in coming to such a conclusion are the operating conditions of the pipework, the degree of inspection and the acceptance requirements (see also appendix A). It is recommended that carbon steels with a carbon content exce
24、eding 0.25 % and all ferritic alloy steels be welded in accordance with BS 2633 irrespective of the operating conditions. Purchasers ordering to this standard are advised to specify in their contracts that the manufacturer operates a quality system in compliance with the appropriate standard in the
25、BS EN ISO 9000 series to assure themselves that pipework claimed to have been welded in accordance with BS 2971 consistently achieves the required level of quality. The following are companion standards to this standard. BS 1821Specification for class I oxy-acetylene welding of ferritic steel pipewo
26、rk for carrying fluids BS 2633Specification for class I arc welding of ferritic steel pipework for carrying fluids BS 2640Specification for class II oxy-acetylene welding of carbon steel pipework for carrying fluids BS 4204Specification for flash welding of steel tubes for pressure applications BS 4
27、677Specification for arc welding of austenitic stainless steel pipework for carrying fluids Inspecting authority. For the purposes of this British Standard the term inspecting authority refers to that competent independent body or association which verifies compliance with this standard. Contracting
28、 parties. For the purposes of this British Standard, the term contracting parties is intended to cover the purchaser, the manufacturer and the inspecting authority in any relevant combination according to the particular circumstances. Pipe and tube. For the purposes of this British Standard the word
29、 pipe, alone or in combination, is used to mean pipe or tube although these terms are often used for different categories of product by different industries. Pipework dimensions. Unless otherwise qualified, for the purposes of this British Standard pipe diameter relates to the nominal value of the o
30、utside diameter and pipe thickness relates to the nominal value of the wall thickness specified in the standard to which the pipe is ordered. It has been assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced peop
31、le. Compliance with a British Standard does not of itself confer immunity from legal obligations. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:53:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2971 : 1991Section 1 4 Section 1. General 1 Scope This British Standard specifies requiremen
32、ts for both shop and site class II arc welding of joints in carbon steel pipework intended to carry fluids. It covers manual, automatic or semi-automatic arc welding or combinations of these processes, but it also allows joints to be made with an oxy-acetylene root run without a backing ring by agre
33、ement between the contracting parties. NOTE 1. For details of oxy-acetylene welding see BS 2640. This standard is only applicable where there is adequate access available for welding and, when required, non-destructive testing. NOTE 2. In cases of poor access, a mechanical connection could be used.
34、In addition to the definitive requirements, this standard also requires the items detailed in clause 2 to be documented. For compliance with this standard, both the definitive requirements and the documented items have to be satisfied. NOTE 3. The titles of the publications referred to in this stand
35、ard are listed on the inside back cover. 2 Information and requirements to be agreed and to be documented 2.1 Information to be supplied by the purchaser The following information to be supplied by the purchaser at the contract stage shall be fully documented. Both the definitive requirements specif
36、ied throughout the standard and the documented items shall be satisfied before a claim of compliance with the standard can be made and verified. a) The application standard to be used, if any. b) Whether records of materials used during fabrication are required (see 3.2). c) Whether permanent backin
37、g rings are required (see 8.1). d) Whether all welds are to be heat-treated after welding (see 18.1). e) Whether completed welds are to be ground (see 32.1). f) The category required for non-destructive testing of butt joints (see 34.1). g) Whether a written welding procedure specification is requir
38、ed (see 39.1). h) Whether an approved welding procedure is required to be used (see 39.2). i) Whether welding procedure tests using pipe of specified diameter and thickness are required (see 39.3). 2.2 Requirements to be agreed The following items to be agreed between the contracting parties, which
39、are specified in the clauses referred to, shall be fully documented. Both the definitive requirements specified throughout the standard and the following documented items shall be satisfied before a claim of compliance with the standard can be made and verified. a) The materials to be used for pipes
40、 and attachments (see 3.1). b) The precautions in inspection and welding procedure required when welding cast parts (see 3.3). c) The joint preparation to be used (see clause 9). d) The precautions to be taken when design factors are such that the meeting of more than two welded seams cannot be avoi
41、ded (see clause 10). e) The service conditions for which gusseted bends are to be used (see 21.1). f) Details of joint design and fabrication when the branch angle is less than 60 (see 23.1). g) The method and amount of inspection for partial penetration welds on structural attachments (see 28.2). h
42、) The use and extent of non-destructive testing (see clause 33). i) The inspection and testing requirements for other than butt joints (see 34.2). j) The use of a joint preparation incorporating a wider root gap for making a repair weld (see 37.3(c). 3 Parent metal 3.1 The parent metal for pipes (in
43、cluding those with a longitudinal or helical welded seam) and attachments shall be carbon or carbon-manganese steel containing not more than 0.25 % carbon. The materials selected shall be agreed between the contracting parties, taking account of their suitability for the service conditions (see 2.2(
44、a). NOTE. Appendix B gives details of grades in British Standards for the type of steel given in 3.1 and nearest similar grades in ASTM and DIN standards for pipe. 3.2 When required by the purchaser, the manufacturer shall maintain records of the materials used during fabrication (see 2.1(b). Licens
45、ed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:53:02 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 19985 Section 1Issue 2, February 1998BS 2971 : 1991 | | 1) Available from The Stationery Office, 49 High Holborn, London WC1 for personal callers, or by post from The Stationery Office, PO Box 27
46、6, London SW8 5DT. | | | | | | | | | | | 3.3 While the requirements of this standard apply also to the welding of cast parts, additional precautions in inspection and welding procedure that may be necessary to deal with the presence of non-metallic inclusions or porosity shall be subject to agreemen
47、t between the contracting parties (see 2.2(b). 4 Weld metal 4.1 Mechanical properties and chemical composition The mechanical properties of the weld metal shall be suitable for the design requirements of the pipework system. NOTE 1. In general, the requirements for yield strength should be at least
48、equal to the minimum in the specification for the parent metal. The chemical composition of the weld metal, including that from fusible inserts, shall be compatible with that of the parent material. The use of hydrogen-controlled weld metal shall be as given in 17.3. NOTE 2. The requirements of this
49、 clause are met by welding consumables of the types stated that comply with the following British Standards: covered electrodes for manual metal-arc welding with BS EN 499; filler materials for gas-shielded arc welding with BS EN 440; filler wire/flux combinations for submerged-arc welding with BS EN 756 and BS EN 760; tubular cored electrodes for arc welding with BS 7084. As submerged-arc welding conditions can have a significant effect on the chemical composition of the weld metal, the welding conditions shall be controlled to ensure that the correct we