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 fluidsBS 2971 : 1991 Issue 2, February 1998 This British Standard, having been prepared under the d
3、irection 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 edition October 1977 Third edition June 1991 The following BSI references relate to the work on this standard:
4、 Committee reference WEE/21 Draft for comment 90/71692 DC ISBN 0 580 19384 5 Amendments issued since publication Amd. No. Date Text affected 9773 February 1998 Indicated by a sideline in the margin Committees responsible for this British Standard The preparation of this British Standard was entruste
5、d 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 Non-ferrous Metals Federation British Nuclear Fuels Ltd. Electricity Association Engineering Equipment a
6、nd Materials Users Association Health and Safety Executive Heating and Ventilating Contractors Association Institute of Refrigeration Institution of Gas Engineers Institution of Mechanical Engineers Joint Industry Board for Plumbing Mechanical Engineering Services in England and Wales National Assoc
7、iation of Plumbing, Heating and Mechanical Services Contractors Power Generation Contractors Association (BEAMA Ltd.) Stainless Steel Fabricators Association of Great Britain United Kingdom Atomic Energy Authority Welding Institute Welding Manufacturers Association (BEAMA Ltd.)Issue 1, February 1998
8、 BS 2971 : 1991 BSI 1998 a Summary of pages The following table identifies the current issue 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
9、 recent changes (amendment, addition, deletion). Page Issue Page Issue Front cover Inside front cover a b 1 2 3 4 5 6 7 8t o1 8 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 ori
10、ginal original original original original original 2 2 2b blankBS 2971 : 1991 1 Contents Page Committees responsible Inside front cover Foreword 3 Section 1. General 1 Scope 4 2 Information and requirements to be agreed and to be documented 4 3 Parent metal 4 4 Weld metal 5 5 Gases for shielding and
11、 purging 5 6 Equipment 5 7 Welding processes 6 8 Backing rings 6 9 Joint preparations 6 10 Proximity of welds 6 11 Fusion faces 6 12 Assembly for welding 7 13 Purging 7 14 Damage to parent metal by arc strikes 7 15 Inter-run cleaning 7 16 Cold pull 7 17 Preheating for cutting and welding 7 18 Heat t
12、reatment after welding 8 Section 2. Butt joints 19 General 9 20 All types of butt joint 9 21 Gusseted bends 9 Section 3. Branches and small bore connections 22 General 12 23 Branches 12 Section 4. Sleeve joints and socket-welding fittings 24 General 13 25 Sleeve joint details 13 26 Socket joint deta
13、ils 13 Section 5. Structural attachments 27 General 14 28 Welding procedure 14 Section 6. Flanges 29 General 15 30 Welding neck flanges 15 31 Welded-on flanges 15 Section 7. Inspection 32 Requirements for visual examination of completed welds 16 33 Testing of completed welds 16 34 Non-destructive te
14、sting 16 35 Flaw limitations 17BS 2971 : 1991 Issue 2, February 1998 2 BSI 1998 | Page Section 8. Rectification of unacceptable welds 36 Removal of flaws 18 37 Preparation for rewelding 18 38 Rewelding 18 Section 9. Welding procedures 39 General 19 40 Attachments to thin pipes and branch welds 19 Se
15、ction 10. Welder approval 41 General 20 42 Attachments to thin pipes 20 Appendices A Classes of operating conditions 21 B Grades of steel in British Standards and similar grades for pipe in ASTM and DIN standards 22 C Typical joint preparations 23 Tables 1 Methods of making initial root runs in butt
16、 joints 6 2 Typical limits for bore difference and alignment for manual welding 9 3 Classes of operating conditions 21 4 Grades of steel in British Standards 22 5 Grades in ASTM and DIN standards of similar weldability to British Standard grades of pipe 22 Figures 1 Segmental bends 10 2 Cut-and-shut
17、 bend 11 3 Sleeve joints 13 4 Fillet welds for sleeve joints 13 5 Socket joint details 13 6 Welding neck flange 15 7 Typical butt joint preparations for use with backing rings 23 8 Typical butt joint preparations for use without backing rings 24 9 Typical set-on branch without weld preparation 25 10
18、 Typical preparation and assembly of set-on branches without backing 26 11 Typical preparation and assembly of set-on right-angle branches with temporary backing 27 12 Typical set-in branch without weld preparation 28 13 Typical curved or easy sweep branch joint 29 14 Typical set-on (shaped) small b
19、ore connections 30 15 Typical set-in small bore connection 30 16 Typical small bore connections for pressures over 10 bar or for refrigerants or corrosive fluids 31 17 Typical slip-on welded-on flange 31 18 Typical slip-on hubbed welded-on flange 31Issue 2, February 1998 BS 2971 : 1991 BSI 1998 3 |
20、| | Foreword This revision of this British Standard has been prepared under the direction of the Welding 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 be
21、en aligned with BS 2633. The relevant application standard, where it exists, should specify whether class 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 accepta
22、nce requirements (see also appendix A). It is recommended that carbon steels with a carbon content exceeding 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 contra
23、cts that the manufacturer operates a quality system in compliance with the appropriate standard in the 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 stan
24、dards to this standard. BS 1821 Specification for class I oxy-acetylene welding of ferritic steel pipework for carrying fluids BS 2633 Specification for class I arc welding of ferritic steel pipework for carrying fluids BS 2640 Specification for class II oxy-acetylene welding of carbon steel pipewor
25、k for carrying fluids BS 4204 Specification for flash welding of steel tubes for pressure applications BS 4677 Specification 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
26、 to that competent independent body or association which verifies compliance with this standard. Contracting 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
27、according to the particular circumstances. Pipe and tube. For the purposes of this British Standard the word 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 otherw
28、ise qualified, for the purposes of this British Standard pipe diameter relates to the nominal value of the outside 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 Britis
29、h Standard that the execution of its provisions is entrusted to appropriately qualified and experienced people. Compliance with a British Standard does not of itself confer immunity from legal obligations.BS 2971 : 1991 Section 1 4 Section 1. General 1 Scope This British Standard specifies requireme
30、nts 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 agr
31、eement 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.
32、 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 stan
33、dard 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 speci
34、fied 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 backi
35、ng 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 requi
36、red (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
37、 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 pipe
38、s 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 avo
39、ided (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).
40、h) 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 (i
41、ncluding 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
42、(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). BSI 1
43、998 5 Section 1 Issue 2, February 1998 BS 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 276, London SW8 5DT. | | | | | | | | | | | 3.3 While the requirements of this standard apply also to the
44、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 agreement between the contracting parties (see 2.2(b). 4 Weld metal 4.1 Mechanical properties and chemical comp
45、osition 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 equal to the minimum in the specification for the parent metal. The chemical composition of the weld me
46、tal, 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 clause are met by welding consumables of the types stated that comply with the following British Stand
47、ards: 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 co
48、nditions can have a significant effect on the chemical composition of the weld metal, the welding conditions shall be controlled to ensure that the correct weld metal composition is consistently achieved. 4.2 Storage and handling Electrodes, filler wires and rods, and fluxes shall be stored and hand
49、led in accordance with the manufacturers recommendations so as to avoid damage or deterioration to them and to the containers in which they are transported. Electrodes, filler wires and rods, and fluxes that show signs of damage or deterioration shall not be used. 5 Gases for shielding and purging 5.1 Shielding gases Where appropriate, gases or gas mixtures of the following quality shall be used. a) Argon, complying with BS EN 439. b) Argon/oxygen mixtures, consisting of argon with up to 5 % added oxygen and complying with BS EN 439. | | | | | | | | | |
