1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 21751:2011Plastics pipes and fittings Decohesion test ofelectrofusion assemblies Strip-bend testBS ISO 21751:2011 BRITISH STANDARDNational forewordThis British Standard is
2、 the UK implementation of ISO 21751:2011.The UK participation in its preparation was entrusted to TechnicalCommittee PRI/88/4, Test Methods - Plastic Piping.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include a
3、ll the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 62582 4ICS 23.040.20; 23.040.45Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Po
4、licy and Strategy Committee on 30 April 2011.Amendments issued since publicationDate Text affectedBS ISO 21751:2011Reference numberISO 21751:2011(E)ISO 2011INTERNATIONAL STANDARD ISO21751First edition2011-04-01Plastics pipes and fittings Decohesion test of electrofusion assemblies Strip-bend test Tu
5、bes et raccords en matires plastiques Essai de dcohsion des assemblages lectrosoudables Essai de pliage dune languette BS ISO 21751:2011ISO 21751:2011(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but sh
6、all not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobes licensing policy. The ISO Central Secretariat accepts no liability in this area
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8、 ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2011 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any
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10、09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2011 All rights reservedBS ISO 21751:2011ISO 21751:2011(E) ISO 2011 All rights reserved iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO membe
11、r bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmenta
12、l and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directi
13、ves, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies
14、 casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 21751 was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings a
15、nd valves for the transport of fluids, Subcommittee SC 5, General properties of pipes, fittings and valves of plastic materials and their accessories Test methods and basic specifications. BS ISO 21751:2011BS ISO 21751:2011INTERNATIONAL STANDARD ISO 21751:2011(E) ISO 2011 All rights reserved 1Plasti
16、cs pipes and fittings Decohesion test of electrofusion assemblies Strip-bend test 1 Scope This International Standard specifies a strip-bend test method for the evaluation of ductility of the fusion joint interface of assemblies of pipe and electrofusion fittings and saddle fittings intended for the
17、 conveyance of fluids. It is applicable to polyolefin assemblies. NOTE The aim of the strip-bend test method is to provide a quick check in order to have an indication of the ductility of the electrofusion interface. 2 Normative references The following referenced documents are indispensable for the
18、 application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 11413, Plastics pipes and fittings Preparation of test piece assemblies between a polyethylene (PE) pipe
19、and an electrofusion fitting 3 Symbols s width of test strip l length of brittle fracture Ld brittle failure, expressed as a percentage y length of fusion zone at location of brittle fracture 4 Principle The purpose of the test is to check the failure behaviour of an electrofusion assembly by examin
20、ation of the fusion interface of a strip test piece, which is bent manually using an appropriate tool. The test is conducted at (23 2) C. The ductility of the fusion joint interface of the assembly is characterized by the type of failure in the fusion zone and by the percentage of fusion area in whi
21、ch there is a lack of cohesion. NOTE It is assumed that the required number of test pieces (see 6.2) is set by the standard or specification making reference to this International Standard. BS ISO 21751:2011ISO 21751:2011(E) 2 ISO 2011 All rights reserved5 Apparatus The apparatus shall include the f
22、ollowing main parts. 5.1 Band-saw or equivalent tool, for preparation of the test pieces. 5.2 Bench vice, with sufficient width to clamp the total length of the fusion zone under test; clamps undamaged. 5.3 Pliers, with clamp width 10 mm for nominal pipe diameters up to and including 75 mm and clamp
23、 width 25 mm for nominal pipe diameters greater than 75 mm; clamps undamaged. 6 Test piece 6.1 Preparation of test pieces Pipes and fittings shall be jointed according to the manufacturers instructions and under conditions given in the product standard. For polyethylene (PE) assemblies, the conditio
24、ns for electrofusion shall be as specified in ISO 11413. The minimum pipe lengths shall be 250 mm or two times the pipe diameter, whichever is the greater. The pipe ends shall be cut back after fusion to achieve at least 25 mm projection from the edge of the electrofusion fitting. For socket assembl
25、ies, cut at least four strips for nominal pipe diameters up to and including 75 mm or at least eight strips for nominal pipe diameters greater than 75 mm from each socket, along the longitudinal axis of the assembly and equally spaced around the circumference, with a width s = (2,5 0,5) mm for nomin
26、al pipe diameters up to and including 75 mm or ()214mms+= for nominal pipe diameters greater than 75 mm. See Figure 1. The length equals the complete length of the assembly. The strips shall include the position of maximum gap between the fitting and the pipe, identified by visual examination prior
27、to sectioning. For saddles, at least four strips shall be taken from planes through the branch axis or axis of the tapping unit, of which one strip shall belong to the main pipe axis and one strip shall be perpendicular to the main pipe axis. The other strips shall be taken at 45 of the aforemention
28、ed strip positions. The width s of the strips shall be s = (2,5 0,5) mm for nominal main pipe diameters up to and including 75 mm or ()214mms+= for nominal main pipe diameters greater than 75 mm. In case of fittings with fusion lengths greater than or equal to 50 mm, the length of the fusion zone ma
29、y be segmented into sections of maximum 25 mm, starting from the ends of the fusion zone. These sections may be obtained by introducing slits in the fitting part of the strips. Key 1 pipe 2 fitting Figure 1 Preparation of strips from an electrofusion socket assembly BS ISO 21751:2011ISO 21751:2011(E
30、) ISO 2011 All rights reserved 36.2 Number of test pieces Unless otherwise specified by the referring standard or specification, the number of test pieces shall be three. 7 Conditioning Between the fusion and the machining operations, the assembly shall be conditioned for at least 4 h at ambient tem
31、perature. Polybutylene (PB) assemblies shall be conditioned according to the recommendations of the manufacturer. After preparation of the strips from the assembly, the strips shall be conditioned at the test temperature of (23 2) C for at least 1 h. 8 Procedure For each strip, carry out the followi
32、ng procedure at (23 2) C. (See Figure 2 for a schematic representation of the test setup.) a) Clamp the fitting part of the strip into the bench vice just below the level of the electrical wires. The bench vice shall be tightened manually. b) Clamp the pipe into the pliers. If the width of clamps do
33、es not cover the complete fusion zone, start from one end of the fusion zone. If adjustable pliers are used, the tightening force shall be set such that slippage of the test piece in the pliers is prevented. c) Move the pliers smoothly in 2 s to 3 s over an angle of about 90 (or until contact betwee
34、n the vice and the pliers) in one direction, then back to the original position. Continue over about 90 in the other direction, then back again to the original position. Reposition the pliers on the pipe at a distance that corresponds to the width of the plier jaws and repeat the operation until the
35、 other end of the fusion zone is reached. d) Report the position and type of break (brittle or ductile). NOTE Typical failure patterns are characterized in Figures 3, 4, 5 and 6; e) Measure and record the largest length of brittle fracture (l) and the total length of the fusion zone at the same loca
36、tion (y). f) Calculate the percentage of brittle failure, Ld, using the following equation: d100 (%)lLy= . NOTE See Annex A for recommended value of Ld. BS ISO 21751:2011ISO 21751:2011(E) 4 ISO 2011 All rights reservedKey 1 pipe 2 fitting 3 bench vice 4 pliers Figure 2 Positioning of strip Figure 3
37、Typical brittle fracture view on fracture surface BS ISO 21751:2011ISO 21751:2011(E) ISO 2011 All rights reserved 5Figure 4 Typical brittle fracture side view Figure 5 Typical ductile fracture between wires view on fracture surface BS ISO 21751:2011ISO 21751:2011(E) 6 ISO 2011 All rights reservedFig
38、ure 6 Typical ductile fracture between wires side view 9 Test report The test report shall include the following information: a) reference to this International Standard; b) identification of each of the components of the assembly; c) nominal size of the fitting; d) fusion conditions used when prepa
39、ring the assemblies; e) test temperature; f) clamping width of plier jaws; g) number of test pieces; h) number of strips per test piece; i) number of sections and section lengths, if applicable; j) type of failure, if any, with reference to the section in which it occurs; k) percentage of brittle fa
40、ilure, Ld, calculated in accordance with Clause 8 f); l) any special observations made during or after the test; m) any factors which could have affected the results, such as any incidents or any operational details not specified in this International Standard; n) identification of the test laborato
41、ry; o) date of the test. BS ISO 21751:2011ISO 21751:2011(E) ISO 2011 All rights reserved 7Annex A (informative) Recommended value for brittle failure The percentage of brittle failure, Ld, should be lower than or equal to 33 % for all test pieces. BS ISO 21751:2011ISO 21751:2011(E) ICS 23.040.20; 23
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