BS 7677-1993 Recommendations for classification of imperfections in pipe joint rings《管道接头用密封圈缺陷分类推荐标准》.pdf

1、BRITISH STANDARD BS 7677:1993 ISO 9691:1992 Recommendations for Classification of imperfections in pipe joint rings UDC 621.643.44 036.4BS7677:1993 This British Standard, having been prepared under the directionof the Plastics and Rubber Standards Policy Committee, was published underthe authority o

2、f the Standards Board and comes intoeffect on 15 July 1993 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference PRM/70 Draft for comment 91/40185 DC ISBN 0 580 22434 1 Committees responsible for this British Standard The preparation of this British Standa

3、rd was entrusted by the Plastics and Rubber Standards Policy Committee (PRM/-) to Technical Committee PRM/70, upon which the following bodies were represented: British Gas plc British Plastics Federation British Precast Concrete Federation Ltd. British Rubber Manufacturers Association Ltd. Clay Pipe

4、 Development Association Ltd. Concrete Pipe Association Ductile Iron Producers Association Fibre Cement Manufacturers Association Ltd. Institution of Water and Environmental Management Malaysian Rubber Producers Research Association RAPRA Technology Ltd. Society of British Water Industries Water Com

5、panies Association Water Research Centre Water Services Association of England and Wales Amendments issued since publication Amd. No. Date CommentsBS7677:1993 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope 1 2 Normative references 1

6、3 Classification of imperfections 1 4 Maximum acceptable limits for imperfections 2 Annex A (informative) Bibliography 12 Figure 1 Flash 3 Figure 2 Off-register 4 Figure 3 Mismatch 5 Figure 4 Backrind and parting-line indentation 6 Figure 5 Excessive trimming 7 Figure 6 Flow marks 8 Figure 7 Surface

7、 depression 9 Table 1 Classification of surface imperfections in zones not involved inthesealing function 10 List of references Inside back coverBS7677:1993 ii BSI 07-1999 National foreword This British Standard has been prepared under the direction of the Plastics and Rubber Standards Policy Commit

8、tee. It is identical with ISO 9691:1992 Rubber Recommendations for the workmanship of pipe joint rings Description and classification of imperfections published by the International Organization for Standardization (ISO). The Technical Committee has reviewed the provisions of ISO 2781:1988, to which

9、 normative reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Complianc

10、e with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International standard Corresponding British Standard ISO 7743:1989 BS 903 Method for physical testing of rubber Part A4:1990 Determination of compression stress-strain properties (Identical) Summary

11、 of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 12, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front

12、 cover.BS7677:1993 BSI 07-1999 1 Introduction International Standards such as ISO 46331, ISO64472 and ISO 64483 (see bibliography) for rubber joint rings for pipelines include some general requirements for the finished rings, particularly for workmanship, in statements such as: “The rings shall be f

13、ree from porosity and shall not have surface defects or irregularities which could affect their functions”. In order to assist manufacturers wishing to comply with such requirements, this International Standard describes manufacturing imperfections which could arise during the production of pipe joi

14、nt rings, and lists criteria by which the quality of workmanship can be assessed. It should be stressed, however, that this International Standard is not a specification. Whether an imperfection is to be considered as a defect will ultimately have to be agreed upon between the interested parties (se

15、eclause 4). 1 Scope This International Standard describes and classifies imperfections in rubber joint rings for pipelines. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of pu

16、blication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain reg

17、isters of currently valid International Standards. ISO 2781:1988, Rubber, vulcanized Determination of density. ISO 7743:1989, Rubber, vulcanized or thermoplastic Determination of compression stress-strain properties. 3 Classification of imperfections 3.1 Surface imperfections There are three types o

18、f surface imperfection: a) imperfections not involving excess or shortage of material (see 3.1.1); b) excess material (see 3.1.2); c) shortage of material (see 3.1.3). NOTE 1Some surface imperfections, e.g. offset and shortage of material, can appear in combination. 3.1.1 Imperfections not involving

19、 excess or shortage of material 3.1.1.1 Bloom: A liquid or solid material which has migrated to the surface of a rubber. 3.1.1.2 Surface inclusion (foreign material): Any extraneous matter embedded in the surface. 3.1.1.3 Cut: A fine incision similar to that made by a scalpel. The cut is not open. I

20、t is usually necessary to stretch the rubber for the edges of the cut to become clearly visible. 3.1.1.4 Cracking: A network of fine cracks or crazing which is not visible unless the rubber is folded. It may be caused, for example, by ageing or incorrect storage. 3.1.2 Excess material 3.1.2.1 Flash

21、(see Figure 1): Excess material which escapes from the moulding cavity during moulding of a moulded ring, or is produced at the weld line of an extruded welded ring, and solidifies to form a film-like appendage. It is caused by mould separation and is present owing to inadequate trimming. 3.1.2.2 Of

22、fset: Joint ring halves that are off-register or mismatched. 3.1.2.2.1 Off-register (see Figure 2): Misalignment of joint ring halves caused by lateral shift of one mould cavity plate or one end of the extrusion relative to the other. 3.1.2.2.2 Mismatch (see Figure 3): Abrupt change in cross-section

23、 of a joint ring, caused when the cross-sectional dimensions of one mould cavity plate are not equal to those of the other plate or, in the case of extruded welded rings, the cross-sectional dimensions of the two ends are unequal. 3.1.3 Shortage of material 3.1.3.1 Backrind see Figure 4 a): A longit

24、udinal imperfection in which the rubber adjacent to the flash line shrinks below the level of the moulding and has a U- or W-shaped cross-section, with the flash frequently being ragged or torn. 3.1.3.2 Parting-line indentation see Figure 4 b): A shallow saucer-like recess, sometimes triangular in s

25、hape, located along the parting line where the two ring ends have been welded together. It is caused by deformation of the mould edge at the parting line. 3.1.3.3 Excessive trimming (see Figure 5): A flattened and often roughened area around the inside and/or outside of the joint ring. It is caused

26、by trimming off too much flash.BS7677:1993 2 BSI 07-1999 3.1.3.4 Flow marks (see Figure 6): Thread-like recesses, usually curved, of very slight depth in the unflexed state, with normal surface texture and rounded edges. Flow marks are caused by incomplete flow and knit in the material. 3.1.3.5 Surf

27、ace depression (see Figure 7): A recess in the surface, usually irregular in shape. It may be caused by: incomplete filling of the mould cavity and/or air trapped in the mould cavity (giving a randomly positioned indentation having a coarser surface texture than the normal product surface); the remo

28、val of foreign material from the surface; the build-up of a hardened deposit on the surface of the mould. 3.1.4 Assessment Surface imperfections are usually observed with a 2 magnifying lens, slightly stretching or bending the joint ring in order to reveal surface imperfections which would not be vi

29、sible without sodoing. Excessive stretching, which could damage the sealing ring, shall be avoided. A magnifying lens equipped with a length gauge should be sufficient. 3.2 Internal imperfections 3.2.1 Description 3.2.1.1 Foreign material (see also 3.1.1.2): Any extraneous matter embedded in the pro

30、duct. 3.2.1.2 Blisters/porosity: Air trapped in the product. 3.2.2 Assessment Internal imperfections may be determined by comparing the compression stress-strain properties (see ISO 7743) or densities (see ISO 2781) of test pieces from a good finished product and test pieces taken from a finished pr

31、oduct containing internal imperfections. 4 Maximum acceptable limits for imperfections 4.1 Surface imperfections In most types of joint ring, a distinction can be made between the zones involved in the sealing function and other zones. 4.1.1 Surface imperfections in zones involved in the sealing fun

32、ction All imperfections (except bloom) in zones involved in the sealing function are likely to result in unsafe conditions in the working of the joint. Therefore the sealing zone shall be free of all surface imperfections other than bloom. The mould design shall take account of this requirement for

33、an imperfection-free sealing zone; in particular, the mould shall not produce a parting line. 4.1.2 Surface imperfections in zones not involved in the sealing function 4.1.2.1 Imperfections may be categorized into two classes as follows: a) Major imperfection: Any imperfection which would seriously

34、impair the use or efficiency of the joint ring, in particular an imperfection which would make it difficult to produce a satisfactory joint. These imperfections are situated along the mould parting line as follows: off-register; flash. b) Minor imperfection: Any imperfection not having an appreciabl

35、e effect on the use or efficiency of the joint ring. 4.1.2.2 Table 1 gives a classification of major and minor imperfections, according to the size of the imperfection, in zones not involved in the sealing function. NOTE 2In order to facilitate the classification of an imperfection, observed imperfe

36、ctions can be compared to: a reference sample; photographs showing the type of imperfection. 4.2 Internal imperfections The joint ring shall not contain foreign material, blisters or porosity which reduces the compressive force. BS7677:1993 BSI 07-1999 3 Figure 1 FlashBS7677:1993 4 BSI 07-1999 Figur

37、e 2 Off-registerBS7677:1993 BSI 07-1999 5 Figure 3 MismatchBS7677:1993 6 BSI 07-1999 Figure 4 Backrind and parting-line indentationBS7677:1993 BSI 07-1999 7 Figure 5 Excessive trimmingBS7677:1993 8 BSI 07-1999 Figure 6 Flow marksBS7677:1993 BSI 07-1999 9 Figure 7 Surface depressionBS7677:1993 10 BSI

38、 07-1999 Table 1 Classification of surface imperfections in zones not involved in the sealing function Surface imperfection Comments Major imperfections Minor imperfections Sub- clause Not involving excess or shortage of material Bloom Minor imperfection 3.1.1.1 Surface inclusion 0,01 internal diam.

39、 or 10 mm u 0,01 internal diam. with a max. of10 mm 3.1.1.2 Cut Defined by its length l and its depth h l 0,01 internal diam. or l 10 mm; h 0,5 mm l u 0,01 internal diam. with a max. of10 mm; hu 0,5 mm 3.1.1.3 Crazing Major imperfection 3.1.1.4 Excess material Moulded ring Extruded welded ring Flash

40、 f 2 % of the dimension concerned aor f 0,6 mm f u 2 % of the dimension concerned awith a max. of0,6 mm 3.1.2.1 Offset e 2 % of the dimension concerned ore 0,5 mm; h 0,5 mm g u 0,5 mm; h u 0,5 mm 3.1.3.1 and 3.1.3.2 Excessive trimming n outside the thickness tolerance limits n within the thickness t

41、olerance limits 3.1.3.3BS7677:1993 BSI 07-1999 11 Table 1 Classification of surface imperfections in zones not involved in the sealing function Surface imperfection Comments Major imperfections Minor imperfections Sub- clause Shortage of material Moulded ring Extruded welded ring Flow marks j 0,01 i

42、nternal diam. or j 10 mm; k 0,5 mm j u 0,01 internal diam. with a max. of10 mm; k u 0,5 mm 3.1.3.4 Surface depressions l 0,01 internal diam. or l 10 mm; m 0,5 mm l u 0,01 internal diam. with a max. of10 mm; m u 0,5 mm 3.1.3.5 a Minimum cross-sectional dimension immediately adjacent to the flash or o

43、ffset.BS7677:1993 12 BSI 07-1999 Annex A (informative) Bibliography 1 ISO 4633:1983, Rubber seals Joint rings for water supply, drainage and sewerage pipelines Specification for materials. 2 ISO 6447:1983, Rubber seals Joint rings used for gas supply pipes and fittings Specification for material. 3

44、ISO 6448:1985, Rubber seals Joint rings used for petroleum product supply pipes and fittings Specification for material.BS7677:1993 BSI 07-1999 List of references See national foreword.BS 7677:1993 ISO 9691:1992 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the indep

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