1、BRITISH STANDARD BS 6997:1990 Specification for Elastomeric toroidalsealing rings(“O”-rings) manufactured from acrylonitrile-butadiene rubbers complying with BS 6996BS6997:1990 This British Standard, having been prepared under the directionof the Rubber StandardsPolicy Committee, waspublished under
2、the authorityof the Board of BSI andcomes into effect on 31 August 1990 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference RUM/5 Draft for comment 84/35373 DC ISBN 0 580 16650 3 Committees responsible for this British Standard The preparation of this Br
3、itish Standard was entrusted by the Rubber Standards Policy Committee (RUM/-) to Technical Committee RUM/5, upon which the following bodies were represented: British Rubber Manufacturers Association Chemical Industries Association Malaysian Rubber Producers Research Association Ministry of Defence A
4、mendments issued since publication Amd. No. Date CommentsBS6997:1990 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Dimensions 1 3 Surface imperfections 1 4 Material 1 5 Physical properties 1 6 Packaging and storage 1 7 Marking 1 Appendix A Method for t
5、he determination of compression set 2 Table 1 Physical properties 1 Publications referred to Inside back coverBS6997:1990 ii BSI 08-1999 Foreword This British Standard was prepared under the direction of the Rubber Standards Policy Committee. It specifies requirements for toroidal sealing rings (“O”
6、-rings) manufactured from acrylonitrile-butadiene rubbers of five hardness grades complying with BS 6996. 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. Compliance with a British Sta
7、ndard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 and 2, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorpo
8、rated. This will be indicated in the amendment table on the inside front cover.BS6997:1990 BSI 08-1999 1 1 Scope This British Standard specifies requirements for the composition and physical properties of toroidal sealing rings (“O”-rings) manufactured from acrylonitrile-butadiene rubbers complying
9、withBS6996. The five hardness grades of acrylonitrile-butadiene rubbers used are B0 50, B060, B0 70, B0 80 and B0 90 of BS 6996. NOTEThe titles of the publications referred to in this standard are listed on inside back cover. 2 Dimensions Dimensions and tolerances of the sealing rings shall be in ac
10、cordance with BS 1806 for “inch” sealing rings and BS 4518 for metric sealing rings. 3 Surface imperfections The sealing rings shall comply with the requirements of grades N or S of BS 6442. 4 Material The sealing rings shall be made from a compound complying with BS 6996. The grade designation of r
11、ubber required shall be stated on all drawings and contracts. 5 Physical properties 5.1 From every batch of compound, samples from the first lot of finished sealing rings shall comply with all the requirements given in Table 1, and samples from each subsequent lot of finished rings shall comply with
12、 the requirements of tests (a) and(c) of Table 1. 5.2 When testing sealing rings of cross section less than 1.70 mm, a test piece of 1.70 mm cross section shall be moulded from the same batch under identical conditions of time and temperature. 6 Packaging and storage Sealing rings shall be packaged
13、and stored in accordance with BS 3574. 7 Marking Every package of sealing rings shall be marked with at least the following information which shall be visible from the outside of the unopened package: a) manufacturers identity; b) size (see clause 2); c) number and date of this British Standard andg
14、rade designation of the rubber used (e.g.BS6997:1990 B0 60) 1) ; d) quarter and year of manufacture; e) grade of sealing ring (grade N or S of BS 6442); f) number of sealing rings in the package. Table 1 Physical properties 1) Marking BS6997:1990 on or in relation to a product represents a manufactu
15、rers declaration of conformity, i.e. a claim by or on behalf of the manufacturer that the product meets the requirements of the standard. The accuracy of the claim is therefore solely the responsibility of the person making the claim. Such a declaration is not to be confused with third party certifi
16、cation of conformity, which may also be desirable. Physical property Required value for grade of rubber used Test method B0 50 B0 60 B0 70 B0 80 B0 90 a) Apparent hardness, (IRHD) Cross section 1.70 mm to 2.79 mm BS 903-A26, method CM, three test pieces, except that rings shall not be fixed to the s
17、pecimen table with wax Cross section over 2.79 mm b) Density, (Mg/m 3 ) Agreed value 0.02 a BS 903-A1, method A c) Maximum compression set, (%) Cross section 1.70 mm to 2.79 mm 40 35 30 30 35 BS 903-A6, method A andAppendix A of this British Standard Cross section over 2.79 mm 30 25 20 20 25 b) Resi
18、stance to liquids, volume change, (%) BS 903-A16, Oil No. 3, h at 100 1 C a No values are specified for density but it is recommended that a value be established for each composition. This may provide a useful check when a series of batches of the same composition has to be tested for compliance wit
19、h this British Standard. 50 +3 9 60 +3 9 70 +3 9 80 +3 9 90 +3 9 50 +5 7 60 +5 7 70 +5 7 80 +5 7 90 +3 7 +30 0 +25 0 +25 0 +20 0 +20 0 72 +0 2BS6997:1990 2 BSI 08-1999 Appendix A Method for the determination of compression set A.1 General The following modifications to method A of BS 903-A6 are nece
20、ssitated by the use of sealing rings as test pieces when determining compression set. A.2 Thickness gauge Use one of the following measuring instruments: a) an electronic thickness comparator, firmly heldin a rigid stand over a flat base plate not lessthan 50 mm in any direction, with a moving conta
21、ct member which has a flat circular contact area of diameter 10 0.1 mm. The force exerted by the moving contact member shall be 0.40 0.04 N; b) a dial gauge, firmly held in a rigid stand over aflat base plate not less than 50 mm in any direction, with a moving contact member whichhas a flat circular
22、 contact area of diameter10 0.1 mm. The gauge shall have a scale graduated in unit divisions of 0.01 mm and shall comply where relevant with BS 907. The force exerted by the moving contact member shall be 0.40 0.04 N. Both instruments shall measure to an accuracy of 0.005 mm, and the axis of movemen
23、t of the moving contact member shall be vertical and in line with the dimension being measured. NOTEThis requirement applies to the instruments only, not to their capability of measuring sealing ring cross sections. A.3 Test pieces In the case of sealing rings having an internal diameter of 13 mm or
24、 more, the test piece shall consist of a section approximately 25 mm in length cleanly cut from a ring by straight cuts across the cord of the ring. In the case of sealing rings having an internal diameter of less than 13 mm, the test piece shall be a whole ring vented by a single cut through the co
25、rd section. The variation in cord diameter along the length of the test piece shall not exceed 2 % of the nominal cord diameter. NOTESee also 5.2. Use three test pieces for each determination. A.4 Measurement of the test pieces Measure the original test piece thickness (t c ) as follows. Measure the
26、 cord diameter of each test piece at a marked point approximately midway along its length, across the cord diameter at right angles to the plane of the ring. The ink or other agent used for marking shall have no deleterious effect on the rubber; shall be of contrasting colour to that of the rubber;
27、and shall be so applied that it does not come into contact with the plates of the compression apparatus when the sealing rings are under compression. Measure the thickness of the test piece after recovery (t r ) in the same manner at the same point. A.5 Spacers Choose the spacer(s) so that each test
28、 piece shall be compressed to a value (t s ) of 75 2 % of its original thickness. Measure the t sto the nearest 0.01 mm. A.6 Lubrication The test pieces shall not be lubricated. A.7 Duration of compression period The duration of the compression period shall be h and the temperature shall be 100 1 C.
29、 24 +0 2BS6997:1990 BSI 08-1999 Publications referred to BS 903, Methods of testing vulcanized rubber. BS 903-A1, Determination of density. BS 903-A6, Determination of compression set after constant strain. BS 903-A16, Determination of the effect of liquids. BS 903-A26, Determination of hardness. BS
30、 907, Specification for dial gauges for linear measurement. BS 1806, Specification for dimensions of toroidal sealing rings (“O”-rings) and their housings (inch series). BS 3574, Specification for the controlled storage and packaging of vulcanized rubber and rubber products. BS 4518, Specification f
31、or metric dimensions of toroidal sealing rings (“O”-rings) and their housings. BS 6442, Specification for limits of surface imperfections on elastomeric toroidal sealing rings (“O”-rings). BS 6996, Specification for mineral oil resistant acrylonitrile-butadiene rubber compounds. BS 6997:1990 BSI 389
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