1、INTERNATIONAL STANDARD IS0 9691 First edition 1992-1 l-15 Rubber - Recommendations for the workmanship of pipe joint rings - Description and classification of imperfections Caautchouc - Recommandations concernant IexbAion des garnitures d b) excess material (see 3.1.2); c) shortage of material (see
2、3.1.3). NOTE 1 Some surface imperfections, e.g. offset and shortage of material, can appear in combination. 3.1.1 Imperfections not involving 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 mat
3、erial): 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. It is usually necessary to stretch the rubber for the edges of the cut to be- come clearly visible. 3.1.1.4 Cracking: A network of fine cracks or crazing which
4、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 (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 weld
5、ed ring, and solidifies to form a film-like appendage. It is caused by mould separ- ation and is present owing to inadequate trimming. 3.1.2.2 Offset: 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 shi
6、ft of one mould cavity plate or one end of the extrusion relative to the other. 1 IS0 9691:1992(E) Flash helght a) Moulded rinq Figure 1 - Flash IS0 9691:1992(E) External a) Moulded ring, ter Extruded welded ring b) Figure 2 - Off-register 3 IS0 9691:1992(E) 3.1.2.2.2 Mismatch (see fIgure3): Abrupt
7、change in cross-section 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 s
8、ee figure4 a): A longitudinal imperfection in which the rubber adjacent to the flash line shrinks below the level of the moulding Mismatch e l-l- 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 figure4 b): A shallow saucer-
9、like recess, sometimes triangular in shape, 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 figure5): A flat- tened and often roughened area around the inside and/or o
10、utside of the joint ring. It is caused by trim- ming off too much flash. a) Moldded ring e b) Extruded welded rlnp Figure 3 - Mismatch IS0 9691:1992(E) -4-L h a) Moulded rlnq b) Extruded welded rho Figure 4 - Backrind and parting-line indentation 5 IS0 9691:1992(E) a) Moulded ring Excessive trlmmlnq
11、 6 b) Extruded welded rlnq Figure 5 - Excessive trimming IS0 9691:1992(E) 3.1.3.4 Flow marks (see figure6): Thread-like re- cesses, usually curved, of very slight depth in the unflexed state, with normal surface texture and rounded edges. Flow marks are caused by incom- plete flow and knit in the ma
12、terial. - 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): 3.1.3.5 Surface depression (see figure7): A recess in the surface, usually irregular in shape. It may b
13、e caused by: - the removal of foreign material from the surface; - the build-up of a hardened deposit on the surface of the mould. Flow mark -J l-J-l a) Mouldedrlng ,-Flow mdrk Depth: k b) Extruded welded ring Figure 6 - Flow marks 7 IS0 9691:1992(E) a) Moulded rlnq Depth: m bl Extruded welded ring
14、Figure 7 - Surface depression 3.1.4 Assessment Surface imperfections are usually observed with a x 2 magnifying lens, slightly stretching or bending the joint ring in order to reveal surface imperfections which would not be visible without so doing. Excessive stretching, which could damage the seal-
15、 ing 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 ex- traneous matter embedded in the product. 3.2.1.2 Blisters/porosity: Air trapped in the product. 8 3.2.2
16、Assessment Internal imperfections may be determined by com- paring the compression stress-strain properties (see IS0 7743) or densities (see IS0 2781) of test pieces from a good finished product and test pieces taken from a finished product containing internal imper- fections. 4 Maximum acceptable l
17、imits 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. IS0 9691:1992(E) 4.1.1 Surface imperfections in zones involved in the sealing function All imperfections (except bloom) in zone
18、s 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 imperfec- tions other than bloom. The mould design shall take account of this requirement for an imperfection-free sealing zone; in partic
19、ular, the mould shall not pro- duce 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 impair the use or efficiency of the joint
20、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 hollows: - off-register; - flash. b) Minor imperfection: Any imperfection not having an appreciable effect on the use or efficiency of t
21、he 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 2 In order to facilitate the classification of an imperfection, observed imperfections can be compared to: - a refere
22、nce 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. 9 IS0 9691:1992(E) Table 1 - Classification of surface imperfections in zones not involved in the seatin
23、g function Surface Comments Major Imperfections Minor SUb- imperfection imperfections clause Yet involving excess or shortage of material 3loom Surface inclusion 0,Ol x internal diam. or 10 mm Minor imperfectton 3.1.1.1 O,Ol x internal l 10 mm; diam. with a max. h 0,5 mm 0flOmm; h 0,5 mm Major imper
24、fection 3.1 .I A Shortage of material Moulded ring Extruded welded ring IS0 9691:1992(E) Surface imperfection Shortage of material Flow marks Moulded ring Comments Extruded welded ring Major imperfections iam. or j 10 mm; Minor imperfections m. with a max. Sub- clause 1) Minimum cross-sectional dime
25、nsion immediately adjacent to the flash or offset. 11 IS0 9691:1992(E) Annex A (informative) Bibliography l IS0 4633:1983, Rubber sea/s - Joint rings for S IS0 6448:1985, Rubber seals - Joint rings used wafer supply, drainage and sewerage pipelines for petroleum product supply pipes and fittings - S
26、pecification for materials. - Specification for material. 2 IS0 6447:1983, Rubber seals -Joint rings used for gas supply pipes and fittings - Specification for material. 12 IS0 9691:1992(E) UDC 621.643.44-036.4 Descriptors: rubber, rubber products, sealing rings, pipelines, pipe joints, defects, classification, description. Price based on 12 pages
