BS EN 681-4 pdf free download

BS EN 681-4 pdf free download.Elastomeric seals – Materials requirements for pipe joint seals used in water and drainage applications – Part 4: Cast polyurethane sealing elements.
4 Requirements 4.1 Materials The materials shall be free of any substances which may have a deleterious effect on the fluid being conveyed or on the life of the sealing element, or on the pipe or ftting. 4.2 Finished seal requirements 4.2.1 Dimensional tolerances Tolerances shall be specified from Class E2 of ISO 3302-1 or in relevant product standards. 4.2.2 Imperfections and defects The seals shall be free of defects or irregularities which affect their function. Classification of imperfections shall be according to ISO 9691:1992 as follows: – surface imperfections in zones involved in the sealing function as described in 4.1.1 of ISO 9691:1992 shall be considered as defects; – surface imperfections in zones not involved in the sealing function as described in 4.1.2.1b) of ISO 9691:1992 shall not be considered as defects. NOTE 1: Major surface imperfections in zones not involved in the sealing function as described in 4.1.2.1a) of ISo 9691:1992 could be considered as defects. This should be agreed between the interested parties; the acceptance criteria depend upon the seals’ type or design respectively.NOTE 2: Internal imperfections as described in 4.2 of ISO 9691:1992 could be considered as defects. The compressive force can be determined according to ISO 7743′. The acceptable limiting values of the compressive force should be agreed between the interested parties; they depend upon the seals’ type or design respectively. 4.2.3 Hardness When determined by the micro-test method specified in ISO 48, the hardness shall comply with the requirement given in table 1. NOTE: If the dimensions of a seal are appropriate, the normal test method specified in ISO 48 can be used, provided that the micro-test method is used for reference purposes. For the same seal, the difference between the minimum and maximum hardness shall not be more than 5 IRHD. Each value shall be within the specified tolerances. 4.2.4 Tensile strength and elongation at break The tensile strength and elongation at break shall be determined by the method specified in ISO 37. Dumb-bell shaped test pieces of types 1, 2, 3 or 4 shall be used. Type 2 is the preferred size. The test report shall state the dumb-bell type whenever type 2 is not used. The tensile strength and the elongation at break shall comply with the requirements given in table 1. 4.2.5 Compression set in air 4.2.5.1 General If the test piece is taken from a seal, then the measurement shall be carried out as far as possible in the direction of compression of the seal in service.4.2.5.2 Compression set at 23 °C and 70 °C When determined by the method specified in ISO 815, at 23 °C and 70。C, using the small Type B test piece, the compression set shall comply with the requirements given in table 1. 4.2.5.3 Low temperature compression set at -10 °C When determined by the method specified in ISo 815 at -10。C using the small Type B test piece, and the (30土3) min recovery measurement, the compression set shall comply with the requirements given in table 1. Alternatively this requirement is satisfied if the maximum hardness at-10 °C土1。C is not greater than 80 IRHD after storage at-10 °C士1 °C for5 h. BS EN 681-4 pdf download.