1、February 2015DEUTSCHE NORM DIN-Normenausschuss Kautschuktechnik (FAKAU)DIN-SprachendienstEnglish price group 9No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of
2、sale for German Standards (DIN-Normen).ICS 83.060; 23.040.80!%C/“2321291www.din.deDDIN 7795Measuring compression set of elastomers in hot water,English translation of DIN 7795:2015-02Bestimmung des Druckverformungsrestes von Elastomeren in Heiwasser,Englische bersetzung von DIN 7795:2015-02Dterminat
3、ion de la dformation rmanente aprs compression pour Caoutchoucvulcanis dans leau chaude,Traduction anglaise de DIN 7795:2015-02www.beuth.deDocument comprises 14 pages08.15 DIN 7795:2015-02 2 A comma is used as the decimal marker. Contents Page Foreword . 3 Introduction 4 1 Scope . 5 2 Normative refe
4、rences . 5 3 Terms and definitions 5 4 Symbols and abbreviations . 5 5 Test setup 6 5.1 Tension device 6 5.2 Pressure vessel. 8 5.3 Heating cabinet . 11 5.4 Thickness measuring device . 11 6 Testing . 11 6.1 General . 11 6.2 Preparation of test specimens 12 6.3 Test procedure 12 Bibliography . 14 DI
5、N 7795:2015-02 3 Foreword This document has been prepared by Working Commitee NA 045-02-09 AA Rohrleitungsdichtungen of the DIN-Normenausschuss Kautschuktechnik (FAKAU) (DIN Standards Committee Rubber Technology). Attention is drawn to the possibility that some of the elements of this document may b
6、e the subject of patent rights. DIN and/or DKE shall not be held responsible for identifying any or all such patent rights. DIN 7795:2015-02 4 Introduction Elastomer seal rings are used in potable water installations where they are employed, amongst others, in press fitting connections. In these per
7、manent connections, which should have a minimum lifetime of 50 years, the elastomers guarantee the leaktightness of the system, thus making an essential contribution to the long-term reliability of the pipe connections. The following method enables conclusions to be drawn regarding the long-term rel
8、iability of elastomers under practice-oriented test conditions. DIN 7795:2015-02 5 1 Scope This standard specifies the setup and procedure for measuring the compression set of elastomer seal rings between 70 IRHD and 80 IRHD in hot water. 2 Normative references The following documents, in whole or i
9、n part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. DIN 12880, Electrical laboratory devices Heat
10、ing ovens and incubators DIN EN 10088-1, Stainless steels Part 1: List of stainless steels DIN ISO 815-1, Rubber, vulcanized or thermoplastic Determination of compression set Part 1: At ambient or elevated temperatures DIN ISO 3601-1, Fluid power systems O-rings Part 1: Inside diameters, cross-secti
11、ons, tolerances and designation codes DIN ISO 23529:2012-10, Rubber General procedures for preparing and conditioning test pieces for physical test methods 3 Terms and definitions For the purposes of this document, the following term and definition applies. 3.1 compression set CS compression set as
12、a measurement of the elasticity of elastomeric seal rings is calculated according to the following equation: %100CSs010=hhhh(1) where 0h is the original seal ring thickness, in mm; 1h is the seal ring thickness after relaxation, in mm; sh is the height of the spacer, in mm. 4 Symbols and abbreviatio
13、ns CS compression set 0h original seal ring thickness 1h seal ring thickness after relaxation sh height of spacer IRHD International Rubber Hardness Degree DIN 7795:2015-02 6 5 Test setup 5.1 Tension device The tension device to accommodate three seal rings each is shown in Figure 1. It consists of
14、the following components: screw ( M 10 80) with welded on butterfly nut; tension plates (diameter 45 mm; thickness 3 mm; roughness Ra 0,4 m) with integrated spacers (height 2,25 mm); cover plate (diameter 45 mm; thickness 3 mm; roughness Ra 0,4 m); butterfly nut M 10 screw-nut: M 10; For the compone
15、nts of the tension device the following stainless steels are applicable: 1.4401, 1.4404 or 1.4571 (according to DIN EN 10088-1). The tension devices shall be positioned parallel to the axis of the pressure vessel and the distance of the first seal ring to the bottom of the pressure vessel shall be (
16、40 10) mm. DIN 7795:2015-02 7 Dimensions in millimetres Key 1 screw (M 10 x 80) 2 butterfly nut M 10 3 cover plate 4 tension plates with integrated spacers 5 screw-nut M 10 Figure 1 Tension device DIN 7795:2015-02 8 5.2 Pressure vessel The pressure vessel is shown in Figure 2. It has the following c
17、haracteristics: pressure vessel inside volume in closed condition: 5,5 l; volume of holding fixtures: 0,4 l; water content: (4,0 0,2) l; holding fixtures for 11 tension devices with 33 seal rings in total. These shall be secured with a screw-nut in order to avoid inadvertent loosening of the nuts in
18、 the tension device. For the pressure vessel the following stainless steels are applicable: 1.4301, 1.4401, 1.4404 or 1.4571 (according to DIN EN 10088-1). As an alternative, when measuring the CS of seal rings made of butyl rubber, the following pressure vessel as shown in Figure 3 can be used: pre
19、ssure vessel inside volume in closed condition: 3,4 l; volume of holding fixtures: 0,3 l; water content: (3,0 0,2) l; holding fixtures for 11 tension devices with 33 seal rings in total. These shall be secured with a screw-nut in order to avoid inadvertent loosening of the nuts in the tension device
20、. For the pressure vessel the following stainless steels are applicable: 1.4301, 1.4401, 1.4404 or 1.4571 (according to DIN EN 10088-1). DIN 7795:2015-02 9 Dimensions in millimetres Key 1 pressure vessel 2 holding fixture for tension device bholding fixture for tension device Figure 2 Pressure vesse
21、l DIN 7795:2015-02 10 Dimensions in millimetres Key 1 pressure vessel for butyl rubber seal rings 2 top cover 3 fixing flange for a manometer ascrew for closing the top cover btap bore for a manometer ctap bore for tension device Figure 3 Pressure vessel DIN 7795:2015-02 11 5.3 Heating cabinet The h
22、eating cabinet used for the CS measurements shall meet the requirements of DIN 12880 and shall be able to maintain the temperature inside the pressure vessel within the limits defined in 6.1. This temperature shall be reached within three hours. 5.4 Thickness measuring device The device to measure t
23、he seal ring thickness consists of a plane solid baseplate on which the seal ring is to be positioned and a plane circular foot with a diameter of (10 0,5) mm, which can be moved perpendicular to the baseplate. The maximum error margin of the thickness measuring device is not permitted to exceed 0,0
24、1 mm (according to DIN ISO 23529:2012-10, 7.1). Using digital measuring units, a resolution of 0,01 mm is required. The force that will push the foot onto the seal ring shall be 0,6 N. The error margin of the time-keeping device for measuring the relaxation time shall not exceed 1 s. 6 Testing 6.1 G
25、eneral A seal ring with known thickness shall be compressed at room temperature (23 2) C exactly in axial direction. This deformation load shall be maintained at increased constant temperature of (110 2,5) C. The deformation load shall be removed and after the seal has been allowed to relax over a c
26、ertain period of time, its thickness shall be measured again. Testing shall be done exclusively with seal rings which have a nominal inside diameter (ID) of (28,2 0,3) mm and a nominal seal ring thickness of (3,0 0,1) mm according to DIN ISO 3601-1 on the main portion of their circumference. compres
27、sion of the seal ring: (25 2,4) %; duration of test: 10 000 h; test medium: deionized water, electrical conductivity 1 S/cm; test temperature: (110 2,5) C (in water). CS values shall be measured after the following periods of time: 1 000 h; 1 500 h; 2 000 h; 2 500 h; 3 000 h. DIN 7795:2015-02 12 If
28、the CS value of 30 % after 3 000 h has been exceeded, a verification of the CS shall be performed at 4 000 h. If the CS value exceeds 30 % again, the test shall be cancelled. If the CS value of 30 % after 3 000 h measurements is kept within, measurements shall be performed after the following time p
29、eriods: 5 000 h; 6 000 h; 7 000 h; 8 000 h; 10 000 h. The periods of time for measuring the CS value may be exceeded up to 72 h. Using regression analysis, the relevant CS values for 3 000 h and 10 000 h shall be calculated based upon the measured values. For a graphic representation of the smoothin
30、g function, a logarithmic time scale shall be chosen. For the regression analysis, the smoothing function selected shall be such that the difference between it and the measured values is kept to a minimum. The test shall deem as passed if the following requirements have been met: CS (3 000 h) 30 % C
31、S (10 000 h) 40 % 6.2 Preparation of test specimens Between vulcanization and testing of the seal rings, the minimum time period shall be 16 h and the maximum time period shall be 3 months. Before testing, the seal rings shall be conditioned at room temperature of (23 2) C for a minimum of 3 h. 6.3
32、Test procedure 1) The seal ring thickness shall be measured in axial direction with the thickness measuring device as described in 5.4. An arithmetic average shall be calculated from at least two measurements along the circumference of the seal ring. These two measuring planes should include a minim
33、um angle of 130. The measuring points shall be marked so that the seal ring thickness is always measured in the same place. 2) Three seal rings at a time shall be positioned in one tension device and shall be axially compressed by (25 2) %. The compression shall be achieved by the height of the spac
34、ers being (25 2) % less than the seal ring thickness. 3) All eleven tension devices for the 10 000 h test shall be attached in the same pressure vessel. 4) The pressure vessel shall be filled with deionized water with an electrical conductivity of 1 S/cm as defined under 5.2. 5) The liquid level sha
35、ll be marked in the pressure vessel. 6) The water in the pressure vessel shall be heated to (110 2,5) C. DIN 7795:2015-02 13 7) Removal of the seal rings for the CS determination: remove the pressure vessel from the heating cabinet; check the pressure vessel has been depressurized, by inspecting the
36、 pressure vessel manometer; open the pressure vessel; withdraw one tension device with its three seal rings; measure the conductivity of the water in the pressure vessel at the start and after 10 000 h; detach the seal rings immediately from the tension device; after removal of the seal rings re-ins
37、ert the tension device into the pressure vessel; refill with water up to the liquid level mark; close the pressure vessel immediately after refilling, and heat to (110 2,5) C. 8) Measure the CS according to DIN ISO 815-1. 9) The balance history shall be continually recorded. The maximum time period
38、between opening of pressure vessel and removal of seal rings from the tension device shall not exceed 15 min. Water loss during testing shall be avoided. An appropriate inspection (e.g. by weight measurement) shall be made at intervals of not more than 500 h. If water loss has been detected, the pre
39、ssure vessel shall be refilled immediately and, if necessary, the seal ring on the pressure vessel shall be replaced, The test specimen shall be bedewed constantly with deionized water. Otherwise the testing shall be cancelled and rerun. DIN 7795:2015-02 14 Bibliography 1 DIN EN 27888, Water quality Determination of electrical conductivity (ISO 7888:1985)
