BS-4832-1987 ISO-6072-1986.pdf

BRITISH STANDARD BS 4832:1987 ISO 6072:1986 Specification for Compatibility between elastomeric materials and hydraulic fluids ISO title: Hydraulic fluid power Compatibility between elastomeric materials and fluids UDC 621.8.032:678.074:620.193.4 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 30 09:06:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4832:1987 This British Standard, having been prepared under the direction of the Machinery and Components Standards Committee, was published under the authority of the Board of BSI and comes into effect on 28 August 1987 © BSI 11-1999 First published July 1972 First revision August 1987 The following BSI references relate to the work on this standard: Committee reference MCE/18 Draft for comment 85/76841 DC ISBN 0 580 16087 4 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Machinery and Components Standards Committee (MCE/-) to Technical Committee MCE/18, upon which the following bodies were represented: Advanced Manufacturing Technology Research Institute Association of British Mining Equipment Companies British Compressed Air Society British Fluid Power Association British Hydromechanics Research Association British Steel Corporation British Telecommunications plc Department of Trade and Industry (National Engineering Laboratory) Electricity Supply Industry in England and Wales Federation of Manufacturers of Construction Equipment and Cranes Institution of Mechanical Engineers Ministry of Defence The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Ball and Roller Bearing Manufacturers Association British Railways Board British Rubber Manufacturers Association Institute of Petroleum Society of British Aerospace Companies Limited Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 30 09:06:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4832:1987 © BSI 11-1999i Contents Page Committees responsibleInside front cover National forewordii 0Introduction1 1Scope and field of application1 2References1 3Definitions1 4Test elastomers2 5Determination of elastomer compatibility index (ECI)5 6Identification statement7 Annex A Prediction of percentage change in volume of commercial rubbers in mineral-based oils8 Annex B Rapid method for indicating the effect of mineral-based oils on elastomers by measuring volume change index (VCI)10 Annex C Information report13 Figure 1 Analytical balance for weighing in air and water6 Figure 2 Relationship between percentage change in volume of commercial rubbers in mineral oils and of standard rubber NBR 19 Figure 3 Tapered rod gauge12 Table 1 Composition by mass of standard acrylonitrile-butadiene rubber (NBR 1)2 Table 2 Control tests for NBR 13 Table 3 Composition by mass of standard fluoroelastomer (FPM 1)3 Table 4 Control tests for FPM 14 Table 5 Composition by mass of standard ethylene propylene diene rubber (EPDM 1)4 Table 6 Control tests for EPDM 15 Table 7 Test conditions for determination of elastomer compatibility index (ECI)5 Table 8 Conversion table for converting percentage linear swell (SD) into percentage volumetric change (SV)11 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 30 09:06:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4832:1987 ii © BSI 11-1999 National foreword This revision of BS 4832 has been prepared under the direction of the Machinery and Components Standards Committee. It is identical with ISO 6072:1986 “Hydraulic fluid power Compatibility between elastomeric materials and fluids”, published by the International Organization for Standardization (ISO), and supersedes the 1972 edition of BS 4832, which has been withdrawn. The standard provides a comparative means of assessing the compatibility of various hydraulic fluids with three standardized elastomeric sealing materials. In view of the ever increasing number of operating fluids and sealing materials available to the designer and user of fluid power equipment, it is desirable that a means should be specified to determine the swelling effect of an hydraulic fluid in relation to a standardized elastomer. This standard will assist in the selection of an appropriate elastomer for seals that will be suitable for use with the fluid under consideration. Conversely, for a given sealing material it will be possible to obtain an indication of interchangeability of hydraulic fluids in relation to that material. This will also provide some guidance as to one of the factors which can affect seal life. It should however be borne in mind that there are other factors which affect seal life and performance, such as seal design, surface finish of the surfaces in contact with the seal, as well as contamination from other sources than oil. Throughout this standard the term “compatibility” is used to indicate that the seal material is not adversely affected by the hydraulic fluid and that they may therefore be used together. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. In clause 6, the last paragraph should be read as follows. “Elastomeric material compatibility with fluids determined in accordance with BS 4832, Specification for compatibility between elastomeric materials and hydraulic fluids.” Cross-references International StandardCorresponding British Standard BS 903 Methods of testing vulcanized rubber ISO 37:1977Part A2:1971 Determination of tensile stress-strain properties (Technically equivalent) ISO 48:1979Part A26:1969 Determination of hardness (Technically equivalent) BS 1673 Methods of testing raw rubber and unvulcanized compounded rubber ISO 289:1985Part 3:1969 Methods of physical testing (Technically equivalent) BS 903 Methods of testing vulcanized rubber ISO 815:1972Part A6:1969 Determination of compression set after constant strain (Technically equivalent) BS 3502 Schedule of common names and abbreviations for plastics and rubbers Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 30 09:06:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4832:1987 © BSI 11-1999iii The Technical Committee has reviewed the provisions of ISO 5598 and ASTM D 2934, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. Additional information. With reference to 4.1.2, suitable elastomer test specimens may be obtained in the United Kingdom from Parker Hannifin (UK) Ltd., Seal Group, Maylands Avenue, Hemel Hempstead, Herts HP2 4SJ. 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 Standard does not of itself confer immunity from legal obligations. International StandardCorresponding British Standard ISO 1629:1976Part 3:1978 Rubbers and latices (Identical) BS 903 Methods of testing vulcanized rubber ISO 1817:1985Part A16 Determination of the effect of liquids (Identical) ISO 2393:1973BS 1674:1976 Specification for equipment and general procedure for mixing and vulcanizing rubber test mixes (Technically equivalent) BS 903 Methods of testing vulcanized rubber ISO 2781:1981Part A1:1980 Determination of density (Technically equivalent) Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 14, 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 cover. Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 30 09:06:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 30 09:06:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4832:1987 © BSI 11-19991 0 Introduction In hydraulic fluid power systems, power is transmitted and controlled through a liquid under pressure within an enclosed circuit. Elastomers are used as seals in fluid power systems. Elastomeric materials are any substances having the ability to return to original size and shape after deformation. Hydraulic fluids are water, oil or other fluids which are forced through an orifice or an enclosed circuit. Elastomeric materials and hydraulic fluids are compatible if they are not altered by chemical interaction. Annex A to this International Standard specifies the percentage volume change of commercial rubbers in mineral-based oils. Annex B describes the rapid method for indicating the effect of mineral-based oils on elastomers by measurement of volume change index (VCI). Annex C provides an information report. 1 Scope and field of application This International Standard provides formulations, mixing and vulcanization procedures for three types of elastomeric compositions: a) acrylonitrile-butadiene rubber (NBR 1); b) fluoroelastomers (FPM 1); c) ethylene propylene diene rubber (EPDM 1). These procedures evaluate the effect of mineral-based and fire-resistant hydraulic fluids upon such compositions by measurement, under controlled conditions, of physical properties of standard test pieces of the suitable test elastomer before and after immersion in the fluids. The elastomeric materials used in these formulations are sensitive to fluid variations and have comparatively high swelling characteristics. Stable cure systems should be used to give adequate storage life. NOTEThis International Standard does not provide formulations of elastomeric materials for actual service. The changes in volume, hardness, tensile strength and elongation at break which standard test specimens of the suitable standard test elastomer undergo when immersed in a certain fluid under specified test conditions (see Table 7) establish an elastomer compatibility index (ECI) for this fluid, which can be expressed in the format given in clause 5. The ECI (which should be quoted by oil suppliers) allows selection of suitable combinations of fluids and elastomeric materials without prolonged testing. In the case of mineral-based oils, it will be possible to predict the percentage volume change of commercial rubbers (see Annex A). NOTEThe ECI may provide enough information so as to eliminate totally unsuitable elastomer/fluid combinations without having to resort to extensive screening tests. Representative standard compositions of various types of elastomers permit evaluation of the effect of hydraulic fluids on such compositions and comparison with commercial elastomeric materials for actual service. They would also assist producers of additives and hydraulic fluids in the development of hydraulic fluids compatible with different elastomer types. 2 References ISO 37, Rubber, vulcanized Determination of tensile stress-strain properties. ISO 48, Vulcanized rubbers Determination of hardness (Hardness between 30 and 85 IRHD). ISO 289, Rubber, unvulcanized Determination of Mooney viscosity. ISO 815, Rubber, vulcanized Determination of compression set at normal and at high temperatures1). ISO 1629, Rubber and latices Nomenclature. ISO 1817, Rubber, vulcanized Determination of the effect of liquids. ISO 2393, Rubber test mixes Preparation, mixing and vulcanization Equipment and procedures. ISO 2781, Vulcanized rubbers Determination of density. ISO 5598, Fluid power systems and components Vocabulary. 3 Definitions For the purposes of this International Standard, the definitions given in ISO 5598 and the following definitions apply. NOTEFor definitions of the types of fluids involved, see Table 7. 3.1 elastomer a macromolecular, rubber-like material that returns rapidly to approximately its initial dimensions and shape after substantial deformation by a weak stress and release of the stress 1) At present at the stage of draft. (Revision of ISO 815:1972.) Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 30 09:06:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4832:1987 2 © BSI 11-1999 3.2 test elastomer a rubber vulcanizate with a known composition, used for evaluating the effect of media on elastomers. In order to minimize error a test elastomer contains only the most essential ingredients for a vulcanizate 3.3 commercial rubber an elastomeric material for actual service the composition of which is not given by the manufacturer and which contains many more ingredients than the standard rubbers in order to fulfil processing and service requirements NOTEIt is not advisable to use commercial rubbers for quality control of media as they are generally subject to larger quality tolerances than test elastomers. 4 Test elastomers 4.1 Recommended practice 4.1.1 The mixing and vulcanization procedures for these test elastomers as laid down in ISO 2393 shall be followed. 4.1.2 A single source for each of the ingredients of the test elastomers shall be used and the quality of each batch produced shall be checked. 4.2 Standard acrylonitrile-butadiene rubber (NBR 1) 4.2.1 Composition by mass The composition by mass is given in Table 1. Table 1 Composition by mass of standard acrylonitrile-butadiene rubber (NBR 1) 4.2.2 Mixing procedure Proceed as follows, maintaining the surface temperature of the rolls at 50 ± 5 °C. 4.2.2.1 Band crude rubber with the mill opening set at 1,4 mm and break down. 4.2.2.2 Add the zinc oxide, then the polymerized 2,2,4-trimethyl 1,2-dihydroquinoline evenly across the rolls at a constant rate. 4.2.2.3 Make 3/4 cuts on the rolls from one end diagonally to the other end. 4.2.2.4 Add approximately half the carbon black evenly across the rolls at a constant rate. 4.2.2.5 Open the mill at intervals to maintain a constant bank. 4.2.2.6 Make three 3/4 cuts from each side. 4.2.2.7 Add the rest of the carbon black, including all the pigment that has dropped through to the pan. 4.2.2.8 Add the dicumyl peroxide evenly across the rolls. 4.2.2.9 Make six 3/4 cuts from each side. 4.2.2.10 Cut the batch from the mill and set the opening to 0,2 mm. 4.2.2.11 Pass the rolled stock endwise through the mill six times. 4.2.2.12 Sheet off samples at 2,2 mm and allow to cool on flat metal surface. 4.2.2.13 Prepare samples for cure. 4.2.3 Preparation of standard vulcanized sheets Cure standard vulcanized sheets 2 ± 0,2 mm thick for 20 min at 170 °C. 4.2.4 Control tests Carry out all the tests specified in Table 2 on sheets 2 ± 0,2