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1、INTERNATIONAL STANDARD IS0 7986 First edition 1997-07-l 5 Hydraulic fluid power - Sealing devices - Standard test methods to assess the performance of seals used in oil hydraulic reciprocating applications Transmissions hydrauliques - Dispositifs dWanchkit6 - M a p=iso; o=isocs; s=central Printed in
2、 Switzerland ii Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 20:56:41 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 IS0 7986: 1997(E) Foreword
3、IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical
4、committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of elect
5、rotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 7986 was prepared
6、 by Technical Committee lSO/TC 131, Fluid power systems, Subcommittee SC 7, Sealing devices. Annexes A, B and C form an integral part of this International Standard. Annex D is for information only. Copyright International Organization for Standardization Provided by IHS under license with ISO Licen
7、see=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 20:56:41 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7986: 1997(E) J IS0 Introduction 0.1 General It is widely recognized that the results from reciprocating seal testing can be unpredictable. The
8、background research carried out in support of the preparation of this International Standard has demonstrated that this unpredictability is primarily a function of lack of control of critical variables affecting seal installation and operation. In order to carry out direct comparisons of seal perfor
9、mance, it is necessary to control these variables to closer limits than may be normal in industrial practice. The major variables that can affect seal performance, often even within normal manufacturing tolerance ranges, are listed in subclause 0.3. 0.2 Purpose of the test The purpose of the test is
10、 to provide comparative data on individual reciprocating shaft seal designs and to provide a basis for the preliminary selection of seals based on their relative performance. To achieve this, it is necessary to carry out the tests under strictly defined operating conditions. This International Stand
11、ard therefore defines standard values of speed, pressure, temperature and surface finish. This will permit comparison of seal test results from sources worldwide. To make the test results as useful as possible, a range of operating conditions has been provided, so that the most appropriate condition
12、s can be selected as a basis for comparison for initial seal selection. The pressures are standard working pressures, selected from IS0 2944:1974, 6,3 MPa (63 barl), 16 MPa (160 bar), and 31,5 MPa (315 bar). The speeds have been selected to include slow speed (where stick-slip and high wear may be p
13、roblems), medium speed for general purpose hydraulics and a representative high speed. The constraints on installation and operation in this procedure have been proved by research (primarily carried out at BHR Group in the United Kingdom, under sponsorship from European companies) and international
14、round robin seal tests to be necessary to achieve repeatable results. Any departure from the standard operating conditions and installation criteria cannot be considered a standard test. 1) 1 bar=O,l MPa=lOsPa. iv Copyright International Organization for Standardization Provided by IHS under license
15、 with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 20:56:41 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7986:1997(E) 0.3 Factors affecting seal performance Factors affecting seal performance include: a) installation; - sealing system
16、, i.e., design of bearing(s), seal(s) and wiper seal; - installation tolerances, including seal groove, shaft and bearings, extrusion gap; - shaft material and hardness; - surface finish of the shaft; variations of surface finish outside the range of Ra 0,08 urn to Ra 0,015 urn, or greater than Rt 1
17、,5 urn, can significantly affect seal performance. Different seal materials also have significantly varying requirements for the optimum surface finish; - surface finish of the groove surfaces. This must be less than Ra 0,8 pm to avoid static leakage and wear of the seal during pressure cycles; - be
18、aring material, including its effects on shaft texture and boundary layer. b) operation; - fluid, i.e., viscosity, lubricity, compatibility with seal material, including additives and contamination level; - pressure, including pressure cycle; - speed, especially speed cycle; - speed/pressure cycle,
19、i.e., stop-start conditions; - stroke, especially short strokes (two times the seal contact widths or less), which prevent formation of a lubricant film; - temperature, i.e., its effect on viscosity and seal material properties; - external environment. It is necessary to consider all the above facto
20、rs and their potential effect on seal performance when comparing potential seal performance in an actual application to results obtained from the standard test. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545
21、001 Not for Resale, 04/18/2007 20:56:41 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD IS0 IS0 7986: 1997(E) Hydraulic fluid power - Sealing devices - Standard test methods to assess the performance of seals used in oil hydraulic reciprocating applic
22、ations 1 Scope This International Standard defines the test conditions and methods for assessing the performance of seals used in oil hydraulic reciprocating applications. The resulting specified characteristics may be published in manufacturer s literature to enable a direct comparison of seal perf
23、ormance. The seal under test may be a single seal or a combination seal package. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were vali
24、d. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Sta
25、ndards. IS0 286-2:1988, /SO system of limits and fits - Part 2: Tables of standard tolerance grades and limit deviations for ho/es and shafts. IS0 1052: 1982, Steels for genera/ engineering purposes. IS0 1629:1995, Rubber and latices - Nomenclature. IS0 2944: 1974, Fluid power systems and components
26、 - Nominal pressures. IS0 3274:1996, Geometrical Product Specification (GPS) - Surface texture: Profile method - Nominal characteristics of contact (stylus) instruments. IS0 4288:1996, Geometrical Product Specification (GPS) - Surface texture: Profile method - Rules and procedures for the assessment
27、 of surface texture. IS0 6743-4:1962, Lubricants, industrial oils and related products (class L) - Classification - Part 4: Family H (Hydraulic systems). IS0 10766:1996, Hydraulic fluid power - Cylinders - Housing dimensions for rectangular-section-cut bearing rings for pistons and rods. Copyright I
28、nternational Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 20:56:41 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7988:1997(E) Q IS0 3 Symbols See table 1. Symbol d D E
29、 F dh 1 L Ptest Pretum SI sh V W Ra Rt Table 1 - Symbols, quantities and units Quantity Seal lip inside diameter Nominal seal housing diameter Seal length Friction force Seal heel inside diameter Leakage Seal housing length Test pressure (forward stroke) Return pressure (return stroke) Radial seal s
30、ection - lip Radial seal section - heel Test speed Leakage collection zone Shaft surface texture, arithmetical mean deviation Shaft surface texture, total height of the surface profile Unit mm mm mm N mm ml mm MPa MPa mm mm m/S mm pm pm 4 Test installation 4.1 General 4.1.1 The tests described in th
31、is specification shall be conducted using a suitable test rig possessing the features shown in figure 1 and detail assembly as shown in figure 2. 4.1.2 The bearing housing shall be designed and constructed as detailed in figure 3 and figure 4 and shall be made of steel. Bearing material shall be pol
32、yester fabric/polyester material and shall contain no glass, ceramic, metallic or other potentially abrasive filler. The bearing shall comply with IS0 10766. 4.1.3 A circuit comprising components capable of cycling the pressure and controlling the flow to the specifications given in table 2 shall be
33、 provided to circulate the test fluid through the test seal housing. Table 2 - Circuit specification Characteristic Specification Fluid flow 4 I/min to 10 Vmin Filtration 10 pm absolute (through which fluid is continuously circulated) Fluid reservoir 20 I to 50 I Filter change after every 1 000 h te
34、st running Test oil change after every 3 000 h test running New test oil shall be circulated through a new filter for 5 h prior to beginning a test with new oil. 2 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972
35、545001 Not for Resale, 04/18/2007 20:56:41 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 IS0 7986:1997(E) 4.2 Mechanical details 4.2.1 Test rig rod A test rod complying with table 3 shall be used. Table 3 - Test rod specification Parameter Diameter Material Surface te
36、xture Specification 36 mm, tolerance f8 (per IS0 286-2) Shaft material in accordance with IS0 1052, induction hardened before coating with hard chrome with a coating thickness of 0,015 mm to 0,03 mm Ground and polished to Ra 0,08 to Ra 0,15 urn when measured in accordance with 9.1 .l 4.2.2 Test rig
37、stroke The length of stroke shall be limited to 500 mm f 20 mm. 4.2.3 Test seal housing dimensions Housings for the test seals shall comply with the dimensions specified in figure 2. 4.2.4 Leakage collection and drain 4.2.4.1 Rod seal (see figures 1 and 2): At the atmospheric extremity of each seal
38、beyond which a wiper seal is installed, a leakage zone, W, of 20 mm + 5 mm shall be provided. Provision shall be made for the collection from within this zone of any leakage that has drained away, for subsequent measurement (see 4.2.4.2). The wiper seals shall be made of nitrile (NBR) rubber (see IS
39、0 1629) with a hardness of 70 IRHD to 75 IRHD and shall conform with the dimensions given in figure 7. New wiper seals shall be installed for each test. 4.2.4.2 Drain: Leakage drains having a minimum bore of 6 mm shall be provided. 5 Test parameters 5.1 Test fluid Test fluid shall be synthetic hydro
40、carbon hydraulic oil, poly-alpha-olefin ISO-L-HS 32 in accordance with IS0 6743-4. An example of an oil that conforms to this specification is Mobil SHC 524 21.1 5.2 Test fluid temperature The temperature of the test fluid throughout the tests shall be maintained at 60 “C to 65 “C when measured in t
41、he centre of the pressure chamber. The test fluid temperature shall be measured with a suitable thermocouple at the position specified in figure 2. 5.3 Test housing rod bearings Rod bearings as specified in 4.1.2 shall be used in housings that comply with figure 3 and IS0 10766. 2) This information
42、is given for the convenience of users of this International Standard and does not constitute an endorsement by IS0 of the product named. Equivalents products may be used if they can be shown to lead to the same results. 3 Copyright International Organization for Standardization Provided by IHS under
43、 license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 20:56:41 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7986:1997(E) 0 IS0 5.4 Test fluid pressure The appropriate test pressure, Ptest, shall be selected from the following lis
44、t, as appropriate to the intended application, in each case with a tolerance of f 2 %: - 6,3 MPa (63 bar); - 16 MPa (160 bar); - 31,5 MPa (315 bar). 5.5 Speed of linear actuator The speed of the reciprocating rod shall be limited to one of the specified linear speeds below, in each case with a toler
45、ance of + 5 %: - 0,05 m/s; - 0,15 m/s; - 0,5 m/s. 5.6 Pressure and stroke cycle for dynamic test The test pressures and strokes shall be cycled as follows: a) a forward stroke at constant pressure, Ptest; b) a return stroke at constant pressure, Pretum. The pressure cycle shall be maintained within
46、the specification given in figure 5 and stroke cycle within the specification given in figure 6. 6 Assembly and dismantling of seals All test seals shall be installed in their housings in the manner prescribed by the seal manufacturer. Lightly wipe test oil onto the test shaft and seal before assemb
47、ly. After assembly, wipe excess oil from the test shaft to avoid erroneous leakage measurements and excess lubrication. 7 Methods of measurement and measuring apparatus 7.1 Seal leakage Measuring cylinders of a maximum capacity of 10 ml and an accuracy of 0,l ml shall be used at the start of each te
48、st. If leakage exceeds 10 ml during the test, then larger measuring cylinders with an accuracy of 1 ml shall be used. 7.2 Seal friction 7.2.1 Load cell The load cell shall be installed on the test rig between the linear actuator and rod and shall be capable of measuring the tensile and compressive forces induced by the friction of the seal. The load cell shall be connected to a suitable conditioning apparatus and chart recorder so that a permanent record of the seal friction may be taken. A chart recorder that has a suitable frequency response and is capable of determining th