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1、BRITISH STANDARD BS ISO 3968:2001 Incorporating Technical Corrigendum No. 1 Hydraulic fluid power Filters Evaluation of differential pressure versus flow characteristics ICS 23.100.60 ? Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO
2、3968:2001 This British Standard, having been prepared under the direction of the Engineering Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 4 February 2002 BSI 4 February 2003 ISBN 0 580 38969 3 National foreword This British
3、 Standard reproduces verbatim ISO 3968:2001, including Technical Corrigendum September 2002, and implements it as the UK national standard. It supersedes BS 6277:1982, which is withdrawn. The UK participation in its preparation was entrusted by Technical Committee MCE/18, Fluid power systems and com
4、ponents, to Subcommittee MCE/18/-/6, Contamination control, which has the responsibility to: A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this doc
5、ument may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract
6、. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for c
7、hange, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 11 and a back cover. The BSI co
8、pyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments 14142 Technical Corrigendum No.1 4 February 2003 Change to footnote of Table 1 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006
9、, Uncontrolled Copy, (c) BSI Reference number ISO 3968:2001(E) INTERNATIONAL STANDARD ISO 3968 Second edition 2001-12-15 Hydraulic fluid power Filters Evaluation of differential pressure versus flow characteristics Transmissions hydrauliques Filtres valuation de la perte de charge en fonction du dbi
10、t Technical Corrigendum 1 2002-09-01 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 3968:2001(E) ii Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 3968:2001(E) iii Contents
11、 Page Foreword.iv Introduction.v 1 Scope1 2 Normative references1 3 Terms and definitions .1 4 Symbols2 4.1 Literal symbols 2 4.2 Graphical symbols.2 5 Test equipment2 5.1 General indications .2 5.2 Pump.2 5.3 Reservoir 3 5.4 Temperature control4 5.5 Clean-up filter.4 5.6 Sampling valve.4 5.7 Mounti
12、ng of filter .4 5.8 Test fluid.4 6 Measurements4 6.1 Pressure measurement.4 6.2 Temperature measurement 5 6.3 Kinematic viscosity measurement.5 6.4 Flow rate measurement.5 6.5 Fluid cleanliness measurement .6 6.6 Accuracy of measuring instruments and test conditions.6 7 Procedure.6 7.1 Pipework corr
13、ection6 7.2 Cleanliness of test circuit.6 7.3 Characteristics of the filter housing6 7.4 Characteristics of the filter assembly7 7.5 Characteristics of the filter element only7 7.6 Characteristics of the bypass valve 7 8 Presentation of results8 9 Identification statement (Reference to this Internat
14、ional Standard).10 Bibliography11 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 3968:2001(E) iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies
15、). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and no
16、n-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Par
17、t 3. The main task of technical committees is to prepare International Standards. 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
18、 a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 3968 was prepared by Technical Committee ISO/TC 131, Fluid power systems,
19、Subcommittee SC 6, Contamination control. This second edition cancels and replaces the first edition (ISO 3968:1981), which has been technically revised. Its primary objective is to bring procedures and equipment as close as possible to those of ISO 16889. It also integrates some recommendations of
20、ISO 9110-11 and ISO 9110-22, which deal with pressure measurements, and of other standards pertaining to the subject matter. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 3968:2001(E) v Introduction In hydraulic fluid power systems, po
21、wer is transmitted and controlled through a fluid under pressure circulating within a closed circuit. Filters maintain the cleanliness of the fluid by retaining the insoluble contaminants. Hydraulic filters normally include a housing that serves as the pressure-containing vessel to direct the flow o
22、f fluid through a filter element that separates contaminants from the test fluid. In operation, fluid flowing through a filter meets resistance due to kinetic and viscous effects. The pressure required to overcome this resistance and to maintain flow is known as the differential pressure. The differ
23、ential pressure is the total pressure difference observed between the filter inlet port and outlet port and represents the sum of the losses recorded in the housing and filter element. Factors which affect clean filter differential pressure are fluid viscosity, fluid specific gravity, flow rate, fil
24、ter element media type and construction, as well as housing design. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTERNATIONAL STAN
25、DARD ISO 3968:2001(E) 1 Hydraulic fluid power Filters Evaluation of differential pressure versus flow characteristics 1 Scope This International Standard specifies a procedure for evaluating differential pressure versus flow characteristics of hydraulic filters and constitutes a basis for agreement
26、between the filter manufacturer and user. It also specifies a method for measurement of the differential pressure generated at different flow rates and viscosities by the relevant parts of a filter assembly, that is the housing, the filter element and any valves contained within the housing that are
27、 in the flow stream. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. Howev
28、er, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of IEC and I
29、SO maintain registers of currently valid International Standards. ISO 1219-1, Fluid power systems and components Graphic symbols and circuit diagrams Part 1: Graphic symbols ISO 3448, Industrial liquid lubricants ISO viscosity classification ISO 4021, Hydraulic fluid power Particulate contamination
30、analysis Extraction of fluid samples from lines of an operating system ISO 4406, Hydraulic fluid power Fluids Method for coding the level of contamination by solid particles ISO 5598, Fluid power systems and components Vocabulary ISO 16889, Hydraulic fluid power filters Multi-pass method for evaluat
31、ing filtration performance of a filter element 3 Terms and definitions For the purposes of this International Standard, the definitions given in ISO 5598 and the following apply. 3.1 filter rated flow rate flow rate recommended by the filter manufacturer for a specified kinematic viscosity 3.2 visco
32、sity index empirical measure of the viscosity/temperature characteristics of a fluid NOTE The smaller the change in viscosity within a given temperature range, the higher the viscosity index. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Uncontrolled Copy, (c) BSI I
33、SO 3968:2001(E) 2 3.3 differential pressure difference between the tested component inlet and outlet pressures under specified conditions 4 Symbols 4.1 Literal symbols The following literal symbols are used in this International Standard: a) qV is the test volume flow rate; b) qR is the filter rated
34、 volume flow rate; c) p is the static pressure; d) p1 is the static pressure measured upstream of the filter; e) p2 is the static pressure measured downstream of the filter; f) p is the differential pressure (p = p1 p2); g) D is the internal pipe diameter. 4.2 Graphical symbols The graphical symbols
35、 used in this International Standard are in accordance with ISO 1219-1. 5 Test equipment 5.1 General indications A suitable test rig consists of a pump, a reservoir, a clean-up filter, the filter under test and, if required, a heat exchanger, together with all the necessary equipment for measuring t
36、he pressure, the flow rate, the temperature and the fluid cleanliness level (see 6.5). Figure 1 shows a typical test rig in schematic form. A test rig in accordance with ISO 16889 is suitable for this test. The test rig shall be constructed so that it does not contain dead legs or zones or quiescent
37、 areas where contaminant can settle out and re-entrain later during the test. When testing return filters to be half-immersed in the reservoir, the test equipment located downstream of the test filter on Figure 1 flow meter, heat exchanger (counter pressure valve is not necessary) shall be located u
38、pstream of the test filter. 5.2 Pump Use a pump with a flow rate equal to or greater than the maximum flow rate required for the test. The delivery pressure shall be sufficient for pumping the required flow through the filter under test and for supplying simultaneously the clean-up filter and the re
39、mainder of the rig. A device shall make it possible to continuously vary the flow rate from zero to maximum. Pressure ripple shall be suppressed, if required, to guarantee pressure readings with the required accuracy. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+00:00 2006, Un
40、controlled Copy, (c) BSI ISO 3968:2001(E) 3 Key 1 Reservoir 2 Variable flow pump 3 Clean-up filter 4 Sampling valve 5 Thermometer 6 Filter under test 7 Absolute pressure transducer 8 Differential pressure transducer 9 Flow meter 10 Counter pressure regulating valve 11 Heat exchanger 12 Bypass flow r
41、egulating valve Figure 1 Example of a test circuit suitable for measuring the differential pressure versus flow rate characteristics of filter assemblies 5.3 Reservoir Use a reservoir with a conical bottom and sized for containing a volume in litres of test fluid of between one and two times the max
42、imum flow rate in litres per minute scheduled for the test. It should be designed to minimize air entrainment (for example by means of a return of the fluid beneath the test fluid surface) and ingression of airborne contamination. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 07:00:49 GMT+0
43、0:00 2006, Uncontrolled Copy, (c) BSI ISO 3968:2001(E) 4 5.4 Temperature control Use a heat exchanger to control the temperature measured upstream of the filter under test to the required value with an accuracy conforming to Table 1. 5.5 Clean-up filter Use a clean-up filter with a filtration ratio
44、(see ISO 16889) greater than that of the filter under test, so that no measurable increase in differential pressure of the filter under test due to partial blocking can occur. 5.6 Sampling valve To verify fluid cleanliness, equip the circuit with a sample valve in accordance with ISO 4021. The sampl
45、e point shall allow connection of an on-line monitor or extraction of a fluid sample for off-line analysis. 5.7 Mounting of filter Mount the filter on the test rig in the normal orientation. Use the correct sizes of standard unions to connect the filter. Use pipes between the filter and the pressure
46、 measuring points with substantially the same internal diameters as the unions. 5.8 Test fluid The type of test fluid shall be either that agreed with the customer, one recommended by the filter manufacturer or a fluid with standard properties. The fluid used shall be reported in clause 8. If it is
47、a fluid with standard properties, it should be a mineral oil with few additives and the following characteristics: a) a viscosity grade of VG 32 (see ISO 3448); b) a viscosity index of 95 to 105; c) a mass density of 850 kg/m3 to 900 kg/m3. Caution should be exercised when testing fine filters (10 7
48、5) on hydraulic fluids with viscosity index improvers at lower temperatures ( 30 C), as the additives can be temporarily removed and can partially block the element. 6 Measurements 6.1 Pressure measurement Measure the differential pressure upstream and downstream of the filter under test using a dif
49、ferential pressure transducer or two gauge pressure transducers with an accuracy conforming to Table 1. The pressure points shall be of the truncated end type (see Figure 2) and placed on pipework without any hydraulic irregularity (for example union, valve, bend) over a length not less than 10D upstream and 5D downstream of the measuring point. NOTE The connecting lines to pressure transducers and gauges should be bled of air before testing. Licensed Copy: sheffieldun
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