1、 Reference number ISO/TR 19972-1:2009(E) ISO 2009TECHNICAL REPORT ISO/TR 19972-1 First edition 2009-02-15 Hydraulic fluid power Methods to assess the reliability of hydraulic components Part 1: General procedures and calculation method Transmissions hydrauliques Mthodes dvaluation de la fiabilit des
2、 composants hydrauliques Partie 1: Modes opratoires gnraux et mthode de calcul ISO/TR 19972-1:2009(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are emb
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7、hed in Switzerland ii ISO 2009 All rights reservedISO/TR 19972-1:2009(E) ISO 2009 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Units of measurement and symbols. 2 5 Reliability concept 2 6 Means for determining r
8、eliability 3 7 Procedures for analysing a design concept 5 8 Procedures for laboratory testing to failure or suspension. 8 9 Procedures for collecting field data 9 10 Procedure for a substantiation test 10 Annex A (informative) Example calculation for analysing a design concept 13 Annex B (informati
9、ve) Calculation examples for laboratory test to failure data analysis 19 Annex C (informative) Example calculation for collecting field data 27 Annex D (informative) Equation development and example calculations for substantiation testing . 33 Annex E (informative) Reference material . 38 Bibliograp
10、hy . 40 ISO/TR 19972-1:2009(E) iv ISO 2009 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical comm
11、ittees. 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 non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
12、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, Part 2. The main task of technical committees is to prepare International Standards. Draft Internation
13、al 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. In exceptional circumstances, when a technical committee has collected data of a different
14、 kind from that which is normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until
15、the data it provides are considered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 19972-1 was prepared by T
16、echnical Committee ISO/TC 131, Fluid power systems, Subcommittee SC 8, Product testing. ISO/TR 19972 consists of the following parts, under the general title Hydraulic fluid power Methods to assess the reliability of hydraulic components: Part 1: General procedures and calculation method It is possi
17、ble that other parts will be developed in the future. ISO/TR 19972-1:2009(E) ISO 2009 All rights reserved v Introduction In hydraulic fluid power systems, power is transmitted and controlled through a liquid or gas under pressure within an enclosed circuit. Fluid power systems are composed of compon
18、ents, and are an integral part of various types of machines and equipment. Efficient and economical production requires highly reliable machines and equipment. Machine producers need to know the reliability of the components that comprise their machines fluid power system. Once they know the reliabi
19、lity characteristic of the component, the producers can model the system and make decisions on service intervals, spare parts inventory and areas for future improvement. There are different methods used to investigate component reliability. A preliminary design analysis is useful to identify potenti
20、al failure modes and to reduce their effect on reliability. In addition, calculation of failure rates is possible. When prototypes are available, in-house laboratory reliability tests are run and initial reliability can be determined. Reliability testing is often continued into the initial productio
21、n run and throughout the production lifetime as a continuing evaluation of the component. Collection of field data is possible when products are operating and data on their failures are available. This, in turn, can be utilized for reduced lab testing on improvements to the products or similar, new
22、products. These methods also offer the user an opportunity to choose the most economical and practical procedure to measure reliability for a given application. TECHNICAL REPORT ISO/TR 19972-1:2009(E) ISO 2009 All rights reserved 1 Hydraulic fluid power Methods to assess the reliability of hydraulic
23、 components Part 1: General procedures and calculation method 1 Scope This part of ISO/TR 19972 provides a means for determining the reliability of hydraulic fluid power components using: a) estimates from a design analysis; b) analysis of laboratory testing to failure or suspension; c) analysis of
24、field data; d) analysis of a substantiation test. These methods apply to the first failures without repairs, but exclude certain infant mortality failures. Specific component test procedures and exclusions will be provided in subsequent parts of ISO/TR 19972. This part of ISO/TR 19972 also provides
25、calculation methods, reporting descriptions and examples of reliability calculations. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of
26、the referenced document (including any amendments) applies. ISO 1000, SI units and recommendations for the use of their multiples and of certain other units ISO 5598, Fluid power systems and components Vocabulary ISO 9110-1, Hydraulic fluid power Measurement techniques Part 1: General measurement pr
27、inciples 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 5598 and the following apply. 3.1 B 10life L 10life life of the component or assembly that has not been altered since its production, where its reliability is 90 %; or time at which 90 % of the
28、 population has survived NOTE The cumulative failure percentage is 10 %. ISO/TR 19972-1:2009(E) 2 ISO 2009 All rights reserved3.2 component individual unit (e.g. cylinder, motor, valve, filter, but excluding piping) comprising one or more parts designed to be a functional part of a fluid power syste
29、m 3.3 mean time to failure MTTF mean lifetime of a component that has not been repaired since its production, based on a statistical mean, using times to failure as the definition of failure 3.4 mean cycles to failure MCTF mean life, expressed as number of cycles, of a component that has not been re
30、paired since its production, based on a statistical mean, using cycles to failure as the definition of failure 3.5 reliability probability that a component can perform continuously, without failure, for a specified interval of time when operating under stated conditions 3.6 failure state at which a
31、component reaches the threshold level or terminates its ability to perform a required function 3.7 termination cycle count number of cycles on a specimen when it reaches any threshold level for the first time 3.8 threshold level the value of a performance characteristic (e.g. leakage, flow and curre
32、nt) against which the components test data is compared NOTE This is an arbitrary value defined by the experts as the critical value for performance comparisons, but not necessarily indicative of the end of component operation. 4 Units of measurement and symbols Units of measurement are in accordance
33、 with ISO 1000, except for Clause 7 and Annex A, which are based on The Handbook of Reliability Prediction Procedures for Mechanical Equipment 9and use imperial units. Symbols for the Weibull parameters: = Slope = Characteristic life t 0or x 0= Minimum life 5 Reliability concept Reliability is the p
34、robability (a percentage) that a component will not exceed the threshold level for a specified interval of time or number of cycles when it operates under stated conditions. This probability can be determined by any of the methods described in Clause 6. There are many different statistical distribut
35、ions that describe the population of failures that result from these methods. Mean time to failure and B 10life are common terms used for expressing reliability. ISO/TR 19972-1:2009(E) ISO 2009 All rights reserved 3 It is also necessary to associate some confidence with a reliability result. This ta
36、kes into account the fact that results will vary if the process is repeated many times, and the confidence describes probability bounds to the distribution of failures. To determine reliability scientifically, it is necessary to define failure. This can be evident in field failures, but for the othe
37、r methods the concept of threshold levels is defined for various performance characteristics. This is necessary because the value of some of these characteristics (e.g. leakage) might not represent a total failure of the component. Examples of analytical methods and test parameters for which thresho
38、ld levels might need to be established include: a) dynamic leakage, both internal and external; b) static leakage, both internal and external; c) changes in performance characteristics (e.g. loss of stability, increase in minimum operating pressure, deterioration of flow rate, increase in response t
39、ime, change in electrical characteristics, performance degradation due to contamination and breakdown of accessory functions). In addition to these threshold levels, failure can also occur from catastrophic events such as burst, breakage, fatigue or loss of function. 6 Means for determining reliabil
40、ity 6.1 General Environmental aspects for any of the methods discussed in this part of ISO/TR 19972 will have an influence on the results. Therefore, it is important to record the assumptions used in 6.2, follow the requirements specified for 6.3, record the observations obtained in 6.4, and use the
41、 original historical conditions in 6.5. 6.2 Design analysis Calculation methods can be used to quantify the reliability of hydraulic components. In cases where neither field data or test data are available or tests cannot be carried out economically, calculation methods are recommended to estimate c
42、omponent reliability. Predicting the reliability of mechanical equipment requires consideration of its exposure to the environment and subjection to a wide range of stress levels (e.g. impact loading). The approach to predicting reliability of mechanical equipment considers the intended operation en
43、vironment, and determines the effect of that environment at the lowest part level where the material properties can also be considered. The combination of these factors permits the use of engineering design parameters to determine the design life of the equipment in its intended operating environmen
44、t, and the rate and pattern of failures during design life. An analysis of a design for reliability and maintenance (R and M) can identify critical failure modes and causes of unreliability as well as providing an effective tool for predicting equipment behaviour. The design evaluation programme inc
45、ludes a methodology for evaluating a design for R and M that considers the material properties, operating environment and critical failure modes at component level. In The Handbook of Reliability Prediction Procedures for Mechanical Equipment 9 , 19 mechanical components have been identified for whi
46、ch reliability prediction equations have been developed. If a hydraulic component includes more than one mechanical component, the individual mechanical component reliabilities can be combined to establish the total equipment reliability. A great advantage of this method is that the influence of par
47、ameters on the life of a component can be determined. This allows the engineer to improve the design in an early phase of development. ISO/TR 19972-1:2009(E) 4 ISO 2009 All rights reserved6.3 Laboratory test to failure or suspension One of the major difficulties encountered in specifying a reliabili
48、ty test is the time it takes to cause a failure without accelerating the test. Accelerated testing, with environmental conditions above those for which the component is rated, is sometimes necessary in order to keep the test time at a reasonable length. The goals and objectives of the test method sh
49、ould be clearly defined. The primary criterion for determining test acceleration factors is that the failure mode or failure mechanism should not change or be different from that expected from a non-accelerated test. Two other important factors are the test stand and measurement of parameters. The test stand should be designed to operate reliably within the planned environmental conditions. Its configuration should not affect the results of the test being run on the component. Evaluation and maintenance of the tes
