BS ISO 6358-3-2014 en_8710 Pneumatic fluid power Determination of flow-rate characteristics of components using compressible fluids Method for calculating steady-state.pdf

1、BSI Standards Publication BS ISO 6358-3:2014 Pneumatic fluid power Determination of flow-rate characteristics of components using compressible fluids Part 3: Method for calculating steady-state flow-rate characteristics of systemsBS ISO 6358-3:2014 BRITISH STANDARD National foreword This British Sta

2、ndard is the UK implementation of ISO 6358-3:2014. Together with BS ISO 6358-1:2013 and BS ISO 6358-2:2013, it supersedes BS 7294:1990 (dual numbered as ISO 6358:1989), which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee MCE/18/-/5, Control components. A

3、list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2014. Published by BSI Standa

4、rds Limited 2014 ISBN 978 0 580 61666 2 ICS 23.100.01 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 October 2014. Amendments issued since publication Date

5、Text affectedBS ISO 6358-3:2014 ISO 2014 Pneumatic fluid power Determination of flow-rate characteristics of components using compressible fluids Part 3: Method for calculating steady-state flow-rate characteristics of systems Transmissions pneumatiques Dtermination des caractristiques de dbit des c

6、omposants Partie 3: Mthode de calcul des caractristiques de dbit stationnaire des assemblages INTERNATIONAL STANDARD ISO 6358-3 First edition 2014-10-01 Reference number ISO 6358-3:2014(E)BS ISO 6358-3:2014ISO 6358-3:2014(E)ii ISO 2014 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2014 All ri

7、ghts reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from

8、either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO 6358-3:2014ISO 6358-3:2014(E)Contents Page F

9、oreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 Terms and definitions . 1 4 Symbols and units . 1 5 Calculation hypotheses 2 5.1 General . 2 5.2 Relationships among component flow-rate characteristics 3 5.3 Flow-rate characteristics 3 6 Organization of calculations for systems of co

10、mponents connected in series 6 6.1 General . 6 6.2 Given parameters 7 6.3 Calculation principle 7 6.4 Calculation of the cracking pressure p c(step 1) 7 6.5 Calculation of an initial value for their sonic conductance if some components are pipes, tubes or hoses defined by their friction factor (opti

11、onal step 2) 7 6.6 Determination of the sonic conductance C (step 3) 8 6.7 Determining the critical back-pressure ratio b and subsonic index m (step 4) 10 6.8 Calculation of pressure dependence coefficient K p(optional step 5) 11 7 Organization of calculations for systems of components connected in

12、parallel .12 7.1 General 12 7.2 Given parameters .12 7.3 Calculation principle .12 7.4 Determination of flow characteristics of pipes, tubes or hoses for the given inlet pressure (step 0) 13 7.5 Determination of the sonic conductance C (step 1) .13 7.6 Determination of the cracking pressure p c(step

13、 2) .13 7.7 Determination of the critical back-pressure ratio b and subsonic index m (step 3) .13 Annex A (informative) Example calculation for a system of components connected in series 15 Annex B (informative) Example calculation for an air blow circuit whose components are connected in parallel .

14、25 Annex C (informative) Flow charts of calculation procedures .32 Annex D (informative) Additional information concerning components whose flow rate characteristics are not expressed in accordance with the ISO 6358 series .41 Annex E (informative) Visualization of calculation results53 Bibliography

15、 .59 ISO 2014 All rights reserved iiiBS ISO 6358-3:2014ISO 6358-3:2014(E) Foreword 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 te

16、chnical 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 non-governmental, in liaison with ISO, also take part in the work. ISO collaborates close

17、ly with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria n

18、eeded for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of pate

19、nt rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used

20、 in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Bar

21、riers to Trade (TBT) see the following URL: Foreword - Supplementary information The committee responsible for this document is ISO/TC 131, Fluid power systems, Subcommittee SC 5, Control products and components. This first edition of ISO 6358-3, together with ISO 6358-1 and ISO 6358-2, cancels and

22、replaces ISO 6358:1989 which has been technically revised. However, Parts 2 and 3 are new standards whose scopes were not included in ISO 6358:1989. ISO 6358 consists of the following parts, under the general title Pneumatic fluid power Determination of flow-rate characteristics of components using

23、compressible fluids: Part 1: General rules and test methods for steady-state flow Part 2: Alternative test methods Part 3: Method for calculating steady-state flow-rate characteristics of systemsiv ISO 2014 All rights reservedBS ISO 6358-3:2014ISO 6358-3:2014(E) Introduction In pneumatic fluid power

24、 systems, power is transmitted and controlled through a gas under pressure within a circuit. Components that make up such a circuit are inherently resistive to the flow of the gas, and it is necessary, therefore, to define and determine the characteristics that describe their flow-rate performance.

25、ISO 6358:1989 specified a method to determine the flow-rate characteristics of pneumatic valves, based upon a model of converging nozzles. The method included two characteristic parameters: sonic conductance, C, and critical pressure ratio, b, used in a proposed mathematical approximation of the flo

26、w behaviour. The result described flow performance of a pneumatic valve from choked (sonic) flow to subsonic flow. Experience has demonstrated that many pneumatic valves have converging-diverging characteristics that do not fit the ISO 6358:1989 model very well. A change was necessary to take into a

27、ccount the influence of the flow velocity on pressure measurements. Furthermore, new developments have allowed the application of this method to additional components beyond pneumatic valves. However, this now requires the use of four parameters (C, b, m, and p c ) to define the flow performance in

28、both the choked (sonic) and subsonic regions. This part of ISO 6358 uses a set of four flow-rate characteristic parameters determined from test results. These parameters are described as follows and are listed in decreasing order of priority: The sonic conductance, C corresponding to the maximum flo

29、w rate (choked), is the most important parameter. This parameter is defined by the upstream stagnation conditions. The critical back-pressure ratio, b, representing the boundary between choked and subsonic flow, is second in importance. Its definition differs here from the one in ISO 6358:1989 becau

30、se it corresponds to the ratio of downstream to upstream stagnation pressures. The subsonic index, m, is used if necessary to represent more accurately the subsonic flow behaviour. For components with a fixed flow path (i.e. one that does not vary with pressure or flow rate), m is distributed around

31、 0,5. In these cases, only the first two characteristic parameters C and b are necessar y. For many other components, m varies widely; in these cases, it is necessary to determine C, b and m. The parameter p c , is the cracking pressure. This parameter is used only for pneumatic components that open

32、 with increasing upstream pressure, such as non-return (check) valves or one-way flow control valves. Several changes to the test equipment were made to overcome apparent violations of the theory of compressible fluid flow. This included expanded inlet pressure-measuring tubes to satisfy the assumpt

33、ions of negligible inlet velocity to the item under test and to allow the inlet stagnation pressure to be measured directly. Expanded outlet tubes allowed the direct measurement of downstream stagnation pressure to better accommodate different component models. The difference between stagnation pres

34、sure upstream and downstream of a component means a loss of pressure energy. For testing a component with a large nominal bore, to shorten testing time or to reduce energy consumption, it is desirable to apply the methods specified in ISO 6358-2, which covers a discharge test and a charge test as al

35、ternative test methods. This part of ISO 6358 can be used to calculate without measurements an estimate of the overall flow rate characteristics of a system of components and piping. In most cases, the flow rate characteristics of components are determined in accordance with Parts 1 or 2 of ISO 6358

36、; however, the flow rate characteristics of some components are expressed by flow rate coefficients other than those defined in ISO 6358. Formulas to calculate nearly equivalent flow rate characteristics are given. ISO 2014 All rights reserved vBS ISO 6358-3:2014BS ISO 6358-3:2014Pneumatic fluid pow

37、er Determination of flow-rate characteristics of components using compressible fluids Part 3: Method for calculating steady-state flow-rate characteristics of systems 1 Scope This part of ISO 6358 specifies a method that uses a simple numerical technique to estimate without measurements the overall

38、flow-rate characteristics of a system of components and piping with known flow-rate characteristics. The formulae used in this part of ISO 6358 describe the behaviour of a compressible fluid flow through a component for both subsonic and choked flows. NOTE The conductance of a tube, silencer or filt

39、er is influenced by the upstream pressure, so the values of C and b are only valid for the upstream pressure at which they are determined. This part of ISO 6358 also provides methods to obtain equivalent flow-rate characteristics for components whose flow-rate characteristics differ from those defin

40、ed in the ISO 6358 series. 2 Normative references The following referenced documents, in whole or in 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 re

41、ferenced document (including any amendments) applies. ISO 5598, Fluid power systems and components Vocabulary ISO 6358-1:2013, Pneumatic fluid power Determination of flow-rate characteristics of components using compressible fluids Part 1: General rules and test methods for steady-state flow 3 Terms

42、 and definitions For the purposes of this document, the terms and definitions given in ISO 5598 and ISO 6358-1 apply. For the purposes of this part of ISO 6358, the term component also includes piping. 4 Symbols and units The symbols and units used in this part of ISO 6358 shall be in accordance wit

43、h ISO 6358-1 and Table 1. INTERNATIONAL ST ANDARD ISO 6358-3:2014(E) ISO 2014 All rights reserved 1BS ISO 6358-3:2014ISO 6358-3:2014(E) Table 1 Symbols and units Symbol Description SI unit b pipe Critical back-pressure ratio of pipe, tube or hose C pipe Sonic conductance of pipe, tube or hose m 3 /(

44、sPa)(ANR) d Inside diameter of pipe, tube or hose m L Length of pipe, tube or hose m Average friction factor of a pipe, tube or hose depending on the Reynolds number p s2 Static pressure downstream of the pipe, tube or hose Pa T Absolute stagnation temperature K Ratio of specific heat capacities (fo

45、r air, it equals 1,4) k Friction coefficient of the pipe, tube or hose resulting from experimental tests Re Reynolds number of the flow within the pipe, tube or hose Dynamic viscosity Pa.s p 11 , p 12 , p 1i , p 1n Upstream pressure at inlet of each component (stagnation pressure) Pa p 21 , p 22 , p

46、 2i , p 2n Downstream pressure at outlet of each component (stagnation pressure) Pa NOTE See Annex D for additional symbols used in that annex. The subscripts used in this part of ISO 6358 shall be in accordance with ISO 6358-1 and Table 2. Table 2 Subscripts used in this part of ISO 6358 Subscript

47、Description i Number of the component (valve, silencer, etc.) or the piping (pipe, tube, hose, connector, etc.), with i = 1 at the start of the system and n at the end pipe Relating to the static downstream pressure of the piping when expressed using a friction factor depending on the Reynolds numbe

48、r e Relating to the inlet f Relating to the final component j Index of step calculation of the system 5 Calculation hypotheses 5.1 General The following hypotheses are considered for the flow-rate characteristics of the equivalent system: Flow is assumed to be adiabatic, to take into consideration t

49、hat stagnation temperatures at the inlet of each component are identical to each other. For components connected in series, the outlet pressure of one component is the same as the inlet pressure of the following component. For components connected in parallel, the inlet pressure to each component is the same, and the outlet pressure from all components is the same.2 ISO 2014 All rights reservedBS ISO 6358-3:2014ISO 6358-3:2014(E) 5.2 Relationships among component flow-rate characteristi