1、BSI Standards PublicationBS ISO 6358-3:2014Pneumatic fluid power Determination of flow-ratecharacteristics of componentsusing compressible fluidsPart 3: Method for calculating steady-stateflow-rate characteristics of systemsBS ISO 6358-3:2014 BRITISH STANDARDNational forewordThis British Standard is
2、 the UK implementation of ISO 6358-3:2014.Together with BS ISO 6358-1:2013 and BS ISO 6358-2:2013, itsupersedes BS 7294:1990 (dual numbered as ISO 6358:1989), which iswithdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee MCE/18/-/5, Control components.A list of organi
3、zations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2014. Published by BSI StandardsLimited 2014ISB
4、N 978 0 580 61666 2ICS 23.100.01Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 October 2014.Amendments issued since publicationDate Text affectedBS ISO 6358-3:
5、2014 ISO 2014Pneumatic fluid power Determination of flow-rate characteristics of components using compressible fluids Part 3: Method for calculating steady-state flow-rate characteristics of systemsTransmissions pneumatiques Dtermination des caractristiques de dbit des composants Partie 3: Mthode de
6、 calcul des caractristiques de dbit stationnaire des assemblagesINTERNATIONAL STANDARDISO6358-3First edition2014-10-01Reference numberISO 6358-3:2014(E)BS ISO 6358-3:2014ISO 6358-3:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All rights reserved. Unless otherwise specif
7、ied, 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 either ISO at the address below or ISO
8、s member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 6358-3:2014ISO 6358-3:2014(E)Contents PageForeword ivIntroduction v1 Scope .12 Normative
9、references 13 Terms and definitions .14 Symbols and units .15 Calculation hypotheses 25.1 General . 25.2 Relationships among component flow-rate characteristics 35.3 Flow-rate characteristics 36 Organization of calculations for systems of components connected in series 66.1 General . 66.2 Given para
10、meters 76.3 Calculation principle 76.4 Calculation of the cracking pressure pc(step 1) 76.5 Calculation of an initial value for their sonic conductance if some components are pipes, tubes or hoses defined by their friction factor (optional step 2) 76.6 Determination of the sonic conductance C (step
11、3) 86.7 Determining the critical back-pressure ratio b and subsonic index m (step 4) 106.8 Calculation of pressure dependence coefficient Kp(optional step 5) 117 Organization of calculations for systems of components connected in parallel .127.1 General 127.2 Given parameters . 127.3 Calculation pri
12、nciple . 127.4 Determination of flow characteristics of pipes, tubes or hoses for the given inlet pressure (step 0) 137.5 Determination of the sonic conductance C (step 1) .137.6 Determination of the cracking pressure pc(step 2) .137.7 Determination of the critical back-pressure ratio b and subsonic
13、 index m (step 3) .13Annex A (informative) Example calculation for a system of components connected in series 15Annex B (informative) Example calculation for an air blow circuit whose components are connected in parallel .25Annex C (informative) Flow charts of calculation procedures .32Annex D (info
14、rmative) Additional information concerning components whose flow rate characteristics are not expressed in accordance with the ISO 6358 series .41Annex E (informative) Visualization of calculation results53Bibliography .59 ISO 2014 All rights reserved iiiBS ISO 6358-3:2014ISO 6358-3:2014(E)ForewordI
15、SO (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 committees. Each member body interested in a subject for which a technical c
16、ommittee 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 International Electrotechnical Commission (IEC) on all matters of electr
17、otechnical 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 needed for the different types of ISO documents should be noted. This document was dra
18、fted 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 patent rights. ISO shall not be held responsible for identifying any or all such patent ri
19、ghts. 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 in this document is information given for the convenience of users and does not consti
20、tute 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 Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe comm
21、ittee 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 replaces ISO 6358:1989 which has been technically revised. However, Parts 2 and 3 are new
22、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 compressible fluids: Part 1: General rules and test methods for steady-state flow Part 2: A
23、lternative 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)IntroductionIn pneumatic fluid power systems, power is transmitted and controlled through a gas under pressure within a circuit.
24、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.ISO 6358:1989 specified a method to determine the flow-rate characteristics of pneumatic valve
25、s, 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 flow behaviour. The result described flow performance of a pneumatic valve from choked (sonic) fl
26、ow 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 account the influence of the flow velocity on pressure measurements. Furthermore, new developmen
27、ts 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 pc) to define the flow performance in both the choked (sonic) and subsonic regions.This part of ISO 6358 uses a set of four flow-rate c
28、haracteristic 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 flow rate (choked), is the most important parameter. This parameter is defined by the upstream stagna
29、tion 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 because it corresponds to the ratio of downstream to upstream stagnation pressures. The subsonic index,
30、 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 0,5. In these cases, only the first two characteristic parameters C and b are necessary. For many
31、 other components, m varies widely; in these cases, it is necessary to determine C, b and m. The parameter pc, is the cracking pressure. This parameter is used only for pneumatic components that open with increasing upstream pressure, such as non-return (check) valves or one-way flow control valves.
32、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 assumptions of negligible inlet velocity to the item under test and to allow the inlet stagnation pressure to
33、 be measured directly. Expanded outlet tubes allowed the direct measurement of downstream stagnation pressure to better accommodate different component models. The difference between stagnation pressure upstream and downstream of a component means a loss of pressure energy.For testing a component wi
34、th 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 alternative test methods.This part of ISO 6358 can be used to calculate without measurements an estimate
35、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; however, the flow rate characteristics of some components are expressed by flow rate coefficients othe
36、r 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 power Determination of flow-rate characteristics of components using compressible fluids Part 3: Method for
37、 calculating steady-state flow-rate characteristics of systems1 ScopeThis part of ISO 6358 specifies a method that uses a simple numerical technique to estimate without measurements the overall flow-rate characteristics of a system of components and piping with known flow-rate characteristics.The fo
38、rmulae 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 filter is influenced by the upstream pressure, so the values of C and b are only valid for the upstream pressure
39、 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 defined in the ISO 6358 series.2 Normative referencesThe following referenced documents, in whole or in part, are
40、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 referenced document (including any amendments) applies.ISO 5598, Fluid power systems and components VocabularyISO
41、 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 flow3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 5598 and ISO 6358-1 appl
42、y. For the purposes of this part of ISO 6358, the term component also includes piping.4 Symbols and unitsThe symbols and units used in this part of ISO 6358 shall be in accordance with ISO 6358-1 and Table 1.INTERNATIONAL STANDARD ISO 6358-3:2014(E) ISO 2014 All rights reserved 1BS ISO 6358-3:2014IS
43、O 6358-3:2014(E)Table 1 Symbols and unitsSymbol Description SI unitbpipeCritical back-pressure ratio of pipe, tube or hose CpipeSonic conductance of pipe, tube or hose m3/(sPa)(ANR)d Inside diameter of pipe, tube or hose mL Length of pipe, tube or hose m Average friction factor of a pipe, tube or ho
44、se depending on the Reynolds numberps2Static pressure downstream of the pipe, tube or hose PaT Absolute stagnation temperature K Ratio of specific heat capacities (for air, it equals 1,4) k Friction coefficient of the pipe, tube or hose resulting from experimental testsRe Reynolds number of the flow
45、 within the pipe, tube or hose Dynamic viscosity Pa.sp11, p12, p1i, p1nUpstream pressure at inlet of each component (stagnation pressure) Pap21, p22, p2i, p2nDownstream pressure at outlet of each component (stagnation pressure) PaNOTE See Annex D for additional symbols used in that annex.The subscri
46、pts 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 6358Subscript Descriptioni 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 a
47、t the endpipe Relating to the static downstream pressure of the piping when expressed using a friction factor depending on the Reynolds numbere Relating to the inletf Relating to the final componentj Index of step calculation of the system5 Calculation hypotheses5.1 GeneralThe following hypotheses a
48、re considered for the flow-rate characteristics of the equivalent system: Flow is assumed to be adiabatic, to take into consideration that 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 t
49、he 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 characteristicsWhenbppppc1 (25)6.6.3.3.2 The downstream pressure p2iof component i can be calculated, using Formula (27), only in a subsonic condition, which means only when the given mass flow rate qm, is
