1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 12242:2012Measurement of fluid flow inclosed conduits Ultrasonictransit-time meters for liquidBS ISO 12242:2012 BRITISH STANDARDNational forewordThis British Standard is t
2、he UK implementation of ISO 12242:2012.The UK participation in its preparation was entrusted to TechnicalCommittee CPI/30/5, Velocity and Mass Methods.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the
3、 necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 70392 8ICS 17.120.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard
4、 was published under the authority of theStandards Policy and Strategy Committee on 31 July 2012.Amendments issued since publicationDate Text affectedBS ISO 12242:2012null nullnullnull 2012Measurement of fluid flow in closed conduits Ultrasonic transit-time meters for liquidMesurage de dbit des flui
5、des dans les conduites fermes Compteurs ultrasoniques pour liquidesnullnullnullnullnullnullnullnullnullnullnullnullnull nullnullnullnullnullnullnullnullISO12242nullnullnullnullnull nullnullnullnullnullnullnull2012null0nullnull01nullnullnullnullnullnullnullnullnull nullnullnullnullnullnullnullnullnul
6、l 12242null2012nullnullnullBS ISO 12242:2012ISO 12242:2012(E)nullnull null nullnullnull 2012 null nullnullnull nullnullnullnullnullnull nullnullnullnullnullnullnullnullCOPYRIGHT PROTECTED DOCUMENTnull nullnullnull 2012All rights reserved. Unless otherwise specified, no part of this publication may b
7、e reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20nullnullnu
8、llnull null 41 22 null49 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgnullnullnull nullnullnullnullnullnullnullnullnullnullnullPublished in SwitzerlandBS ISO 12242:2012ISO 12242:2012(E)null nullnullnull 2012 null nullnullnull nullnullnullnullnullnull nullnullnullnullnullnullnullnull nullnullnull
9、Contents PageForeword . vIntroduction .vi1 Scope 12 Normative references . 13 Terms and definitions . 13.1 Quantities 13.2 Meter design . 23.3 Thermodynamic conditions 33.4 Statistics 33.5 Calibration . 53.6 Symbols and subscripts 53.7 Abbreviated terms . 74 Principles of measurement . 74.1 Descript
10、ion 74.2 Volume flow . 94.3 Generic description 104.4 Time delay considerations 114.5 Refraction considerations .144.6 Reynolds number 154.7 Temperature and pressure correction .155 Performance requirements .156 Uncertainty in measurement 166.1 Introduction .166.2 Evaluation of the uncertainty compo
11、nents 167 Installation .187.1 General .187.2 Use of a prover .197.3 Calibration in a laboratory or use of a theoretical prediction procedure .197.4 Additional installation effects 218 Test and calibration 228.1 General .228.2 Individual testing Use of a theoretical prediction procedure .228.3 Indivi
12、dual testing Flow calibration under flowing conditions 239 Performance testing .249.1 Introduction .249.2 Repeatability and reproducibility 259.3 Additional test for meters with externally mounted transducers .259.4 Assessing the uncertainty of a meter whose performance is predicted using a theoreti
13、cal prediction procedure 269.5 Fluid-mechanical installation conditions 269.6 Path failure simulation and exchange of components .2710 Meter characteristics 2710.1 Meter body, materials, and construction 2710.2 Transducers 2910.3 Electronics 2910.4 Software .3010.5 Exchange of components .3110.6 Det
14、ermination of density and temperature .3111 Operational practice .3211.1 General .32BS ISO 12242:2012ISO 12242:2012(E)nullnull null nullnullnull 2012 null nullnullnull nullnullnullnullnullnull nullnullnullnullnullnullnullnull11.2 Audit process .3211.3 Operational diagnostics 3411.4 Audit trail durin
15、g operation; inter-comparison and inspection 3611.5 Recalibration .37Annex A (normative) Temperature and pressure correction 42Annex B (informative) Effect of a change of roughness 48Annex C (informative) Example of uncertainty calculations .52Annex D (informative) Documents .65Bibliography .67BS IS
16、O 12242:2012ISO 12242:2012(E)ForewordISO (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 intereste
17、d 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 International Electrotechnical Com
18、mission (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 International Standards adopted by the technica
19、l 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.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall
20、 not be held responsible for identifying any or all such patent rights.ISO 12242 was prepared by Technical Committee ISO/TC 30, Measurement of fluid flow in closed conduits, Subcommittee SC 5, Velocity and mass methodsnullnull nullnullnull 2012 null nullnullnull nullnullnullnullnullnull nullnullnull
21、nullnullnullnullnull nullBS ISO 12242:2012ISO 12242:2012(E)IntroductionUltrasonic meters (USMs) have become one of the accepted flow measurement technologies for a wide range of liquid applications, including custody-transfer and allocation measurement. Ultrasonic technology has inherent features su
22、ch as no pressure loss and wide rangeability.USMs can deliver diagnostic information through which it may be possible to demonstrate that an ultrasonic liquid flowmeter is performing in accordance with specification. Owing to the extended diagnostic capabilities, this International Standard advocate
23、s the addition and use of automated diagnostics instead of labour-intensive quality checks. The use of automated diagnostics makes possible a condition-based maintenance system.nullnull null nullnullnull 2012 null nullnullnull nullnullnullnullnullnull nullnullnullnullnullnullnullnullBS ISO 12242:201
24、2Measurement of fluid flow in closed conduits Ultrasonic transit-time meters for liquid1 ScopeThis International Standard specifies requirements and recommendations for ultrasonic liquid flowmeters, which utilize the transit time of ultrasonic signals to measure the flow of single-phase homogenous l
25、iquids in nullnullnullnullnullnull nullnullnullnullnullnullnullnullnullThere are no limits on the minimum or maximum sizes of the meter.This International Standard specifies performance, calibration and output characteristics of ultrasonic meters (USMs) for liquid flow measurement and deals with ins
26、tallation conditions. It covers installation with and without a dedicated proving (calibration) system. It covers both in-line and clamp-on transducers (used in configurations in which the beam is non-refracted and in those in which it is refracted). Included are both meters incorporating meter bodi
27、es and meters with field-mounted transducers.2 Normative referencesThe 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 the referenced document (including any ame
28、ndments) applies.ISO 4006, Measurement of fluid flow in closed conduits Vocabulary and symbols3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 4006 and the following apply.3.1 Quantities3.1.1volume flowrateqVqVtV=nullnullnullnullnullnullnullV nullnull
29、nullnullnullnullnullnullnullt nullnull nullnullnullnullNOTE Adapted from ISO 80000-4:2006,424-30.3.1.2metering pressureabsolute fluid pressure in a meter under flowing conditions to which the indicated volume of liquid is related3.1.3mean velocity in the meter bodyvfluid flowrate divided by the cros
30、s-sectional area of the meter bodyINTERNATIONAL STANDARD ISO 12242:2012(E)null nullnullnull 2012 null nullnullnull nullnullnullnullnullnull nullnullnullnullnullnullnullnull 1BS ISO 12242:2012ISO 12242:2012(E)3.1.4mean pipe velocityvpfluid flowrate divided by the cross-sectional area of the upstream
31、pipeNOTE Where a meter has a reduced bore, the mean velocities in the upstream pipe and within the meter body itself differ.3.1.5path velocityaverage fluid velocity on an ultrasonic path3.1.6Reynolds numberdimensionless parameter expressing the ratio between the inertia and viscous forces3.1.7pipe R
32、eynolds numberReDdimensionless parameter expressing the ratio between the inertia and viscous forces in the pipeRevD vDD=ppkvnullnullnullnullnull is mass density;vnullis the mean pipe velocity;D is the pipe internal diameter;m is the dynamic viscosity;nullnullis the kinematic viscosityNOTE Where a m
33、eter has a reduced bore, it is possible also to define the throat Reynolds number, in whose definition the mean velocity in the meter body, the meter internal diameter and the kinematic viscosity are used.3.2 Meter design3.2.1meter bodypressure-containing structure of the meter3.2.2ultrasonic pathpa
34、th travelled by an ultrasonic signal between a pair of ultrasonic transducers3.2.3axial pathpath travelled by an ultrasonic signal either on or parallel to the axis of the pipe3.2.4diametrical pathultrasonic path whereby the ultrasonic signal travels through the centre-line or long axis of the pipe3
35、.2.5chordal pathultrasonic path whereby the ultrasonic signal travels parallel to the diametrical path2 null nullnullnull 2012 null nullnullnull nullnullnullnullnullnull nullnullnullnullnullnullnullnullBS ISO 12242:2012ISO 12242:2012(E)3.2.6field mountedexternal to the pipe, attached on site, not pr
36、ior to a laboratory calibration3.3 Thermodynamic conditions3.3.1metering conditionsconditions, at the point of measurement, of the fluid of which the volume is to be measuredNOTE Also known as operating conditions or actual conditions.3.3.2standard conditionsdefined temperature and pressure conditio
37、ns used in the measurement of fluid quantity so that the standard volume is the volume that would be occupied by a quantity of fluid if it were at standard temperature and pressureNOTE 1 Standard conditions may be defined by regulation or contract.NOTE 2 Not preferred alternatives: reference conditi
38、ons, base conditions, normal conditions, etc.NOTE 3 Metering and standard conditions relate only to the volume of the liquid to be measured or indicated, and should not be confused with rated operating conditions or reference conditions (see ISO/IEC Guide 99:2007,444.9 and 4.11), which refer to infl
39、uence quantities (see ISO/IEC Guide 99:2007,442.52).3.3.3specified conditionsconditions of the fluid at which performance specifications of the meter are given3.4 Statistics3.4.1errormeasured quantity value minus a reference quantity valueISO/IEC Guide 99:2007,442.163.4.2repeatability (of results of
40、 measurements)closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurementNOTE 1 These conditions are called repeatability conditions.NOTE 2 Repeatability conditions include: the same measurement procedure; the s
41、ame observer; the same measuring instrument, used under the same conditions; the same location; repetition over a short period of time.NOTE 3 Repeatability may be expressed quantitatively in terms of the dispersion characteristics of the results.ISO/IEC Guide 98-3:2008,43B.2.15null nullnullnull 2012
42、 null nullnullnull nullnullnullnullnullnull nullnullnullnullnullnullnullnull 3BS ISO 12242:2012ISO 12242:2012(E)3.4.3reproducibility (of results of measurements)closeness of the agreement between the results of measurements of the same measurand carried out under changed conditions of measurementNOT
43、E 1 A valid statement of reproducibility requires specification of the conditions changed.NOTE 2 The changed conditions may include: principle of measurement; method of measurement;null nullnullnullnullnullnullnullnullnull measuring instrument; reference standard; location;null nullnullnullnullnulln
44、ullnullnullnullnull nullnull nullnullnullnullnull nullnullnullnullnullNOTE 3 Reproducibility may be expressed quantitatively in terms of the dispersion characteristics of the results.NOTE 4 Results are here usually understood to be corrected results.ISO/IEC Guide 98-3:2008,43B.2.163.4.4resolutionsma
45、llest difference between indications of a meter that can be meaningfully distinguished3.4.5zero flow readingflowmeter reading when the liquid is at rest, i.e. both axial and non-axial velocity components are essentially zero3.4.6linearizationway of reducing the non-linearity of an ultrasonic meter,
46、by applying correction factorsNOTE The linearization can be applied in the electronics of the meter or in a flow computer connected to the USM. The correction can be, for example, piece-wise linearization or polynomial linearization.3.4.7uncertainty (of measurement)parameter, associated with the res
47、ult of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurandNOTE 1 The parameter may be, for example, a standard deviation (or a given multiple of it), or the half-width of an interval having a stated level of confidence.NOTE 2 Uncertaint
48、y of measurement comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of the results of series of measurements and can be characterized by experimental standard deviations. The other components, which can also be characterized by standar
49、d deviations, are evaluated from assumed probability distributions based on experience or other information.NOTE 3 It is understood that the result of the measurement is the best estimate of the value of the measurand, and that all components of uncertainty, including those arising from systematic effects, such as components associated with corrections and reference standards, contribute to the dispersion.ISO/IEC Guide 98-3:2008,43B.2.184 null nullnullnull 2012 null nullnullnull nullnullnullnullnullnull nullnullnullnullnullnullnullnul
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