1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 17089-1:2010Measurement of fluid flow in closed conduits Ultrasonic meters for gasPart 1: Meters for custody transfer and allocation measurementBS ISO 17089-1:2010 BRITISH
2、 STANDARDNational forewordThis British Standard is the UK implementation of ISO 17089-1:2010.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 secretar
3、y.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2010ISBN 978 0 580 59899 9ICS 17.120.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published u
4、nder the authority of theStandards Policy and Strategy Committee on 30 November 2010.Amendments issued since publicationDate Text affectedBS ISO 17089-1:2010Reference numberISO 17089-1:2010(E)ISO 2010INTERNATIONAL STANDARD ISO17089-1First edition2010-11-15Measurement of fluid flow in closed conduits
5、 Ultrasonic meters for gas Part 1: Meters for custody transfer and allocation measurement Mesurage du dbit des fluides dans les conduites fermes Compteurs ultrasons pour gaz Partie 1: Compteurs pour transactions commerciales et allocations BS ISO 17089-1:2010ISO 17089-1:2010(E) PDF disclaimer This P
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9、T ISO 2010 All rights reserved. Unless otherwise specified, no part of this publication may be 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
10、 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 Switzerland ii ISO 2010 All rights reservedBS ISO 17089-1:2010ISO 17089-1:2010(E) ISO 2010 All rights reserved iiiCo
11、ntents Page Foreword iv Introduction.v 1 Scope1 2 Normative references1 3 Terms, definitions, and symbols .2 4 Principles of measurement 8 5 Meter characteristics.20 6 Test and calibration.36 7 Audit trail and operational practice .45 8 Valve characterization and noise in a metering and regulating s
12、tation 53 Annex A (informative) Registration of error bands .60 Annex B (informative) Derivation and correction of USM errors .62 Annex C (informative) The flow reference meter method for USMs in series 66 Annex D (informative) Documents 72 Annex E (informative) Detailed calculation of geometry-rela
13、ted temperature and pressure corrections .74 Annex F (informative) Disturbance tests 94 Bibliography96 BS ISO 17089-1:2010ISO 17089-1:2010(E) iv ISO 2010 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO m
14、ember 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 committee has been established has the right to be represented on that committee. International organizations, governm
15、ental 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 electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Dir
16、ectives, Part 2. 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 bo
17、dies 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 not be held responsible for identifying any or all such patent rights. ISO 17089-1 was prepared by Technical Committee ISO/TC 30, Measurement of fluid
18、flow in closed conduits, Subcommittee SC 5, Velocity and mass methods. ISO 17089 consists of the following parts, under the general title Measurement of fluid flow in closed conduits Ultrasonic meters for gas: Part 1: Meters for custody transfer and allocation measurement The following part is plann
19、ed: Part 2: Meters for industrial applications BS ISO 17089-1:2010ISO 17089-1:2010(E) ISO 2010 All rights reserved vIntroduction Ultrasonic meters (USMs) for gas flow measurement have penetrated the market for meters rapidly since 2000 and have become one of the prime flowmeter concepts for operatio
20、nal use as well as custody transfer and allocation measurement. Next to the high repeatability and high accuracy, ultrasonic technology has inherent features like: negligible pressure loss; high rangeability; and the capability to handle pulsating flows. USMs can deliver extended diagnostic informat
21、ion through which it may be possible to demonstrate the functionality of an USM. Also, the measured speed of sound of the USM may be compared with the speed of sound calculated from pressure, temperature, and gas composition, to check the mutual consistency of the four instruments involved. Due to t
22、he extended diagnostic capabilities, this part of ISO 17089 advocates the addition and use of automated diagnostics instead of labour-intensive quality checks. This part of ISO 17089 focuses on meters for custody transfer and allocation measurement (class 1 and class 2 meters). Meters for industrial
23、 gas applications, such as utilities and process, as well as flare gas and vent measurement, will be the subject of part 2. Typical performance factors of the classification scheme are: Class Typical applications Typical uncertainty Reference 1 Custody transfer qV, t2 Allocation Within 1,5 % for qV
24、qV, taMeter performance, inclusive of total meter uncertainty, repeatability, resolution, and maximum peak-to-peak error, depends upon a number of factors which include pipe inside diameter, acoustic path length, number of acoustic paths, gas composition and associated SOS, and meter timing repeatab
25、ility. The two classes represent different measurement specifications commonly applied in industry. Depending on the importance of measurement with respect to regulatory or custody transfer demands, the total uncertainty budget for the system differs. 4.6 Reynolds number The flow profile is a functi
26、on of the Reynolds number, for changes in which, most USMs correct. The Reynolds number is calculated from the known inside diameter of the body, d, the measured average velocity, v, a preset value of the actual density, , and the dynamic viscosity, . dRe= (12) During calibration, as well as during
27、operation, the actual values for the density and the dynamic viscosity should be entered in the USM computer. See also 5.8.3. For values over 50 000, the impact of fluctuations in the Reynolds number is not large and ranges from approximately 1 % per decade for the path through the centre of the pip
28、e to less than 0,3 % per decade for the half-radius path. For most ultrasonic multi-path meters, the impact on the measurement is less than 0,1 % for a change of a factor of 2 in the Reynolds number (to be confirmed by the manufacturer). 4.7 Temperature and pressure correction 4.7.1 Introduction Dur
29、ing dynamic (wet) calibration, all of the systematic errors are brought down to zero by determining and then applying the meter flow calibration factor. From that moment onwards, the pressure and temperature reference conditions of the meter are those encountered during the dynamic calibration. Any
30、subsequent change in temperature or pressure alters the physical dimensions of the meter and, if not corrected for, introduces a systematic flow measurement error. In general, the pressure and temperature during calibration differ from those encountered under operating conditions. In 4.7.2 to 4.7.5,
31、 a simple approach is given to allow an initial estimate to be made of the flow error caused by temperature and pressure conditions that differ from the calibration reference condition. If this error is significant relative to the uncertainty required for custody transfer or allocation purposes, a m
32、ore detailed assessment of flow error has to be performed as described in 4.7.6. Annex E provides an extensive and detailed explanation of the process which readers are advised to consult for the background to many of the statements made in 4.7.2 to 4.7.6. 4.7.2 Correction for the temperature For al
33、l meter types, the geometry-related temperature correction can be given as a straightforward analytical solution (see E.2). In consequence, the correction has a very high precision and the only uncertainties related to this correction are the uncertainties related to the material constants. BS ISO 1
34、7089-1:2010ISO 17089-1:2010(E) ISO 2010 All rights reserved 15The flow correction factor due to a body temperature change, T, is given by: ( ) ()()323,1,01133VVqTTTTq=+ =+ + + (13) where qV, 1is the volume flow rate under operating conditions; qV, 0is the volume flow rate under the conditions at whi
35、ch the meter was calibrated; T is T1 T0in which T1is the temperature under operating conditions, T0is the temperature under the conditions at which the meter was calibrated. Other than in extreme situations, T is generally very small and Equation (13) can be simplified to: ,1,0b, 13VVTqTq=+ (14) Or
36、alternatively, expressed as a flow error: b, 3VVTqTq=(15) Table 5 gives typical coefficients of thermal expansion for common body materials. Table 5 Common coefficients of thermal expansion in the 0 C to 100 C range Material Thermal expansion coefficient K1Carbon steel 12 106Stainless steel AISI 304
37、 17 106Stainless steel AISI 316 16 106High elastic-limit stainless steel AISI 420 10 106The thermal expansion coefficients for a given material vary with temperature and the treatment process of the steel. The values given in Table 5 and used in the example in Figure 8 are for illustrative purposes
38、only. It is consequently recommended that, for more precise calculations, the coefficient of thermal expansion data be obtained from the material manufacturer. A graphical presentation of Equation (15) is shown in Figure 8 for two materials from Table 5. BS ISO 17089-1:2010ISO 17089-1:2010(E) 16 ISO
39、 2010 All rights reservedKey qV/qVflow measurement error T temperature difference 1 austenitic stainless steel 2 ferritic stainless steel 3 example Figure 8 Temperature related flow error for two example material types Figure 8 can be used to quickly estimate the percentage correction required for a
40、 given temperature change. The example point for a +23 C temperature change with an austenitic stainless steel body shows a +0,07 % correction (i.e. the meter would underestimate the flow by 0,07 % without the correction). If T is negative, qV/qVis negative (i.e. the meter will overestimate the flow
41、). 4.7.3 Pressure correction 4.7.3.1 General The geometry-related pressure correction is complex and depends on the design of the meter body, its end connections and the way the meter ends are supported in operation. Looking at the market, the various meter designs offered can be grouped into three
42、broad categories: a) welded-in cylindrical body designs; b) meter bodies consisting of a pipe with welded-on flanges; c) non cylindrical meter body designs, for example those based on casting. In 4.7.3.2 to 4.7.3.4, a means of making an initial estimate of the flow error for any body type is provide
43、d. BS ISO 17089-1:2010ISO 17089-1:2010(E) ISO 2010 All rights reserved 174.7.3.2 General simplified expression for any body type As a first stage in estimating the pressure effects, a general basic expression can be derived assuming the meter body consists simply of a cylindrical pipe. An estimate o
44、f the maximum expected flow error due to a body pressure change, p, is (as described in E.5) given by: 2222b, ,max44VVpq rRr pqr ERr+= +(16) If the meter body is irregular or non-cylindrical (e.g. as might be the case for a cast body), then, for the purposes of this initial estimate, the outside rad
45、ius value, R, should be taken as the point where the wall is thinnest since this gives the largest estimate of flow error. Equation (16) can be presented in graphical form as shown in Figure 9 for a range of values of /r, i.e. the ratio of wall thickness to internal radius. Key /r 1 0,050 p pressure
46、 difference 2 0,100 qV/qVflow measurement error 3 0,150 r inside pipe radius 4 0,200 pipe wall thickness 5 0,250 6 0,300 Figure 9 Maximum expected pressure-related flow error for different /r ratios Figure 9 provides a rapid means of estimating the maximum expected flow error due to body pressure ch
47、anges. The figure is plotted for a body material with a Young modulus of 2 1011Pa and a Poisson ratio of 0,3. The example of p = 6,3 MPa shows the maximum expected pressure-induced error to be 0,06 % for a /r = 0,25. If p is negative, qV/qVis negative (i.e. the meter will overestimate the flow). Sin
48、ce Equation (16) and Figure 9 provide a maximum expected error, the reader can, if desired, go straight to 4.7.5 (taking KE= Ks= 1) to assess the significance of the error without the need of the refinement in the initial estimate provided in 4.7.3.3 and 4.7.3.4 since these result in a lower value f
49、or the flow error. BS ISO 17089-1:2010ISO 17089-1:2010(E) 18 ISO 2010 All rights reserved4.7.3.3 Refinement in initial estimate to account for different meter body designs Flanged ends or irregular shape to the body stiffen the body compared to the simple cylindrical pipe approach used in 4.7.3.2. Consequently, the body expansion and resulting flow error is less than that given by Equation (16) and Figure 9. To compensate f
