# ISO 3354-2008

Reference numberISO 3354:2008(E)©ISO 2008INTERNATIONAL STANDARD ISO3354Third edition2008-07-15Measurement of clean water flow in closed conduits — Velocity-area method using current-meters in full conduits and under regular flow conditions Mesurage de débit d eau propre dans les conduites fermées — Méthode d exploration du champ des vitesses dans les conduites en charge et dans le cas d un écoulement régulier, au moyen de moulinetsCopyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3354:2008(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe s licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe s licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT © ISO 2008 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 ISO s 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 copyright@iso.org Web www.iso.org Published in Switzerland ii © ISO 2008 – All rights reservedCopyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3354:2008(E) © ISO 2008 – All rights reserved iiiContents Page Foreword. v 1 Scope 1 2 Normative references 1 3 Terms and symbols .2 3.1 Terms 2 3.2 Symbols 3 4 Principle4 4.1 General4 4.2 Measurement of the measuring cross-section .5 4.3 Measurement of local velocities.6 4.4 Location and number of measuring points in the cross-section .7 5 Description of the current-meter9 6 Requirements for the use of current-meters 9 6.1 Selection of the measuring cross-section 9 6.2 Devices for improving flow conditions10 6.3 Calibration of the current-meter.11 6.4 Limits of use.11 6.5 Inspection and maintenance of current-meters .13 7 Setting of current-meters into the conduit13 7.1 Setting of current-meters13 7.2 Mounting in a circular cross-section.13 7.3 Mounting in a rectangular cross-section 14 8 Determination of the mean axial fluid velocity by graphical integration of the velocity area .16 8.1 General16 8.2 Circular cross-sections.16 8.3 Rectangular cross-sections18 9 Determination of the mean axial fluid velocity by numerical integration of the velocity area20 9.1 General20 9.2 Circular cross-sections.21 9.3 Rectangular cross-sections22 10 Determination of the mean axial fluid velocity by arithmetical methods.23 10.1 General23 10.2 Log-linear method23 10.3 Log-Chebyshev method25 11 Uncertainty in the measurement of flow-rate .27 11.1 General27 11.2 Sources of error in local velocity measurements 27 11.3 Sources of error in estimation of flow-rate .28 11.4 Propagation of errors 29 11.5 Presentation of results29 11.6 Calculation of uncertainty.30 Annex A (normative) Measuring sections other than circular or rectangular sections 33 Annex B (normative) Corrections for blockage effect.38 Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3354:2008(E) iv © ISO 2008 – All rights reservedAnnex C (normative) Recommendations for the selection of the type of current-meter and mounting strut. 39 Annex D (normative) Example of measuring point distribution along a radius for velocity measurement in a conduit of circular cross-section in the case of the graphical and numerical methods . 41 Annex E (normative) Determination of boundary layer coefficient, m, for extrapolation near the wall 43 Annex F (normative) Definition of terms and procedures used in the uncertainty calculation . 45 Annex G (normative) Student s t distribution 48 Annex H (informative) Examples of values of component uncertainties 49 Annex J (informative) Example of calculation of the uncertainty in the flow-rate measurement using current-meters 51 Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3354:2008(E) © ISO 2008 – All rights reserved vForeword 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 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 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 Directives, 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 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 not be held responsible for identifying any or all such patent rights. This International Standard was prepared by Technical Committee ISO/TC 30, Measurement of fluid flow in closed conduits, Subcommittee SC 5, Velocity and mass methods. This third edition results from the reinstatement of ISO 3354:1988 which was withdrawn in 2003 and with which it is technically identical. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---INTERNATIONAL STANDARD ISO 3354:2008(E)© ISO 2008 – All rights reserved 1Measurement of clean water flow in closed conduits — Velocity-area method using current-meters in full conduits and under regular flow conditions 1 Scope This International Standard specifies a method for the determination of the volume flow-rate in a closed conduit by means of the velocity-area method using propeller-type current-meters under the following conditions: a) the velocity distribution is regular (see 6.1.2); b) the fluid is water which is clean or considered to be clean 1); c) the conduit is full; d) the flow is steady 2). It deals in particular with the technology and calibration of propeller-type current-meters, the measurement of local velocities and the calculation of the flow-rate by velocity integration. 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 the referenced document (including any amendments) applies. ISO 3455, Hydrometry — Calibration of current-meters in straight open tanks ISO 4006, Measurement of fluid flow in closed conduits — Vocabulary and symbols ISO 5168, Measurement of fluid flow — Procedures for the evaluation of uncertainties ISO 7194, Measurement of fluid flow in closed conduits — Velocity-area methods of flow measurement in swirling or asymmetric flow conditions in circular ducts by means of current-meters or Pitot static tubes 1) This method may be applied to other single-phase fluids but special precautions should be taken in this case. 2) The steady flows observed in conduits are in practice flows in which quantities such as velocity, pressure, density and temperature vary in time about mean values independent of time; these are actually “mean steady flows”. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3354:2008(E) 2 © ISO 2008 – All rights reserved3 Terms, definitions and symbols For the purposes of this document, the terms and definitions given in ISO 4006 and the following apply. 3.1 Terms 3.1.1 current-meter device provided with a rotor the rotational frequency of which is a function of the local velocity of the fluid in which the device is immersed NOTE 1 This International Standard is concerned only with propeller-type current-meters, i.e. current-meters the rotor of which is a propeller rotating around an axis approximately parallel to the direction of flow. NOTE 2 Obviously this definition does not prohibit the use of self-compensating propellers (see 6.1.5), the merit of which is, in particular, that they can be used at a rather high angle relative to the local direction of the flow. However, the use of cup-type current-meters is not allowed for the purposes of this International Standard. 3.1.2 stationary array set of current-meters mounted on one or more fixed supports which sample simultaneously the whole measuring cross-section 3.1.3 peripheral flow-rate the volume flow-rate in the area located between the pipe wall and the contour defined by the velocity measuring points which are closest to the wall 3.1.4 mean axial fluid velocity ratio of the volume flow-rate (the integral over a cross-section of the conduit of the axial components of the local fluid velocity) to the area of the measuring cross-section 3.1.5 relative velocity ratio of the flow velocity at the considered point to a reference velocity measured at the same time, which is either the velocity at a particular point (e.g. at the centre of a circular conduit) or the mean axial fluid velocity in the measuring section 3.1.6 straight length portion of a conduit whose axis is straight, and in which the cross-sectional area and cross-sectional shape are constant; the cross-sectional shape is usually circular or rectangular, but could be annular or any other regular shape 3.1.7 irregularity any pipe fitting or configuration of a conduit which renders the conduit different from a straight length or which produces a considerable difference in wall roughness NOTE In the case of the method of measurement specified in this International Standard, those irregularities which create the most serious disturbances are generally bends, valves, gates and sudden widening of the cross-section. 3.1.8 hydraulic diameter diameter equal to four times the hydraulic radius, i.e. four times the ratio of the wetted cross-sectional area to the wetted perimeter EXAMPLE In a conduit of circular cross-section running full, the hydraulic diameter is equal to the geometric diameter. Copyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3354:2008(E) © ISO 2008 – All rights reserved 33.1.9 index of asymmetry 〈for circular ducts〉 ratio of the standard deviation of the mean velocities calculated along each radius (i.e. along each radial line from the pipe centre to the wall along which velocity measuring positions are located) to the mean axial fluid velocity calculated for the pipe, i.e. ()1/ 22111iniUiUUYUU nσ=⎡⎤⎢⎥−==−⎢⎥⎣⎦∑where Uiis the mean velocity, calculated, in accordance with the integration method agreed, from the individual point velocity measurements on the ith radius (see 8.2 and 9.2); U is the mean axial fluid velocity calculated from all the individual point velocity measurements throughout the cross-section; n is the number of radii along which measurements are made 3.1.10 regular velocity distribution distribution of velocities which sufficiently approaches a fully developed velocity distribution to permit an accurate measurement of the flow-rate to be made 3.2 Symbols Symbol Quantity Dimension SI unit A area of the measuring cross-section L2m2a, a′ distance along a measuring line in a rectangular cross-section from the extreme measuring point to the nearest wall L mD pipe diameter L m d propeller diameter L m e uncertainty (absolute value) —a —aerrandom uncertainty —a—aessystematic uncertainty —a—aE relative uncertainty — — Errelative random uncertainty — — Esrelative systematic uncertainty — — H length of the smaller side of the cross-section of a rectangular conduit L m h distance from a given measuring point to the reference wall, in the direction parallel with the smaller side of the cross-section L m k equivalent uniform roughness L m L length of the larger side of the cross-section of a rectangular conduit L mCopyright International Organization for Standardization Provided by IHS under license with ISO Not for ResaleNo reproduction or networking permitted without license from IHS--`,,```,,,,````-`-`,,`,,`,`,,`---ISO 3354:2008(E) 4 © ISO 2008 – All rights reservedSymbol Quantity Dimension SI unit l distance from a given measuring point to the reference wall, in the direction parallel with the larger side of the cross-section L mm boundary layer coefficient — — n frequency of rotation of a propeller T−1r/s p number of measuring points along a radius (circular cross-section) or a straight line (rectangular cross-section) — — qVvolume flow-rate L3T−1m3/s R pipe radius L m r measuring circle radius L m r*measuring circle relative radius, *rrR= — — Re Reynolds number — — U mean axial fluid velocity LT−1m/s u mean velocity along a measurement circumference or line LT−1m/s v local velocity of the fluid LT−1m/s v0local velocity of the fluid at the centre-line of the pipe LT−1m/s Y index of asymmetry of the flow — — y distance from a meas