ISO INTERNATIONAL STANDARD 20456 First edition 2017-09 Measurementoffluidflowinclosed conduits Guidance for the use of electromagnetic flowmeters for conductive liquids Mesuragedudebitdesfluidesdansles conduitesfermees-Lignes directricespourI'utilisationdes debitmetres électromagnetiques dans lesliquidesconducteurs Referencenumber IS020456:2017(E) @IS02017 IS020456:2017(E) COPYRIGHTPROTECTEDDOCUMENT IS02017,Published in Switzerland All rights 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 the requester. ISOcopyrightoffice Ch.deBlandonnet8·CP 401 CH-1214Vernier,Geneva,Switzerland Tel.+41227490111 Fax+412274909 47 [email protected] www.iso.org ii IS02017-Allrightsreserved IS020456:2017(E) Contents Page Foreword iv Introduction 1 Scope 1 2 .1 Normativereferences 3 Termsanddefinitions 1 4 Symbols .3 5 Theoryand basicformulae .4 6 Constructionandprincipleofoperation 4 6.1 General 4 6.2 Sensor 5 6.3 Transmitter 7 6.3.1 General. 7 6.3.2 Alternatingmagneticfield inthemeasuringsystem 7 6.3.3 MeasuringsystemwithappliedpulsedDCexcitation (simplifiedmodel) .7 6.3.4 MeasuringsystemwithappliedACexcitation (simplifiedmodel) .8 6.4 Flowmeter/Transmitteroutput 9 7 Equipmentmarking 9 7.1 Recommendeddata 9 7.1.1 Sensor.. 9 7.1.2 .10 Transmitter 8 Installationdesignandpractice .10 8.1 Sensor 10 8.1.1 Sizing. .10 8.1.2 Mountingconditions 11 8.1.3 PotentialequalizationGeneralrequirements 12 8.1.4 Electricalconnections 13 8.1.5 Sensormounting .13 8.1.6 Installationdimensionsforflanged connections. .14 8.2 Transmitterlocation 15 8.3 Operational considerations 16 8.3.1 General. .16 8.3.2 Effect oftheliquidconductivity 16 8.3.3 Reynoldsnumbereffect. 16 8.3.4 Velocityprofileeffect. .16 Flowmetercalibration,validation,andverification .16 9.1 Flowmetercalibration. .16 9.2 Flowmeterverification (in-situelectronicverification) .16 10 Evaluationofflowmeterperformance .17 10.1 General 17 10.2 Applicationswithinthescopeofotherstandards 17 11 Uncertainty analysis .17 AnnexA(informative)Materialsforconstructionofsensors .19 AnnexB(informative)PracticalconsiderationsformeasuringsystemwithACandDCexcitation22 AnnexC(informative)Cathodicprotection. 23 AnnexD(informative)ConversionofnominaldiametersfrommetrictoUSunits .24 AnnexE(informative)Manufacturers'accuracyspecifications .25 Bibliography .29 @IS0 2017- All rights reserved ili