ISO INTERNATIONAL STANDARD 21857 First edition 2021-03 Petroleum, petrochemical and natural gas industries Prevention of corrosion on pipeline systems influenced by stray currents Industries du pétrole, de la pétrochimie et du gaz naturel - Prevention de la corrosion sur les systemes de conduites soumis a I'influence de courants vagabonds Referencenumber IS0 21857:2021(E) OS1 @ IS0 2021 IS0 21857:2021(E) COPYRIGHTPROTECTEDDOCUMENT IS02021 All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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's member body in the country of the requester. ISO copyright office CP 401 · Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +41 22 749 01 11 Email: [email protected] Website: www.iso.org Published in Switzerland ii @ IS0 2021 - All rights reserved IS0 21857:2021(E) Contents Page Foreword V Introduction. .vi 1 Scope. 1 2 Normative references ..1 3 Terms and definitions .2 4 Abbreviations and symbols .3 4.1 Abbreviations 3 4.2 Symbols. 5 Information exchange and co-operation .5 6 Common sources of interference that can affect corrosion .6 6.1 General. 6 6.2 Direct current 7 6.2.1 General. 7 6.2.2 Traction systems. 6.2.3 Industrial systems 7 6.3 Alternating current. 7 6.3.1 General. 7 6.3.2 Overhead and buried power lines. 8 6.4 High-voltage direct current transmission systems 8 6.5 Natural interference 6.5.1 General.. .8 6.5.2 Geomagnetic (telluric) interference. 8 6.5.3 Tidal interference effects... 9 7 Identification and measurement of stray current interference .9 7.1 Principle. 7.2 Stray Current interference. .10 7.2.1 Inductive and conductive coupling from remote sources .10 7.2.2 Conductivecouplingfromnearby sources .10 7.3 Measurement of electrical parameters. .10 7.3.1 Data acquisition systems. .10 7.3.2 Possible errors in AC measurements .11 7.3.3 Potential measurement. .11 7.3.4 Current measurement on probes .11 7.3.5 IR-free potential measurement on coupons or probes 11 7.3.6 Duration of the measurement. .11 7.3.7 Specific requirements for coupons or probes. .12 7.4 Corrosion rate measurement. .12 8 Acceptance criteria for DC interference .12 8.1 Overview of criteria .12 8.2 Corrosion rate .13 8.3 Criteria for steel and cast iron .14 8.3.1 Time constant interference .14 8.3.2 Time variant interference ..15 8.4 Criteria for steel pipes in concrete based on potential measurements without cathodic protection ..16 8.4.1 Time constant anodic interference .16 8.4.2 Time variant interference... ..16 9 Reduction of DC stray current interference .16 9.1 General .16 9.2 Modifications to the source of interference .17 9.2.1 Principles. .17 @ IS0 2021 - All rights reserved iii IS0 21857:2021(E) 9.2.2 Direct current systems at industrial sites .17 9.2.3 Directcurrentsystemsatports .17 9.2.4 Direct current traction systems .17 9.2.5 Cathodic protection systems. .18 9.2.6 Telluric interference .19 9.2.7 Direct current communication systems. .19 10 Modifications to the interfered structure ..19 10.1 General .19 10.2 Design prerequisites 20 10.2.1 Coatings 20 10.2.2 Isolation from other structures. 20 10.2.3 Distance to be maximized 20 10.2.4 Installation of mitigation devices 20 10.2.5 Modifying the electrical continuity of the interfered structure 21 11 Inspection and maintenance. ..22 Annex A (informative) Use of current probes to evaluate fluctuating stray current interference on cathodically protected structures .23 Annex B (informative) Determining the relevant position for placing reference electrodes, .26 Annex C (informative) Operating principles of electrical resistance probes ..33 Annex D (informative) Geomagnetic interference... ..34 Annex E (informative) High voltage direct current interference