1、BRITISH STANDARD BS EN 12474:2001 Cathodic protection of submarine pipelines The European Standard EN 12474:2001 has the status of a British Standard ICS 23.040.01 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 12474:2001 This British Standard, having been prepared under
2、 the direction of the Electrotechnical Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 25 October 2001 BSI 25 October 2001 ISBN 0 580 38543 4 National foreword This British Standard is the official English language version of
3、EN 12474:2001. Attention is drawn to the fact that BS 7361-1:1991, Cathodic protection Part 1: Code of practice for land and marine applications, provides general information on cathodic protection. Note that BS 7361-1:1991 will eventually be withdrawn when all the CEN standards relating to cathodic
4、 protection currently being prepared are published. The UK participation in its preparation was entrusted to Technical Committee GEL/603, Cathodic protection which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-refe
5、rences The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Cata
6、logue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the te
7、xt; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside
8、 front cover, the EN title page, pages 2 to 26, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN12474 April
9、2001 ICS23.040.99;77.060 Englishversion Cathodicprotectionofsubmarinepipelines Protectioncathodiquedescanalisationssousmarines KatodischerKorrosionsschutzfrunterseeische Rohrleitungen ThisEuropeanStandardwasapprovedbyCENon7March2001. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhi
10、chstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheManagementCentreortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English
11、,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheManagementCentrehasthesamestatusasthe official versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Icel
12、and,Ireland,Italy,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2001CEN Allrightsofexploitationinanyformandbyanymeansreserved
13、worldwideforCENnationalMembers. Ref.No.EN12474:2001EPage2 EN12474:2001 Contents Foreword3 Introduction .4 1 Scope4 2 Normativereferences 4 3 Termsanddefinitions. 4 4 Criteriaandprinciplesforcathodicprotectiondesign .5 5 Designofsacrificialanodessystem . 8 6 Installationofsacrificialanodes 10 7 Desig
14、nofimpressedcurrentsystems. .11 8 Installationofimpressedcurrentsystems. 12 9 Commissioningofcathodicprotectionsystems.13 10 Controlofinterferencecurrents . .14 11 Monitoringandsurveyingofcathodicprotectionsystem16 12 Safety17 13 Documentation 18 AnnexA (informative)Guidanceoncurrentrequirementsforc
15、athodicprotectionofpipelineandrisers .19 AnnexB (informative)Anodesizingcalculations21 AnnexC (informative)Attenuationcurves. .22 AnnexD (informative)Safetyprecautionsforimpressedcurrentsystem 24 AnnexE (informative)Typicalelectrochemicalcharacteristicsforcommonlyusedimpressedcurrent anodes25 Biblio
16、graphy26Page3 EN12474:2001 Foreword ThisEuropeanStandardhasbeenpreparedbyTechnicalCommitteeCEN/TC219“CathodicProtection“,the secretariatofwhichisheldbyBSI. ThisEuropeanStandardshallbegiventhestatusofanationalstandard,eitherbypublicationofanidenticaltextor byendorsement,atthelatestbyOctober2001,andco
17、nflictingnationalstandardsshallbewithdrawnatthelatest byOctober2001. AccordingtotheCEN/CENELECInternalRegulations,thenationalstandardsorganizationsofthefollowing countriesareboundtoimplementthisEuropeanStandard:Austria,Belgium,CzechRepublic,Denmark,Finland, France,Germany,Greece,Iceland,Ireland,Ital
18、y,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden, SwitzerlandandtheUnitedKingdom.Page4 EN12474:2001 Introduction Cathodicprotection,togetherwithacorrosionprotectioncoating,isusuallyappliedtoprotecttheexternalsurface ofsubmarinepipelinesfromcorrosionduetoseawaterorsalinemud. Thecorrosionprotecti
19、oncoatingisappliedontheexternalsurfaceofthepipelinetoinsulatethesteelsurfacefrom theaggressiveenvironmentintowhichthepipelineissurrounded. Thecathodicprotectionensurestheprotectionoftheareasofthepipelinewhicharedirectlyexposedtothe aggressivemarineenvironmentduetodamageordefectsinthecoating. Thecath
20、odicprotectionsuppliessufficientdirectcurrenttotheexternalsurfacesofthepipelinetoreducethepipe toelectrolytepotentialtovalueswherethereisinsignificantcorrosion. ThegeneralprinciplesofcathodicprotectionaredetailedinEN12473. 1 Scope ThisEuropeanStandardestablishesthegeneralcriteriaandrecommendationsfo
21、rthedesign,installation, monitoringandcommissioningofthecathodicprotectionsystemsforsubmarinepipelines. Thisstandardisapplicabletoallgradesofcarbonmanganesesteelandtostainlesssteelpipelines;itcoversall typesofseawaterandseabedenvironmentsencounteredinsubmergedconditions. Thecathodicprotectionofshort
22、lengthsofsubmarinepipelinesandtheirbranches,whicharedirectlyconnectedto cathodicallyprotectedonshorepipelines,areoutsideofthescopeofthisstandard(seeEN12954:2001). Thecathodicprotectionofrisersisincludedinthisstandardonlyiftheyareinsulatedfromthesupportingstructure. Thecathodicprotectionoftherisersin
23、directelectricalcontactwiththesupportingstructureisincludedin EN12495. 2 Normativereferences ThisEuropeanStandardincorporatesbydatedorundatedreference,provisionsfromotherpublications.These normativereferencesarecitedattheappropriateplacesinthetextandthepublicationsarelistedhereafter.For datedreferen
24、ces,subsequentamendmentstoorrevisionsofanyofthesepublicationsapplytothisEuropean Standardonlywhenincorporatedinitbyamendmentorrevision.Forundatedreferencesthelatesteditionofthe publicationreferredtoapplies(includingamendments). EN12473:2000, Generalprinciplesofcathodicprotectioninseawater. EN12495,
25、Cathodicprotectionforfixedsteeloffshorestructures. prEN12496:1996, Sacrificialanodesforcathodicprotectioninseawater. EN12954:2001, CathodicprotectionofburiedorimmersedmetallicstructuresGeneralprinciples . ENISO8044, CorrosionofmetalsandalloysBasictermsanddefinitions(ISO8044:1999). 3 Termsanddefiniti
26、ons ForthepurposesofthisEuropeanStandardthetermsanddefinitionsinENISO8044andthefollowingapply:Page5 EN12474:2001 3.1 weightcoating coatingusuallymadeofsteelwirereinforcedconcrete,appliedtothepipestoprovideantibuoyancyand/or mechanicalprotectionofthepipeline 3.2 remotelyoperatedvehicle(R.O.V.) unmann
27、edsubmarinevehicleoperatedbyasurfacevesselandusedforinspectionandsurveyofthepipeline 3.3 “J“tube curvedtubularconduitdesignedandinstalledonastructuretosupportandguideoneormorepipelinerisersor cables 3.4 riser verticalornearverticalportionofanoffshorepipelinewhichconnectstheplatformpipingtothepipelin
28、eatorbelow theseabed 4 Criteriaandprinciplesforcathodicprotectiondesign 4.1 Protectivecriteria 4.1.1 Protectivepotentials Toachieveadequatecathodicprotectionasubmarinepipelineshouldhavetheprotectivepotentialsindicatedin thefollowingtable.Thesepotentialsapplytosalinemudandnormalseawatercompositions(s
29、alinity32to 38). Table1Summaryofpotentialversussilver/silverchloride/seawaterreferenceelectroderecommended forthecathodicprotectionofsteelmaterialsinseawater Material Minimumnegativepotential volt Maximumnegativepotential volt Ironandsteel aerobicenvironment anaerobicenvironment 0,80 0,90 1,10 1,10
30、Stainlesssteel Austeniticsteel (PREN 40) (PREN40) Duplex 0,30 0,60(seenote1) 0,60(seenote1) nolimit nolimit (seenote2) NOTE1 Formostapplicationsthesepotentialsareadequatefortheprotectionofcrevicesalthoughmorenegative potentialsmaybeconsidered. NOTE 2 Dependingonmetallurgicalstructurethesealloysmaybe
31、susceptibletocrackingandmorenegative potentialsshouldbeavoided(inaccordancewith8.3.2.2ofEN12473:2000). 4.1.2 Referenceelectrodes Thefollowingtypesofreferenceelectrodesmaybeusedtomeasurethepotentialbetweenthepipelinesurface andseawater: silversilverchloride/seawater(Ag/AgCl/seawater);Page6 EN12474:20
32、01 highpurityzinc(99,9%min.ofzincwithironcontentnotexceeding0,0014%)/seawater; anodezincalloy/seawater; saturatedKClcalomel(Hg/HgCl 2 /KClsaturated)forreferenceelectrodecalibrationpurposesonly. 4.2 Corrosionprotectioncoating Acorrosionprotectioncoatingisnormallyappliedtoasubmarinepipelineinconjuncti
33、onwithcathodicprotectionto controlexternalcorrosion.Thecoatingreducesthecurrentrequiredtoachieveeffectivecathodicprotectionand enhancesthedistributionofthecathodicprotectioncurrentoverthepipelinesurface(seetableA.3). 4.3 Basicparameters Thefollowingshouldbetakenintoconsiderationwhendesigningacathodi
34、cprotectionsystem: characteristicsofthesubmarinepipelinetobeprotected,suchasdiameter,wallthickness,length,route,laying conditionsontheseabottom,temperatureprofilealongitswholelength,typeandthicknessofcorrosion protectioncoating(s)forpipesandfittings,presence,typeandthicknessofthermalinsulation,mecha
35、nical protection,and/orweightcoating; existingorproposedinstallations(pipelines,platformsetc.)incloseproximitytoorcrossingofthepipeline route; therequirementforelectricalisolationfromadjoiningsteelstructures,platform,onshorepipelinesetc.; presenceof“J“tubes,risersandclamps; environmentalconditions;
36、designlifeofthepipeline; pipelinelaymethod; protectioncriteria; offshoresitei.e.accessibilityforrepairandreplacement; performancedataofcathodicprotectionsystemsinthesameenvironmentsite; availabilityofelectricpower; safetyrequirements; applicablecodes; riskassessment. 4.4 Environmentalparameters Thef
37、ollowingenvironmentalparametersshouldbeevaluatedthroughfieldmeasurementsifexperiencefromthe areaislimited. temperature; seawaterandmudresistivity; seawatervelocity; p H ; waterpressure(depth)alongtheroute;Page7 EN12474:2001 presenceandquantityofH 2 Sproducingbacteria(e.g.SRB); watercompositionwithpa
38、rticularreferencetotheoxygencontent; presenceofstrayand/ortelluriccurrentsinthearea(see10.2). 4.5 Protectivecurrentdensity Oneofthemainparameterstobedefinedinthedesignofthecathodicprotectionsystemforasubmarinepipeline isthecurrentdensityrequiredtoprotectthesteelsurfaceofthepipelinethroughoutallitsde
39、signlife. Threevaluesofcurrentdensityaresignificant.Theinitial,maintenanceandrepolarizationvalueswhichrefer respectivelytothecurrentdensityrequiredtopolarizethepipelinewithinareasonabletimeperiod(i.e.1to2 months)thecurrentdensitynecessarytomaintainthepolarizationandthecurrentdensitynecessaryforan ev
40、entualrepolarizationwhichmayoccurforexampleafteranheavystorm. Theselectionofthedesigncurrentdensitiesmaybebasedonexperiencefromsimilarpipelinesinthesame environmentoronfieldmeasurementscarriedoutinthesamearea. Dueconsiderationshouldbegiventothefollowing: thecurrentdensitydemandisnormallynotconstantw
41、ithtime;forbaresteelareasofpipelinesinseawateror theseabedthecurrentdensityrequirementsmaydecreaseduetotheformationofcalcareousdeposits causedbythecathodiccurrent; forcoatedareasofpipelinesthecurrentrequirementsmayincreasewithtimeasthecoatingdeteriorates. Guidelinesonthedesigncurrentdensitiesaregive
42、ninannexA. 4.6 Selectionofthecathodicprotectionsystem Eithersacrificialanodeand/orimpressedcurrentcathodicprotectionsystemmaybeusedtoprotectasubmarine pipeline. Theselectionbetweenthetwosystemsshouldbebasedonthefollowingconsiderations: theimpressedcurrentsystemmayonlyprotectafinitelengthofpipeline,d
43、eterminedbythefollowing: practicallimitationsonthelocationsforimpressedcurrentsysteminstallations,e.g.theendsofthe pipelineandintermediateplatformsorlandfalls, thevalueoftheinsulationresistanceofthecoatedpipelineversusthesurroundingelectrolyteattheend ofitsdesignservicelife(seeannexC), thelongitudin
44、alresistanceofthepipeline(seeannexC); thelackofasourceofexternalpowermayprecludetheuseofimpressedcurrentsystems; sacrificialanodesystemsdonotrequireanyoperationcontrolormaintenanceduringtheservicelifeofthe pipeline; sacrificialanodesystemsseldomcauseseriousinteractionproblemsonforeignneighbouringstructures, whereasimpressedcurrentsystemmayhaveasignificanteffect. 4.7 Electricalisolation Electricalisolationbetweena
