BS EN 13173-2001 Cathodic protection for steel offshore floating structures《近海浮式钢制结构件的阴极保护》.pdf

1、BRITISH STANDARD BS EN 13173:2001 Cathodic protection for steel offshore floating structures The European Standard EN 13173:2001 has the status of a British Standard ICS 75.180.10; 77.060 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 13173:2001 This British Standard, ha

2、ving been prepared under the direction of the Electrotechnical Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 June 2001 BSI 06-2001 ISBN 0 580 37634 6 National foreword This British Standard is the official English language version of EN 13

3、173:2001. Reference should also be made to BS 7361, Code of practice for land and marine applications, which will eventually be withdrawn when all the CEN standards relating to cathodic protection currently being prepared, are published. The UK participation in its preparation was entrusted to Techn

4、ical 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-references The British Standards which implement international or European publications referred to in this document

5、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 Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of Britis

6、h 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 text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, a

7、nd 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 front cover, the EN title page, pages 2 to 25 and a back cover. The BSI copyright date displayed in this documen

8、t indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN13173 January2001 ICS47.020.01;77.060 Englishversion Cathodicprotectionforsteeloffshorefloatingstructures Protectioncathodiquedesstructuresenacier

9、flottanten mer KathodischerKorrosionsschutzfrschwimmendeOffshore AnlagenausStahl ThisEuropeanStandardwasapprovedbyCENon6July2000. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalteration.

10、Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheManagementCentreortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoitsow

11、nlanguageandnotifiedtotheManagementCentrehasthesamestatusasthe official versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Iceland,Ireland,Italy,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROP

12、EANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2001CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.EN13173:2001EPage2 EN13173:2001 Contents Foreword4 Introduction .

13、4 1Scope 5 1.1Structures 5 1.2Materials .5 1.3Environment 5 1.4Safetyandenvironmentprotection .6 2Normativereferences 6 3Termsanddefinitions 6 4Designbasis .7 4.1Objectives 7 4.2Cathodicprotectioncriteria .7 4.3Designparameters 7 4.4Electricalcurrentdemand 8 4.5Cathodicprotectionsystems .10 4.6Elect

14、ricalcontinuity 11 4.7Interactions 11 5Impressedcurrentsystemdesign 11 5.1Objectives 11 5.2Designconsiderations 12 5.3Equipmentconsiderations .12 6Galvanicanodesystemdesign .14 6.1Objectives 14 6.2Designconsiderations 14 6.3Factorsdeterminingtheanodecurrentoutputandoperatinglife .15 6.4Locationofano

15、des .16Page3 EN13173:2001 7Cathodicprotectionsystemmonitoring 16 7.1Objectives 16 7.2Potentialmeasurements 16 7.3Measurementoftheimpressedcurrentanodeelectricalcurrentoutput 17 7.4Impressedcurrentpowersourcecontrol .17 7.5Additionalmonitoringmethods .17 8Documentation .18 8.1Objectives 18 8.2Impress

16、edcurrentsystem .18 8.3Galvanicanodesystems 19 AnnexA(informative)Guidanceforcurrentrequirementsforcathodicprotectionofoffshorefloating structures.20 AnnexB (informative)Anoderesistanceandlifedetermination 21 AnnexC (informative)Typicalelectrochemicalcharacteristicsofimpressedcurrentanodes .23 Annex

17、D (informative)Typicalcofferdamarrangements .24Page4 EN13173:2001 Foreword ThisEuropeanStandardhasbeenpreparedbyTechnicalCommitteeCEN/TC219“Cathodicprotection“,the secretariatofwhichisheldbyBSI. ThisEuropeanStandardshallbegiventhestatusofanationalstandard,eitherbypublicationofanidenticaltextorby end

18、orsement,atthelatestbyJuly2001,andconflictingnationalstandardsshallbewithdrawnatthelatestbyJuly 2001. AccordingtotheCEN/CENELECInternalRegulations,thenationalstandardsorganizationsofthefollowingcountries areboundtoimplementthisEuropeanStandard:Austria,Belgium,CzechRepublic,Denmark,Finland,France, Ge

19、rmany,Greece,Iceland,Ireland,Italy,Luxembourg,Netherlands,Norway,Portugal,Spain,Sweden,Switzerland andtheUnitedKingdom.Page5 EN13173:2001 Introduction Cathodicprotectionisusuallyapplied,mostlyasacomplementtoprotectivecoatingorpaint,toprotecttheexternal surfacesofsteeloffshorefloatingstructuresandapp

20、urtenancesfromcorrosionduetoseawaterorsalinemud. Cathodicprotectionworksbysupplyingsufficientdirectcurrenttotheimmersedsurfaceofthestructureinorderto changethesteeltoelectrolytepotentialtovalueswherecorrosionisinsignificant. ThegeneralprinciplesofcathodicprotectionaredetailedinEN12473. 1Scope ThisEu

21、ropeanStandarddefinesthemeanstobeusedtocathodicallyprotectthesubmergedmetallicsurfacesof steeloffshorefloatingstructuresandappurtenancesinseawaterandsalinemud. 1.1Structures ThisEuropeanStandardcoversthecathodicprotectionoftheexternalsurfaceofoffshorefloatingstructureswhich arestaticduringtheirusual

22、operatingconditions.Thisessentiallyincludes:barges,jackups,semisubmersible platforms,storagetankers,buoys,etc. Italsocoversthesubmergedareasofappurtenances,suchaschains,attachedtothestructure,whenthesearenot electricallyisolatedfromthestructure. Itdoesnotcoverthecathodicprotectionofships,fixedoffsho

23、restructures,elongatedstructures(pipelines,cables)or harbourinstallations,whicharecoveredbyotherstandards. ThisEuropeanStandardconcernsonlythecathodicprotectionofexternalsurfacesimmersedinseawater,including seachestsandwaterintakesuptothefirstvalve. ThisEuropeanStandarddoesnotincludetheinternalprote

24、ctionofsurfacesofanycomponentssuchasballasttanks andhullinternalsoffloatingstructures. 1.2Materials ThisEuropeanStandardcoversthecathodicprotectionofstructuresfabricatedprincipallyfrombareorcoatedcarbon manganesesteels Assomepartsofthestructuremaybemadeofmetallicmaterialsotherthancarbonmanganesestee

25、ls,thecathodic protectionsystemshouldbedesignedtoensurethatthereisacompletecontroloveranygalvaniccouplingand minimiserisksduetohydrogenembrittlementorhydrogeninducedcracking(seeEN12473). ThisEuropeanStandarddoesnotcoverconcretestructures. 1.3Environment ThisEuropeanStandardisapplicableforthewholesub

26、mergedzoneinseawater,brackishwaters,salinemudwhich cannormallybefoundwherethefloatingstructureisanchored,mooredormoving. ThisEuropeanStandardisalsoapplicabletoappurtenanceswhichmaybeincontactwithmuds(e.g.chains).Page6 EN13173:2001 Forsurfaceswhicharealternatelyimmersedandexposedtotheatmosphere,theca

27、thodicprotectionisonlyeffective whentheimmersiontimeissufficientlylongforthesteeltobecomepolarised. 1.4Safetyandenvironmentprotection ThisEuropeanStandarddoesnotcoversafetyandenvironmentalprotectionaspectsassociatedwithcathodic protection.Therelevantnationalorinternationalregulationsshallapply. 2Nor

28、mativereferences ThisEuropeanStandardincorporates,bydatedorundatedreferences,provisionsfromotherpublications.These normativereferencesarecitedattheappropriateplacesinthetextandthepublicationsarelistedhereafter.Fordated references,subsequentamendmentstoorrevisionsofanyofthesepublicationsapplytothisEu

29、ropeanStandardonly whenincorporatedinitbyamendmentorrevision.Forundatedreferencesthelatesteditionofthepublicationreferred toapplies(includingamendments). EN12473, Generalprinciplesofcathodicprotectioninseawater. prEN12496, Galvanicanodesforcathodicprotectioninseawater. 3Termsanddefinitions Forthepur

30、posesofthisEuropeanStandardthetermsanddefinitionsinEN12473andthefollowingapply: 3.1 atmosphericzone zonelocatedabovethewettedzone;thatmeansabovethelevelreachedbythenormalswell,whetherthestructureis movingornot 3.2 boottopping sectionofthehullbetweenlightandfullyloadedconditions,whichmaybeintermitten

31、tlyimmersed 3.3 CathodicProtectionzone thatpartofthestructurewhichcanbeconsideredindependentlywithrespecttocathodicprotectiondesign 3.4 immersedzone zonelocatedbelowthewaterlineatdraughtcorrespondingtonormalworkingconditions 3.5 submergedzone zoneincludingtheimmersedandtheburiedzones 3.6 underwaterh

32、ull partofthehullvitalforitsstabilityandbuoyancyofafloatingstructure,i.e.belowthelightwaterlinePage7 EN13173:2001 4Designbasis 4.1Objectives Themajorobjectiveofacathodicprotectionsystemistodeliversufficientcurrenttoprotecteachpartofthestructure andappurtenancesanddistributethiscurrentsothatthepotent

33、ialofeachpartofthestructureiswithinthelimits givenbytheprotectioncriteria(see4.2). Potentialsshouldbeasuniformaspossibleoverthewholestructure.Thisobjectivemayonlybeapproachedbyan adequatedistributionoftheprotectivecurrentoverthestructureduringitsnormalserviceconditions.However,itmay bedifficulttoach

34、ieveinsomeareassuchaschains,waterintakes,seachests,whensupplementarycathodic protectionsystemsshouldbeconsidered. Thecathodicprotectionsystemforafloatingstructureisgenerallycombinedwithacoatingsystem,eventhough someappurtenances,suchaschains,maynotbenefitfromacoatingprotection. Dielectricshieldsmayb

35、eusedinconjunctionwithanodestominimisetheriskoflocaloverprotection. Thecathodicprotectionsystemshouldbedesignedeitherforthelifeofthestructureorforaperiodcorrespondingto themaintenancedrydockinginterval. Theaboveobjectivesshouldbeachievedbythedesignofacathodicprotectionsystemusinggalvanicanodesor imp

36、ressedcurrentsystemsoracombinationofboth. 4.2Cathodicprotectioncriteria ThecriteriaforcathodicprotectionaredetailedinEN12473. Toachieveanadequatecathodicprotectionlevel,steelstructuresshouldhavepotentialsasindicatedhereafter. Theacceptedcriterionforprotectionofsteelinaeratedseawaterisapotentialmoren

37、egativethan0,80Vmeasured withrespecttoAg/AgCl/seawaterreferenceelectrode. Anegativelimitof1,10V(Ag/AgCl/seawaterreferenceelectrode)isgenerallyrecommended. Wherethereisapossibilityofcoatingdisbondmentandcorrosionfatigue,thenegativelimitshouldbemorepositive. Thisnegativelimitshouldbedocumented. 4.3Des

38、ignparameters Thedesignofacathodicprotectionsystemshouldbemadeinaccordancewiththefollowingparameters:structure subdivision,componentsdescriptionandserviceconditions. 4.3.1Structuresubdivision AfloatingstructurecanbedividedintodifferentCathodicProtectionzones,(CPzones),whicharethenconsidered independ

39、entlywithrespecttocathodicprotectiondesign,althoughtheymaynotnecessarilybeelectricallyisolated. EXAMPLE1 Forastoragetanker,somespecificcomponentsmaynotbeincludedintheunderwaterhullCPzoneand thereforeconstituteaCPzonebythemselves(e.g.:seachests). EXAMPLE2 Forbuoys,asinglezoneisgenerallyconsidered,inc

40、ludingtwocomponents:thebodyofthebuoyandthe influencedpartofthemooringchain(s). 4.3.2DescriptionofCPzones EachC.P.zonemayconsistofseveralcomponentswhichshouldbefullydescribedincludingmaterial,surfacearea andcoatingcharacteristics(type,lifetimeandcoatingbreakdownfactor).Page8 EN13173:2001 4.3.3Service

41、conditions Thedesignofthecathodicprotectionsystem(s)willdependonserviceconditionswhichinclude:expectedlifetime, environmentandoperatingconditions. Lifetime:eitherthewholedesignlifeordrydockinginterval(s)shouldbeconsidered. Environment:theseawaterpropertiesshouldbeestablished(seeEN12473). Operatingco

42、nditions:thecathodicprotectiondesignnormallyconsidersonlythestaticconditionsofthestructure becausethedurationswhendynamicconditionsprevailaregenerallynegligible. 4.4Electricalcurrentdemand 4.4.1General Toachievethecriteriaforprotectionfortheconditionsoutlinedin4.3,itisnecessarytoselecttheappropriate

43、current densityforeachcomponent. Thecurrentdemandofeachmetalliccomponentofthestructureistheresultoftheproductofitssurfacearea multipliedbytherequiredcurrentdensity. 4.4.2Protectioncurrentdensityforbaresteel Thecurrentdensityrequiredmaynotbethesameforallcomponentsofthestructureastheenvironmentaland s

44、erviceconditionsarevariable. Theselectionofdesigncurrentdensitiesmaybebasedonexperiencegainedfromsimilarstructuresinasimilar environmentorfromspecifictestsandmeasurements. Thecurrentdensitydependsonthekineticsofelectrochemicalreactionsandvarieswithparameterssuchasthe protectionpotential,surfacecondition,dissolvedoxygencontentinseawater,