MaureenHeratyWOOD

AnaLisaVETEREARELLANO

LorenzoVANWIJK

2013

EUR26331EN

CorrosionRelatedAccidentsinPetroleumRefineries

LessonslearnedfromaccidentsinEUandOECDcountries

European Commission Joint Research Centre Institute for the Protection and Security of the Citizen ContactinformationMaureenHeratyWOODAddress:JointResearch Centre, Via Enrico Fermi 2749, TP 720, 21027 Ispra (VA), Italy E-mail: Maureen.Wood@jrc.ec.europa.eu Tel.: +39 0332 78 9140 http://ipsc.jrc.ec.europa.eu/ http://www.jrc.ec.europa.eu/ LegalNoticeNeither the European Commission nor any person acting on behalf of the Commission is responsible for the use which might be made of this publication. Europe Direct is a service to help you find answers to your questions about the European UnionFreephone number (*): 00 800 6 7 8 9 10 11 (*)Certain mobile telephone operators do not allow access to 00 800 numbers or these calls may be billed. A great deal of additional information on the European Union is available on the Internet. It can be accessed through the Europa server http://europa.eu/. JRC84661 EUR 26331 EN ISBN 978-92-79-34652-1 (pdf)ISBN 978-92-79-34653-8 (print) ISSN 1831-9424 (online)ISNN 1018-5593 (print) doi: 10.2788/37909 Luxembourg: Publications Office of the European Union, 2013 European Union, 2013 Reproductionisauthorizedprovidedthesourceisacknowledged Printed in Italy .

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Table of contents

EXECUTIVESUMMARY.......................................................................................................................... 1

CHAPTER1 INTRODUCTIONANDBACKGROUND...........................................................................8

1.1 Background........................................................................................................................ 12

1.2 AimsoftheStudy............................................................................................................... 14

1.3 Corrosionasamajorhazardconcernforthepetroleumrefineryindustry.........................15

1.4 Descriptionofaccidentreportsourcesusedinthestudy...................................................17

1.5 Typeofeventsandconsequencesofaccidents..................................................................22

CHAPTER2 ANALYSISOFTHEPOTENTIALCONTRIBUTIONOFPROCESSANDEQUIPMENTCONDITIONS 30

2.1 Processconditionscontributingtocorrosioninstudycases..............................................31

2.2 Analysisofcasesinassociationwithspecificprocessconditions.......................................34

2.3 Corrosionriskassociatedwithchemicalrefiningprocesses...............................................39

2.4 Involvementofrefineryequipmentincorrosionrelatedaccidents...................................44

2.5 Frequencythatvariousequipmentvulnerabilitieswerecitedintheaccidentsstudied.....50

CHAPTER3 ANALYSISOFTHEPOTENTIALCONTRIBUTIONOFRISKMANAGEMENTFAILURES.....57

3.1 Inadequateawarenessoforattentiontoknowncorrosionhazards..................................58

3.2 Failuretoconductanadequatehazardidentificationorriskassessmentforlifecycleplanningandevents........................................................................................................................ 61

3.3 Inadequateriskanalysisatdesignandconstructionstage.................................................64

3.4 Inadequateriskanalysispriortoachange.........................................................................68

3.5 Inadequateriskanalysisforplanninginspections..............................................................71

3.6 Inadequateidentificationofhazardsandrisksforotherpurposes.....................................74

CHAPTER4 CONCLUSIONS........................................................................................................... 77

APPENDIX1:LISTOFACCIDENTSSTUDIED.........................................................................................80

APPENDIX2:REFERENCES.................................................................................................................. 88

TABLE OF FIGURES

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Figure1.Totalcasedistributionbycountry........................................................................................17

Figure2.Accidentsbyyearofoccurrence...........................................................................................18

Figure3.Percentageofcasesinwhichsomelessonslearnedinformationcouldbeextracted...........21

Figure4.Accidentsclassifiedbytypeofevent....................................................................................22

Figure5.Substancesreleasedinrefineryaccidentsinvolvingcorrosionbynumberofaccidents........23

Figure6.Distributionofeventtypeforeachtypeoffailure................................................................24

Figure7.Severityofaccidentconsequencespreandpost2000........................................................25

Figure8.Distributionofeventtypeforeachtypeoffailure................................................................26

Figure9.Levelofconsequencevs.typeofconsequence....................................................................27

Figure10.Processconditionscitedascontributingtocorrosiveconditionsaccidentsstudied...........31

Figure11.Processrelatedsubstancescitedascontributingtocorrosionfailures...............................36

Figure12.Processsubstancescontributingtocorrosionfailureinassociationwiththeprocessunitoforigin...................................................................................................................................................37

Figure13.Observationsonprocessconditionsrelatedtoaccidentoccurrence..................................38

Figure14.Simplifieddiagramofarefineryprocess.............................................................................39

Figure15.Unitofaccidentbyoriginofcasesstudied.........................................................................42

Figure16.Severityofconsequencesassociatedwithunitoforiginofaccidentsstudied....................43

Figure17.Accidentoriginbyequipmentcomponent..........................................................................46

Figure18.Descriptionsfromcasestudiesofcorrosionfailuresinstoragetanks................................49

Figure19.Typesofvulnerabilitiessitedforpipeworkandpipelinescontributingtocorrosionaccelerationofequipmentinvolved....................................................................................................51

Figure20.Observationsfromcasesonrelatedequipmentconditions................................................52

Figure21.Observationsfromcasesoninadequateanticorrosionprotection....................................55

Figure22.Percentageofaccidentswhereaninadequateawarenessorattentionconcerningaknowncorrosionhazardwasindicated........................................................................................................... 58

Figure23.Indicationsofamanagementfailureincasesstudied........................................................59

Figure24.Observationsfromcasesstudiedindicatingpotentialinadequateawarenessoforattentiontoknowncorrosionhazards............................................................................................................... 60

Figure25.Exampleofconsequenceeventtree...................................................................................62

Figure26.Illustrationofbarriersinfluencingaprocessincident.........................................................63

Figure27.BasicSafetyBarrierDiagram...............................................................................................63

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Figure28.Percentageofaccidentswhereriskanalysispriortodesignandconstructionwascitedaspotentiallyinadequate........................................................................................................................ 66

Figure29.Observationsfromcasesoninadequateriskassessmentpriortodesignandconstruction66

Figure30.Percentageofaccidentswhereriskanalysispriortoadesignorprocesschangewascitedaspotentiallyinadequate........................................................................................................................ 69

Figure31.Observationsfromcasesoninadequateriskassessmentpriortoachange........................70

Figure32.Percentageofaccidentswhereriskanalysisforplanninginspectionswascitedaspotentiallyinadequate..........................................................................................................................................71

Figure33.Observationsfromcasesoninspectiondeficiencies...........................................................73

Figure34.Observationsfromcasesoninadequatehazardevaluationpriortorepairwork................74

Figure35.Observationsfromcasesontheabsenceofadequatedetectionandmitigationsystems..75

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TABLE OF TABLES

Table1.TotalOilSupply....................................................................................................................... 9

Table2.NumberofOperatingRefineriesinOECDandEUMemberCountries....................................11

Table3.Typicalrefineryelementscontributingtoelevatedcorrosionrates.......................................16

Table4.Primarysourcesofaccidentreportsanalysedinthisstudy....................................................19

Table5.ConsequenceRankingCriteria...............................................................................................25

Table6.Cumulativetotalsofconsequencefiguresforallaccidents....................................................29

Table7.ExamplesofstresscorrosioncrackingdamagemechanismsproposedbyAPI571...............32

Table8.Typicalprocesssubstancesassociatedwithrefinerycorrosion..............................................35

Table9.Typicalrefineryprocesses...................................................................................................... 40

Table10.Classificationoftypeofdamagevs.systems/componentsinprocessplantsfromtheRIMAPproject................................................................................................................................................45

Table11.Factorscontributingtocorrosionandagingequipmentfailuresidentifiedinvariousstudies............................................................................................................................................................47

Table12.Corrosionandagingfailuresassociatedwithpipework.......................................................47

Table13.Factorscontributingtocorrosionandagingfailuresassociatedwithatmosphericstoragetanks...................................................................................................................................................49

Table14.Pressurevesselssubjecttopotentiallyrapiddeterioration..................................................50

Table15.Exampleofguidancefordesigningtominimizecorrosionandchallengesinmonitoringandmaintainingcorrosionvulnerableareas..............................................................................................65

Table16.ExamplesofcriteriausedtodetermineinspectionfrequencyforpressureandpipeequipmentinvariousRBImethodologies............................................................................................72

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EXECUTIVE SUMMARY

Petroleumrefiningindustrycontinuestobeofcentralimportancetotheglobaleconomy.Refinedpetroleumproductsarenotonlyaprimarysourceofenergyforhomesandbusinessesbutalsoarefundamentaltoathrivingtransportindustry.Refineryoilproductsandbyproductsoftheproductionprocesssuchasammoniaandsulphur,alsoformthebasicingredientsforavastrangeofproductssuchasplasticsandothermaterialsforconsumerandindustrialproducts,clothandindustrialfabric,paintsanddyes,pharmaceuticals,fertilizers,andnumerousothermanufacturedgoods.Thepresenceofthissectorinanycountryisconsideredtobeasignificantadvantagenotonlytothecountrybutalsotothesurroundingregion.

Petroleumrefiningisalsoahighhazardindustrywithmostsitesprocessingthousandsoftonnesofoilintovariousproductlineseachyearmanyofwhichareflammable,toxictohumanhealthortoxictotheenvironment.Atthesametimerefineriesarealsolarge,complexsiteswithmanyprocesses,severalofwhichoperateatveryhighlevelsofpressureandtemperature,andavastpipelinetotransportprocessfluidsthroughoutthesiteandeventuallytoexternalmodesoftransport.Thiscombinationoffactorsmakerefinerysitesveryvulnerabletoavarietyofcorrosionphenomenathatcaneventuallycausealossofcontainmentofprocessfluids,sometimesleadingtoaseriousaccidentaffectingworkers,theenvironment,thesurroundingeconomyandevenonoccasionthelargereconomy.

ThemajorityofEUandOECDcountriesarehosttoatleastonepetroleumrefinery,ifnotseveral,andthosecountrieswithoutrefineriesallhavepetroleumstoragedepotswhosharesomeofthesamestorageandhandlingissuesasrefineries.OECDcountriesrepresentanestimated49.2%[1]ofglobalrefiningcapacity,andalltogetherEUcountries(includingnonOECDmembers)representanapproximate18%ofglobalrefiningcapacity.[2]Ithasbeennotedbyanumberofexpertsovertheyearsthatmechanicalintegrityconsistentlyremainsacontributortomajoraccidentsinthesecountriesdespitenumerousgainsinknowledgeaboutvulnerabilitiesofrefineriesandhowtheycanbemanaged.Notably,ofthe137majorrefineryaccidentsreportedbyEUcountriestotheEUseMARSdatabasesince1984,around20%indicatedcorrosionfailureasanimportantcontributingfactor.ThisproportionofrefineryaccidentsineMARSwiththisprofilehasremainedconstantwellintothe21stcentury.

ThisreportfocusesoncorrosionrisksinrefineriesinEUandOECDcountries,lookingatlessonslearnedfrompastcorrosionrelatedaccidentsatthesesites.TheanalysiswasconductedaspartofthelongstandingcollaborationonlessonslearnedbetweentheEuropeanUnionandOECDcountriesintheOECDWorkingGrouponChemicalAccidents.Theaimofthestudywastoanalysethereportsintermsofknowncorrosionrisksassociatedwithoilrefineriesanddeterminetowhatextentafailuretorecognizeorcontrolvariousknownfactors,technicaland/ormanagerial,mayhavecontributedtotheaccident.Thestudyisaimedmanagersandinspectorsofvariousexpertisewhoarechargedwithoverseeingormonitoringaspectsofriskmanagementatrefinerysites.Fortheseprofessionals,itishopedthattheanalysismayprovidesomeinsightintospecifictypesofvulnerabilitiesandpotentialrisksthatonoccasionmaybeoverlookedandleadtoaseriousevent.

Thisstudyofcorrosionrelatedaccidentsinrefineriesisbasedon99reportsofimportantrefineryaccidentsinwhichcorrosionofanequipmentpartwasidentifiedorsuspectedasbeingthekeyfailureleadingtotheaccidentevent.Onlyreportslistedinopensourcesandproducedbyorwiththecollaborationofpartiesdirectlyinvolvedintheaccidentinvestigationwereused.Therefore,witha

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fewexceptions,onlinegovernmentdatabasesofaccidentreportswerethemainsourceofaccidentreports.Moreover,sincethestudywasconductedonrefineriesinaspecificgeographicarea,reportsthatdidnotspecifygeographiclocationoftherefinerycouldnotbeused.

Theaccidentscannotbeusedforcomputingstatisticaltrendseitherbyyearoronageographicbasis.ThevastmajorityofEUandOECDcountrieshavenotconsistentlycollecteddataorreportsonmajorchemicalaccidentsovertheperiodbythisstudyorinsomecasesthedataarenoteasilyavailable.ThereisasignificantoverrepresentationofaccidentsoccurringinJapan,FranceandtheotherEuropeancountrieswhowerepartoftheEuropeanUnionpriorto2004.However,acollectiveanalysisoftheseaccidentscanhelptoidentifyareasofongoingconcerngenerallyforrefineries.Theyalsocanprovideinsightastowhethertheprofileofcorrosionrelatedaccidentsoccurringinrefineriesafewdecadesagohasevolvedorhasstayedrelativelythesame.

Consequences of corrosion-related accidents in refineries Uncontrolledcorrosioncancausereleaseofhazardoussubstancesandcomponentsorcanreduceboththeperformanceandreliabilityofequipmentuntiltheirfailure.Assuch,corrosionhazardscanputatriskthesafetyandwellbeingofbothplantemployeesandthegeneralpublicaswellasleadtoseveredamageofprocessunits,andinsomecasesshutdownofrefineryoperations.Agoodportionoftheaccidentsstudiedappearedtobefairlyrepresentativeofthetypesofhighriskscenariosassociatedwithpetroleumrefineries.Manyoftheseeventswerenotifiedtothedatasourcesusedbythestudyonthebasisofhighimpactsintermsofeffectsonhumanhealthortheenvironmentorsignificantcosteithertotheoperatororintermsofoffsitepropertydamageordisruption.Asevidence,itisobservedthatnearly50%ofthereportsstudiedbothpreandpost2000werehighorveryhighconsequences[seeFigure7].Accidentswithlowconsequencesrepresentaboutathirdoftheaccidentsstudiedandalsotheratiooflowimpactaccidentstototalaccidentsremainedvirtuallyunchangedforpreandpost2000accidentsstudied.Manyoftheselatteraccidentscontributedimportantinsightstothestudyonconditionsthatcontinuetoplayaroleinelevationofcorrosionriskonrefinerysites.

Publicserviceinterruptionandpropertydamagewerethedominantconsequencesoverall.Takingintoaccountproductionlossaswell,55%oftheaccidentsstudiedwereprojectedtohaveaveryhigheconomicimpact.Significantenvironmentaldamagewasreportedfornearlyathirdofaccidentsandmainlyassociatedwithtoxicreleasestowater.Althoughtherehavebeennodeathsandonly17injuriesrecordedincorrosionrelatedaccidentsinrefineriessince2000,potentialforcatastrophichumanhealtheffectsfromanytypeofchemicalaccidentinarefinerycannotbediscounted.Therehavebeenseveralfatalaccidents(relatedtoothercausesthancorrosion)occurringinrefineriesintheEUandOECDinthelast10years(andeveninthelasttwo),manyoftheminplantsseveraldecadesold.Thepotentialforacorrosionfailuretocauseahumandisasterdoesnotappeartohavegreatlydiminished.

Process conditions contributing to corrosion in study cases Refineriesaremostvulnerabletocorrosionduetointernalprocessconditions.Thestudyanalysedthecasestoidentifywhattypesofsubstancesandprocessunitswereassociatedwiththeaccidents.In53casesprocessconditionswereidentifiedascontributingtothecorrosiveconditionsprecedingtheaccident.Themostcommonlycitedcontributorwasthesubstance(cited46times).Flow(eitherhigh,low,turbulentorunequal)wascitedin10cases,andtemperature(mostlyhigh,butinafewcases,low)andpressure(mostlyhigh)werecitedascontributorsin11and7casesrespectively.In8casesotherexacerbatingprocessconditionswerepresent,includingoperationoutsidedesignparametersandvariationacrossprocesscycles.

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Refineryprocessesgenerallyconsistofeitherrefiningortreatmentprocesses.Refiningprocesses,suchasdistillationandthermalcracking,breakdownandmanipulatethemoleculesinthecrudeoilfeedstocktoconvertitintomarketableproducts.Treatmentprocessesremoveimpuritiesandbyproductsfromthefeedstockandrefiningoutput.Asmuchaspossibletheseunwantedsubstancesareeitherrecycledintotherefiningortreatmentprocess(e.g.,hydrogen)orsoldasproductsintheirownright(e.g.,sulphur).

Outof99cases,thehighestpercentage(23%)startedinthedistillationunit,followedcloselybyhydrotreatmentunits(20%).Inthecasesstudiedthereweresubstantiallyfewercasesinvolvingsuchunitsafter2000comparedtoprioryears.Conversely,thenumberofcasesinvolvingthepipelinetransfernetworkisproportionallysomewhathigherafter2000.TheOthercategoryincludesunitsforsulphurrecovery,solventextraction,saturatedgas,olefinmanufacturingandoilgasification.Thestudydoesnotshowanypatternlinkingspecificunitswithaccidentconsequencesofaparticularlevelofseverity.

Involvement of refinery equipment in corrosion-related accidents Themagnitudeofapetroleumrefineryunitandthecomplexoftheprocessesissuchthatawidevarietyofequipmenttypescanbesubjecttocorrosiondependingontheprocess.Ingeneral,thepipelineinfrastructureandthepipeworkassociatedwithinaparticularunitand/orpieceofequipmentarequitevulnerable.Storagetankfailurescanalsooccurduetocorrosionandgenerallyhavehighriskprofilesduetothevolumesthattheymaycontain.Corrosioncanalsooccurinotherequipmentcomponentssuchastrays,drums,andtowers.Someequipmenttypesaremorevulnerabletocorrosion,ortocertaintypesofcorrosion,thanothersusuallyduetotheirroleintheprocess,thedesignofthepipework,orphysicallocationonthesite.Sometimesfaultyrepairsorprocessredesigncanincreasecorrosionvulnerability.Hence,equipmentdesignandmaintenancepracticesarecriticaltocontrollingrefinerycorrosion.Afewtypesofequipment,notablytheheatexchanger(anecessarycomponentofmanyprocessunits)andthestoragetank,arealsohighlycorrelatedwithelevatedcorrosionrisk.

Ofthecasesstudied,corrosionfailureoriginatedpredominantlyinpipeworks,causing71%oftheaccidentsstudied.Fiftypercentofaccidentsinvolvedtheinternalpipeworkoftheequipment.Asnotedintheprevioussection,17%oftheoriginalfailurestookplaceinthepipelineinfrastructureoftheplantfortransferbetweenunitsandtoandfromtransportmodes,and4%tookplaceintubesassociatedwithheatexchangeandcoolingunits.FIfteenpercentoftheaccidentsoccurredinstoragetanks.

Variousfactorsmakesomeequipmentcomponentsmorevulnerabletotheaccelerationofthecorrosionratethanothers.Configurationanddesignofequipmentplayaparticularroleincreatingopportunityforcorrosivedepositstoaccumulate.Functionandlocationcanalsodeterminethelevelofexposuretocorrodingagents.Integrityofcorrosionprotectionandrepairareapplicationsthatcanalterthecharacteroftheequipmentwithanimpactonitsvulnerabilitytocorrosivefactors.Moreover,inanyrefinery,therewillusuallybepointsatwhichthepipeworkfailstomeetthenecessarydesignstandardsforanumberofreasons.Thesereasonsincludeage,processchange,designchange,riskassessmenterrors,andpoorrepairandmaintenance.Thesevulnerabilitiesarecommoncausalfactorsforothertypesofmechanicalintegrityfailuresbesidescorrosion.

Thestudyhighlightedthefollowingvulnerabilitiesthatwerecitedinnumerousreports,individuallyorincombinationwithotherfactors,ascontributingtoanaccidentevent.

Materialcompositionofthecomponent

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Configuration Function Location Adequacyofanticorrosionprotection WeldedpartsThestudyrevealedthatinninecases,theinadequacyofthematerialcompositionindesignorrepairofthepipecomponentwasconsideredacontributorfactortothecorrosionfailure.Sixcasesindicatedthatinfrequentusemayhaveresultedinareductioninthefrequencyofmonitoringandmaintenanceofanequipmentcomponent.Overallfailureoftheanticorrosionprotectionwascitedin16oftheaccidentsstudied.Corrosionfailurewasattributedtopotentialweldingerrorinnineofthecasesstudied.Onlyfourcasesmentionedtheageoftheequipmentasacontributingfactor,althoughinseveralreportstherewerealsoreferencestotheadvancedageoftheequipmentinvolvedintheaccidentwithoutindicatingitasacausalelement.

Inparticular,configurationofthepipeworkplaysastrongroleinthecorrosionprocess.Somedesignfeaturescreateweakpointsinthesystemthatareparticularlyvulnerablepotentialstresses,includingcorrosion.Theelbowjointisthemostcommongeometricconfigurationinvolvedinacorrosionrelatedfailureinthestudy,notedin18%ofallcasesastheoriginalsiteofcorrosion.Elbowjointshavepracticalandengineeringadvantagesbuttheyalsoarevulnerabletocertaintypesofstresses,particularlyerosion/corrosion,lowofunevenflow,vibration,andexternalpressurefromnaturalforcessuchaswindandfloods.Aslightlyhigherproportionofthepre2000casescitedanelbowjointastheoriginofthecorrosionfailure.

Intotal8differentcasesreferredtovalvesorbranchedpipingastheoriginallocationofthecorrosionfailure.Valves,nozzlesandbranchedpipeworkallrepresentpipeintersectionsthatarejoinedtothesystembyvariousmechanisms,includingwelding.Whiletheconstructionanddesignofthesecomponentsvariesconsiderably,itcangenerallybesaidthattheprocessofmakinganintersectioncreatesaweakpointinthepipesystem.

Asidefromprocesslocation,otherlocationfactorsalsomayaffectcorrosionvulnerability.Inthisstudytwoadditionallocationissueswerehighlightedin13separatecases:exposuretotheexternalenvironmentandaccessibility.Inonecaseasectionofequipmentpipeworkwaspoorlyaccessibleforroutineinspection.Sevencasesconcernedpipesthatwereonthegroundorunderground,4ofwhichwereconsideredalsofairlyinaccessibleforroutineinspection.Pipelinestandardsgenerallyrecommendthatburiedandsubmergedmetallicequipmentshouldhaveadequateprotectivecoating.Fivecasesconcernedpipessubmergedinwater.

Potential contribution of risk management failures Everyrefineryisexpectedtohaveanappropriateriskmanagementstrategytominimizetheriskswithadequatelayersofprotectionsupportedbyaneffectivesafetymanagementsystem.Fromthereports,therewasanindicationthatafailureinriskmanagementwasacontributingcausetothevastmajorityofaccidentsstudied.

Duetothevariationinreportingdetailandstyle,itwasnotpossibletoanalysetheriskmanagementfailuresassociatedwiththeseaccidentsinasystematicway.Nonetheless,thestudywasabletosummarizepotentialriskmanagementfailuresintermsoffivegeneraldeficiencies:

Inadequateawarenessorattentiontoknowncorrosionhazards

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Inadequateriskanalysisatdesignandconstructionstage

Inadequateriskanalysispriortochange,whichisessentiallyalackoforfailureinthemanagementofchangeprocess

Failuretoidentifyoraddressprocessrisksinplanninginspections

Inadequateidentificationofhazardsandrisksforotherpurposes,suchassafeperformanceofrepairsandestablishmentofdetectionandmitigationsystems

Accordingtothestudy,aninadequateawarenessorattentionofmanagementtoknowncorrosionhazardscouldwasimpliedasacontributingfactorin23%ofthecasesstudied.Thisincidencewasflaggedincaseswhereoneormoreofthefollowingconditionsappearedtoexistaccordingtotheobservationsfoundintheaccidentreport:

Generallackofmanagementattentiontocorrosionissues

Lackofawarenessintheprocessunitofpotentiallyunsafeconditionsandpotentialaccidenttriggers

Inadequatecorrosionmonitoringandfeedbackmechanismsforknownareasofelevatedcorrosionrisk.

Theremainingfourcategoriesofriskmanagementfailureidentifiedinthestudycanbetracedtoafailureassociatedwithhazardidentificationorriskassessmentatanimportantstageinthelifeoftheequipment.Mostmajoraccidentsimplyatleastapartialfailureintheidentificationandriskassessmentofamajorhazardresultinginaninadequateevaluationofthehazardandassociatedrisk.Forcorrosionhazards,riskisnormallyexpressedastheproductoftheprobabilityofacorrosionrelatedfailureandtheconsequencesofsuchafailure.Theoutcomeoftheassessmenthasimplicationsfordownstreamdecisionsassociatedwithdesign,operationandmaintenanceoftheprocess.

Itcouldbededucedfromnumerousaccidentreportsstudiedinthisanalysisthataninadequateriskassessmentoftheprocessatacriticaloperationalphasewasacontributingcauseoftheaccident.Usuallytheriskassessmentwasinadequateforanumberofreasons,including:

Thehazardwasnotidentifiedandariskassessmentforthathazardwasneverperformedatacriticalpointinthesafetylifecycle

Criticalinformationaboutthehazardandpotentialriskwasavailablebutomittedfromtheriskassessment.

Criticalinformationaboutthehazardandpotentialwasnotfullyavailablefortheriskassessment

Thisstudyfoundthattheseinadequaciesintofourdifferentcategoriesaccordingtotheiroccurrenceinthesafetymanagementprocess,asfollows:

Inadequateriskanalysisatdesignandconstructionstage

Inadequateriskanalysispriortochange,whichisessentiallyalackoforfailureinthemanagementofchangeprocess

Failuretoidentifyoraddressprocessrisksinplanninginspections

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Inadequateidentificationofhazardsandrisksforotherpurposes,suchassafeperformanceofrepairsandestablishmentofdetectionandmitigationsystems

Accordingtothestudy,theriskassessmentpriortooriginaldesignoralaterequipmentdesignchangewasnotadequateoverathirdofallaccidents.Someofthereportswerenotentirelyclearastowhetheradesignerrorwastheresultofadecisionintheoriginaldesignoftheprocessorwaspartofachangetoprocessequipmentatalaterstage.Asapracticalmatter,thestudyassumedthat,ifchangewasnotmentioned,theerrorwaspartoftheoriginaldesign;however,thischoicecouldnotbefullyverified.

Changesandmodificationstoprocessesandprocessequipmentareanaturalpartofarefineryplantlifecycle.Acoreelementofanysafetymanagementsystemisaproperlyfunctioningmanagementofchangeprocess.The1974Flixboroughexplosionisperhapsthemostwellknowncatastropheassociatedwithafailureinthemanagementofchangeprocess.Eightoutof60accidentsinvestigatedbytheU.S.ChemicalSafetyBoardbetween1998and2012alsowereassociatedwithfailuretomanageaprocessorequipmentchange.Inthisstudy10%ofaccidentswerecitedaspotentiallyresultingfromafailureinthemanagementofchangeprocess.

Theestimatedcorrosionriskassociatedwithaprocessorpieceofequipmentshouldbealeadingfactorinschedulingroutineinspectionsofequipmentintegrity.Amoredetailedriskassessmentmayalsobewarrantedtoidentifyspecificdegradationthreats,theremaininglifeoftheequipmentandtofeedbackinformationintotheoverallriskassessmentandcontrolsystem.Theinitialcorrosionriskassessmentshouldidentifyalsopointsinthelifecyclewhenthecorrosionriskassessmentshouldbeupgraded.Accordingtothereportsstudied,athirdoftheaccidentsmighthavebeenavoidedwithappropriateplanningofinspectionsonthebasisofknownriskcriteria.

Severalreportsalsohighlightedothersituationswhereariskanalysismighthavebeenusedtoavoidapotentialaccident.Insixcasesitwasreportedthatadequateassessmentofconditionswasnotconductedpriortorepairwork.Ingeneralthistypeoffailureisprimarilyassociatedwithneglectingtofollowgoodpracticeforperforminghotwork.

Insevencasestherewereobservationsintheassociatedreport(s)concerningdetectionandmitigationmechanismsthatcouldhavepreventedareleasefrombecomingaseriousaccidentiftheyhadbeeninplace.Aneffectiveriskmanagementapproachreliesonassigningappropriatetechnicalmeasurestoreduceandeliminatetherisks.Theseverityofconsequencesassociatedwithsomecases,forexample,anaccidentoccurringduringaloadingoperationinwhich478tonnesoffuelwerespilled,suggestedthat,inadditiontomeasurestopreventlossofcontainmentprevention,secondorderprotection,suchassensors,alarms,automaticshutoffcontrolsand/orotherpossiblemeasures,couldhavesignificantlyreducedtheimpactoftheevent.

Conclusions Corrosioncontrolremainsaparticularlychallengingphenomenonintheefforttoreducerefineryaccidentrisks,furtherelevatedinmanyEUandOECDcountriesbytheaginginfrastructureandvariationincrudeoilsupplyandmarketconditions.Thestudyidentified40accidentsoccurringsince2000,manyofthemserious,indicatingthatmajoraccidentsatrefineriesinvolvingcorrosionfailurecontinuebeaparticularcauseofconcerninthe21stcentury.

Generally,significantcorrosionfailuresoccureitherbecausethehazardwasnotproperlyidentifiedorthehazardwassubstantiallyignored.Itappearedfromthestudiesthatexpertssometimesoverlookedhowthevariouselementsofaprocesscouldcombinetocreatetheconditionsforacceleratedcorrosion.Thereisalsoaquestionabouthowmuchexperiencespecificallyinmechanicalintegritydisciplinesisavailableatsomerefineriestodiagnosetheseproperly.However,there

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appearedtobeanumberofcasesstudiedinwhichthecorrosionriskwasquiteobvious,andyetthemanagementchosetoignoreorunderestimateit.

Thestudyseemstoindicatethatoneofthemostimportantchallengesinmanagingrefinerycorrosionisalsotheelementofchange.Alreadychangestoprocessdesignandequipmentposeachallengeandneedacertaincompetencytoidentifyifanewcorrosionriskhasbeenintroduced.However,otherchangesthatcanaffectcorrosionratesmaygounrecognizedandthusnotbeevaluatedforanelevatedrisk.Inconspicuouschanges,suchaslossofexperiencedpersonnel,lackofknowledgeoftheoriginalprocessandequipmentdesign,andagingequipment,canalsocreateriskandinthisregard,therefinerysgreatestriskmaybechangeovertime.

Neglectingtoidentifyormanagecorrosionhazardsalsocontinuestobeaproblemonsomerefinerysites.Someaccidentreportsarequiteclearthatthelessonlearnedwaslessaboutthetechnicalchallengeofmanagingcorrosionbutsimplyabouthavinganeffectiveriskmanagementprogram.Theworkofinspectionauthoritiesismostcertainlychallenginginthesesituations.

Inessencethisstudyprovidessomeevidencetoconfirmconcernsamongexpertsinbothgovernmentandindustrythattheriskofcorrosionfailurescausingmajoraccidentsremainsastrongareaofconcern.Inillustratingthekindsofdecisionsthatmayhaveledtocertainaccident,ortheseverityoftheirconsequences,itishopedthatinspectorsandrefineryengineerswhoarelookingtoimprovetheirawarenessofcorrosionriskswillhavegainedsomeknowledgethatwillhelpthemintheirwork.Inaddition,itispossiblethatthefindingscanalsohelpkeyleadersingovernmentandindustrypointoutthatcorrosionremainsasignificantrefineryhazarddeservingseriousandsustainedmanagementattention.

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CHAPTER 1 INTRODUCTION AND BACKGROUND

Petroleumrefineriesaregenerallyacknowledgedtobehighhazardsitesduetothenatureofpetroleumproductsandtheprocessingtechnologiesthatproducetheminthecurrentera.Forthemostpart,however,therisksarewellknownandrefineryoperatorshaveappliedconsiderableknowledgeandresourcesoverthepastdecadestocontrolandminimizeriskpotential.Nonetheless,majoraccidentsinrefineriestendtoregularlyoccurwithimpactsnotonlyonhumanhealthandtheenvironment,butalsoinmanycasesonsocialandeconomicwellbeing.Arecurringcauseofaccidentsinpetroleumrefineriesiswellknowntobecorrosion.ThisreportstudiescorrosionrelatedaccidentsinrefinerieswithintheEuropeanUnion(EU)andtheOrganizationforEconomicCooperationandDevelopment(OECD),comparingaccidentoccurringbeforeandafter2000andwiththeviewtoprovidinginsightsintorecentcausaltrendsandidentifyinglessonslearnedthatcouldinfluencepreventionstrategiesinfuture.

ThisreportwasdevelopedonbehalfoftheEUCommitteeofCompetentAuthoritiesfortheSevesoDirective(CCASeveso)1andOECDsWorkingGroupofChemicalAccidents(WGCA)whichmanagestheOECDProgrammeonChemicalAccidentsandconsistsofrepresentativesofOECDmembercountriesaswellasexpertsfromobservercountries,internationalorganizations,industry,labour,andenvironmentalorganizations.TheEuropeanCommissionisrepresentedontheWGCAbyDGENVandtheJointResearchCentresMajorAccidentHazardsBureau(MAHB).Inaddition,OECDmemberscontributeaccidentreportsonavoluntarybasistotheeMARSdatabaseofchemicalaccidentsmanagedbyMAHB.AlistofOECDMemberCountries,indicatingthosethatarealsoEUMembers,isprovidedinTable2onpage12.

ThemajorityofEUandOECDcountriesarehosttoatleastonepetroleumrefinery,ifnotseveral,andthosecountrieswithoutrefineriesallhavepetroleumstoragedepotswhosharesomeofthesamestorageandhandlingissuesasrefineries.OECDcountriesrepresentanestimated49.2%Error!Referencesourcenotfound.ofglobalrefiningcapacity,andalltogetherEUcountries(includingnonOECDmembers)representanapproximate18%ofglobalrefiningcapacity.[2]Studiesaboutcausesassociatedwithrefineryproductionandstorageremainhighlyrelevant.Moreover,itcanbeassumedthatmostorallrefineriesinEU/OECDcountriesstrivetofollowcommoninternationalstandardsofgoodpracticeformanagingrefineryrisks.

1Directive2012/18/EUoftheEuropeanParliamentandoftheCouncilof4July2012onthecontrolofmajoraccidenthazardsinvolvingdangeroussubstances.AllEUMemberStatesareobligedtoimplementtheSevesoDirectiveintheirnationallegislation.

9

TABLE1.TOTALOILSUPPLY(THOUSANDBARRELSPERDAY)[1]

2008 2009 2010 2011 2012

EU-27 2647.227 2542.01 2413.188 2162.712 1992.969 Austria 27.35455 28.19153 28.71441 30.39195 29.48281 Belgium 8.5207 12.60347 12.70007 10.53035 10.53035 Bulgaria 3.51701 3.3409 3.58363 3.38363 3.38363 Cyprus 0.2 0.2 0.1 0.1 0.00847 Czech Republic 10.90856 10.38968 10.28301 13.01232 10.00915 Denmark 290.3941 264.3081 249.4648 226.2842 207.3841 Estonia 7.6 9 10 11 11 Finland 8.53291 9.54122 15.30335 14.2309 13.5309 Former Czechoslovakia -- -- -- -- -- France 73.07799 76.31161 76.5425 75.88213 72.30336 Germany 124.8994 133.0608 125.0016 141.0002 144.5077 Germany (Offshore) 20.81967 23.72877 20.88219 24.08767 25 Germany, East -- -- -- -- -- Germany, West -- -- -- -- -- Greece 6.00839 6.41675 8.47986 7.57805 7.49677 Hungary 36.9994 35.36659 34.45847 27.64039 27.9886 Ireland -0.45946 -0.2957 1.07504 0.72561 0.72561 Italy 160.7857 145.5256 156.1428 152.7214 154.5105 Latvia 0.9 1.2 1.1 1 1 Lithuania 10.04207 9.45376 9.71077 9.11077 9.11077 Luxembourg 0 0 0 0 0 Malta 0.02 0.02 0 0 0 Netherlands 31.47712 37.83117 34.84203 40.98095 54.7248 Netherlands (Offshore) 34.07377 25.56438 20.30137 17.5863 16.99727 Poland 35.27595 34.24601 28.65921 28.33946 27.68447 Portugal 6.96014 5.41664 5.57404 5.17594 5.24991 Romania 116.9844 112.6989 107.1448 105.3409 101.6478 Slovakia 10.30085 7.53781 7.68135 9.85793 9.27711 Slovenia 0.165 0.145 0.405 0.305 0.305 Spain 25.3903 29.48995 28.75125 28.45621 29.29182 Sweden 8.4702 11.19146 10.41947 11.26664 11.26664 United Kingdom 85.14396 87.38141 87.13009 82.65457 86.17039 United Kingdom (Offshore) 1502.864 1422.145 1318.737 1084.068 922.3808 OECD 20968.22 21160.93 21505.25 21623.91 22571.73 Australia 587.717 592.4863 604.1056 530.5067 519.065 Austria 27.35455 28.19153 28.71441 30.39195 29.48281 Belgium 8.5207 12.60347 12.70007 10.53035 10.53035 Canada 3343.577 3318.829 3441.73 3597.333 3868.956 Chile 12.12632 12.97693 18.42176 18.36149 17.33709

10

2008 2009 2010 2011 2012

Czech Republic 10.90856 10.38968 10.28301 13.01232 10.00915 Denmark 290.3941 264.3081 249.4648 226.2842 207.3841 Estonia 7.6 9 10 11 11 Finland 8.53291 9.54122 15.30335 14.2309 13.5309 Former Czechoslovakia -- -- -- -- -- France 73.07799 76.31161 76.5425 75.88213 72.30336 Germany 124.8994 133.0608 125.0016 141.0002 144.5077 Germany (Offshore) 20.81967 23.72877 20.88219 24.08767 25 Germany, East -- -- -- -- -- Germany, West -- -- -- -- -- Greece 6.00839 6.41675 8.47986 7.57805 7.49677 Guam 0 0 0 0 0 Hawaiian Trade Zone -- -- -- -- -- Hungary 36.9994 35.36659 34.45847 27.64039 27.9886 Iceland 0 0 0 0 0 Ireland -0.45946 -0.2957 1.07504 0.72561 0.72561 Israel 4.023 5.98119 5.839 5.839 5.839 Italy 160.7857 145.5256 156.1428 152.7214 154.5105 Japan 125.2716 137.6242 142.4722 136.257 135.5125 Korea, South 33.6573 54.65003 58.47474 59.78946 61.04358 Luxembourg 0 0 0 0 0 Mexico 3184.164 3000.791 2978.599 2959.989 2936.009 Netherlands 31.47712 37.83117 34.84203 40.98095 54.7248 Netherlands (Offshore) 34.07377 25.56438 20.30137 17.5863 16.99727 New Zealand 65.27087 61.02682 60.77085 52.17398 48.19111 Norway 2463.917 2352.555 2134.621 2007.35 1902.084 Poland 35.27595 34.24601 28.65921 28.33946 27.68447 Portugal 6.96014 5.41664 5.57404 5.17594 5.24991 Puerto Rico 0.66277 0.53813 0 0.8536 0.6737 Slovakia 10.30085 7.53781 7.68135 9.85793 9.27711 Slovenia 0.165 0.145 0.405 0.305 0.305 Spain 25.3903 29.48995 28.75125 28.45621 29.29182 Sweden 8.4702 11.19146 10.41947 11.26664 11.26664 Switzerland 3.65681 3.87793 3.60576 3.61281 3.61281 Turkey 47.73348 54.59644 57.75023 57.63345 56.65329 U.S. Territories NA NA NA NA NA United Kingdom 85.14396 87.38141 87.13009 82.65457 86.17039 United Kingdom (Offshore) 1502.864 1422.145 1318.737 1084.068 922.3808 United States 8564.232 9133.129 9692.433 10135.55 11124.05 Virgin Islands, U.S. 16.64497 16.76659 14.88036 14.88036 14.88036

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OECDMembersOnly OECDandEUMembers

Australia 7 Austria 1

Canada 18 Belgium 4

Israel 2 CzechRepublic 3

Japan 30 Denmark 2

Korea 6 Estonia 0

Mexico 6 Finland 2

Switzerland 2 France 12

UnitedStates 144 Germany 13

Norway* 2 Greece 4

Turkey 6 Ireland 1

Italy 16

EUMembersOnly Luxembourg 0

Bulgaria 1 Netherlands 7

Cyprus 0 Poland 2

Latvia 0 Portugal 2

Lithuania 1 SlovakRepublic 1

Malta 0 Slovenia 0

Romania 6 Spain 9

Sweden 5

UnitedKingdom 11

TotalEU&OECD 317

*EuropeanEconomicArea(EEA)Member

EUCandidateCountry

.

TABLE2.NUMBEROFOPERATINGREFINERIESINOECDANDEUMEMBERCOUNTRIES[3][4][5]

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1.1 Background

Chemical,refineryandpetrochemicalindustriesarecomplexlargeestablishmentsthatbynatureoftheiroperationsaresubjecttoanumberofhighriskfactors,amongthemthemaintenanceofthemechanicalintegrityofprocessandstorageequipment.Ithasbeennotedbyanumberofexpertsovertheyearsthatmechanicalintegrityconsistentlyremainsacontributortomajoraccidentsdespitenumerousgainsinknowledgeaboutvulnerabilitiesofrefineriesandhowtheycanbemanaged.Theseconcernshavebeendrivenbyrecentaccidents,observationsfromthefieldbynumerousgovernmentsafetyinspectors,andageneralawarenessofchangingconditionsinrefineriespotentiallyaffectingmechanicalintegritysuchasplantaging,thechemicalandphysicalpropertiesofcrudefeedstocksincurrentsupply,andothereconomicandmarketfactors.

Toillustrate,ofthe137majorrefineryaccidentsreportedbyEUcountriestotheEMARSdatabase2since1984,around20%indicatedcorrosionfailureasanimportantcontributingfactor.ThisproportionofrefineryaccidentsineMARSwiththisprofilehasremainedconstantwellintothe21stcentury.Consideringgainsinknowledgeinregardtobothcontroltechnologiesandriskmanagementoverthepast30years,theunchanginginfluenceofcorrosiononrefineryaccidentratesintheEUcouldbeconsideredasevidencethattheseexpertsconcernsarenotmisplaced.

Uncontrolledcorrosioncancausereleaseofhazardoussubstancesandcomponentsorcanreduceboththeperformanceandreliabilityofequipmentuntiltheirfailure.Corrosionhazardscanputatriskthesafetyandwellbeingofplantofbothplantemployeesandthegeneralpublicaswellasleadtoseveredamageofprocessunits,andinsomecasesshutdownofrefineryoperations.Thehumanimpact,fromdeath,injury,trauma,incomeorpropertylossresultingfromanaccidentcanbeparticularlydevastating.Thoughlessfrequent,theenvironmentalimpactswhentheyoccurtendtobesevereinanindustrywherehighvolumeproductionisthenorm.

Inparticular,theeconomicimpactofcorrosionphenomenaanditsconsequencesonrefineriesissignificant,takingintoaccountmaintenanceandrepaircostsandproductionlossfromplannedandunplannedshutdowns.Assuch,indirectconsequencesassociatedwithshortandlongtermsocialandeconomicdisturbances(e.g.,infrastructureoutages,jobloss,fuelpriceincreases)fromarefineryaccidentmaybeparticularlysevere.

Ofallpotentialimpacts,thefinancialimpactofcorrosionismostconsistentlyandalarminglyhigh.Corrosioninrefineriesalsocansignificantlydecreasethefinancialefficiencyofthedifferentrefineryprocessessincefailureofequipmentduetocorrosioncanresultinashutdownofallorpartofthefacility.AccordingtoRuschauetal.,yearlycostsrelatedtocorrosionintheoilindustryhavebeenestimatedintherangeof$3.7billionperyearintheU.S.Thisstudyalsoestimatedthattotalpropertydamagelossesfrommajorrefineryaccidentsbetween1972and2001equatedtoaround$5billion(January2002dollars).Arefineryoperationmayhaveinexcessof3,000processingvesselsofvarying

2TheMajorAccidentReportingSystem(MARSandlaterrenamedeMARS)wasfirstestablishedbytheEUsSevesoDirective82/501/EECin1982andhasremainedinplacewithsubsequentrevisionstotheSevesoDirectiveineffecttoday.ReportinganeventintoeMARSiscompulsoryforEUMemberStateswhenaSevesoestablishmentisinvolvedandtheeventmeetsthecriteriaofamajoraccidentasdefinedbyAnnexVIoftheSevesoIIIDirective(2012/18/EU).FornonEUOECDandUNECEcountriesreportingaccidentstotheeMARSdatabaseisvoluntary.

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size,shape,form,andfunction.Inaddition,atypicalrefineryhasabout3,200km(2,000mi)ofpipeline,muchofwhichisinaccessible.Someofthesepipelinesarehorizontal;somearevertical;someareupto61m(200ft)high;andsomeareburiedundercement,soil,mud,andwater.Thediametersrangefrom10cm(4in)upto76cm(30in).[6]

SomecommongeneralconditionsassociatedwithrefineriesinEUandOECDcountriestodayarebelievedtobeleadingtoanelevationincorrosionrisks,notablyaging,changesintheoverallrefineryinfrastructure,andthequalityofcrudeoilavailableinthemarketplace.Forexample,in2003MarshPropertyRiskConsultingindicatedthatlossesintherefineryindustrywerecontinuingtoincreasemostnotablyduetoagingfacilitiesinthiscategory.[7]AgingwascitedasoneofthemostimportantfactorscreatingthepotentialforthedisasterthatoccurredattheBPTexasCityrefineryintheU.S.in2005.Recently,aspateofguidanceandexpertrecommendationshavebeenproducedbymajoroilrefiningcountries,notablytheUnitedKingdomandFrance,onmanagingagingplantsandrefineries.ThemajorityofrefineriesinOECDandEUcountriesareover20yearsold.

Demandandsupplytrendsintheoilindustryinthesecountriesalsohavegivenrisetoaconcernregardingimpactsofreducedprofitmarginsonplantmaintenanceandnewinfrastructureinvestment.Refineryprofitabilityisparticularlyvulnerabletomarketfluctuationbecausetheoperatorhaslittleinfluenceoverthepricingofbothinput(crudeoilfeedstock)andoutputwhicharedrivenbyworldwide,andtosomeextentalsoregional,markets.In2009profitmarginsforEUrefinerieswerereportedasthelowestobservedinfifteenyears.[2]

Thefallinprofitabilityhascausedseveralrefineriestoclose,acircumstancethatincreasesdemandonremainingrefineries,someofwhichmaybeoperatingnearcapacitylimits.Notably,theEU,theUSandJapanhaveexperiencedclosuresofmajoroilrefineriessince2008andmoreclosuresarepredictedinfuture.[8]Intheseregions,therefiningindustryhasmaintainedcapacitydemandslargelybyexpandingexistingfacilitycapacity,oftenbyincreasingthecapacityofindividualprocesses,particularlythecrudedistillationprocess,andstorageunitsandtankstomanagegreatervolumes.[1]Nonetheless,olderprocessunitsremaininuseoftenoperatingatanincreasedrateofproductionthaninpastyears.

AtthesametimeintheEUregioninparticular,marketconditionshaveincreaseddependenceoncrudeoilfeedstocksthatareheavierandmoresulphurous,requiringmoreintenseprocessingwiththeaccompanyinghighercorrosionriskassociatedwithhigherproportionsofnapthenicacids.InEuropeNorthSeacrudeproduction(fromNorway,UK,Denmark)fellfrom6.4to4.3millionbarrelsperdaybetween2000and2008.Overthesameperiod,thesuppliestoEuropeofheavier,sourer/moresulphurous,crudesfromRussiaandAfricahavebeengrowing.TheresulthasbeenanincreaseintheproportionofheavyandsulphurouscrudespurchasedbyEUrefineriesandresultingheavierprocessingdemands.[2]3[2]

AsnotedbyYeung,crudeselectionisthemostimportantdecisionrefinersmustmakeonadailybasis.Thecompositionofcrudevarieswiththesourceandcansignificantlyimpactonthecorrosionresistanceofrefineryequipment,andparticularlyinrefineriesthatweredesignedwithheavycrudesinmind.Theoperatorhastoevaluatemarketcostssuchasoilsourcereliabilityandtermdeals,deliveryadvantages,discountversusothercrudes,andproductdemandmixagainstthepotentialimpactonoperationalcostsrelatedtoplantoperationalflexibility,potentialprocessingproblemsand

3Thecorrosionriskisnotnecessarilylessenedinproductionofbiofuelsandsyntheticgaseswherevariousconditionscanpresentpotentiallydifferentbutequallyseriouscorrosionrisks(e.g.,theuseofchloriderichbiomassforbiofuelproduction).[9]

14

risks,mitigationoptionsandcosts,andenvironmentalconcerns.[9]Heavycrudecanthereforebringchangesinotherindirecteconomicforces,suchasprofitmargins,maintenancepractices(e.g.,outsourcing),theavailability/relianceoninhouseexpertiseforcorrosionengineeringandtheincreasinglossofhistoricalknowledgeregardingthedesignandoperationalhistoryofolderequipment.[10]4

AllthesefactorshaveraisedconcernsabouttheriskofaseriousaccidentduetotheelevatedpresenceofcorrosionriskinrefinerysitesinEUandOECDcountries.Aseriousrefineryaccidentcanhavegraveimpactsonproductionalonewhichthreatenstheeconomicviabilityoftherefineryitself.Moreover,numerouspastaccidentshavedemonstratedthepotentialforrefineryaccidentstocauseinjuryanddeathtoworkersonthesite,environmentaldamagetonaturalresourcescovering,onoccasion,vastgeographicregions,threatenthehealthandsafetyofthecommunity,andsignificantlydisruptitsqualityoflifefordaysorweeksatatime.Thisstudyofcorrosionrelatedaccidentsinrefineriesexploreslessonslearnedfrompastaccidentsisintendedtoprovideinsightsthatmayassistoperatorsandtheenforcementcommunityinevaluatingvulnerabilityofrefineriestocorrosionrelatedrisksinfuture.

1.2 Aims of the Study

Overthepastfewdecades,avastamountofscientificliteraturehasbeengeneratedonthesubjectofcorrosioninprocessingandstorageactivitiesassociatedwithindustrialactivity,asignificantportionofwhichisdevotedtocorrosionspecificallyintheenergysector.Fromthesepublications,itisevidentthatcorrosionsubdividesintoanumberofsubcategoriesofcorrosionphenomenawithvariedandcomplexprofilesdependentonproductandequipmentcompositionandinteractionsaswellassomefactorsindependentofoperationalactivity(e.g.,location,atmosphericconditions).Thecorrosionpotentialinpetroleumrefineriesismadeinfinitelymorevariedandcomplexduetotheadditionalsize,variationandcomplexityofactivityinmostrefineries.ForthisreasonthereisaconcernthatcorrosioncontrolinEUandOECDrefineriesmaybeinconsistentlyeffectiveacrosstheindustryandgeographiclocationsincurrenttimes.

Asmallbutsignificantportionofcorrosionliteraturehasbeenaimedatsummarizingtheresearch,lessonslearnedandtrendstofacilitatepracticalapplicationofcorrosioncontrolmeasuresinawidevarietyofindustrialsectorsandeconomiccircumstances.Notably,variousindustryassociationsassociatedwiththeenergysectorhavemadesubstantialcontributionstothetheoreticalframeworkandgoodpracticerecommendationsavailableforcorrosioncontrolinrefineries.Moreover,alarmedbyrecentaccidentsinolderrefineries,anumberofEUandOECDnationalgovernmentauthoritieshaveinvestedeffortoverthelastseveralyears,conductingsubstantialscientificresearch,fieldstudiesandaccidentanalyses,inordertoassesstheextentandseverityoftheagingphenomenainrefineriesandhowtocontrolitsassociatedriskssuchascorrosion.

4TheU.S.isanothersignificantOECDrefiningcountrythathasexperienceadowngradeinthequalityofcrudeoilsupplyoverthelasttwodecades,withanassociatedimpactontheintegrityofitsrefininginfrastructure.However,infuturetheU.Smayeventuallybenefitfromgreateravailabilityoflighter,lowersulphurfeedstocksasaproportionofitstotallysupplywiththeexploitationofshaleoilreservoirs.

15

ThisreportcitesparticularpublicationsproducedbytheAmericanPetroleumInstitute(API),theInstituteofChemicalEngineers(IChemE),theInstituteofEnergy(IE),theUnitedKingdomHealthandSafetyExecutive(UKHSE),theFrenchNationalInstituteofEnvironmentandIndustrialRisk(INERIS),theU.S.DepartmentofEnergy,theU.S.DepartmentofTransportation,theU.S.OccupationalSafetyandHealthAdministrationandNACEinternational.Whiletherearenodoubtothervalidpublicationsthatthisreportignores,thesereportswereconsideredtobesufficientlyexhaustiveandrecenttorepresentthestateofthearttheoryandpracticeinEUandOECDcountries.Moreover,language,accessibilityandprominenceofthesereportsasreferencesforrefineryoperatorsplayedaroleindefiningthescientificreferencesforthisstudy.

Theseworksaddconsiderablevalueascataloguesofcorrosionandcorrosioninducingphenomenaandbyprovidinganincreasinglyrobustarsenalofeffectivecontrolstrategiesastimegoeson.However,thedauntingtaskofprioritizingandprocessingthisinformationtominimizerisknecessarilyremainswiththerefineryoperator.Likewise,enforcementagenciesmustsiftthroughthiswealthinformationandwithrelativelylittletimeorotherresources,trytofindaneffectivefocusandapproachthatcangivemeaningfuloversightandassistancetotheoperatorsownefforts.

Withthisinmind,theauthorsofthisstudyaimedtoprovideinsightonthecollectiveknowledgebasefromanotherperspective,thatis,usingaccidentdatarelatedtooneparticular,corrosioninrefineries,tohelpoperatorsandinspectorstorefreshtheirknowledgeandperhapsalsofocustheirattentiononparticularaspectsassociatedwiththisphenomenon.Usingreportsfromanumberofopensourcesoverthelastfewdecades,theauthorsaimedtoidentifyrepeatedpatternsinaccidentoccurrencesbothintermsofspecificcausalfactorsandfailuresincontrolstrategies.

Theintentionisnotsimplytoreemphasizethesignificanceofsomeknownchallenges,forexample,corrosionunderinsulationorthelackofsufficientprotectivecoating,butalsotoidentifypotentialfailuresandopportunitiesregardingstrategicapproachestocorrosioncontrolthatmayberelevantforfutureplanningofcontrolstrategies.Moreover,theanalysisalsocomparesfindingsbetweenaccidentspreandpost2000toidentifywhethercertaincausalandcontrolfailuresmayhavebecomemoreorlessrelevantinrecenttimes.Itishopedthatthisinformationisofparticularassistancetoinspectorsbyprovidingaconcisesummaryofrefinerycorrosionhazardsandexamplesofhowtheyhavebeenmanifestedinpastaccidents.Thefindingsmaybealsousefultooperatorsinrenewingaspectsoftheirriskmanagementstrategyortrainingpersonnelonhowtorecognizeandevaluatepotentialcorrosionrisks.

1.3 Corrosion as a major hazard concern for the petroleum refinery industry

Corrosiondoesnotstandforasinglephenomenonbutisageneralizedtermtocoveradestructiveattackonametalasaresultofeitherachemicalorelectrochemicalreactionbetweenthemetalandvariouselementspresentintheenvironment.Forinstance,ironisconvertedintovariousoxidesorhydroxideswhenreactingwiththeoxygenpresentinair/water,whenincontactwithamorenoblemetalsuchastinorwhenexposedtocertainbacteria.Theinternationalstandarddefinescorrosionmorespecificallyasaphysicochemicalinteractionbetweenametalanditsenvironmentwhichresultsinchangesofthepropertiesofthemetalandwhichmayoftenleadtoimpairmentofthefunctionofthemetal,theenvironment,orthetechnicalsystemofwhichtheseformapart.[11]Accordingtootherauthors,corrosionderivesfromthenaturaltendencyofmaterialstoreturnto

16

theirmostthermodynamicallystablestate.[12]Table3belowidentifiesfourbroadcategoriesofrefineryelementsthatcancontributetocorrosionrisk.

Corrosionofametaloccurseitherbytheactionofspecificsubstancesorbytheconjointactionofspecificsubstancesandmechanicalstresses.Dependinguponenvironmentalconditions,corrosioncanoccurinvariousformssuchasstresscorrosion,pittingcorrosion,embrittlementandcracking.Theparticulartypeofcorrosionoccurringinaspecificcomponentcanoftenbedifficulttoclassify.Forexample,severalformsofcorrosion(e.g.,galvaniccorrosion,pittingcorrosion,hydrogenembrittlement,stresssulphidecorrosioncracking)arecharacterizedbythetypeofmechanicalforcetowhichthemetalcomponentisexposed.Itisnotwithinthescopeofthisworktoaddressindeptheithercorrosionelectrochemistryortheidentificationofdifferentformsofcorrosion.Thebasicsofcorrosionmechanismsaredescribedasabasisforunderstandingtheconditionsthatmakecorrosionriskshighlyrelevantforrefineryoperationsandmorespecificallytoprovidesomeinsightintotheunderlyingcausesofthecorrosioneventsleadingtotheaccidentsanalysedinthisreport.Also,corrosionofcertainmetals(e.g.aluminium)enhancestheircorrosionresistance,butinthisworkcorrosionisassumedtobesolelyanundesirablephenomenon.

TABLE3.TYPICALREFINERYELEMENTSCONTRIBUTINGTOELEVATEDCORROSIONRATES

Refineryelement Examples

Corrosivesubstancesinfeedstockoraddedorproducedinprocess

Hydrogenchloride,hydrofluoricacid,amines,sulphuricacid,polythionicacidsandothersulphurcompounds,oxygencompounds,nitrogencompounds,tracemetals,saltscarbondioxide,andnaphthenicacids

Refineryprocessesinvolvingextremesoftemperatureorvelocity

Distillation,desulphurization,catalyticreformers,fluidcatalyticcracker,hydrocracker,alkylation

Localconditions Ageofequipment,volumeandrateofproduction,atmosphericconditions(e.g.,climate),plannedandunplannedshutdowns

Riskmanagementmeasures Frequencyofinspection,riskassessmentandrankingpractices,equipmentinventorymanagement,maintenanceandrepairprocedures,auditingandimplementationoffeedback,useofsafetyperformanceindicators

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1.4 Description of accident report sources used in the study

Thisstudyofcorrosionrelatedaccidentsinrefineriesisbasedon99reportsofimportantrefineryaccidentsinwhichcorrosionofanequipmentpartwasidentifiedorsuspectedasbeingthekeyfailureleadingtotheaccidentevent.Onlyreportslistedinopensourcesandproducedbyorwiththecollaborationofpartiesdirectlyinvolvedintheaccidentinvestigationwereused.Therefore,withafewexceptions,onlinegovernmentdatabasesofaccidentreportswerethemainsourceofaccidentreports.Moreover,sincethestudywasconductedonrefineriesinaspecificgeographicarea,reportsthatdidnotspecifygeographiclocationoftherefinerycouldnotbeused.

Table4providesadescriptionofalltheprimarysourcesofaccidentreportsusedinthisstudy.Whenavailable,officialinvestigationreports,orsummariesproducedbygovernmentorindustry,wereusedtosupplementinformationintheprimarysources.Mainstreammediareportscontaininginformationonanaccidentwerenotconsideredsufficientlyreliabletechnicalsourcesforthisstudyandtherefore,werenotused.

Somereportswerelistedinmorethanonedatabaseandsometimesadditionalreportsonthesameaccidentfromothercrediblesourceswereusedtosupplementthefirstreport(e.g.,anindepthinvestigationreport,aworkshoppresentationoftheaccident).SincereportingaccidentswithsignificantconsequencestoeMARSiscompulsoryunderEUlaw,anyaccidentwithsignificantconsequencesrecordedintheFrenchnationaldatabase(ARIA)ortheGermannationaldatabase(ZEMA)willalsobereportedtotheeMARSdatabase.

Theseparticularsourcesalsotendtocollectaccidentsbasedonreportingcriteriaorotherwisebasedonscreeningcriteriaappliedbythesource.Thisfactorwasconsideredtoprovidesomeadditionalweighttothelessonslearnedofferedbythecollectiveexperiencerepresentedbytheseaccidents.

FIGURE1.TOTALCASEDISTRIBUTIONBYCOUNTRY

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ThestudycoversaccidentsreportedinEUandOECDcountriesoveraspanofnearlyfiftyyears,from1965through2012.Thereisnoparticularstatisticalsignificanceintermsofvariationsinthefrequencyorlocationofaccidentsstudiedperyearorgeographic.Notably,severalsourcesusedforthisstudy,includingeMARS,ARIA,MHIDASandLeesLossPreventionintheProcessIndustrieswereallestablishedinthemid1980s.Fewerdatabasesrecordedsuchincidentspriortothisdateandinanycasemuchofthedataarenotavailableinelectronicformwhichwastheprinciplesourceofinformation.

Theaccidentsreportedineachyeararenotinanywayrepresentativeofatrend.ThevastmajorityofEUandOECDcountrieshavenotconsistentlycollecteddataorreportsonmajorchemicalaccidentsovertheperiodbythisstudyorinsomecasesthedataarenoteasilyavailable.Insomecasesitispossiblealsothatreportsmaybeavailableelectronicallybutnotinlanguagesknowntothestudysauthors.Forallthesereasons,thestudywaslimitedtothesourcesidentifiedinTable4suchthatthereisasignificantoverrepresentationofaccidentsoccurringinJapan,FranceandtheotherEuropeancountrieswhowerepartoftheEuropeanUnionpriortoenlargementin2004(thesocalledEU15)5andasignificantunderrepresentationofpotentialimportantchemicalaccidentsoccurringinallotherEUandOECDcountries.WiththeexceptionoftheU.S.andJapan,findingasignificantcollectionofaccidentreportsfromOECDcountriesoutsidetheEUischallenging.

FIGURE2.ACCIDENTSBYYEAROFOCCURRENCE

5Austria,Belgium,Denmark,Finland,France,Germany,Greece,Ireland,Italy,theNetherlands,Luxembourg,Portugal,Spain,Sweden,andtheUnitedKingdom.

19

TABLE4.PRIMARYSOURCESOFACCIDENTREPORTSANALYSEDINTHISSTUDY6

Source No. Timespan

Geographicalcoverage

Comments

eMARShttps://emars.jrc.ec.europa.eu

AccidentsreportedtotheEuropeanCommissionincompliancewithSevesoDirectiveAnnexVIcriteria.

29 >1984;

EU/OECD

Completenessandprecisionofdescriptionsvariesconsiderably.Includesdetailsonsubstances,consequencesandcost.

ARIA(France)http://www.aria.developpementdurable.gouv.fr/

AdatabaseoperatedbytheFrenchMinistryofEcology,Energy,SustainableDevelopmentlistingtheaccidentaleventswhichhave,orcouldhavedamagedhealthorpublicsafety,agriculture,natureortheenvironment.Chemicalaccidentsarereportedthatmeetestablishedcriteria.

47 >1970

France,someGermany&UK/US

Concise,comprehensivetechnicalsummaries.Reportsareverifiedbytechnicalexperts.

JSTFailureKnowledgeDatabasehttp://www.sozogaku.com/fkd/en/index.html

CreatedbytheJapanScienceandTechnologyAgency.AmainpurposeincreatingtheFailureKnowledgeDatabasewaspreciselytoprovideameansofcommunicatingfailureknowledge.

18 >1970

Japan

Selectedmajoraccidentsanalysedbyexperts.Scenariodiagrammesinclude.

LeesLossPreventionintheProcessIndustries,3rdedition[13]

Firstpublishedin1980,thiscomprehensivesourceforprocesssafetymanagementintheprocesssafetyindustries.

4 >1911 Wellknownoraccidentswithimportantlessonslearnedorsignificantimpactsonlifeand/orproperty

6Thistableonlycountscasesinwhichthereferencewasusedastheoriginalsourceforcasesstudiedthoughinmanycasesitturnedoutthatitwasnottheprimarysourceoftheinformation.Whenavailable,originalinvestigationreportsorothermoredetailedsummarieswereusedwhenavailabletosupplementinformationonthesedatasources.Moreover,manyaccidentswererecordedinmorethanonesourceabovewithoftendifferentandcomplementaryinformationaboutthesameevent.

20

Source No. Timespan

Geographicalcoverage

Comments

Marsh100LargestLosses,20thedition,19722001[7]

Everyotheryearthisinsurancecompanypublishesareviewofthe100largestpropertydamagelossesthathaveoccurredinthehydrocarbonchemicalindustriessince1972.

3 19722001

World

Lowlevelofdetail.Preciselossfigures.

MHIDAS

MHIDASwasestablishedbytheU.K.Health&SafetyExecutivein1986,andprovideskeyinformationonmajoraccidentsinvolvingchemicals.ItdoesnotappeartobeavailableanymoreontheInternetfordownloading.

3 19592005

World

Mainlyasecondarysourceofinformationonaccidentsanalysedinthisstudy.

ZEMA(Germany)http://www.infosis.uba.de/index.php/de/site/12981/zema/index.html

DatabasemanagedbytheGermanFederalEnvironmentAgencyofhazardousincidentsandincidentsinprocessengineeringfacilities.

5 >1980

Germany

Concisetechnicalsummariesofchemicalaccidents.

U.S.ChemicalSafetyBoard(CSB)

TheCSBisanindependentfederalagencyoftheUnitedStatesgovernmentchargedwithinvestigatingindustrialchemicalaccidents.www.csb.gov

4 >1998

USA

Comprehensiveanalysisbyexperts.

LouisianaDepartmentofEnvironmentalQuality(LDEQ)

UnderU.S.law(EPCRAsection304),ifanaccidentalchemicalreleaseexceedstheapplicableminimalreportablequantity,thefacilitymustnotifystateauthoritiesandprovideadetailedwrittenfollowupassoonaspracticable.

http://www.labucketbrigade.org/article.php?id=498

3 20052008 AnadvocacygrouppostedanumberofofficialcompanyaccidentreportssubmittedtotheLDEQbetween20052008includingrefineryaccidentsinvolvingcorrosion.

21

FIGURE3.PERCENTAGEOFCASESINWHICHSOMELESSONSLEARNEDINFORMATIONCOULDBEEXTRACTED

Alsoitshouldbenotedthatreportsvariedconsiderablyintheirdetail.Forexample,inmanycaseslessonslearnedpersefromanaccidentwerenotgiven(seeFigure3above)Inmostcasesthetypeofaccident(e.g.,toxicrelease,fire,explosion),location(pipeortank,processunit)andknownconsequenceswereprovided.IngeneraltheleastdetailwasprovidedinreportsfromtheMHIDASandMarshaccidentregisterswhiletheJapaneseFailureKnowledgeDatabaseandtheU.S.ChemicalSafetyBoardreportswereextremelydetailed.ARIA,ZEMAandeMARSweremoreuneveninthisregard,butforthemostpartcontainednumerousdetailedreportsaswellassomereportswithsparsedetail.Insomecasesalsomoredetailscouldbefoundforthesameaccidentinamoreextensiveinvestigationreportpublishedseparatelyonlineasanacademicstudyorbytheresponsiblecompetentauthorityitself.

Intheinterestsofidentifyingdifferencesandsimilaritiesovertime,thestudylooksatfindingsfrompre2000accidentstothoseofaccidentsoccurringin2000orlater.Inparticular,onaqualitativebasis,itremainsinterestingastowhethervarioustypesoferrorsorfailuresarerepeated(andtowhatdegree)inaccidentsreportedbefore2000andin2000andafterwards.Thecomparisonmayalsorevealsomenewtypesoffailuresorerrorsbeingrecordedafter2000.Whileinitselfsuchfindingscouldnotbeconfirmedasatrendforexample,itcanbearguedthatinmanycasescertaindetailsarerecordedmorefrequentlyinrecentyearsduetobetterqualityreportingthecomparisonhelpsidentifywhattypesoferrorsandfailuresremainrelevanttotodaysrefineries.Moreover,ifsuchfindingsareanalysedincombinationwithexperienceandotherfindingsrelatedtosafetymanagementinrefineriestoday,itmaybepossibletohavemorepreciseinsightonthepatternsthataremostrelevantfromthisanalyses.

22

1.5 Type of events and consequences of accidents

Becauseofthevolumeofflammableandexplosivesubstancestypicallypresentinrefineries,scenariostendtoincludefiresandexplosionswithpotentiallyhighconsequencesifnotadequatelycontrolled.Inparticular,productionofhydrocarbonproductsleadstoahighpresenceofflammablecompoundsonsite.Notsurprisingly,therefore,nearly80%oftheeventsstudiedinvolvedafireorexplosion(seeFigure4below).Inaddition,asignificantamountoftoxicsubstancesmaybepresentsuchthatrefineriesarealsoexposedtotheriskofpotentialtoxicreleases.Manycrudeoilscontainasignificantpercentageofhydrogensulphidethatiseventuallyseparatedfromthecrudeandusuallyprocessedtoproducesulphurforthemarketplace.Otherprocessesrequirethepresenceofsulphuricacidorhydrofluoricacid(foralkylation)orammonia(toremovenitrogenfromthecrudefeedstock).Infact,overonethirdoftherefineryaccidenteventsinvolvingcorrosionhavealsogeneratedtoxicreleases.Toxicreleasestothesoilwereslightlyhigherinrelationtotoxicreleasestowaterandair,probablyresultingfromanumberofaccidentsstemmingfromtankandundergroundpipefailuresincludedinthedatabase.

Releasesweremostoftenhydrogenandhydrocarboncompoundsincludingprocessgases,naphtha,crudeoilandvarioustypesoffuels.(SeeFigure5onthenextpage).Thelargestreleasewasestimatedtobearound100,000tonnesofcrudeoilfollowedby50,000tonnesoffuel.Hydrogensulphidewasthetoxicgasreleasedmoreoftenthananyother(16cases).Fewerthan10%ofaccidentsinvolvedreleasesofothertoxicgasessuchashydrogenfluoride,carbonmonoxideandsulphurdioxide.Thehighest(known)releaseofasubstancetoxictohumanhealthwas15tonnesoffurfural,followedby1tonneofsulphurdioxide.

FIGURE4.ACCIDENTSCLASSIFIEDBYTYPEOFEVENT7

7Theremaybemorethanonetypeofeventperaccident.

23

FIGURE5.SUBSTANCESRELEASEDINREFINERYACCIDENTSINVOLVINGCORROSIONBYNUMBEROFACCIDENTS8

AsshowninFigure6onthenextpage,mosteventswereinitiatedbyaleak,ruptureorstructuralcollapse.Aleakconsistsofareleasefromasmallopeningthatovertimefacilitatetheformationofapoolofdangeroussubstancesthatmayeventuallycatchfireorexplode.Arupturegenerallyresultsfromaleakthatreleasesaflammablesubstanceinternallywhichovertimeincreasespressureandexplodesinsideapipeortank,causingarupture.Structuralcollapseisdefinedasanaccidentinwhich,accordingtothereport,corrosionwasfirstmanifestedinthedestructionorcollapseoftheunit(e.g.,collapseofthedistillationtower)ratherthaninalocalizedleakorrupture.Intheaccidentsstudied,leakswerelesslikelytoleadtoexplosions(vapourclouds)thanrupturesandruptureswerelesslikelytoleadtotoxicreleases.However,bothscenariosseemedtobeequallycapableofresultinginafire.Twostructuralcollapseswererecorded.Oneoccurredafterthestartofthefireinwhichthedistillationtower,weakenedbycorrosion,collapsed.Intheotherthestructurecollapsedfirstandafirefollowed.

8Anaccidentmayhaveinvolvedthereleaseofmorethanonesubstanceandtherefore,thetotalnumberofaccidentscountedinthefigureaboveexceedsthetotalnumberofaccidentsstudied.

24

EFFECT TOXIC RELEASE FIRE EXPLOSION UNDECLARED

LEAK 28 24 10 0 RUPTURE 9 18 19 2 STRUCTURAL COLLAPSE 0 1 0 0 UNDECLARED 2 2 0 0 GRAND TOTAL 39 45 29 2

FIGURE6.DISTRIBUTIONOFEVENTTYPEFOREACHTYPEOFFAILURE

Toevaluateimpacts,theauthorsdevelopedasimplifiedmethodologybasedontheEuropeanGravityScale.(SeeTable5onthenextpage).Thesimplifiedversioncombinessomecategoriesandcriteriaofthegravityscaleforanalyticalpurposesandalsoinrecognitionofthesometimeslimitedconsequencedataprovidedinsomereports.Inthecaseofenvironmentalimpacts,additionalcalculationswerealsomadeonthedataprovidedtofacilitateaconsistentrankingofenvironmentalimpactsbasedonthescale.9Usingthisconsequencerankingmethodology,theaccidentsstudiedappeargenerallyrepresentativeofthetypesofhighriskscenariosthataretypicallyassociatedwithpetroleumrefineries.Mostoftheseeventswerenotifiedonthebasisofhighimpactsintermsofeffectsonhumanhealthortheenvironmentorsignificantcosteithertotheoperatororintermsofoffsitepropertydamageordisruption.Asevidence,itisobservedthatnearly50%ofthereportsstudiedbothpreandpost2000werehighorveryhighconsequences.[SeeFigure7onthenextpage).Accidentswithlowconsequencesrepresentmorethanathirdoftheaccidentsstudiedandalsotheratiooflowimpactaccidentstototalaccidentsremainedvirtuallyunchangedforpreandpost2000accidentsstudied.

9Inparticularenvironmentalimpactsarenotrecordedinaconsistentmanner.Thereportsstudiedcitedenvironmentalimpactsoftenprovidedoneoracombinationofthefollowingasanindicatorofimpact:costofrestorationandcleanup,areaofcontamination,orvolumeormassoftherelease.Tofacilitatecomparisonofenvironmentalimpactsbetweenaccidents,thestudyusedinformationfromthescientificliteraturetoestimateenvironmentalcostsfrommassorvolumeofthereleasewhensuchcostswerenotavailable.ThepriceofcleanuppercubicmetreofcontaminatedsoilwasprovidedbyKhanetal.[15]andastudybyEtkinwasthesourceofalgorithmstoestimatecleanupofcontaminatedwaterbodiesindifferentworldregions.[16]

25

FIGURE7.SEVERITYOFACCIDENTCONSEQUENCESPREANDPOST2000

TABLE5.CONSEQUENCERANKINGCRITERIA

Forhumanconsequences,production lossandpublicdisruption, the scaleapproximates theEuropeangravityscale(condensed into5categories).[14]Formaterialandenvironmentaldamage, levelof impactwasassessedusingalogarithmicscalefromLowtoHighforcostsstartingwith100 >1000 >1,000,000 1,000,000 >1month

High 11100 101 1000 100,0011,000,000

100,0011,000,000

1weekto1month

Medium 010 11100 10,001100,000

10,001100,000 1dayto1week

Low 0 110 110,000 110,000 >1day

None 0 0 0 0 0

26

SOURCE VERY HIGH HIGH MEDIUM LOW

NONE/UNKNOWN

GRAND TOTAL

ARIA 17 1 3 21 5 47 CSB 3 0 1 0 0 4 EMARS 21 2 1 5 0 29 JST 6 2 1 8 1 18 LDEQ 0 0 0 2 1 3 LEES' 4 0 0 0 0 4 MARSH 3 0 0 0 0 3 MHIDAS 2 0 0 1 0 3 ZEMA 4 0 1 0 0 5 GRAND TOTAL 60 5 7 37 7 116

FIGURE8.DISTRIBUTIONOFEVENTTYPEFOREACHTYPEOFFAILURE10

FromFigure8above,itcanalsobeobservedthatsomesourcesfocusedmoreexclusivelyonhighimpactaccidents,inparticular,theMarshandCSBreports.Ontheotherhand,accidentsreportedwithinARIA,JSTandZEMAincludealsoaccidentswithlowerimpacts,basedoncriteriaotherthandamageseverity,e.g.,releasevolumeoreventduragion.EUMemberStatesmustreportmajoraccidentsatSevesosites(whichincludesallpetroleumrefineries)usingtheseveritycriteriainAnnexVIoftheDirective.Therefore,eMARSisgenerallyassociatedwithpredominantlyhigherconsequenceaccidentsreviewedinthisstudythatoccurredintheEU.11AccidentsineMARSoccurringinFranceandGermanywerealsorecordedinARIAandinZEMA(startingin1993),respectively.

10Someaccidentswerereportedordescribedbymorethanonesourcesothenumberofsourcecitationsexceedsthenumberofaccidentsstudied.11SomeEUaccidentsreportedinotherdatabases(e.g.,ARIA,ZEMA)maybeassociatedwithhighimpactsinthisstudyeventhoughtheywerenotrequiredtobereportedtoeMARS.Thestudyusedanadditionalcriterion(productionloss)withrespecttoeMARStoevaluateseverity.Inaddition,thestudyusedcleanupandrestorationcostsratherthanareatoestimateenvironmentalimpacts.

27

Publicserviceinterruptionandpropertydamagewerethedominantconsequencesoverall.(SeeFigure9below.)Takingintoaccountproductionlossaswell,57%oftheaccidentsstudiedwereprojectedtohaveasignificant(veryhigh)economicimpact.Notably,sixteenOECD/EUaccidentsresultedinshutdownofentireproductionunitsorentirerefineriesforweeksormonths.Twelveaccidents(12%)reportedthattherefinerywaspartiallyorcompletelyshutdownforaperiod.(Notethatthisconsequenceislikelytobeunderreported.)AsnotedinTable6,estimatesofshutdowntimesrangedfrom10daystoapproximately240days.Inonereportashutdownofthehydrocracker,desulphurization,andhydrogenprocessingunitsforapproximately7months(~210days)resultedina30%reductioninproductiongeneratingabusinesslossestimatedatabout90,000,000fortherefinery[7].

LEVEL OF IMPACT DEATH INJURY ENVIR

PROP DAM

PROD LOSS

PUB SRVC

VERY HIGH 5 4 8 32 13 41 HIGH 0 0 1 4 0 2 MEDIUM 2 0 1 3 2 5 LOW 0 2 16 13 6 31 NONE 0 0 0 1 0 8 Grand Total 7 6 26 53 21 87

FIGURE9.LEVELOFCONSEQUENCEVS.TYPEOFCONSEQUENCE12

12Theremaybemorethanonetypeofdominantconsequenceperevent.For8accidentsitappearedthatminimalornoconsequencesresulted.

28

Whilelessthanonethirdofaccidentsstudiedinvolveddeathandinjuries,potentialhealthimpactsremainhigh.Forexample,twoaccidentsaccountforthemajorityofdeathsandinjuriesrecordedfortheaccidentsstudied.AsshowninTable6onthenextpage,intotalthenumberofdeathsreported,onandoffsite,equals67,or0.68deathsperaccident.Thenumberofinjuriestotaled219or2.21peraccident.Evacuationnumberswerereportedlessfrequently,butintotal7500peoplewerereportedasevacuatedacrossthe99accidents.

Althoughtherehavebeennodeathsandonly19injuriesrecordedincorrosionrelatedaccidentsinrefineriessince2000,potentialforcatastrophichumanhealtheffectsfromanytypeofchemicalaccidentinarefinerycannotbediscounted.Therehavebeenseveralfatalaccidents(relatedtoothercausesthancorrosion)occurringinrefineriesintheEUandOECDinthelast10years(andeveninthelasttwo),manyoftheminplantsseveraldecadesold.Thepotentialforacorrosionfailuretocauseahumandisasterappearstobeundiminished.

Environmentaldamagewasreportedfornearlyathirdofaccidentsandmainlyassociatedwithtoxicreleasestowater.Sixoutof14accidentsinwhichcleanupandrestorationcostswereprovidedorcouldbecalculated,theenvironmentalcosts(usualsoilorsurfacewatercontamination)werefairlyhigh.Oneaccidentaloneaccountedforenvironmentalcleanupandrestorationcostsofapproximately624,000,000.Eightaccidentswereestimatedtocostunder50,000andthefiveremainingaccidentsrangedfrom300,000to32,000,000.(SeeTable6onthenextpage.)

29

TABLE6.CUMULATIVETOTALSOFCONSEQUENCEFIGURESFORALLACCIDENTS

Category #ofaccidents Totalreported

Totalfatalitiesreported 8 67

Onsitefatalities 8 67

Offsitefatalities 0 0

Totalinjuriesreported 18 219

Onsiteinjuries 16 193

Offsiteinjuries 5 27

Totalreportedpopulationevacuated 5 7450

Totalmaterialcostsofaccidentsreported13 42 748,386,332

Onsitepropertydamage 10 172,712,786

Offsitepropertydamage 2 8,235,999

Operatinglosses 6 165,164,253

Estimatedenvironmentalrestorationandcleanupcosts 14 698,615,706

Estimatedtimeoffullorpartialshutdown14 10 1036days

13Thetotalmaterialcostsrepresentthesumofpropertydamage,onandoffsite,andoperatinglosses.Inmanycases,accidentreportsdidnotprovideabreakdownofthesecosts.Therefore,thetotalmaterialcostscategoryismuchgreaterthanifoneaddsupthetotalsofthesubcategories(e.g.,onsitepropertydamage).Thesubcategoriesrepresentonlythetotalfigureforcaseswherethisbreakdownwasprovided.

14Temporaryshutdownwasmanagedasaconsequencein12casesbut2didnotspecifyatimeframe.

30

CHAPTER 2 ANALYSIS OF THE POTENTIAL CONTRIBUTION OF PROCESS AND EQUIPMENT CONDITIONS

Corrosionrepresentsaparticularlyrelevantrisktopetroleumrefineriesbecauserefineriestypicallyhaveseveralhighriskfactorsbecauseofthetypeofsubstancesandprocessesinvolvedinrefineryoperations.Otherlocalconditionsmayalsocontributetoanaccelerationinthecorrosionrate,includingphysicallocationofequipmentandtheclimate.Moreover,certainoperatingconditionsinarefinery,bothnormalandabnormal,bytheirnatureareparticularlylikelytopresentfavourableopportunitiesforacorrosionfailuretoinitiateachainofeventsleadingtoamajoraccident.Theaccidentsreviewedinthisstudyconsistofseveralcaseswheretypicalconditionsconducivetoasignificantcorrosionfailureweresomehowoverlookedorifrecognized,sufficientmeasureswerenotappliedtoavoidanaccident.Thischaptersummarizesthestudyfindingsinthecontextoftheprocessandequipmentconditionswithknownriskpotential,highlightinginparticularthosewhichwereidentifiedasrelevantinanalysesofthecasesstudied.

Corrosioncanappearaseitheruniformcorrosionorlocalizedcorrosion.Uniformcorrosionisalsoknownasgeneralcorrosionandistheclassicformofcorrosioninwhichtheentiresurfacearea,oralargefractionofthetotalarea,isaffectedbyageneralthinningofthemetal.Inchemicalprocessinguniformcorrosionisconsideredtheleastdangerousformofcorrosionbecauseitiseasilyvisiblelongbeforeitisdegradedenoughtofail.Nonetheless,uniformcorrosionmaysometimesbeacauseofaccidents,forexample,inpipelinesthatareinremotelocations,underground,orotherwise,notviewedfrequently,generalcorrosionmaycontinueforalongtimeundetected.

Conversely,therearenumeroustypesoflocalizedcorrosionthatarefarmoredifficulttodetectwithouttargetedeffort.Thus,consequencesoflocalizedcorrosioncanbemoreseverethanuniformcorrosionasfailureoccurswithoutwarningandoftenafteronlyashortperiodofuseorexposure.Typically,localizedcorrosionoccursbetweenjoints(crevicecorrosion)orunderapaintcoatingorinsulation.Stresscorrosioncrackingandhydrogenassistedstresscorrosionarealsoformsoflocalizedcorrosion.Theyareoftengroupedtogetherwithhydrogenembrittlementandstressembrittlement,eventhoughthesearenotcorrosionphenomena,becausetheconditionsandtheresultingfailuremechanism(cracksinthemetal)areremarkablysimilar.Assuch,itisnotnecessarilyeasytodeterminewhichphenomenoncausedsuchafailurefollowinganaccident;hence,bynecessity,analysesofaccidentsinvolvingcorrosionrelatedfailuresgenerallyincludebothphenomena.

Generallyspeakingrefineriesarevulnerabletocorrosionbothduetointernalprocessconditionsaswellasotherfactors.Inthemajorityofcasesstudiedforthisreport,itwaspossibletoidentifysomeofthecausalfactorsandhaveageneralknowledgeaboutwhichoneswerelikelytobedominant.Thefollowingsections,presenttheresultsoftheanalysisofcorrosionconditionsthatmayhavebeenresponsibleforequipmentfailureinthesecases.

31

2.1 Process conditions contributing to corrosion in study cases

Refineriesaremostvulnerabletocorrosionduetointernalprocessconditions.Ironically,despitetheexistenceofseveralcorrosionreferencesandstandards,auniformapproachtodescribingandorganizingcorrosiontypesdoesnotexist.TheAmericanPetroleumInstituteRecommendedPractice571(API571)listsover25commoncorrosiondamagemechanismstoindustrialactivityplus11additiontypesthatarespecifictorefineries.[17]Inaddition,studiesofagingfacilitiesmayclassifycorrosioneffectsintodifferentgroupingsonthebasisofcharacteristicssuchasfailuremechanisms(e.g.,wallthinning,crackingandfracture,physicaldeformation),commoncausalfactors(e.g.,stressdrivendamage,metallurgical/environmentaldamage)orothercommonalities.Table7onpages33and34showsexamplesofsometypicalcorrosionphenomenainrefineriesasclassifiedinAPI571bydamagemechanism.15Thetableshowsonlyaportionofthevastnumberofcorrosionphenomenaidentified.

In53casesprocessconditionswereidentifiedascontributingtothecorrosiveconditionsprecedingtheaccident.Themostcommonlycitedcontributorwasthesubstance(46).Flow(eitherhigh,low,turbulentorunequal)wascitedintencases,andtemperature(mostlyhigh,butinafewcases,low)andpressure(mostlyhigh)werecitedascontributorsin11and7casesrespectively.Ineightcasesotherexacerbatingprocessconditionswerepresent,includingoperationoutsidedesignparametersandvariationacrossprocesscycles.

FIGURE10.PROCESSCONDITIONSCITEDASCONTRIBUTINGTOCORROSIVECONDITIONSACCIDENTSSTUDIED(53CASESINTOTAL)

15Notethaterosion/corrosionisincludedbecauseitissostronglyassociatedwithcorrosion.However,severalothermechanicalandmetallurgicalfailuresnotlistedhereareacceleratedbycorrosionphenomena(e.g.,creepandstressrupture).

N=99

32

TABLE7.EXAMPLESOFSTRESSCORROSIONCRACKINGDAMAGEMECHANISMSPROPOSEDBYAPI571[17]16

DamageMechanism Velocity,TemperatureandpHInfluences

SubstancesInvolved OtherInfluences ProcessesAffected

MechanicalandMetallurgicalFailureMechanisms

Erosioncorrosion Highvelocity,HighTemperature,High,LowpH

Varied Particularlyoccursinpockets,elbowsandsimilarconfigurations.

Affectsalltypesofequipmentexposedtomovingfluids,gasbornecatalyticparticles.

UniformorLocalizedLossofThickness(Generic)

Galvaniccorrosion Varied

Atmosphericcorrosion Lowtemperature Cyclic:Fluctuationbetweenambientandtemperature.

Coolingwatercorrosion Lowvelocity,Hightemperature

Freshorsaltwater,potentialchlorides

HighTemperatureCorrosion(Generic)

Sulphidation Hightemperature Sulphurconcentration FCC,coker,vacuumdistillation,visbreakerandhydroprocessing

HightemperatureH2/H2S Hightemperature H2 andH2S Desulphurizers,hydroprocessing,hydrotreaters,hydrocracking

Nitriding Hightemperature Nitrogencompounds

16Thistableisbynomeansacompletelist.ItonlyshowsanumberofexamplesofsometypicalrefinerycorrosionphenomenaclassifiedanddescribedinAPI571.Formoreinformationpleaseconsultthereferencedocument.

33

DamageMechanism Velocity,TemperatureandpHInfluences

SubstancesInvolved Otherinfluences ProcessesAffected

UniformorLocalizedThicknessPhenomena(RefinerySpecific)

Aminecorrosion Highvelocity/temperature Ammonia,H2SandHCN Higherturbulence

HCLcorrosion

LowpH HCLwhenwaterisavailable(presenceofoxidizingagents)

Crudeunit,hydroprocessingunit,catalyticreformingunits

Hydrofluoricacidcorrosion

Highvelocity/temperature HFconcentration+O2andsulphur,higherpresenceofwatertoHFconcentration

Higherturbulence HFalykylation,deadlegs

Naphthenicacidcorrosion Highvelocity/temperaturelowpH

Naphthenicacid,sulphurcontent

Twophaseflow(liquidandvapou),Highturbulence

Crudeandvacuumheatertubesandlines,cokers,pipingsystems

Phenolcarbolicacidcorrosion

Hightemperature Sulphurandorganicacidsandverydilutephenolsolutions

Sourwatercorrosion Hightemperature,lowpH HigherconcentrationsofH2S,Oxygen

FCCandcokers

Phosphoricacidcorrosion LowvelocityandpH Solidphosphoricacidcatalysts,freewater,contaminants

Polymerizationunits

EnvironmentallyAssisted(Refineries)

Polythionicacidstresscorrosioncracking

Sulphur acids&oxygen heatexchangertubes,hydroprocessing,crudeandcokerunits,FCCunits,boilers

Chloridestresscorrosioncracking

Hightemperature,pH>2 Chloridecontent,oxygen Cyclicfluxbetweenwetdryconditions,tensilestress

34

2.2 Analysis of cases in association with specific process conditions

Thestudyalsoanalysedthecasestoidentifywhattypesofsubstances,processunitsandequipmentwereassociatedwiththeaccidents.AsnotedinSection2.1abovecertainsubstanceshavepropertiesthatmaycausethemtobecorrosiveagents.Table8onthenextpagehighlightssometypicalsubstancesthathavenotableinfluenceoncorrosionratesinvariousrefineriesdependingonthecrudeoilinputsandtypesofprocessespresentInaddition,differentprocessesandequipmenthavegreaterorlessertendenciestobeassociatedwithacorrosionrelatedincident.Forthesereasons,itwasconsideredinterestingtodeterminetheprevalenceofvariouscategoriesofsubstances,processesandequipmentinassociationwiththeaccidents.Althoughtrendsidentifiedcouldnotbeconsideredconclusive,becauseofthenonrepresentativenatureofthedata,itisstillworthnotinghowfrequentlysometypicalassociatedcausalfactorsappearinthedata.Afundamentalingredientofcorrosionisexposuretoacorrosiveagentviaarefineryprocess,thatis,asubstancethatundercertainprocessingconditionsactsuponthemetalandweakensit.Thesecorrosiveagentsareineffectoxidizingsubstances,whichmayincludewater,avarietyofacidcompoundsintroducedorgeneratedintheprocessaswellasthecrudeoilandfinalandinterimproducts,suchascokeandkerosene.AsnotedinTable7inthepreviouspages,somesubstanceshaveuniquecorrosionsignatures,thatis,thecorrosionproducedischaracterizedbyaparticularspecificvisualortexturalpattern,reactswithspecificmetalcompounds,andfrequentlyoccursinthesametypesoflocations.Figure11onpage36indicatesthefrequencywithwhichvarioustypesofsubstanceswerecitedintheaccidentreportsaspotentialagentswhichmayhaveacceleratedcorrosionratesultimatelyleadingtoequipmentfailure.Outof96cases,49(51%)identifiedtheprocesssubstancesthatweremostlikelytoberesponsibleforacceleratingthecorrosionrateoftheequipmentinvolved.

Substancescitedmostcommonlyweresulphurandsulphurcompoundsandwater(14caseseach)followedbyhydrogensulphide(11cases),alongwithcrudeoil(8cases),asnotedinFigure11.ThesubstancesidentifiedinFigure11fromtheaccidentsstudiedarenormallypresentinthehighestvolumesandinavarietyofprocessesthroughoutarefinerysite.Carbonisanothercommoncorrosiveagentwithanimportantpresenceinrefineriesbutitwasnotmentionedasbeinginvolvedinanyoftheaccidentsstudiedforthisreport.

35

TABLE8.TYPICALPROCESSSUBSTANCESASSOCIATEDWITHREFINERYCORROSIONSubstance RoleandSignificance

Crudeoil Crudeoilsconsistofmanydifferenthydrocarboncompoundsandvaryconsiderablydependingontheirsource.Crudeoilsrangeinconsistencyfromwatertotarlikesolids,andincolorfromcleartoblack.An"average"crudeoilcontainsabout84%carbon,14%hydrogen,1%3%sulphur,andlessthan1%eachofnitrogen,oxygen,metals,andsalts.[18]Therefiningindustrydifferentiatescrudeoilsinanumberofwaysinrelationtotheirpredominantproperties.Forexample,theycanbegenerallyclassifiedasparaffinic,naphthenic,oraromatic,basedonthepredominantproportionofsimilarhydrocarbonmolecules.Theyarealsooftenclassifiedassweetorsouronthebasisofsulphurcontent.Refinerycrudefeedstockoftenconsistsofmixturesoftwoormoredifferentcrudeoilsandthestockislargelyinfluencedbyregionaleconomics,inparticular,wheretheclosestsourcesofcrudeoilarelocated.

Naphthenicacid

Naphthenicacidisthegenericnameusedforalloftheorganicacidspresentincrudeoilsandthistypeofacidcanbehighlycorrosive.Naphthenicacidcorrosionoccursprimarilyinhighvelocityareasofcrudedistillationunitsinthe220Cto400C(430Fto750F)temperaturerange.Whencombinedwithhightemperatureandhighvelocity,evenverylowlevelsofnaphthenicacidmayresultinveryhighcorrosionrates.Thepresenceofnaphthenicacidandsulphurcompoundsconsiderablyincreasescorrosioninthehightemperaturepartsofthedistillationunits.[6]

Sulphurcompounds

Aftercarbonandhydrogen,sulphuristypicallythemostavailableelementonarefinerysite.Sulphursmaybepresentincrudeoilashydrogensulfide(H2S),assulphurcompounds,suchasmercaptans,sulphides,disulphides,thiophenes,andpolythionicacids,oraselementalsulphur.Infact,allhightemperaturesulphidationiscausedbyhydrogensulphurandtherateofcorrosionviasulphidationdependsonthedegreetowhichallthesulphurcompoundsinthecrudefeedstockdecomposetoH2S.OvertheyearstheaverageconcentrationofsulphurinthecrudefeedstockinOECDEUrefinerieshasbeenrisingforatleastadecadeandthistrendhascontributedtopotentialincreaseincorrosionrisk.Hence,regardlessofthetypesofprocesseshostedbytherefinery,mostrefineriesarevulnerableinvaryingdegreestooneormoreformofcorrosionassociatedwithsulphurthroughouttheplant.

Hydrogen Hydrogenisplaysaparticularlyimportantroleintheremovalofimpurities,mostnotablyinthehydrotreatingandhydrocrackingprocesses.Theprocessingofheaviercrudeoilandstricterenvironmentalregulationshasincreasedtheuseofanddemandforhydrogeninrefineriesinrecentyears.Accordingtoonesource,asrecentlyas2008petroleumrefineriesaccountedforapproximately90%ofglobalhydrogenconsumption.[19]Atelevatedtemperaturesandpressures,hydrogencanhaveacorrosiveeffectoncarbonandlowalloysteels.Typicalcorrosionphenomenaresultingfrompipelineexposuretohydrogenunderintenseprocessconditionsincludesgalvaniccorrosion,hightemperaturehydrogenattack,chemicalreactionsofmetalwithacids,orwithotherchemicalsasinsulfidestresscracking.Althoughhydrogenembrittlementandblisteringarenotcorrosionmechanisms,theymaycreatesimilarweaknessesinthemetalleadingtomaterialfailure.Expertknowledgeisoftennecessarytodistinguishthespecifichydrogendamagemechanism(s)responsibleforaparticularequipmentfailure.

Water Waterisassociatedwithcorrosionasaconductorofpotentiallycorrosiveagentsbutalsoasacatalystforgeneratingcorrosiveagents.Thepresenceofthechlorideioninthecrudeoil(frombrinywater),coolingwaterthathasbeenrecycledandpickedupvariousoxidizingagentsorthatthathasbeenpretreatedwithchlorine(e.g.,fromthepublicwatersupply).Thecorrosivityofthewaterthereforevariesgreatlydependingonitsorigin.Waterisalsoassociatedwiththeformationofcorrosiveagentssuchashydrochloricacidandacceleratingtheircorrosivebehavior.

Hydrofluoricacid

Theaqueoussolutionofhydrogenfluoride(hydrofluoricacid)isaweakacidasthehighstrengthofhydrogenfluorinebondsdonotallowcompletedissociationwithwater.Hydrofluoricacidisusedasthecatalystofrefineryalkylationwhichfacilitatesthereactionoflowolefins(typicallybutene)andisoparaffins(typicallyisobutane)toformhigherisoparaffins.

Ammoniaandammoniacompounds

Asmallpercentageofcrudeoilconsistsofnitrogencompoundsaswellasammoniachlorides.Theseproductsaregenerallyextractedandprocessedtoproduceammonia.Ammoniumchlorideandammoniumsulphatesarecorrosive,asgas,assolid,orinsolutionandareofparticularconcern(butnotlimitedto)distillation,hydrotreating,hydrocracking,catalyticreforming,andcatalyticcrackingprocesses.

Carbonandcarbondioxide

Carbondioxideisfoundintraceamountsincrudeoilandalsoincondensateandproducedwater.ItisreleasedfromcrudestypicallyproducedinCO2floodedfieldsandcrudesthatcontainahighcontentofnaphthenicacid.Whencombinedwithwater,carbondioxideproducescarbonicacid(H2CO2),whichishighlycorrosivewithsteelandothermetallurgies.Conditionsalsoexistinrefineries(hightemperatures,amplecarbonsources)thatareconducivetocarburizationanddecarburization.

36

FIGURE11.PROCESSRELATEDSUBSTANCESCITEDASCONTRIBUTINGTOCORROSIONFAILURES17

Ammoniaandammoniacompounds,chlorineandchlorideions,andhydrogenwereeachcitedineightcasesasapotentiallydominantcorrosiveagentinfluencingtheequipmentfailure,mainlyinthedistillationandstorageunits.Hydrogenchloridewasreportedasthecorrosiveagentintwooftheaccidentsstudied.Onlyoneaccidentstudiedidentifiedhydrofluoricacidasacontributingfactor.Manyrefineriesdonotusehydrogenfluorideforalkylationandhence,thisriskisnotnecessarilypresentinallrefineries.Otherprocessrelatedsubstancescitedintheaccidentsincludedrecycledcontent,phosphoricacidandnitrogenandnitrogencompounds.

17Oneaccidentcouldincludemorethanoneprocesssubstanceasacontributortocorrosion.Hence,thetotalfrequencyofallsubstancesaddedtogetherexceedsthenumberofcaseswherethisphenomenonwasnoted.Waterwasonlycitedasacontributingsubstanceifitwasintroducedintoorgeneratedbytheprocess.Wherewaterwasintroducedbyth