GlobalCongressonProcessSafety-2016____________________________________________________________________________________IdentifySIFandSpecifyNecessarySIL,andotherIPLs,aspartofPHA/HAZOP–or-Whyitisnotnecessaryto“BoldlyGoBeyondHAZOPandLOPA”WilliamG.Bridges,PresidentPROCESSIMPROVEMENTINSTITUTE,INC.(PII)1321WatersideLane,Knoxville,TN37922Phone:(865)675-3458Fax:(865)622-6800e-mail:wbridges@piii.comA.M.(Art)Dowell,III,PEPROCESSIMPROVEMENTINSTITUTE,INC.(PII)2437BayAreaBlvdPMB260HoustonTX77058-1519phone:713-865-6135e-mail:adowell@piii.com2016©CopyrightreservedbyProcessImprovementInstitute,Inc.“PII”PreparedforPresentationat12thGlobalCongressonProcessSafetyHouston,TXApril10-13,2016UNPUBLISHEDAIChEshallnotberesponsibleforstatementsoropinionscontainedinpapersorprintedinitspublicationsGlobalCongressonProcessSafety-2016_____________________________________________________________________________________IdentifySIFandSpecifyNecessarySIL,andotherIPLs,aspartofPHA/HAZOP–or-Whyitisnotnecessaryto“BoldlyGoBeyondHAZOPandLOPA”WilliamG.Bridges,PresidentPROCESSIMPROVEMENTINSTITUTE,INC.(PII)A.M.(Art)Dowell,III,PEPROCESSIMPROVEMENTINSTITUTE,INC.(PII)Keywords:PHA,HAZOP,HazardandOperabilityanalysis,riskassessment,riskanalysis,LOPA,IPL,independentprotectionlayer,layerofprotectionanalysisAbstractThispapershowshowtoapplythequalitativedefinitionofIPLswithinthesettingofaprocesshazardanalysis(PHA)togetmostofthegainfromLOPAwithoutdoingaLOPA(withoutusingnumericalvalues).ThepaperincludesanimplementationpathtodevelopPHAleadercompetenciestoguidethequalitativeapproach.WealsoshowthewayweuseaPHAteamtoidentifywhenaSIFisneededandtoselectthepropertargetSIL.ThisportionoftheSILevaluationandtheidentificationandlabelingoftheIPLsduringthePHA/HAZOPdoesnottakeanylongerthananormalPHA/HAZOP,oncetherighthabitsareestablished.NotethatthisapproacheliminatestheneedforaseparateSILEvaluationStudytoidentifytheSIFsandselectthetargetSIL.Finally,thepapertiestogetherthesetwospecifictopics,alongwiththetopicofmakingriskjudgments,toshowthereislessthan5%needtogobeyondHAZOP,andlessthan0.01%needtogobeyondLOPA.GlobalCongressonProcessSafety–2016_________________________________________________________________________________BackgroundIdentifyingsafetyinstrumentedfunctions(SIFs)andotherindependentprotectionlayers(IPLs)isimportantforanyorganization.FeaturesthataredesignatedasIPLs(includingSIFs)arenowbeingtreatedas“SafetyCritical”or“BusinessCritical”or“MissionCritical”features.1Theseneedtobemaintainedsuchthatthepredictedprobabilityoffailureondemandofthefeatureisactuallyachieved.Thesecanbeidentifiedinasimplifiedriskassessment,suchaLayerofProtectionAnalysis(LOPA).2But,thesealsocanbeidentifiedwithrelativeeaseinapurelyqualitativesettingofaprocesshazardanalysis(PHA)usinghazardandoperabilityanalysis(HAZOP)orotherPHAmethods.Similarly,aPHAteamcanusuallyidentifyinaqualitativesenseifaninstrumentedsafeguardloopmeetstherestrictionsofaSIF.PHAteamscanalsobetaughttoassignqualitativelythenecessarySafetyIntegrityLevel(SIL)fortheSIF.PerANSI/ISA84.00.01Part3,Section3.8:AqualitativemethodmaybeusedasafirstpasstodeterminetherequiredSILofallSIFs.ThosewhichareassignedaSIL3or4bythismethodshouldthenbeconsideredingreaterdetailusingaquantitativemethodtogainamorerigorousunderstandingoftheirrequiredsafetyintegrity3Manybelievethatonlyaquantitativeanalysis,suchasLO...
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