PROCESSSAFETYMANAGEMENTANDRISKHAZARDANALYSISBYGORDONMCKAYPhD,DSc9.11HAZOPSTUDYANALYSISCOURSE1.0INTRODUCINGHAZARDANDOPERABILITYSTUDIES-SUMMARY11.1WhatisaHAZOP?1.2WhyisaHAZOPCarriedOut?1.3WhenisaHAZOPCarriedOut?1.4IntroductiontotheHAZOPStudyProcedure1.5HowareHAZOPsDone?1.6HAZOPTerminology1.7TheHistoryoftheHAZOPStudy21.0INTRODUCINGHAZARDANDOPERABILITYSTUDIES-SUMMARY(HAZOPs)1.1WHATisaHAZOP?Ahazardandoperabilitystudy(orHAZOP)isasystematic,criticalexaminationbyateamoftheengineeringandoperatingintentionsofaprocesstoassessthehazardpotentialofmal-operationormal-functionofindividualitemsofequipmentandtheconsequentialeffectsonthefacilityasawhole.Itisquitenormaltocarryoutsafetyreviews.Thesemaytakedifferentforms.Expertsmaybeconsultedinisolation,withoutreferencetoeachother.Theymayinsteadbegatheredinlengthymeetingstodiscusstheparticulartopic.Hazopsaremeetingswithadistinctstructure,thestructureimposingacertainorganization,toenhanceeffectiveness.Theyareageneralizedstudytechnique,equallyapplicabletomicrochipmanufacture,pharmaceuticalsynthesis,effluentplantoperationoranyprocess.Theyshouldnotbeseen,however,asasolutiontoallills,theultimatereview.Theprocedureisonlyanthertoolinthesafetylockerandshouldbeseenascomplementarytoothertechniques.Indeeditisbestappliedasonestageofamulti-stageprocedure,applyingdifferenttechniquesasrelevanttoeachstage.Itdoesnotreplace,butrathersupplements,existingCodesofPractice.Neithercanittotallysubstituteforexperience.But,bothCodesofPracticeandexperienceareevolvedfromexistingsituations.Innovativedevelopmentsrequireareviewwhichinvestigatestheunknown.Hazopsareasystematic,logicalapproachtodeterminingproblems.1.2WHYisaHAZOPcarriedout?Thereasonsforcarryingouthazardandoperabilitystudies,are:i.Primarily,toidentifyhazards,andii.Toalesserextent,toresolvethesehazards.Insayingthis,hazardsareverygenerallydefined.Theyareunderstoodtobeevents,which:-i.Leadtoinjuryofpeople,eitherinsideoroutsidetheplant.ii.Injuretheenvironment.iii.Insulttheenvironment.Harmfuleffectsmaynotoccur,butdisturbanceitselfisunacceptable.iv.Damagetheplant,anobvioushazard.v.Resultinlossofproductionquantity,qualityorschedule.Inpractice,someresolutionofhazardsisnormallyaccepted.Howeveracarefulbalancemustbemaintainedtoensurethattheprimarypurposeofhazardidentificationisnotcompromised.31.3WHENisaHAZOPcarriedout?Thetimingofahazardandoperabilitystudyisdeterminedbytheobjectivesofastudy,andinturndeterminesthebenefitsthatmaybegained.Theoutlineconceptofaprocessmaybeexaminedtohighlightanymajoromissionsorsignificantfeatures.Asfurtherdetailingiscarriedout,e.g.whentheprocessdesigniscomplete,thefullstudyproceduremaybestbeapplied.Operatingproceduresmaybeexaminedtoensurethatalleventualitieshavebeenconsidered.Modificationsincludingso-called“minormodifications”,generallybenefitfromarigorousstudy.Oftenanapparentlysimple,uncomplicatedmodificationcangiverisetoagreaterproblemthanitwasintendedtosolve.Existingplantandnewequipmentareotherexamplesoftopicsthatmaybenefitfromstudy.Thereforeaprojectmaybestudiedseveraltimesinitslife-time.DespitethesecommentsthereisquiteadistinctbenefitfromcarryingoutaproperHAZOPStudyintermsofthecorrecttimingandtoobtainthemaximumcostbenefit.Therefore,ahazopcannotbecarriedoutbeforethelinediagrams(orprocessinstrumentationdiagramsastheyareoftencalled)arecomplete.Itshouldbecarriedoutassoonaspossiblethereafter.Ifa...
