Equipment Configurationand Layout
3.1.Introduction
Properequipmentconfigurationandlayoutcanmakeasignificantcontributiontothesafetyofaprocessingfacility.Safeseparationdistancesareusuallybasedonhazardconsiderations,butoftenthedemandsforsafeaccessduringcon-struction,operation,andmaintenancearegoverningfactors.Inbatchprocesses,wherethematerialutilizedintheprocesscanchangefrequently,providingsafeseparationdistancespresentsanevengreaterchallenge.Ingeneral,largerspac-ingbetweenequipmentleadstoasaferlayout.However,thismayleadtoanincreaseinpipework,whichinitselfmayincreasetheprobabilityofaccidentalreleases.Thelargerspacingbetweenequipmentmayalsoincreaseoperatoreffort and workload in operating the process.
Oftenbatchprocessequipmentneedstobelocatedinsidebuildings.Thisisusuallythecasewhentheprocessneedstobeshieldedfromextremeheat/coldconditions,theelements,and/orneedstobekeptsterile.Thisleadstotheneedtoprovideadequatebuildingventilationtoavoidbuildupofhazardousmaterialduetoleaksandotherprocessemissions.Whentheoperationofaprocessinvolvesopening,cleaning,chargingetc.,pointsourceventilationmayalsoneedto be provided.
Layoutalsohasasignificantroleinminimizingtheprobabilityofignitionofaflammablerelease.Areaelectricalclassificationprovidesthebasisforthecontrolofelectricalignitionsources.Thisclassificationisalsousedtodeterminetheareasthatrequireprotectionfromvehicularaccess,etc.Frequently,highlyhazardousprocessesthatcanresultinoverpressure(e.g.,hydrogenation)areplaced behind blast resistant structures/walls.
Anotherimportantissueinlayoutistheprovisionofsafeaccesstoequip-mentforemergencyresponseneedssuchasfire-fightingetc.Thelayoutalsoneedstoprovideforsafeescapeandrescueroutes.Asfarasoff-sitepopulationisconcerned,themostimportantsitingfactoristhedistancebetweentheprocess
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3.EQUIPMENT CONFIGURATION AND LAYOUT
andtheoff-sitereceptors.Physicaleffectsofaccidentalreleases,firesandexplo-sionsdecayrapidlywithdistance.Lowpopulationdensityintheimmediatevicinityoftheplantreducesthenumberofpeoplepotentiallyaffectedbytheaccidental releases.
3.2.Case Studies
Pump Leak Incidents
Ahigh-pressurereciprocatingpump,originallyusedforpumpingheavyhydro-carbons,wasputintoservicetopumppropyleneinanunventilatedbuilding.Aleakoccurredfromtheglandduetofailurebyfatigueofthestudsholdingtheglandinposition.Theescapingliquidvaporizedandwasignitedbyafurnace76metersaway.Fourmenwerebadlyburnedandtheglasswindowsonthebuild-ingswerebroken.Thefailurewasattributedtothefactthatplantmanagementhadnotimplementedeffectivemanagementofchangeprocedures.Asaresultofthedeflagration,gasdetectorsandremoteisolationcapabilitywereprovided.Also,thepumpwasmovedtoanopenbuildingwheresmallleakswouldbedis-persed by natural ventilation (CCPS G-39).
Tank Farm Fire
InNovember1990afireoccurredataflammableliquidtankfarmsupportingDenver’sStapletoninternationalairport.Eightofthefarm’stwelvestoragetankscontainedjetfuel,totalingalmost4.2milliongallons.Thefireburnedfor55 hours, destroying seven tanks.
Investigatorsconcludedthatadamagedpumpinavalvepitnearthestoragetanksmayhavecausedtheinitialleakandalsomayhaveignitedthefuel.Inaddition,theinvestigatorsconcludedthatapipesimultaneouslycracked,thusreleasingfuelintothefirearea.Thesubsequentfirefedonthefuelcollectinginthepitandspewingfromthetwoleaks,andimpingedonpipingandrelatedequipmentinthevalvepit.Asthisfirecontinuedtoburn,flangegasketsdeterio-rated,causingmoreleaksandallowingmorefueltoflowoutofthestoragetanks.Thegrowingfireencroachedontwostoragetanksadjacenttothevalvepit.Approximately12hoursintotheincident,africtioncouplingparted,allow-ingfuelfromonestoragetanktosuddenlyincreasethefiresize.Thefirespreadto an impounding area and involved two more fuel tanks.
Thefollowingchangestothetankfarmsitewouldhavemitigatedtheout-come of this incident:
•Increased distance between the tanks and the pumping/valve area•Increased tank-to-tank separation
3.4.Process Safety Practices
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•Installationofinternalexcessfloworfail-saferemotelyoperatedvalvesfor tanks at locations where piping connects
•Provisionsfortheremovaloffuelintheeventthestoragetanks’primarydischarge means becomes inoperable
•Simpleandrecognizablemeansforfirefighterstoshutofffuelflowintothe facility
•Increased structural support for piping (CCPS G-39)
3.3.Key Issues
SafetyissuesinbatchreactionsystemsrelatingtoequipmentconfigurationandlayoutarepresentedinTable3.Thistableismeanttobeillustrativebutnotcomprehensive. A few key issues are presented below.
•Sharedventsystems,utilitysystems,orequipmentmayresultinincom-patible materials coming together.
•Potential for fire traveling through the shared vent system.
•Possibility of combining incompatible materials in drainage and dikes.•Thereisagreaterneedtoprovidereadyaccesstoequipmentinbatchplantsbecausetheserequiremoremanualoperations.Iftheaccessisdiffi-cult,itmayleadtooperatorinjuryand/orinabilityofoperatortocarryout responsibilities.
•Closeproximityofhazardousprocessesmayresultinreleasesorotherhazardousconditionsinoneprocessaffectingtheneighboringprocessareas, thereby resulting in escalation of the hazard.
3.4.Process Safety Practices
Listedbelowaresafetypracticesaimedatminimizinghazardsduetoequipmentconfiguration and layout.
•Providesafeseparationdistancesfornormaloperation,maintenance,emergency egress, ergonomics
•Design systems to prevent incompatible materials coming together•Provide appropriate area electrical classification
•Provide appropriate building, and point source ventilation•Provide ignition source control
•Monitor utility systems for contamination•Proper control room design
•Use damage limiting construction•Provide spill control
•Install adequate sprinkler protection
303.EQUIPMENT CONFIGURATION AND LAYOUTTable 3:Equipment Configuration and LayoutNo.Concern/IssueShared Systems1.Shared vent systems.Possibility of incom-patible materialscoming together.•Design to avoid incompatible materialspresent in the same vent system•Install deflagration suppression systems•Design vent to preventbackflow/accumulation•Prescrub vent discharge before transfer tovent header•Monitor circulating utility systems forcontamination2.Shared utility supply•Design to avoid common utility supplysystems. Possibility ofheaders and/or systems to processes withincompatible materialsincompatible materialscoming together via•Install backflow protection on supply linescontamination of the•Implement mechanical integrity programshared utility systemto prevent contamination of utility systems•Monitor circulating utility systems forcontamination3.Shared equipment•Design to avoid or minimize use of(e.g. auxiliary process-common equipment for incompatibleing “scrubbers”). Pos-materialssibility of incompatible•Implement proper cleaning procedurematerials comingbetween incompatible uses to preventtogether.cross contamination•Prescrub or treat process streams beforetransfer to common equipment4.Shared transfersystems.•Avoid the use of incompatible materials inshared transfer systems•Ensure cleaning procedures are followed•Avoid pockets in lines•Install dedicated transfer systemAPI RP 750CCPS G-7CCPS G-22CCPS G-29CCPS G-57NFPA-91API RP 750CCPS G-11CCPS G-22Kletz 1991Lees 1996NFPA-91API RP 750Kletz 1991Lees 1996NFPA-91ACGIH 1986CCPS G-11NFPA-69NFPA-91Potential Solutionsand Control MechanismsAdditionalResourcesTable 3:Equipment Configuration and Layout31AdditionalResourcesNo.Concern/IssueIgnition SourcesPotential Solutionsand Control Mechanisms5.Ignition of flammable•Provide safe separation distancesrelease resulting in fire•Develop appropriate area electricalor explosion.classification•Provide ignition source control•Place ignition sources in positive pressureenclosure and buildings•Provide adequate ventilationFire/ExplosionAPI RP 500BS 5345BS 5958NFPA-70NFPA-776.Shared vent systems.Potential for fire trav-eling through theshared vent system.•Design vent system to preventbackflow/accumulation•Prescrub or treat vent discharge beforetransfer to the vent header•Install detonation and / or deflagrationarresters•Install deflagration suppression system•Provide explosion venting and isolationmechanism•Provide vent system inerting or purging•Install dedicated vent systems33 CFR 154NFPA-69NFPA-917.Liquid spills. Possibil-ity of accumulation offlammable liquidsresulting in fire orexplosion hazard.•Provide spill control through adequatedrainage and curbs or dikes•Provide adequate ventilation•Wash down systems•Minimize possibility of ignition•Minimize possibility of spillsAPI RP 750CCPS G-22CCPS G-24CCPS G-30Lees 1996NFPA 69NFPA-15API RP 750CCPS G-22CCPS G-22CCPS G-24CCPS G-30NFPA-328NFPA-3298.Liquid spills. Possibil-•Provide segregation storage of incompati-ity of combiningble materialsincompatible materials•Don’t put incompatible materials in thein drainage and dikes.same dike•Use segregated drainage & sewer systems•Wash down systems•Minimize possibility of ignition•Minimize possibility of spills323.EQUIPMENT CONFIGURATION AND LAYOUTNo.Concern/IssueFire/ExplosionPotential Solutionsand Control MechanismsAdditionalResources9.Control room sitedcloser to the batchprocess due to needfor more operatorinteraction with batchprocesses. Infiltrationof flammable/toxicrelease from outside.Possible overpressurefrom externalexplosion.•Proper location of air intakeAPI RP 752.•Provide adequate control room ventilationCCPS G-26systemNFPA-101•Provide positive control room pressure toprevent inflow of hazardous material•Provide flammable/toxic detection systemsin buildings•Provide control room or facility alarm towarn occupants•Provide personal protective equipment•Provide sufficient bottled air / SCBA•Provide doors on the side of the controlroom opposite to expected hazard sources•Provide wind direction indication visiblefrom inside the building / control room•Employ damage limiting construction•Develop emergency response procedures•Develop evacuation plans•Provide exterior (and interior) fire extin-guishing equipment•Design control room to withstand blastoverpressure10.Batchequipmentlocatedindoors.Areleaseofflamma-ble/toxicmaterialtendstodisperseslowerthanifthereleaseisout-doors.Mayleadtolargeconcentrationbuildupandresultinoperatorexposure.Confinedflammablereleasesarealsomorelikelytoresultinexplosionwithlargeroverpressures.•Provide adequate building ventilation•Install flammable/toxic detection systemsin buildings with alarms to warn buildingoccupants of hazardous accumulations•Provide personal protective equipment•Provide sufficient bottled air/SCBA•Develop emergency response procedures•Develop evacuation plans•Install explosion venting for room and/orbuilding•Damage limiting construction of process-ing buildingACGIH 1986CCPS G-3CCPS G-13CCPS G-26NFPA-68Table 3:Equipment Configuration and Layout33AdditionalResourcesNo.Concern/IssueOperator ExposurePotential Solutionsand Control Mechanisms11.Operating equipmentis opened, cleaned,emptied, or chargedfrequently. Operatorexposure to toxic orflammable materialsduring normal processoperation.•Install point source ventilation•Install building ventilation•Install flammable/toxic detection systemsin buildings with alarms to warn buildingoccupants of hazardous accumulations•Use personal protective equipment•Provide sufficient bottled air/SCBA•Develop emergency response procedures•Develop appropriate evacuation plansAPI 2007CCPS G-22CCPS G-32General12.Close proximity offeed chemicals for dif-ferent processes result-ing in possibility ofusing wrong material.Close proximity ofprocess equipment andprocess areas impedesemergency responseand evacuation. Possi-bility of operatorexposure and/orreduction in efficiencyof emergencyresponse.•Provide segregated storage•Separate the processesSee also Chapter 6•Provide unique loading devices•Design equipment layout to accommodateemergency needs—response, ingress,egress•Maintain good house keeping•Schedule materials used•Investigate alternate methods of deliveryto occupy less workspace (pipeline insteadof drums)•Perform prestartup walk-through•Perform audits/inspection•Clearly mark and maintain the integrity ofroutes and pathways•Schedule processes to reduce amount ofmaterial•Redesign and modification•Use dedicated staging and storage areasCCPS G-29Kletz 1991NFPA-101Mecklenburgh1985CCPS G-29CCPS G-313.343.EQUIPMENT CONFIGURATION AND LAYOUTNo.Concern/IssueGeneralPotential Solutionsand Control MechanismsAdditionalResources14.Operator access toequipment. There is agreater need to pro-vide ready access toequipment in batchplants because theserequire more manualoperations. If theaccess is difficult, itmay lead to operatorinjury and/or inabilityof operator to carryout responsibilities.Close proximity ofhazardous processes.Possibility of releasesor other hazardousconditions in one pro-cess affecting theneighboring processareas resulting in esca-lation of the hazard.Close proximity ofhazardous process.High pressure vesselswhich may failexplosively.•Provide shortest, most direct and safestroute to items requiring most frequentattention•Consider ergonomics during layout designCCPS G-23NFPA-101Mecklenburgh198515.•Maintain safe separation distances•Consider the need for fire walls, solidfloors, etc. in building design andconstruction•Provide emergency relief design to vent tosafe locationAPI RP 752CCPS G-26CCPS G-24CCPS G-11DIERSDow F&EIAPI RP 750CCPS G-26Dow F&EI16.•Maintain safe separation distances
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