Hazardous Area Classification and Control of Ignition Sources

5/24/2015 HazardousAreaClassificationandControlofIgnitionSources

http://www.hse.gov.uk/comah/sragtech/techmeasareaclas.htm 1/17

HazardousAreaClassificationandControlofIgnitionSourcesThisTechnicalMeasuresDocumentreferstotheclassificationofplantintohazardousareas,andthesystematicidentificationandcontrolofignitionsources

TherelevantLevel2Criteriaare5.2.1.3(29)c [1],5.2.1.11(63)f [2],5.2.1.13 [3]and5.2.4.2(93)a [4].

Designofplant,pipeworkandgeneralplantlayoutisconsideredinTechnicalMeasures

DocumentsonPlantLayout [5],DesignCodesPlant [6],DesignCodesPipework [7],Plant

Modification/ChangeProcedures [8],MaintenanceProcedures [9].

TheDangerousSubstancesandExplosiveAtmospheresRegulations2002(DSEAR)provideforthefirsttimeaspecificlegalrequirementtocarryoutahazardousareastudy,anddocumenttheconclusions,intheformofzones.

GeneralPrinciplesHazardousAreaClassificationforFlammableGasesandVapours

Areaclassificationmaybecarriedoutbydirectanalogywithtypicalinstallationsdescribedinestablishedcodes,orbymorequantitativemethodsthatrequireamoredetailedknowledgeoftheplant.Thestartingpointistoidentifysourcesofreleaseofflammablegasorvapour.Thesemayarisefromconstantactivitiesfromtimetotimeinnormaloperationorastheresultofsomeunplannedevent.Inaddition,insideprocessequipmentmaybeahazardousarea,ifbothgas/vapourandairarepresent,thoughthereisnoactualrelease.

Catastrophicfailures,suchasvesselorlinerupturearenotconsideredbyanareaclassificationstudy.AhazardidentificationprocesssuchasaPreliminaryHazardAnalysis(PHA)oraHazardandOperabilityStudy(HAZOP)shouldconsidertheseabnormalevents.

ThemostcommonlyusedstandardintheUKfordeterminingareaextentandclassificationisBS

EN60079part101,whichhasbroadapplicability.Thecurrentversionmakesclearthedirectlinkbetweentheamountsofflammablevapourthatmaybereleased,theventilationatthatlocation,



andthezonenumber.Itcontainsasimplisticcalculationrelatingthesizeofzonetoarateofreleaseofgasorvapour,butitisnothelpfulforliquidreleases,wheretherateofvaporisationcontrolsthesizeofthehazardousarea.

Othersourcesofadvice,whichdescribemoresophisticatedapproaches,aretheInstituteofPetroleumModelCodeofPractice(AreaClassificationCodeforPetroleumInstallations,2002),andtheInstitutionofGasEngineersSafetyRecommendationsSR25,(2001).TheIPcodeisforusebyrefineryandpetrochemicaltypeoperations.TheIGEcodeaddressesspecificallytransmission,distributionandstoragefacilitiesfornaturalgas,ratherthangasutilisationplant,butsomeoftheinformationwillberelevanttolargerscaleusers.

Zoning

HazardousareasaredefinedinDSEARas"anyplaceinwhichanexplosiveatmospheremayoccurinquantitiessuchastorequirespecialprecautionstoprotectthesafetyofworkers".Inthiscontext,'specialprecautions'isbesttakenasrelatingtotheconstruction,installationanduseof

apparatus,asgiveninBSEN60079101.

Areaclassificationisamethodofanalysingandclassifyingtheenvironmentwhereexplosivegasatmospheresmayoccur.Themainpurposeistofacilitatetheproperselectionandinstallationofapparatustobeusedsafelyinthatenvironment,takingintoaccountthepropertiesoftheflammablematerialsthatwillbepresent.DSEARspecificallyextendstheoriginalscopeofthisanalysis,totakeintoaccountnonelectricalsourcesofignition,andmobileequipmentthatcreatesanignitionrisk.

Hazardousareasareclassifiedintozonesbasedonanassessmentofthefrequencyoftheoccurrenceanddurationofanexplosivegasatmosphere,asfollows:

Zone0:Anareainwhichanexplosivegasatmosphereispresentcontinuouslyorforlongperiods

Zone1:Anareainwhichanexplosivegasatmosphereislikelytooccurinnormaloperation

Zone2:Anareainwhichanexplosivegasatmosphereisnotlikelytooccurinnormaloperationand,ifitoccurs,willonlyexistforashorttime.

Varioussourceshavetriedtoplacetimelimitsontothesezones,butnonehavebeenofficiallyadopted.Themostcommonvaluesusedare:



Zone0:Explosiveatmosphereformorethan1000h/yr

Zone1:Explosiveatmosphereformorethan10,butlessthan1000h/yr

Zone2:Explosiveatmosphereforlessthan10h/yr,butstillsufficientlylikelyastorequirecontrolsoverignitionsources.

Wherepeoplewishtoquantifythezonedefinitions,thesevaluesarethemostappropriate,butforthemajorityofsituationsapurelyqualitativeapproachisadequate.

Whenthehazardousareasofaplanthavebeenclassified,theremainderwillbedefinedasnonhazardous,sometimesreferredtoas'safeareas'.

Thezonedefinitionstakenoaccountoftheconsequencesofarelease.Ifthisaspectisimportant,itmaybeaddressedbyupgradingthespecificationofequipmentorcontrolsoveractivitiesallowedwithinthezone.Thealternativeofspecifyingtheextentofzonesmoreconservativelyisnotgenerallyrecommended,asitleadstomoredifficultieswithequipmentselection,andillogicalitiesinrespectofcontroloverhealtheffectsfromvapoursassumedtobepresent.WhereoccupierschoosetodefineextensiveareasasZone1,thepracticalconsequencescouldusefullybediscussedduringsiteinspection.

Asanexample:

AproposalwasmadetozoneanaircrafthangerasZone1,althoughtheuseoffuelshandledabovetheirflashpointwouldbearareevent.ItproveddifficulttoobtainafloorcleaningmachinecertifiedforZone1areas,thoughthefloorneededsweepingregularly.TheoptionofwritingoutanexceptiontonormalinstructionstoallowanonExprotectedmachinetobeusedregularlyisnotrecommended.Instead,amorerealisticassessmentofthezonesisneeded,andspecialinstructionsissuedfortherareeventofusingmorevolatilefuels.

Ahazardousareaextentandclassificationstudyinvolvesdueconsiderationanddocumentationofthefollowing:

Theflammablematerialsthatmaybepresent

Thephysicalpropertiesandcharacteristicsofeachoftheflammablematerials

Thesourceofpotentialreleasesandhowtheycanformexplosiveatmospheres

Prevailingoperatingtemperaturesandpressures

Presence,degreeandavailabilityofventilation(forcedandnatural)



Dispersionofreleasedvapourstobelowflammablelimits

Theprobabilityofeachreleasescenario.

Thesefactorsenableappropriateselectionofzonetypeandzoneextent,andalsoofequipment.TheIPcodegivesamethodologyforestimatingreleaseratesfromsmalldiameterholeswithpressurisedsources,andshowshowboththebuoyancyandmomentumofthereleaseinfluencetheextentofazone.IttabulatesvaluesforanLPGmixture,gasoline,naturalgas,andrefineryhydrogenforpressuresupto100barg.SimilarlytheIGEcodegivesamethodologyfornaturalgas,relatingtheleakratetotheholesizeandtheoperatingpressure.Thetablesofdispersiondistancestothezoneboundaryaddressinthemainquitelargediameterdeliberatevents.Thereisinpracticelittleoverlapbetweenthecodes.

TheresultsofthisworkshouldbedocumentedinHazardousAreaClassificationdatasheets,supportedbyappropriatereferencedrawingsshowingtheextentofthezonesaround(includingaboveandbelowwhereappropriate)theplantitem.

SelectionofEquipment

DSEARsetsoutthelinkbetweenzones,andtheequipmentthatmaybeinstalledinthatzone.Thisappliestonewornewlymodifiedinstallations.TheequipmentcategoriesaredefinedbytheATEXequipmentdirective,setoutinUKlawastheEquipmentandProtectiveSystemsforUseinPotentiallyExplosiveAtmospheresRegulations1996.Standardssetoutdifferentprotectionconcepts,withfurthersubdivisionsforsometypesofequipmentaccordingtogasgroupandtemperatureclassification.Mostoftheelectricalstandardshavebeendevelopedovermanyyearsandarenowsetatinternationallevel,whilestandardsfornonelectricalequipmentareonlyjustbecomingavailablefromCEN.

TheDSEARACOPdescribestheprovisionsconcerningexistingequipment.

Therearedifferenttechnicalmeans(protectionconcepts)ofbuildingequipmenttothedifferentcategories.These,thestandardcurrentinmid2003,andthelettergivingthetypeofprotectionarelistedbelow.

Zone0 Zone1 Zone2

Category1 Category2 Category3

'ia'intrinsicallysafeEN50020,2002

'd'Flameproofenclosure

ElectricalType'n'EN50021



EN500182000 1999NonelectricalEN134631,2001

ExsSpecialprotectionifspecificallycertifiedforZone0

'p'PressurisedEN500162002

'q'PowderfillingEN50017,1998

'o'OilimmersionEN50015,1998

'e'IncreasedsafetyEN50019,2000

'ib'IntrinsicsafetyEN50020,2002

'm'EncapsulationEN50028,1987

's'Specialprotection

Correctselectionofelectricalequipmentforhazardousareasrequiresthefollowinginformation:

Classificationofthehazardousarea(asinzonesshowninthetableabove)

Temperatureclassorignitiontemperatureofthegasorvapourinvolvedaccordingtothetablebelow:

TemperatureClassification

MaximumSurfaceTemperature,C

IgnitionTemperatureofgasorvapour,C

T1 450 >450

T2 300 >300

T3 200 >200

T4 135 >135

T5 100 >100

T6 85 >85



Ifseveraldifferentflammablematerialsmaybepresentwithinaparticulararea,thematerialthatgivesthehighestclassificationdictatestheoverallareaclassification.TheIPcodeconsidersspecificallytheissueofhydrogencontainingprocessstreamsascommonlyfoundonrefineryplants.Considerationshouldbeshownforflammablematerialthatmaybegeneratedduetointeractionbetweenchemicalspecies.

IgnitionSourcesIdentificationandControl

Ignitionsourcesmaybe:

Flames

Directfiredspaceandprocessheating

Useofcigarettes/matchesetc

Cuttingandweldingflames

Hotsurfaces

Heatedprocessvesselssuchasdryersandfurnaces

Hotprocessvessels

Spaceheatingequipment

Mechanicalmachinery

Electricalequipmentandlights

Spontaneousheating

Frictionheatingorsparks

Impactsparks

Sparksfromelectricalequipment

Straycurrentsfromelectricalequipment

Electrostaticdischargesparks:

Lightningstrikes.

Electromagneticradiationofdifferentwavelengths

Vehicles,unlessspeciallydesignedormodifiedarelikelytocontainarangeofpotentialignitionsources



Sourcesofignitionshouldbeeffectivelycontrolledinallhazardousareasbyacombinationofdesignmeasures,andsystemsofwork:

Usingelectricalequipmentandinstrumentationclassifiedforthezoneinwhichitislocated.Newmechanicalequipmentwillneedtobeselectedinthesameway.(Seeabove)

Earthingofallplant/equipment(seeTechnicalMeasuresDocumentonEarthing [10])

Eliminationofsurfacesaboveautoignitiontemperaturesofflammablematerialsbeinghandled/stored(seeabove)

Provisionoflightningprotection

Correctselectionofvehicles/internalcombustionenginesthathavetoworkinthezoned

areas(seeTechnicalMeasuresDocumentonPermittoWorkSystems [11])

Correctselectionofequipmenttoavoidhighintensityelectromagneticradiationsources,e.g.limitationsonthepowerinputtofibreopticsystems,avoidanceofhighintensitylasersorsourcesofinfraredradiation

Prohibitionofsmoking/useofmatches/lighters

Controlsovertheuseofnormalvehicles

Controlsoveractivitiesthatcreateintermittenthazardousareas,e.g.tankerloading/unloading

Controlofmaintenanceactivitiesthatmaycausesparks/hotsurfaces/nakedflamesthroughaPermittoWorkSystem

Precautionstocontroltheriskfrompyrophoricscale,usuallyassociatedwithformationofferroussulphideinsideprocessequipment

DirectFiredHeaters,HotOilSystemsandProcessesOperatingAboveAutoIgnitionTemperaturesArangeofpetrochemicalandrefineryprocessesusedirectfiredheaters,e.g.steamcrackersforethyleneproduction.Clearly,ifthefuelsupplytotheheaterorthepipeworkcarryingtheprocessfluidleaksclosetothefurnace,anyleakmustbeexpectedtofindasourceofignition,eitherdirectlyattheflames,orbyasurfaceheatedbyaflame.Inthesecircumstances,hazardousareaclassification,andappropriateselectionofATEXequipmentisnotsuitableasabasisofsafetyfor



preventingfireandexplosionrisks.

Instead,safetyshouldbeachievedbyacombinationofahighstandardofintegrityoffuelandprocesspipelines,togetherwithameansofrapiddetectionandisolationofanypipesthatdofail.TheconsequencesofthefailureofapipecarryingprocessmaterialswithinthefurnaceshouldbeconsideredinanyHAZOPstudy.

Otherprocesses(suchashotoilheatingcircuits)mayhandleproductsabovetheirautoignitiontemperature.Anysuchprocessesshouldbespecificallyidentifiedinasafetycase.Again,areaclassificationisnotasuitablemeansofcontrollingtheignitionrisks,andthesameconsiderationsapply,aswithfiredheaters.

LightningProtectionProtectionagainstlightninginvolvesinstallationofasurgeprotectiondevicebetweeneachnonearthbondedcoreofthecableandthelocalstructure.FurtherguidancecanbefoundinBS

6651:19991(Codeofpracticeforprotectionofstructuresagainstlightning).Ignitionscausedbylightningcannotbeeliminatedentirely,particularlywithfloatingrooftanks,wherevapourisusuallypresentaroundtherimseal.Inthesecircumstances,measurestomitigatetheconsequencesofafireshouldbeprovided.

VehiclesMostnormalvehiclescontainawiderangeofignitionsources.Thesewillincludeelectricalcircuitstheinletandexhaustofanyinternalcombustionengineelectrostaticbuildupoverheatingbrakes,andothermovingparts.Siterulesshouldbeclearwherenormalroadvehiclesmaybetaken,andareaswheretheymustbeexcluded.

StandardEN17551setsouttherequirementsfordieselpowderedATEXcategory2or3lifttrucks.Electricpoweredvehiclescanalsobebuiltusingacombinationofthisstandardandthenormalelectricalstandards.Nospecificationisavailableforvehicleswithsparkignitionengines,anditisunlikelythatsuchanenginecouldbebuilteconomically.VehiclescertifiedtoATEXrequirementsarehoweverexpensive,andformanyapplicationsanunprotectedtypehastobeextensivelyrebuilt.Consequently,manyemployersarelikelytotryandjustifynotzoningstoragecompounds,wherelifttruckshandleflammableliquidsorgasesincontainers.Insomestores,perhapswithlimiteduseofavehicle,thismaybeacceptable.DiscussionshavebeenheldwiththeBritishChemicalDistributorsandTradersAssociation,withtheobjectiveofclarifyingwhen



storageareasshouldbeclassifiedaszone2.Theconclusionsfromthisexercisewillbemadeavailableinduecourse.Discussionsarealsoongoing,aboutvehicleswithgasdetectionsystems,designedtoshuttheengineandisolateothersourcesofignitionintheeventofagasrelease.AtpresentthesearesoldwithoutanyclaimforATEXcompliance,butwiththesuggestiontheymaybeusefulincasesofremoterisk.

ForthepurposesofCOMAH,anassessmentisneededoftheriskthatanignitionwithinastoragecompoundwillproduceamajoraccident,eitherdirectlyorbecauseafireorexplosionspreadstoinvolveothermaterials.Ifthisispossible,itismoreappropriatetoprovidecontrolstopreventthespread,ratherthansimplyapplymoreconservativezoning,andmorerestrictiverulesontheequipmentusedinthestore.

Wherespecialistvehicles(e.g.cranes)areneededduringmaintenanceoperations,propercontrolsandplantisolationmayallowthenormalzonestobesuspended.Typicallythesewillinvolvewritteninstructions,asspecifiedinDSEARschedule1,oraformalpermittoworksystem.

Manysiteswillhaveoperationsoffillingandemptyingroadtankerswithflammablematerials.Controlswillbeneededtopreventorminimisethereleaseofgasorvapourbutcontrolsoverignitionsourcesarealsoneeded.Hazardousareasmaybeconsideredtoexistduringthetransferoperation,butshouldnotbepresentoncethetransferiscomplete.Safesystemsofworkareneededtoensuresafetywheresuch'transient'zonesexist.

FactorsforAssessorofaSafetyCasetoConsiderIsafullsetofplansidentifyinghazardousareasavailable?Foralargesitetheyneednotallbeprovidedinthereport,butthoseexamplesrelevanttotherepresentativesetofmajoraccidentsuponwhichtheALARPdemonstrationisbasedmustbeincluded.

Haveallflammablesubstancespresenthavebeenconsideredduringareaclassification,includingrawmaterials,intermediatesandbyproducts,finalproductandeffluents?Commonlythesewillbegroupedforthepurposesofanyareaclassificationstudy.

Locationswherealargereleaseispossibleandtheextentofhazardousareashasbeenminimisedbytheuseofmechanicalventilationshouldbeidentified,e.g.gasturbinepowergenerationunits,compressorhouses.Somereferencetodesigncodes,andcommissioningcheckstoensuretheventilationachievesthedesignaim,shouldbeprovided.Theconsequencesofalossofpowertothesystemshouldbeincludedinanysectionlookingatotherconsequencesofpowerloss.



Haveappropriatestandardsbeenusedforselectionofequipmentinhazardousareas?ExistingplantwillnotmeettheformulainDSEAR,butolderstandardsdistinguishedbetweenelectricalequipmentsuitableforzones0,1and2.Doesthereportidentifyoldelectricalequipmentstillinserviceinahazardousarea,andwhatassessmenthasbeenmadetoensureitremainssafeforuse?

Isthereareferencetotheimpactuponextentandclassificationofhazardousareasinthesectiondescribingplantmodification(seeTechnicalMeasuresDocumentonPlant

Modification/ChangeProcedures [12])passiveitemslikenewwallsandbuildingscaninfluencethisiftheyobstructnaturalventilationofadjacentplant

Haveallignitionsourcesbeenconsidered?AchecklistisprovidedintheDSEARACOP

oncontrolandmitigationmeasures,andBSEN1127part11(Explosiveatmospheres.Explosionpreventionandprotection.Basicconceptsandmethodology).

FactorsthatcouldbeconsideredduringanonsiteinspectionIfthereareanylargeareasofzone1onthedrawings,isthereevidencethatbydesignandoperationcontrols,thesourcesofreleaseandconsequentlythelocationandextentofhazardousareashavebeenminimised?

Doanyzone2areasextendtoplaceswheretheoccupierhasinadequatecontroloveractivitiesthatcouldcreateanignitionsource,oristhereanysuggestionthatthezoneboundarieshavebeenarbitrarilyadjustedtoavoidthis?

Hasignitionprotectedelectricalequipmentbeeninstalledandmaintainedbysuitablytrainedstaff.

Aretherisksfromstaticdischargescontrolledproperly?Earthingofplant,drumsandtankersisthemostbasicrequirementotherprecautionsaredescribedinthereferences

Whatcontrolmeasuresoverignitionsourcesareadoptedinhazardousareasduringmaintenancewhereignitionsourcesmustbeintroduced,typicalprecautionsincludetheuseofsupplementaryventilation,portablegasdetectors,andinertingofsectionsof

plant.AlocalprojectonElectricalEquipmentinFlammableAtmospheres [13]wasundertakenandareportoftheproject'sconclusionscompleted.

DustExplosionsTheCOMAHRegulationsdonotapplytoanymaterialiftheonlyriskcreatedisthatofadust



explosion.However,manytoxicmaterialsarehandledinfinepowderform,andaseriousdustexplosioncouldcauseamajoraccident.Adustexplosioninvolvinganontoxicdustlikepolyethylenewouldnotresultinamajoraccidentasdefinedintheregulations,unlessitalsoledtolossofcontainmentofaCOMAHsubstance.Adustexplosioncouldthenbeaninitiatorofamajoraccident.Measurestopreventmajoraccidentsshouldaddressallpotentialinitiators.

DSEARrequiresthathazardousareaclassificationforflammabledustsshouldbeundertakeninthesamemannerasthatforflammablegasesandvapours.Zoningasdescribedabovemaybeapplied,replacing'gasatmosphere'with'dust/airmixtures'.Thezonenumbersusedare20,21and22,correspondingto0,1and2usedforgases/vapours

TheonlyrelevantstandardtohelppeoplezonetheirplantisBSEN50281part3,20021,whichisanadaptationoftheIECequivalent.

Wheretoxicdustsareprocessed,releasesintothegeneralatmosphereshouldbeprevented,andtheextentofanyzone21or22outsidethecontainmentsystemshouldbeminimalornonexistent.Theinsideofdifferentpartsoftheplantmayneedtobezonedas20,21or22,dependingontheconditionsatparticularlocations.

Classificationofdustsrelatingtoautoignitionandminimumignitioncurrentisundertakensimilarlytogases/vapours,butinvolvesadditionalcomplications.

Theexplosibilityofdustsisdependentuponanumberoffactors:

chemicalcomposition

particlesize

oxygenconcentration

Wheretoxicdustsarehandled,inmostcasesoccupierswillneedtocarryouttestingoftheproductforitsexplosionproperties.CompaniesabletoundertakensuchtestingarelistedintheIChemE'sbookonthepreventionofdustexplosions.Thereisnolegallydefinedtestforanexplosibledust.However,formanyyearswehaveusedasmallscalescreeningtest,thevertical

tubetest,describedinHSG1032.Theissuesaboutrepresentativesamplesofdust,andotherfactorsthatmightcausetheresultstovaryarealsodiscussedinthisguidance.Ingeneral,dustswithaparticlesizegreaterthan500mareunlikelytocauseanexplosion.Formostchemicalproductsitispreferabletotestdusttakenfromtheprocess,butiftheparticlesizedistribution



varies,itiscommontotestmaterialthatpassesa63micronsieve,andtakethisastheworstcase.

Ignitionduetoahotsurfaceispossible,butthetemperatureneededtoigniteadustlayerdependsonlayerthicknessandcontacttime.ForCOMAHsiteswithtoxicdusts,themostlikelyhazardwouldariseindryingprocesses,ifsubstantialquantitieswereheldforextendedperiodshotenoughtostartselfheatingorsmoulderingcombustion.

StatusofGuidanceExistingcodesofpracticeprovideinformationwithrespecttogoodpracticeforhazardousareaclassification.Thestandardsdetailingselectionofappropriateelectricalapparatushavebeenupdatedtotakeintoconsiderationventilationeffects.

Europeanequipmentstandardsmaybecome'harmonised'whenareferencetothemispublishedintheOfficialJournaloftheEuropeanCommunity.AlistofATEXharmonisedstandardscanbe

checkedontheEUwebsite [14]:

Equipmentbuilttosuchaharmonisedstandardmayassumeautomaticconformitywiththoseessentialsafetyrequirementsofrelevantdirectivesthatarecoveredbythestandard.TheEPSregulationsdescribetheconformityassessmentproceduresthatapplytodifferenttypesofequipment.

ReferenceDocumentsHS(G)512Storageofflammableliquidsincontainers,HSE,1998.Appendix3describestherequirementsforhazardousareaclassification.TheuseofBS

EN6007910:20031,andtheInstituteofPetroleumCode'AreaClassificationCodeforPetroleumInstallations:ModelCodeofpracticeinthePetroleumIndustry'Part15arerecommended.Itsuggestsalldrumstoresshouldbezone2,toaheight1mabovethestack.ThesameadviceappearsinHSG166andHSG113onignitionprotectedlifttrucks.Discussionswithindustryontherelaxationofthisinparticularcircumstancesareongoing.

HS(G)712Chemicalwarehousing:thestorageofpackageddangeroussubstances,HSE,1998.Thiscontainsverylimitedinformationonhazardousareaclassificationorcontrolof



ignitionsources

HS(G)1032Safehandlingofcombustibledusts:precautionsagainstexplosions,HSE,2ndEdition,2003

HS(G)1132Lifttrucksinpotentiallyflammableatmospheres.ThecontentsofthishavebeenovertakentosomedegreebyDSEAR,andtheEPSregulations.

HS(G)1402Safeuseandhandlingofflammableliquids,HSE,1996.Appendix3describestherequirementsforhazardousareaclassification.TheuseofBS

EN60079141andtheInstituteofPetroleumCode'AreaClassificationCodeforPetroleumInstallations:ModelCodeofpracticeinthePetroleumIndustry'Part15arerecommended.Thisisaimedmainlyatsmallscalehandling,withcontainersof200litresorless.

HS(G)1662Formulaforhealthandsafety:guidanceforsmallandmediumsizedfirmsinthechemicalindustry,HSE,1997.Theguidancedescribestherequirementsforhazardousareaclassification,andgivessometypicalexamples.Theseshouldnowbeseenasratherconservative.Theuseof

BSEN6007914,BSEN50281andBSEN605291arerecommended.Thisisbasiclevelguidance,andCOMAHreportsshouldnormallyreferencemorespecificpublications,suchastheotherHSGseriesbookslisted,andotheritemsinthislist.

HS(G)1762Thestorageofflammableliquidsintanks,HSE,1998.Paragraphs35to39describetherequirementsforhazardousareaclassification.This

crossreferencesBSEN6007910:20031,andtheInstituteofPetroleumCode'AreaClassificationCodeforPetroleumInstallations:InstituteofPetroleumModelCodeofSafePractice,part15,areaclassificationforinstallationshandlingflammablefluids,2ndedition2002.

HS(G)1862Thebulktransferofdangerousliquidsandgasesbetweenshipandshore,HSE,1999.Appendix2describestherequirementsforhazardousareaclassification.TheuseofBS

EN60079101andtheInstituteofPetroleumCode'AreaClassificationCodeforPetroleumInstallations:ModelCodeofpracticeinthePetroleumIndustry'Part15arerecommended.Containsusefulinformationaboutelectrostatichazardsduringunloading.

LPGACOP1BulkLPGstorageatfixedinstallations.Part1:Design,installationand



operationofvesselslocatedaboveground,LPGasAssociation,1998.

LPGAcodeshavenotpreviouslydrawnacleardistinctionbetweenhazardousareas,andseparationdistancesrequiredforotherreasons.Thesearecurrentlyunderrevision,andwillspecifyhazardousareas,thatinmostcaseswillbesmallerthantheseparation

distance.CurrentcodesarelistedontheUKLPGwebsite [15].

ModelCodeofpracticeinthePetroleumIndustry'Part15isrecommended.Theguidancealsorecommendsthatzonesberecordedinaplantopreventsourcesofignitionbeingbroughtin.

ElectricalEquipment

StandardsproducedbyEuropeintheBSEN50014rangearegraduallybeing

supersededbyinternationalstandardsproducedintherangeBSIEC600791.Equipmentbuilttoolderstandards,includingpurelynationalstandardsmayremaininservice,provideditisproperlymaintained.TheIECrangeofstandardsalsoincludesdocumentsonselection,installationandmaintenanceofequipmentforuseinexplosiveatmospheres.

Nonelectricalequipment

ThefirststandardforexplosionprotectednonelectricalequipmentisBSEN13463part

11.Itdescribesrequirementsfor"Category3"equipment.Furtherpartsofthisstandardarewelladvancedandwillappearduring2004.

BSEN11271:19981ExplosiveatmospheresExplosionpreventionandprotectionPart1:Basicconceptsandmethodology,BritishStandardsInstitution.ThisgivesadditionalgeneraladviceonthemanyoftheissuescoveredinthisTMD.

Electrostaticignitionrisks

ThemostrecentgeneralsourceofadvicewasdraftedbyaEuropeanstandardsworkinggroup,butwaspublishedintheUKasBSPDR044001andnotasafullstandard.Itcontainsmuchusefuladviceaboutlimitingpumpingspeeds,electrostaticrisksfromclothing,andmanydetailed

operations.ThetwopartsoftheolderBS5958:19911CodeofPracticeforthecontrolofundesirablestaticelectricityremaincurrent,becausetheycontainsomeusefulinformationnotduplicatedbythePD.Thetwopartsare:



Part1:1991Generalconsiderations

Part2:1991Recommendationsforparticularindustrialsituations

BSEN502811.Thedifferentpartsofthisstandardsetoutrequirementsforconstructionofequipmentforuseinatmospherescontainingexplosivedustsinformationaboutselectionandmaintenanceand

BSEN502813:20021coverstheclassificationofareaswherecombustibledustsareormaybepresent.

BS6651:19991.Codeofpracticeforprotectionofstructuresagainstlightning,BritishStandardsInstitution.Section9providesguidanceonlightningprotectionofstructureswithinherentexplosiverisks.

BS7430:19981Codeofpracticeforearthing,BritishStandardsInstitution.Lightningprotection.Section23providesguidanceonlightningprotection.

FurtherReadingMaterialCox,A.W.,Lees,F.P.andAng,M.L.,'ClassificationofHazardousLocations',1993.

Thiswasastudyledbyaconsortiumofthechemical,electricalandmechanicalengineeringinstitutes,andshowedhowthesubjectspannedthetraditionaldivides.Itwasimportantinthedevelopmentofideas,butprovidesnonewmethodologyforusers.

AGuidetoSafetyinAerosolManufacture,BAMA,ThirdEdition,1999.

DustExplosionPreventionandProtection:APracticalGuide,IChemE,ISBN0852954107

Apractitioner'shandbookElectricalinstallationandmaintenanceinpotentiallyexplosive

atmospheres [16],PublicationNo.186,TheEngineeringEquipmentandMaterialsUsersAssociation.

References1. ForfurtherinformationontherelevantBritishStandards,pleaseaccesstheBritish

Standardswebsite [17]andusethesearchfacility.



Pagelastupdated:22ndSeptember2004

LinkURLsinthispage

1. 5.2.1.3(29)chttp://www.hse.gov.uk/comah/sram/index.htm

2. 5.2.1.11(63)fhttp://www.hse.gov.uk/comah/sram/index.htm

3. 5.2.1.13http://www.hse.gov.uk/comah/sram/index.htm

4. 5.2.4.2(93)ahttp://www.hse.gov.uk/comah/sram/index.htm

5. PlantLayouthttp://www.hse.gov.uk/comah/sragtech/techmeasplantlay.htm

6. DesignCodesPlanthttp://www.hse.gov.uk/comah/sragtech/techmeasplant.htm

7. DesignCodesPipeworkhttp://www.hse.gov.uk/comah/sragtech/techmeaspipework.htm

8. PlantModification/ChangeProcedureshttp://www.hse.gov.uk/comah/sragtech/techmeasplantmod.htm

9. MaintenanceProcedureshttp://www.hse.gov.uk/comah/sragtech/techmeasmaintena.htm

10. Earthinghttp://www.hse.gov.uk/comah/sragtech/techmeasearthing.htm

11. PermittoWorkSystemshttp://www.hse.gov.uk/comah/sragtech/techmeaspermit.htm

12. PlantModification/ChangeProcedureshttp://www.hse.gov.uk/comah/sragtech/techmeasplantmod.htm

13. ElectricalEquipmentinFlammableAtmosphereshttp://www.hse.gov.uk/comah/sragtech/images/flamatmosphere.pdf

14. EUwebsitehttp://europa.eu/index_en.htm

15. UKLPGwebsite



http://www.uklpg.org/

16. Electricalinstallationandmaintenanceinpotentiallyexplosiveatmosphereshttp://www.eemua.org/Products/Publications/Print/EEMUAPublication186.aspx

17. BritishStandardswebsitehttp://www.bsiglobal.com/index.xalter

Hazardous Area Classification and Control of Ignition Sources

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