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ElectricalApparatusandHazardousAreas(Published2007)

Thisbookgivesfullinformationofbothelectricalandnonelectricalhazardousareatechnology

andcoversterminology,equipmentmarking,ATEX,DSEAR,AreaClassification,TypesofProtectionetc.

Clickherefordetails

Hazardousareasaredefinedbythreemaincriteria:ThetypeofhazardThelikelihoodofthehazardbeingpresentinflammableconcentrationsThe(auto)ignitiontemperatureofthehazardousmaterial

Thetypeofhazard(Groups)

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Thehazardwillbeintheformofagas,vapour,dustorfibre.GasesandVapours

Gasesandvapoursarecategorizedintermsoftheirignitionenergyorthemaximumexperimentalsafegap(inrespectofflameproofprotection).ThiscategorizationleadstotheGasGroups:

Mining SurfaceIndustryGroupI GroupII

MethaneIIA IIB IIC

Propane Ethylene Hydrogen

(Thegasesnotedinthetablearetypicalgasesforeachgroup.)

GroupIICisthemostseveregroup.Hazardsinthisgroupcanbeignitedveryeasilyindeed.

EquipmentmarkedassuitableforGroupIICisalsosuitableforIIBandIIA.

EquipmentmarkedassuitableforIIBisalsosuitableforIIAbutNOTforIIC.

Ifequipmentismarked,forexample,ExeIIT4thenitissuitableforallsubgroupsIIA,IIBandIIC.

DustsandFibres(GroupIII)

GroupIIIissubdividedintothreesubgroups:

IIIACombustibleflyings

IIIBNonconductivedust

IIICElectricallyconductivedusts

Dustsandfibresarealsodefinedintermsoftheirignitionpropertiesincludingdustcloudignitionproperties.

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Thelikelihoodofthehazardbeingpresentinflammableconcentrations(Zones)

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Thelikelihoodofthehazardbeingpresentinflammableconcentrationswillvaryfromplacetoplace.Alocationveryclosetoanopensourceofhazardwillhaveahighlikelihoodofaflammableatmosphere.Ontheotherhand,outsideaflangedpipecontainingaflammableliquid,thelikelihoodofaflammableatmospherebeingpresentismuchlowersinceitwillonlyoccuriftheflangeleaks.Ratherthanworkwithaninfiniterangeofpossibilities,threezonesaredefined.

GasesandVapours

Therearethreezonesforgasesandvapours:

Zone0 Flammableatmospherehighlylikelytobepresentmaybepresentforlongperiodsorevencontinuously

Zone1 Flammableatmospherepossiblebutunlikelytobepresentforlongperiods

Zone2Flammableatmosphereunlikelytobepresentexceptfor

shortperiodsoftimetypicallyasaresultofaprocessfaultcondition.

Zonezeroisthemostseverezone(thehighestprobabilityofflammableatmospherepresence).Equipmentforthiszoneneedstobeverywellprotectedagainstprovidingasourceofignition.

Dusts

Therearethreezonesfordusts:

Zone20 Dustcloudlikelytobepresentcontinuouslyorforlongperiods

Zone21 Dustcloudlikelytobepresentoccasionallyinnormaloperation

Zone22 Dustcloudunlikelytooccurinnormaloperation,butifitdoes,willonlyexistforashortperiod

(Thepresenceofdustlayersdoesnotautomaticallyleadtothedustzone.Thelikelihoodofthedustlayerbeingdisturbedtocreateacloudneedstobeconsidered.Dustlayersalsoneedcarefulconsiderationintermsofignitiontemperature.Becausethedustlayercanmaketheequipmentunderithotterthennormal,afactorofsafetyisappliedtothelayerignitiontemperature.)

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The(auto)ignitiontemperatureofthehazardousmaterial(TemperatureClasses)Aswellasconsideringtheprotectionagainstelectricalarcsandsparksignitingaflammableatmosphere,considerationneedstobegiventothesurfacetemperatureofequipment.(Mostelectricalapparatusdissipatessomeheat!)Flammablematerialsarecategorizedaccordingtotheirignitiontemperature.Again,ratherthanworkwithaninfiniterange,sixtemperatureclassesaredefinedasfollows:

TClass Hazardswhichwillnotigniteattemperaturesbelow:T1 450CT2 300CT3 200CT4 135CT5 100CT6 85C

ThebiggertheTnumbertheloweristhetemperature.

TheTemperatureclassificationwillbemarkedonitemsofequipment.IfthehazardousareainwhichyouareinstallingequipmenthasgasesorvapourswithalowautoignitiontemperaturethenyouwillneedequipmentwithabiggerTNumbersoastoensurethatanyhotsurfacesontheequipmentwillnotignitethehazard.

Forexample,ifahazardhasanautoignitiontemperatureof180C,thenitwouldbesafetouseequipmentwhichismarkedT6orT5orT4.ItwouldnotbesafetouseequipmentmarkedT3orT2orT1asthisequipmentcouldexhibitsurfacetemperatureswhicharehotenoughtoignitethehazardousatmosphere.

Don'tforgetthat,unlessthecertificationdocumentsstateotherwise(inwhichcasetherewillbeanadditiontotheTClassificationcodeontheequipmentlabelsuchasT4(60CAmb))theequipmentisonlycertifiedinambienttemperaturesupto40C.Ifexposedtohighertemperaturestherearetwopossibledangers.FirstthestatedTClasstemperaturemaybeexceededandsecondlysafetycomponentswithintheequipmentcouldfailtoanunsafecondition.Ifyouexpectequipmenttobesubjectedtotemperaturesabove40C(suchasindirectsunshineorinaroofspace)youshouldinstallequipmentwhichiscertifiedforahigherambienttemperature.

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ProtectingElectricalApparatustomakeitsuitableforuseinhazardousareas

Electricalapparatusforuseinhazardousareasneedstobedesignedandconstructedinsuchawaythatitwillnotprovideasourceofignition.Therearetenrecognizedtypesofprotectionforhazardousareaelectricalapparatus.Eachtypeofprotectionachievesitssafetyfromignitionindifferentwaysandnotallareequallysafe.InadditiontotheequipmentbeingsuitablefortheGasGroupandtheTemperatureClassrequired,thetypeofprotectionmustbesuitableforthezoneinwhichitistobeinstalled.Thedifferenttypesofprotectionandthezonesforwhichtheyaresuitableareasfollows:

Forinformationonequipmentmarking,clickhere(opensnewpage)

TypesofProtectionforGas/VapourHazards

SeealsoinformationonTypesofProtection,Clickhere(opensnewpage)

EquipmentCode Description

Suitableforzones...

EquipmentCategory...

Exia Intrinsicsafety'ia' 0,1,2 1GExib Intrinsicsafety'ib' 1,2 2GExic IntrinsicSafety'ic' 2 3GExd Flameproofprotection 1,2 2GExp Purge/pressurizedprotection 1,2 2G

Expx Purge/pressurizedprotection'px' 1,2 2G

Expy Purge/pressurizedprotection'py' 1,2 2G

Expz Purge/pressurizedprotection'pz' 2 3G

Exe Increasedsafety 1,2 2GExm Encapsulation 1,2 2GExma Encapsulation 0,1,2 1G

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Exmb Encapsulation 1.2 2GExmc Encapsulation 2 3GExo Oilimmersion 1,2 2GExq Sand/powder(quartz)filling 1,2 2GExn Typenprotection 2 3GExs Specialprotection Normally1and2

EquipmentcomplyingwithEuropean(CENELEC)standardswillfrequentlybearthecodeEEx(asopposedtoEx)ButnotethattheuseofEExisbeingphasedout,andequipmentdesignedandcertifiedtothelatesteditionsoftheEuropeanStandardswillbecodedEx...(asopposedtoEEx...).

Ingeneral,theEuropeanstandardsforhazardousareaelectricalequipmentaretechnicallyidenticaltotheIEC(InternationalElectrotechnicalCommission)standards.EquipmentmanufacturersoftenhhavetheirequipmentdesignscertifiedtoboththeEuropeanandIECrequirementssothattheycanmarkettheirequipmentworldwide.Thisdoes,unfortunatelymaketheequipmentlabellingplatemorecomplex.

TypesofProtectionforEquipmentforDustHazardLocations

EquipmentCode Description

SuitableforZones...

EquipmentCategory..

tDA20 Protectionbyenclosure 20,21,22 1DtDB20 Protectionbyenclosure 20,21,22 1DiaD IntrinsicSafety 20,21,22 1DmaD Encapsulation 20,21,22 1DtDA21 Protectionbyenclosure 21,22 2DtDB21 Protectionbyenclosure 21,22 2DibD IntrinsicSafety 21,22 2DmbD Encapsulation 21,22 2DpD Pressurization 21,22 2D

tDA22 Protectionbyenclosure 22 3DtDB22 Protectionbyenclosure 22 3D

icD IntrinsicSafety 22 3D

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EquipmentProtectionLevelsEPLFrom2007onwards,theIECTechnicalStandardsintheseriesIEC60079,andinparticularIEC60079Part14,haverecognisedthattheremaybeoccasionswhereitisnecessarytoincrease,abovethenormallevels,theprotectionagainstignitionsources.Thisconceptallowsforconsiderationofrisk(ieconsequencesofanexplosion)asopposedtojusttheprobabilityofaflammableatmosphereexistingtheconventionalselectioncriteriabetweenthetypesofprotectionandthezoneofuse.

ThreeEquipmentProtectionLevelsarespecifiedasshowninthetablebelow.

InnormalcircumstancestheeffectoftheseEPLswillbetoretainthenormalzone/equipmentprotectionrelationship.If,however,theriskisconsideredespeciallysevere,thentherequiredEPLforthezonemaybeincreased.Similarly,iftheriskisdeemedtobeespeciallysmallornegligible,theEPLmaybereducedfromthenorm.

ThefollowingtwotablesshowthenormalrelationshipbetweenEPLandzone,andtheEPLawardedtoeachtypeofprotection.

EquipmentProtectionLevel(EPL) NormalApplicableZone(s)

Ga 0(and1and2)Gb 1(and2)Gc 2

EquipmentCode Description EPLExia Intrinsicsafety'ia' GaExib Intrinsicsafety'ib' GbExic IntrinsicSafety'ic' GcExd Flameproofprotection GbExp Purge/pressurizedprotection GbExpx Purge/pressurizedprotection'px' GbExpy Purge/pressurizedprotection'py' GbExpz Purge/pressurizedprotection'pz' Gc

Exe Increasedsafety Gb

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Exm Encapsulation GbExma Encapsulation GaExmb Encapsulation GbExo Oilimmersion GbExq Sand/powder(quartz)filling GbExn Typenprotection Gc

Exs SpecialprotectionRefertoequipment

markinganddocumentation

Fordusthazards,theEPLsareasfollows:

EquipmentProtectionLevel(EPL) NormalApplicableZone(s)

Da 20(and21and22)Db 21(and22)Dc 22

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StandardsTherearevariousstandardswhichgivedetailsofhazardousarearequirements.Inthemain,theIECstandardsarenowparallelvotedbyCENELEC(Europe).Newstandardsarebeingintroducedatabewilderingrateanditisalwaysworthcheckingagainst,forexample,theBSIwebsite.(SeeUsefulLinksPage)

ItisimportantforequipmentdesignerstodesigntothelatesteditionofATEXharmonisedstandardstheuptodatelistcanbefoundontheECATEXwebsite.(SeeUsefulLinksPage)

Gradually,thetechnicalstandardsforthetechnologyforgas/vapourhazardsandthosefordusthazardsarebeingincorporatedintothesameseries.ForexampleIEC6007910coversareaclassificationIEC60079101dealswithgas/vapourhazardsandIEC60079102dealswithdusthazards.Similarnumberingwillapplyforotheraspectssuchasinstallation.

Toplevelstandard

EN11271Explosiveatmospheres:Explosionpreventionandprotection.Part1:Basicconceptsandmethodology

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StandardsforEquipment

IEC60079ELECTRICALAPPARATUSFOREXPLOSIVEGASATMOSPHERESPart0GeneralrequirementsPart1ConstructionandtestofflameproofenclosuresofelectricalapparatusPart2ElectricalapparatustypeofprotectionpPart3SparktestapparatusforintrinsicallysafecircuitsPart4MethodoftestforignitiontemperaturePart5PowderfillingqPart6OilimmersionoPart7Increasedsafetye'Part11ConstructionandtestofintrinsicallysafeandassociatedapparatusPart15Electricalapparatusforexplosivegasatmospheres,typeofprotectionnPart18EncapsulationmPart25IntrinsicallysafesystemsPart26Specialrequirementsforconstructiontestandmarkingofzone0electrical

apparatusPart27Fieldbusintrinsicallysafeconcept(FISCO)

StandardsforInstallationetc.(gasesandvapours)

IEC60079ELECTRICALAPPARATUSFOREXPLOSIVEGASATMOSPHERESPart10ClassificationofhazardousareasPart14Installation(andselection)ofequipmentinhazardousareasPart17InspectionandmaintenanceofequipmentNotethatthe60079seriesofstandardswillgraduallyaddressdusthazardsaswellasgas/vapourhazards.Thestandardnumberwillhaveanadditionalsuffix1or2.Thus,forexample,6124114(seebelow)willbereplacedby60079142[installationforequipmentindusthazards],with60079141dealingwithinstallationsingas/vapourhazards.

StandardsforDustHazardEquipmentandInstallation

IEC61241ELECTRICALAPPARATUSFORUSEINTHEPRESENCEOFCOMBUSTIBLEDUST

Part0GeneralRequirements

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Part1ProtectionbyenclosuretDPart21MethodsfordeterminingtheminimumignitiontemperatureofdustsPart22MethodfordeterminingtheresistivityofdustinlayersPart23MethodfordeterminingminimumignitionenergyofdustairmixturesPart4TypeofprotectionpDPart10ClassificationofareaswherecombustibledustsareormaybepresentPart11ProtectionbyintrinsicsafetyiDPart14SelectionandinstallationPart17InspectionandmaintenancePart18ProtectionbyencapsulationmD

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ATEXDirectives

FordetailedinformationonATEX,pleasenavigatetotheATEXpagesonthiswebsite

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