WAROMGROUP

HAZARDOUSAREASTECHNICALGUIDE

WAROMGROUP

WaromGroup,setup in1987, lead theway inexplosionproof technology inChinaandoperate internationally.

Withourwiderangeofproductscoveringexplosionprooflightfittings,pushbuttons,switches,junctionboxes,plug

and sockets, board panels, etc., we are the manufacturer to offer different explosionproof (corrosionproof,

dustproof&waterproof)productsandOEMservicetomeetdifferentrequirementsanddemand.

Ourkeyaccountsaretheoilandgasindustry,inadditiontothechemicalandpharmaceutical industry.However,

wealsoservecustomersinthefoodindustry,themilitaryindustry,theaerospaceindustry,theshipbuildingsector

andthebiofuelindustrywhoalsoneedtouseexplosionproofproducts.

ThestandardsofWaromproductsareinlinewithIEC(InternationalElectricalCommission)andEN(EuropeanNorm)

standardswhich are similar to American standards (NEC) and are approved by IEC EX and ATEX (PTB, LCIE &

NEMKO). We focus on improving products and process through an ongoing commitment to research and

developmentandmakingmoreproductsIECEXandATEXapproved.

Waromproductsareusedbymajoroilandgascompanies likeSinopec,CNOOC,CNPC,SEI,etc. inChinaandby

someinternationalcompanieslikeAramco,BP,Total,Shell,Basf,ExxonMobil,ENOC,NIOC,etc.intheworld.Our

sales network among over 40 countries can ensure you fullcoverage sales service and international project

handling.

Winningreputationhomeandabroad,ourobjectiveistoprovidestateoftheartqualityproductsandservicesto

clients and make Warom globally renowned as one of the best supplier of explosionproof products and

technology.

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WAROMGROUP

INTRODUCTION.......................................................................................................................................................06DIRECTIVES,STANDARDSANDREGULATIONS.........................................................................................................082.1ECdirectives...............................................................................................................................................................082.1.1Directive94/9/ECATEX95...................................................................................................................................082.1.2Directive1999/92/ECATEX137...........................................................................................................................122.2NorthAmerica............................................................................................................................................................122.3InternationalIECExscheme........................................................................................................................................132.3.1IECExschemeobjective..........................................................................................................................................132.3.2IECExinternationalcertificationscheme................................................................................................................132.3.3Schemeparticipationlevels....................................................................................................................................132.3.4Howthesystemwillworkduringtransition............................................................................................................142.3.5Complyingwithadditionalrequirements................................................................................................................14BASICPRINCIPLESOFEXPLOSIVEATMOSPHERES.....................................................................................................153.1Explosiveatmosphere................................................................................................................................................153.2Ignitionsources.........................................................................................................................................................153.3Thehazardtriangle....................................................................................................................................................15GASESANDVAPOURS............................................................................................................................................164.1Characteristicsofgasesandvapours........................................................................................................................164.1.1Principles................................................................................................................................................................164.1.2Temperatureclassification.....................................................................................................................................174.2Areaclassification......................................................................................................................................................184.2.1General....................................................................................................................................................................184.2.2Definitionofzones..................................................................................................................................................184.2.3Gradesofrelease,extentofzones,ventilation......................................................................................................194.3Gasexplosionprotectionconceptsforelectricalequipment....................................................................................214.3.1Zonesofuse...........................................................................................................................................................214.3.2Protectionconcepts................................................................................................................................................214.4Installations...............................................................................................................................................................324.4.1Selectionofelectricalapparatus............................................................................................................................324.4.2Protectionagainstdangerousincendivesparking...................................................................................................324.4.3Electricalprotection................................................................................................................................................334.4.4Wiringsystems.......................................................................................................................................................334.4.5Additionalrequirementsforflameproofenclosures'd'........................................................................................334.4.6Additionalrequirementsforincreasedsafety'e'...................................................................................................344.5Inspectionandmaintenance......................................................................................................................................354.5.1Generalrequirements.............................................................................................................................................354.5.2Inspections.............................................................................................................................................................364.5.3Regularperiodicinspections...................................................................................................................................364.5.4Continuoussupervisionbyskilledpersonnel.........................................................................................................374.5.5Maintenance..........................................................................................................................................................374.5.6Repair.....................................................................................................................................................................37COMBUSTIBLEDUSTS.............................................................................................................................................385.1Definitionsanddustcharacteristics..........................................................................................................................385.1.1General....................................................................................................................................................................385.1.2Directivesandstandardsrelevanttodust..............................................................................................................385.1.3Dustdefinitions......................................................................................................................................................395.1.4Dustcharacteristics.................................................................................................................................................395.2Areaclassification......................................................................................................................................................405.2.1Definitionsofzones.................................................................................................................................................405.2.2Gradesofrelease,extentofzones,housekeeping..................................................................................................415.3Dustexplosionprotectionmeasures.........................................................................................................................425.3.1Protectivesystems..................................................................................................................................................425.3.2Protectionbyenclosure'tD'....................................................................................................................................435.3.3Protectionbypressurisation'pD'...........................................................................................................................44

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5.3.4Protectionbyencapsulation'mD'..........................................................................................................................445.3.5Protectionbyintrinsicsafety'iD'.............................................................................................................................445.3.6Otherprotectionconcepts......................................................................................................................................445.3.7Selectionofapparatus............................................................................................................................................445.4Installations...............................................................................................................................................................455.4.1Typesofcable........................................................................................................................................................465.4.2Cableinstallation...................................................................................................................................................465.4.3Cableentrydevices.................................................................................................................................................465.5.Inspectionandmaintenance.....................................................................................................................................465.5.1Inspection...............................................................................................................................................................465.5.2Maintenance..........................................................................................................................................................465.5.3Repair.....................................................................................................................................................................46EXPLOSIONPROTECTIONINNORTHAMERICA.........................................................................................................476.1RegulationsinNorthAmerica....................................................................................................................................476.2Hazardous(classified)locations.................................................................................................................................476.2.1Classificationoflocations........................................................................................................................................476.2.2Materialgroups......................................................................................................................................................486.2.3Temperatureclassification.....................................................................................................................................486.2.4Protectiontechniques............................................................................................................................................496.2.5Marking..................................................................................................................................................................496.3ClassI,zone0,1and2locations...............................................................................................................................506.3.1Classificationoflocations........................................................................................................................................506.3.2Materialgroups......................................................................................................................................................506.3.3Temperatureclassification.....................................................................................................................................506.3.4Protectiontechniques............................................................................................................................................506.3.5Marking..................................................................................................................................................................516.3.6MarkingsforIECbasedzonecertification..............................................................................................................52APPENDICES...........................................................................................................................................................53I.Definitionsandabbreviations......................................................................................................................................54II.ECDeclarationofConformity......................................................................................................................................56III.Ingressandimpactprotectionforenclosures............................................................................................................57IV.Terminalcontentusingthe'Definedarrangementmethod'.....................................................................................58V.Glandselection...........................................................................................................................................................60VI.Genericpermittowork..............................................................................................................................................61VII.Inspectionschedulesforgasatmospheres................................................................................................................62VII.1Ex'd',Ex'e'andEx'n'.................................................................................................................................................62VII.2Ex'i'...........................................................................................................................................................................63VII.3Ex'p'.........................................................................................................................................................................64VIII.Inspectionscheduleforcombustibledusts...............................................................................................................65IX.UL/NEMAtypedesignationsforenclosures................................................................................................................66X.ExplosionprotectionmethodsaccordingtoNEC........................................................................................................67XI.HarmonisedstandardsforATEX95.............................................................................................................................68XII.ConstructionregulationsforNorthAmerica.............................................................................................................69XIII.Certifications............................................................................................................................................................70Thedatawascompiledandverifiedwithduecareinkeepingwiththelateststandardsandregulations.Theprevailing standardsandstatutoryrequirementsarebinding.Noliabilitywillbeassumedforanydamagesthatmayarisefromtheuseofthisdata.

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SSEECCTTIIOONN11IINNTTRROODDUUCCTTIIOONNWAROMistheleadingmanufacturerofexplosionproofproducts.Wedevelop,produce andsellawidespectrumofproductsincludinglightingfixture,junctionbox,cablegland,panel,switch,controlstation,plugandsocket,etc.TheWAROMGROUPisstronglyrepresentedworldwidewithmanufacturingsites,salescompaniesand representativesin40countriesallovertheworld.AlthoughinChina,weofferproductsdesignedandmanufacturedtotheEuropeanstandardsforElectrical ApparatusforPotentiallyExplosiveAtmospheres,thenewATEXdirective,alreadyinusesince1996andmandatory throughoutEUcountriessinceJuly2003.WAROMoffersthecomprehensiverangeofATEXcertifiedlightingfixturesandelectricalapparatus.Thispublicationprovidesabriefoverviewoftheessentialaspectsofexplosionprotection.Ultimately,safetyina potentiallyexplosiveatmosphereisateameffort.Manufacturershavearesponsibilitytoensureonlysafeequipment isplacedonthemarket.Installersmustfollowtheinstructionsprovidedandusetheequipmentonlyforitsintended purpose.Finally,theuserhasadutytoinspectandmaintaintheequipmentinasafeworkingorder.Thedirectives, andnationalandinternationalstandardsprovideabasisforasaferfuture.

WAROMGROUP

SSEECCTTIIOONN22DDIIRREECCTTIIVVEESS,,SSTTAANNDDAARRDDSSAANNDDRREEGGUULLAATTIIOONNSS

2.1ECdirectivesFreemovementofgoodsisacornerstoneofthesinglemarket.Themechanismsinplacetoachievethisaimare basedonpreventionofnewbarrierstotrade,mutualrecognitionandtechnicalharmonisation.The'old'directivewasrestrictedtoelectricalequipmentforhazardousareas,andwasstrictlybasedontechnical standardsregulatedbytestauthorities.Whentechnicalprogressallowedfornewproductdevelopment,thelack ofstandardsmadeitbasicallyimpossibletoobtaincertification.The'newapproach'directivesarebasedonthefollowingprinciples:HarmonisationislimitedtoEssentialHealthandSafetyRequirements(EHSR)OnlyproductsfulfillingtheEHSRmaybeplacedonthemarketandputintoserviceHarmonisedstandardswhicharetransposedintonationalstandards,arepresumedto conformtothecorrespondingEHSRApplicationofharmonisedstandardsorothertechnicalspecificationsremainsvoluntary, andmanufacturersarefreetochooseanytechnicalsolutionthatcomplieswiththeEHSRManufacturersmaychoosebetweendifferentconformityassessmentsproceduresprovidedforin theapplicabledirective EquipmentthatcomplieswiththenewdirectivesmaycarrytheCEmark.Thetwodirectivesconcernedwithhazardous areasarecalledtheATEX95andATEX137.ATEXisanabbreviationfromtheFrenchAtmosphresExplosibles.2.1.1Directive94/9/ECATEX952.1.1.1ScopeandgeneraldefinitionsATEX95,formerlyknownasATEX100a,isaimedatmanufacturers.Itappliestoequipmentandprotectivedevices intendedforuseinpotentiallyexplosiveatmospheres.Safetyandcontrollingdevicesforuseoutsidethehazardousareabutessentialforthesafeoperatingofequipmentinsideitarealsocovered.Thedirectiveappliestoelectricalaswellasmechanicalequipmentandappliestogases,vapoursanddustatmospheres.Complianceiscompulsorysince1July2003.IntheUK,ATEX95isimplementedthroughStatutoryInstrument192.InGermany,theimplementation isthroughthenewExVO.'Equipment'meansmachines,apparatus,fixedormobiledevices,controlcomponentsandinstrumentationthereof,anddetectionorpreventionsystemswhich,separatelyorjointly,areintendedforthegeneration,transfer,storage,measurement,controlandconversionofenergyfortheprocessingofmaterial,andwhicharecapableofcausinganexplosionthroughtheirownpotentialsourcesofignition.'Protectivesystems'meansdesignunitswhichareintendedtohaltincipientexplosionsimmediately,and/ortolimittheeffectiverangeofexplosionflamesandexplosionpressures.Protectivesystemsmaybeintegratedintoequipmentorseparatelyplacedonthemarketforuseasautonomoussystems.'Components'meansanyitemessentialtothesafefunctioningofequipmentandprotectivesystemsbutwithnoautonomousfunction.'Safetydevices,controllingdevicesandregulatingdevices'meansdevicesintendedforuseoutsidepotentiallyexplosiveatmospheresbutrequiredfororcontributingtothesafefunctioningofequipmentandprotectivesystemswithrespecttotherisksofexplosion.'Assembly'meansacombinationoftwoormorepiecesofequipment,togetherwithcomponentsifnecessary,placedonthemarketand/orputintoserviceasasinglefunctionalunit.Assembliescanbeplacedonthemarketindifferentways.

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Assemblieswithafullyspecifiedconfigurationofpartsareputtogetherandplacedonthemarketasasinglefunctionalunitbythemanufactureroftheassembly.Themanufacturerassumesresponsibilityforcompliancewiththedirectiveandmustthereforeprovideclearinstructionsforassembly,installation,operationandmaintenance,etc.Assembliesformingamodularsystem.Inthiscase,theassemblyisnotnecessarilycompletedbythemanufactureroftheproductandplacedonthemarketasasinglefunctionalunit.However,theuser/installerselectsandcombinesthepartsfromamanufactureroforiginforagivenrange,themanufacturerisstillresponsibleforthecomplianceoftheassemblywiththedirective.'Installation'meansacombinationoftwoormorepiecesofequipmentwhichwerealreadyplacedonthemarketindependentlybyoneormoremanufacturers.InstallingandcombiningtheequipmentontheuserspremisesisnotconsideredmanufacturingandthereforetheresultinginstallationisoutsidethescopeofATEX95butwillbesubjecttothelegalrequirementsapplicablesuchasATEX137.Thedirectivedoesnotcoverthefollowingapplications:MedicaldevicesintendedforuseinamedicalenvironmentEquipmentandprotectivesystemswheretheexplosionhazardresultsexclusivelyfromthepresenceofexplosivesubstancesorunstablechemicalsubstancesEquipmentintendedforuseindomesticandnoncommercialenvironmentswherepotentiallyexplosiveatmospheresmayonlyrarelybecreated,solelyasaresultoftheaccidentalleakageoffuelgasPersonalprotectiveequipmentcoveredbydirective89/686/EEC(1)Seagoingvesselsandmobileoffshoreunitstogetherwithequipmentonboardsuchvesselsorunits.FPSOsarenotconsideredmobileoffshoreunitsMeansoftransport,i.e.vehiclesandtheirtrailersintendedsolelyfortransportingpassengersbyairorbyroad,railorwaternetworks,aswellasmeansoftransportinsofarassuchmeansaredesignedfortransportinggoodsbyair,bypublicroadorrailnetworksorbywater.Vehiclesintendedforuseinapotentiallyexplosiveatmosphereshallnotbeexcluded.2.1.1.2GroupsandcategoriesofapparatusApparatusaredividedintogroupsandcategories:GroupIappliestominingoperationsandgroupIIappliestoallotherareas.GroupIisfurthersubdividedintocategoriesM1andM2.GroupIIissubdividedintocategories1,2and3.Theequipmentselectionisshowninthetablebelow:

2.1.1.3CEmarkUptonow,freemovementofgoodsforhazardousareaswasindicatedbythedistinctivecommunitymark.Since1July2003onlyproductcarryingtheCEmarkmaybeplacedonthemarketandputintoservice.Throughtheapplicationoftheconformityassessmentprocedures,manufacturerscanissueanECDeclarationofConformity,statingcompliancewiththerelevantdirective(s)andapplytheCEmarkontheirequipment.Thewillstillappearonthelabel,butitsonlyfunctionistoindicatethattheproductisintendedforuseinpotentiallyexplosiveatmospheresoriscontributingtoitssafety.Thefigurebelowshowstheconformityassessmentprocedures.

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2.1.1.4OtherdirectivesthatmaybeapplicableProductsmightbeinthescopeofotherdirectives,andtheCEmarkmighthavetobeappliedevenifATEX95statesitisnotallowed.TheECDeclarationofConformityistheonlywaytofindoutwhichdirectiveshavebeenappliedtoaproduct.ElectromagneticCompatibility89/336/EEC(EMC)appliestoanyproductinahazardousareathatcouldcauseinterferenceorissusceptible.ProductsforuseinhazardousareasareexplicitlyexcludedfromtheLowVoltageDirective73/23/EEC(LVD)butallLVDobjectiveshavetobecoveredbyATEX95.Thestandardsusedforcompliancecanbelistedonthedeclaration.However,productsthatareusedoutsidethehazardousareabutarecontributingtothesafetyinsidehavetocomplywithbothdirectives.TheMachineryDirective98/37/ECcontainsonlygeneralrequirementsagainstexplosions.Therefore,ATEX95takesprecedenceregardingexplosionprotectionbuttheMachineryDirectivehastobeappliedtoallotherrelevantrisksconcerningmachines.2.1.1.5MarkingAllequipmentandprotectivesystemsmustbemarkedlegiblyandindeliblywiththefollowingminimuminformation:

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NameandaddressofthemanufacturerCEmarkDesignationofseriesortypeSerialnumber,ifanyYearofconstructionThecommunitymarkForgroupII,theletter'G'forexplosivegasatmospheresand/ortheletter'D'forexplosivedustatmospheresInaddition,otherrelevantsafetyinformationneedstobeadded2.1.1.6InstructionsAllequipmentandprotectivesystemsmustbeaccompaniedbyinstructions,includingatleastthefollowinginformation:Arecapitulationoftheinformationwithwhichtheequipmentorprotectivesystemismarked,exceptfortheserialnumber,togetherwithanyappropriateadditionalinformationtofacilitatemaintenance(e.g.addressoftheimporter,repairer,etc.)Instructionsforsafe:PuttingintoserviceUseAssemblinganddismantlingMaintenance(servicingandemergencyrepair)InstallationAdjustmentWherenecessary,anindicationofthedangerareasinfrontofpressurereliefdevicesWherenecessary,traininginstructionsDetailswhichallowadecisiontobetakenbeyondanydoubtastowhetheranitemofequipmentinaspecificcategoryoraprotectivesystemcanbeusedsafelyintheintendedareaundertheexpectedoperatingconditionsElectricalandpressureparameters,maximumsurfacetemperaturesandotherlimitvaluesWherenecessary,specialconditionsofuse,includingparticularsofpossiblemisusewhichexperiencehasshownmightoccurWherenecessary,theessentialcharacteristicsoftoolswhichmaybefittedtotheequipmentorprotectiveSystemThemanufacturerorhisauthorisedrepresentativeestablishedintheCommunitymustdrawuptheinstructionsinoneoftheCommunitylanguages.Onbeingputintoservice,allequipmentandprotectivesystemsmustbeaccompaniedbyatranslationoftheinstructionsinthelanguageorlanguagesofthecountryinwhichtheequipmentorprotectivesystemistobeused,andbytheinstructionsintheoriginallanguage.Eitherthemanufacturermustmakethistranslation,orhisauthorisedrepresentativeestablishedintheCommunity,orthepersonintroducingtheequipmentorprotectivesystemintothelanguageareainquestion.

2.1.2 Directive1999/92/ECATEX1372.1.2.1ScopeATEX137,previouslyknownasATEX118a,isaimedattheemployers,andrequiresthemtoprotectworkersfromtherisksofexplosiveatmospheres.Thedirectivedoesnotapplyto:AreasuseddirectlyforandduringthemedicaltreatmentofpatientsTheuseofappliancesburninggaseousfuelsinaccordancewithdirective90/396/EECThemanufacture,handling,use,storageandtransportationofexplosivesorchemicallyunstablesubstancesMineralextractingactivitiesatmines,quarriesandoffshoreinstallations(directives92/91/EECand92/104/EEC)Theuseofmeansoftransportbyland,waterandair,towhichthepertinentprovisionsoftheinternationalagreements(e.g.ADNR,ADR,ICAO,IMO,RID),andtheCommunitydirectivesgivingeffecttothoseagreements,apply.Meansoftransportintendedforuseinapotentiallyexplosiveatmosphereshallnotbeexcluded.2.1.2.2Requirements

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Since30June2003,placeswithpotentiallyexplosiveatmospheresmustbe: ClassifiedintozonesZones0,1and2forgasesandvapours.Zones20,21and22fordusts.EquipmentselectedinaccordancewithATEX95Markedwithan'EX'sign,wherenecessaryInworkplaceswheresafetyrestrictionsapplythroughoutthesite,e.g.refineries,thesignmightbeappliedattheentranceofthesite.Individualsignsaroundthepotentialexplosiveatmosphereswouldnotberequired.VerifiedbyacompetentpersonbeforefirsttimeuseSafetymeasuresmustbecoordinatedinsharedworkplacesUsuallyitistheemployerthatcreatesthepotentialexplosiveatmospherethatisresponsibleforthe coordinationProvideinformation,instructionsandtrainingtotheemployeesIntheUK,ATEX137isimplementedthroughthe'DangerousSubstancesandExplosiveAtmospheresRegulations'(DSEAR).InGermany,theimplementationisthroughthenewElexV.Existingequipmentthatisinusebefore30June2003 withariskassessmentthatindicatesthattheyaresafeforuseinahazardousarea,cancontinuetobeused.Workplaces inusebefore30June2003haveuntil30June2006toimplementtheminimumrequirementsofATEX137. Anymodificationsandchangestoexistingworkplacesafter30June2003mustcomplyimmediately.

2.1.2.3SelectionofequipmentandprotectivesystemsIftheexplosionprotectiondocumentbasedonariskassessmentdoesnotstateotherwise,equipmentandprotectivesystemsforallplacesinwhichexplosiveatmospheresmayoccurmustbeselectedonthebasisofthecategoriessetoutinATEX95.Thefollowingcategoriesofequipmentmustbeusedinthezonesindicated,providedtheyaresuitableforgases,vapoursormistsand/ordustsasappropriate:Zone0orzone20usecategory1equipmentZone1orzone21usecategory1or2equipmentZone2orzone22usecategory1,2or3equipmentNorthAmericaInNorthAmerica,CanadahasadoptedtheIECStandardsforExplosionProtectionofelectricalapparatusand,giventhemauniqueCSAidentity.TheUSAhasalsoadoptedthezoneclassificationconcept,andnewstandardshavebeenpublishedbasedonIEC,butnotexactlythesame.ThepublicationofthenewNationalElectricalCode(NEC)2002has incorporatedmoredetailregardingzoneclassification.Itwillhelpusersselecttherightequipmentandoffersanalternativetodivisions.TheprotectionconceptsintheUSAarediscussedinmoredetailinsection6.

2.3InternationalIECExscheme2.3.1IECExschemeobjectiveTheobjectiveoftheIECExschemeistofacilitateinternationaltradeinelectricalequipmentintendedforuseinexplosive atmospheres(Exequipment):ReducedtestingandcertificationcoststomanufacturerReducedtimetomarketInternationalconfidenceintheproductassessmentprocessOneinternationaldatabaselisting

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2.3.2IECExinternationalcertificationschemeTheaimoftheIECExschemeistofacilitateinternationaltradeinelectricalequipmentintendedforuseinexplosiveatmospheres(Exequipment)byeliminatingtheneedformultiplenationalcertificationswhilepreservinganappropriate levelofsafety.TheIECExschemeprovidesthemeansformanufacturersofExequipmenttoobtaincertificatesofconformitythatwillbeacceptedatnationallevelinallparticipatingcountries.Acertificateofconformitymaybeobtainedfromanycertification bodyacceptedintothescheme.ThecertificatewillattestthattheequipmentdesignconformstotherelevantIEC standardsandthattheproductismanufacturedunderaqualityplanassessedbyanACB(acceptedcertificationbody). ManufacturersholdingcertificatesofconformitymayaffixtheIECExMarkofConformitytoequipmentthattheyhave verifiedascomplyingwiththecertifieddesign.FortheIECExschemetoachieveitslongtermobjective,everynationalstandardforwhichapplicationismadebyparticipatingcountrieswillneedtobeidenticaltothecorrespondingIECstandard,andtheIECExCertificatesofConformity issuedbyallacceptedcertificationbodieswillneedtoberecognisedinallparticipatingcountriesasequivalenttotheir ownnationalcertification.ForcountrieswhosenationalstandardsarenotyetidenticaltotheIECstandards,atransitionalperiodwillbenecessary.Thetransitionalperiod,whichcouldbedifferentfordifferentstandards,istoallowtimefor:TheIECstandardsandthenationalstandardstobemadeidentical,andNationalacceptanceofIECExCertificatesofConformityandtheIECExMarkofConformity.AcceptedcertificationbodiesinparticipatingcountriesduringthetransitionalperiodwillberequiredtoacceptIECExassessmentandtestreportsproducedbyotheracceptedcertificationbodiesforthepurposeofissuingtheirownnational certification,whichmayincludenationaldifferences.ThefinalobjectiveoftheIECExschemeisworldwideacceptanceof:OnestandardOnecertificateOnemark2.3.3SchemeparticipationlevelsTheschemeprovidesfortwolevelsofparticipation:FullparticipationParticipationatatransitionallevel2.3.3.1FullparticipationParticipationatthislevelprovidesfortheissuingofanIECExCertificateofConformityaswellasalicencetousetheIECExmark.AnIECCertificateofConformitycanonlybeissuedagainstanIECstandard.ThereforeIECExCertificatesofConformitycannotcovernationaldifferences.InthiscontextnationaldifferencesarethedifferencesordeviationsbetweenanationalandanIECstandard.Toensureintegrityandequityintheschemearemaintained,strictobligationsonacountry'sparticipationatthislevel arepartoftherules,i.e.:ThecorrespondingnationalstandardmustbeidenticaltotheIECstandardforwhichparticipationissoughtandTheIECExCertificateofConformitymustbegivenequaltreatmenttothecountry'snationalcertification.

2.3.3.2ParticipationatatransitionallevelRightnow,therangeofdifferingnationalExstandardsmeansthatlargescaleparticipationatthefulllevelissometime away.Tocaterfortodaysneeds,thereisprovisionforparticipationatanintermediateortransitionallevelforthosecountries:

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WhosenationalstandardsarenotyetidenticaltoIECstandardsorWhichdonotyetacceptIECExCertificatesofConformityasequaltotheirownnationalcertification.ParticipationatthetransitionallevelprovidesforthemutualacceptanceofATRs(assessmentandtestreport)forthepurposeofissuingnationalcertification.Whilenationaldifferencesexist,theindividualcountriesmayrequireadditional 'topup'testingunlessthedifferencesarealreadycoveredintheATR.2.3.4HowthesystemwillworkduringtransitionThebasicsofthesystemareinplaceandATRshavealreadybeenissued.Thefollowingcountriesarecurrentlyparticipatinginthescheme:Australia,Canada,China,Denmark,Finland,France,Germany,Hungary,Italy,Korea,Netherlands,Norway,NewZealand, Romania,Russia,Slovenia,SouthAfrica,Sweden,Switzerland,UK,USAandYugoslavia.Thecertificationprocessisclarifiedwithanexample.AnExejunctionboxismanufacturedintheUKanddestinedforuseinoilrefineries.ThemanufacturersendsthejunctionboxtoanExTL(Extestinglaboratory)intheUK,whichtestsitforconformitytoIECstandardsandpossiblenationaldeviations.Followingasuccessfultest,theACBissuesanIECExATR.BoththeExTLandACBcanbeoneandthesameorganisation.WishingtosellthejunctionboxinCanadaandinChina,theUKmanufacturersendstheseIECExdocumentstoaCanadianandaChinesecertificationbodyintheIECExscheme.ProvidedthenationaldifferencesarecoveredintheATR,theCanadianandChinesebodieswilleachissueacertificatewithoutretestingtheequipmentbecausetheyrecognisetheUKlaboratoryasamemberoftheIECExscheme andhavefullconfidenceinthetestingandassessmentthathasalreadybeendone.TheUKmanufacturermaynowaffix thenationalmarkofconformityoftheCanadianandChinesebodiestothejunctionbox,andisfreetoexportittoboth CanadaandChina.SomecertificationbodiesmayrequireafactoryinspectioninadditiontotheATR.Inresponsetothisindustryneed,the IECExhasintroducedaqualityassessmentreport.Inourexample,thiswillmeanthattheUKtestingandcertification bodywillbeabletoconductbothproducttestingandassessment,aswellasthefactoryinspectionacceptabletothe bodiesinbothCanadaandChina.2.3.5ComplyingwithadditionalrequirementsThenationalcertificationauthoritieswillcontinuetoberesponsibleforrequirementsotherthanexplosionprotection, i.e.EMC,machinery,generalelectricalsafety,etc.Also,theIECExschemedoesnotcovertheinstallationandmaintenancerequirementsinthedifferentcountries.Neither doesitmeanthatthedivisionclassificationsystemwillhavetobeeliminatedintheUSA.Thetwosystemswillcoexist fortheforeseeablefuture,togetherwiththeirspecificinstallationandproductrequirements.IntheEC,onlyATEXcertified equipmentcouldbeinstalledsince1July2003.Therefore,productsimportedinEuropeviatheIECExscheme wouldhavetocomplywiththeEHSRinaccordancewithdirective94/9/EC.

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SSEECCTTIIOONN33BBAASSIICCPPRRIINNCCIIPPLLEESSOOFFEEXXPPLLOOSSIIVVEEAATTMMOOSSPPHHEERREESS3.1 ExplosiveatmosphereAn'explosiveatmosphere'isamixturewithair,underatmosphericconditions,offlammablesubstancesintheformof gases,vapours,mistsordustsinwhich,afterignitionhasoccurred,combustionspreadstotheentireunburnedmixture. TheATEXdirectivedoesnotdefineatmosphericconditions,butnormallyatemperaturerangeof20oCto+60oCanda pressurerangeofbetween0.8and1.1barisaccepted.Itshouldbenotedthatelectricalproductsareusuallydesigned andtestedforuseinanambienttemperaturerangeof20oCto+40oCinconformitywithEN50014.3.2IgnitionsourcesThefollowingignitionsourcesareexamplesthatcancauseanexplosionintherightcircumstances:ElectricarcsandsparkFlamesHotsurfacesElectrostaticsparksThermitesparksMechanicalfrictionMechanicalsparksproducedbygrindingSmoulderingdepositsCompressionignitionElectromagneticradiationChemicalreactionsUltrasonicsThemechanicalignitionsourcesandtheirprotectionconceptsarenotconsideredinthisguide.3.3ThehazardtriangleThehazardtriangleisusedtounderstandthethreebasicconditionsthatmustbesatisfiedtocreateafireorexplosion.1.Fuelmustbepresentinsufficientquantityandconcentration.Thiscouldbeaflammableliquid,vapourorcombustibledust.2.Supplyofoxygen.Asweareconsideringanexplosiveatmosphereatatmosphericconditions,thesurroundingaircontainsabout20%oxygen.3.Anignitionsource.Successfullysuppressingorseparatingoneormoreofthesethreecomponentscanavoidafireorexplosion.Wewillbelookingatanumberofprotectionconceptsforgasesandvapoursaswellasdustatmospheres,allofwhichusethesesimpleprinciples.

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SSEECCTTIIOONN44GGAASSEESSAANNDDVVAAPPOOUURRSS4.1Characteristicsofgasesandvapours4.1.1PrinciplesElectricalapparatusforuseinflammablegasesandvapoursaredividedintogroups:GroupIisforelectricalormechanicalapparatusforminessusceptibletofiredamp.GroupIequipmentwillnotbediscussedinthisguide.GroupIIisforelectricalandmechanicalapparatususedinplacesotherthanmines.GasesofgroupIIarefurtherdividedintosubdivisions,i.e.IIA,IIBandIIC.Thesubdivisionsarebasedonexperimentalworkconductedwithflameproofandintrinsicallysafeapparatus. Thegasesarecategorisedbyone(orboth)oftwomethods.ForflameproofenclosuresitisbasedontheMaximum ExperimentalSafeGap(MESG)andforintrinsicallysafeapparatusitisbasedontheMinimumIgnitionCurrent(MIC).MaximumExperimentalSafeGap(MESG)Thegasinsidethetestchamberisignited.Agapexistsbetweenthecoverandthechamberwithagaplengthof25mm. Thehotburninggasisnowforcedthroughthenarrowgap.Iftheescapinggasignitesthesurroundinggas,thetestwill havetoberepeatedwithasmallergap.Thegap,whichpreventstheignitionofthesurroundinggas,istheMESG.MinimumIgnitionCurrent(MIC)Inordertoigniteagasorvapour,asparkneedsacertainamountofenergy.The intrinsicallysafequalityofacircuitisbasedonthefactthattheenergyavailable inthecircuitisinsufficienttoignitethegas.Thenecessaryminimumenergy contentisaspecificcharacteristicofflammablegasesandvapours.Thegases aresubsequentlyclassifiedwitharatiorelativetothatofmethane(MIC=85mA).

ExplosivelimitsBasically,allgasesandvapoursrequireoxygentomakethemflammable.Too muchortoolittleoxygenandthemixturewillnotignite.Theonlyexceptionisacetylene,whichdoesnotrequireoxygentoignite.Theupperandlowerconcentration isknownasthe'explosivelimit'. LowerExplosiveLimit(LEL):theconcentrationofgasinair,belowwhichthegas atmosphereisnotexplosive.UpperExplosiveLimit(UEL):theconcentrationofgasinair,abovewhichthegas atmosphereisnotexplosive.

Ignitionenergy

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ThisisthesparkenergyinJoules,requiredtoignitethegases. Theignitionenergyofsometypicalgasesis:Flashpointsarenormallyassociatedwithliquids,butafewmaterialsgiveoffvapourswhenstillinthesolidstate.Theflashpointofaflammablesubstanceistheminimumtemperatureatwhichthematerialgivesoffvapoursinaquantitysuch thatitiscapableofforminganignitablevapour/airmixture.Vapourdensityofagasisgivenrelativetothatofair.Manygasesarelighterthanair.Anyvapourreleasewillriseanddilute rapidly.Whenindoors,thesegaseswillcollectintheroofspace.Wheregasesareheavierthanair,theywillfalltothelowest pointandfillsumps,trenchesorhollowsintheground.Thesegasescanremaintherelongafterthereleasehasbeenstopped andcontinuetoposeadanger.4.1.2TemperatureclassificationThemaximumsurfacetemperatureofelectricalormechanicalapparatusmustalwaysbelowerthantheignitiontemperature ofthesurroundinggasesorvapoursmixedwithairatnormalpressure.Theignitiontemperatureofaflammablesubstance istheminimumtemperatureatwhichthematerialwilligniteandsustaincombustion.Thisisalsoknownasthe'autoignition temperature'.Theignitiontemperatureofdifferentgasesvariesconsiderably.Amixtureofairwithhydrogenwilligniteat 560oCbutamixtureofairwithgasolinewilligniteat280oC.Tohelpmanufacturersdesigntheirequipment,apparatusaregivenatemperatureclassificationconsistingof6temperatures rangingfrom85oC(T6)to450oC(T1).The6'T'classesaregivenintablebelow:

Apparatuswillbemarkedaccordingtothemaximumsurfacetemperatureofanyrelevantpartthatmightbeincontactwith theflammablegas.For'flameproof'and'pressurised'equipment,themaximumsurfacetemperatureisontheoutsideofthe enclosure,whereasfor'Increasedsafety'thehottestpointisinside.ThetemperatureclassificationforgroupIIelectrical apparatuswillbeeither:TclassasgivenintableaboveActualmaximumsurfacetemperatureSpecificgasforwhichitisdesignedApparatussuitablefor,e.g.T3temperatureclasscanalsobeusedinT1andT2.Electricalapparatusshallnormallybedesignedforuseinanambienttemperatureof20oCand+40oC.Whendesignedforuseinadifferentrange,theambienttemperaturemustbestatedbythemanufacturerandspecifiedinthecertificate.The markingmustincludeeitherthespecialtemperaturerange,e.g.35oCTa+55oC,ortheletter'X'afterthecertificatenumber. Thetablebelowgivestheclassificationofsomegasesinexplosiongroupsandtemperatureclasses.

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2.Areaclassification2.1GeneralInstallationsinwhichflammablematerialsaremanufactured,handledorstoredshouldbedesigned,operatedandmaintainedsothatanyreleasesofflammablematerialandtheextentofhazardousareasarekepttoaminimum.Insituationswheretheremaybeanexplosivegasatmosphere,thefollowingstepsshouldbetaken:Eliminatethelikelihoodofanexplosivegasatmosphereoccurringaroundthesourceofignition;orEliminatethesourceofignitionWherethisisnotpossible,protectivemeasures,processequipment,systemsandproceduresshouldbeselectedsothelikelihoodofbothbeingpresentatthesametimeisacceptablysmall.Inthefirstinstance,itispreferabletoeliminate thepresenceofaflammableatmosphere.Thisispossibleby:Substitutingwithanonflammablesubstance;orRaisingtheflashpointabovetheprocesstemperature,e.g.byaddingwaterLoweringtheprocesstemperature,e.g.coolingLimitingtheconcentrationbelowtheLEL,e.g.dilution/ventilationorinertingExplosionproofdesign(containment)Inpractice,however,itisverydifficulttoensurethatanexplosivegasatmospherewillneveroccur.Inthiscase,apparatus withspecialprotectivemeasuresshouldbeused.2.2Definitionsofzones2.2.1Zone0Aplaceinwhichanexplosiveatmosphereispresentcontinuously,forlongperiodsorfrequently.2.2.2Zone1Aplaceinwhichanexplosiveatmosphereislikelytooccurinnormaloperation,occasionally.2.2.3Zone2Aplaceinwhichanexplosiveatmosphereisnotlikelytooccurinnormaloperationbut,ifitdoesoccur,willpersistforashortperiodonly.2.2.4Zoneidentification

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4.2.3Gradesofrelease,extentofzones,ventilation

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4.2.3.1GradesofreleaseThebasicelementsforestablishingthehazardouszonetypesaretheidentificationofthesourceofreleaseandthedeterminationofthegradeofrelease.Eachitemofprocessequipment,e.g.tank,pump,pipeline,vessel,etc.,shouldbeconsideredasapotentialsourceofrelease.Items,whichcontainflammablematerialbutcannotreleaseittotheatmosphere,e.g.allweldedpipelines,arenotconsideredtobesourcesofrelease.Releasesarecategorisedasfollows:ContinuousgradeofreleaseAreleasewhichiscontinuousorisexpectedtooccurforlongperiods.Exampleofcontinuousgradeofrelease:SurfaceofaflammableliquidinafixedrooftankSurfaceofanopenreservoir,e.g.oil/waterseparatorPrimarygradeofreleaseAreleasewhichcanbeexpectedduringnormaloperation,occasionally.Exampleofprimarygradeofrelease:Sealsofpumps,compressorsorvalvesthatareexpectedtoreleaseflammablematerial,particularlyduringstartupWaterdrainagepointsonvesselswhichcontainflammableliquidsSamplepointsfromwhichanalyticalsamplesaredrawnReliefvalves,ventsandotheropeningswhichareexpectedtoreleaseduringnormaloperationSecondarygradeofreleaseAreleasewhichisnotexpectedtooccurinnormaloperationand,ifitdoesoccur,islikelytodosoforshortperiods.Exampleofsecondarygradeofrelease:Sealsofpumps,compressorsorvalvesthatarenotexpectedtoreleaseflammablematerialduringnormalFlanges,connectionsandpipefittingswherereleaseofflammablematerialsisnotexpectedduringnormaloperationReliefvalves,ventsandotheropeningswhicharenotexpectedtoreleaseduringnormaloperationAcontinuousgradeofreleasenormallyleadstoazone0,aprimarygradetozone1andasecondarygradetozone2.4.2.3.2ExtentofzoneQuiteanumberoffactorscaninfluencetheextentofthezone.Ifthegasislighterthanair,itrisesonreleaseandcanbecometrappedintheroofspace;orifthegasisheavierthanair,itwillfallandspreadatgroundlevel.Thishasanimpactonthelocationofthesiteisitonahillorinahollow?Whensourcesofreleaseareinanadjacentarea,themigrationcanbepreventedby:PhysicalbarriersStaticoverpressureintheareaadjacenttothehazardousarea.Purgingtheareawithasignificantairflow.4.2.3.3VentilationGasorvapourreleasedintotheatmospherecanbedilutedbydispersionordiffusionintotheairuntilitsconcentration isbelowtheLEL.Suitableventilationratescaninfluencethetypeofzone.Therearetwotypesofventilationavailable:NaturalventilationArtificialventilation,generalorlocalNaturalventilationiscreatedbythemovementofaircausedbythewindand/orbytemperaturegradients.

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Artificialventilationisprovidedbyartificialmeans,e.g.fansorextractors.Withtheuseofartificialventilation,itispossibletoachieve:ReductionintheextentofthezoneShorteningofthetimeofpersistenceofanexplosiveatmospherePreventionofthegenerationofanexplosiveatmosphereVentilationisthepreferredoptionforgasturbines,asitpreventstheformationofanexplosiveatmosphere.Inorderthat thedilutionventilationensuresanegligibleriskofanexplosiveatmosphereatalltimes,theventilationsystemhassafety featuressuchas:a100%standbyfan;oranuninterruptiblepowersupplytotheventilationfans;interlockssothatthe gasturbinescannotstartwithoutsufficientventilation;plusprovenautomaticisolationoffuelsupplyifventilationfails. Theeffectivenessoftheventilationincontrollingthedispersionandpersistenceoftheexplosiveatmospherewilldepend onthedegreeandavailabilityofventilationandthedesignofthesystem.ThethreedegreesofventilationHighventilation(VH)Canreducetheconcentrationatthesourceofreleasevirtuallyinstantaneously,resultinginaconcentrationbelowtheLEL.Azonewillbeverysmall(evennegligible).Mediumventilation(VM)Cancontroltheconcentration,resultinginastablesituationinwhichtheconcentrationbeyondthezone boundaryisbelowtheLELduringrelease.Theextentandtypeofthezonedependonthedesignparameters.Lowventilation(VL)Cannotcontroltheconcentrationwhilstreleaseisinprogressand/orcannotpreventunduepersistenceofaflammable atmosphereafterreleasehasstopped.AvailabilityofventilationThreelevelsofavailabilityofventilationshouldbeconsidered.GoodVentilationispresentvirtuallycontinuously.Naturalventilation,whichisgenerallyobtainedoutdoors,isconsideredtobegoodwhenthewindspeedisgreaterthan0.5m/s(approx1.1mileperhour).FairVentilationisexpectedtobepresentduringnormaloperation.Discontinuitiesarepermitted,providedtheyoccurinfrequentlyandforshortperiods.PoorVentilationwhichdoesnotmeetthestandardoffairorpoor.Discontinuitiesarenotexpectedtooccurforlongperiods.Ventilationwhichislessthanpoorisignored.Influenceofventilationontypeofzone

4.3Gasexplosionprotectionconceptsforelectricalequipment

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4.3.1ZonesofuseSince1July2003,equipmentforuseinzone0mustconformtotherequirementsofcategory1inaccordancewithATEX95andATEX137.Equipmentforuseinzone1andzone2mustcomplywithcategory2andcategory3respectively. Severalmethodsmaybeusedtomakeequipmentsafeforuseinanexplosiveatmosphere.Thefollowingtablegivesanoverviewoftheavailableconceptsandtheirprinciples.

4.3.2Protectionconcepts4.3.2.1Increasedsafety'e'BasicprinciplesIncreasedsafetyisintendedforproductsinwhicharcsandsparksdonotoccurinnormalorunderfaultconditions.Thesurfacetemperaturesoftherelevantpartsarecontrolledbelowincendivevalues.Increasedsafetyisachievedbyreducingcurrentratingsandenhancinginsulationvaluesandcreepageandclearancedistancesabove thoserequiredfornormalservice.Maximumvoltagefortheprotectionconceptis11kV(d.c.ora.c.r.m.s.).TheprotectionconceptprovidesahighlevelofsafetyinaccordancewithATEX95,makingitsuitableforcategories2andM2,gasgroupsIandII.Typicalproductsarejunctionboxes,luminaries,inductionmotors,transformersandheatingdevices.Thekeydesignfeaturesforincreasedsafetyare:Enclosuresmustbeconstructedsuchthattheycanwithstandthemechanicalimpacttestandprovideaspecifieddegreeofingressprotection.Nonmetallicmaterialsmustcomplywiththefollowingrequirements:ThermalendurancetoheatThermalendurancetocoldResistancetolightInsulationresistanceThermalindex(TI)Terminalsmustbegenerouslydimensionedfortheintendedconnectionsandensurethattheconductorsaresecurelyfastenedwithoutthepossibilityofselfloosening.Clearancebetweenbareconductivepartsmustnotbelessthanthevaluesspecifiedfortheratedvoltage.Creepagedistancesmustnotbelessthanthevaluesspecifiedfortheratedvoltageandthecomparativetrackingindex(CTI)oftheinsulatingmaterial.Electricalinsulatingmaterialsmusthavemechanicalstabilityuptoatleast20Kabovethemaximumservicetemperature.

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Temperaturesofpartsofequipmentmustbelimitedsoasnottoexceedvaluesthatcouldaffectthethermalstabilityofthematerialandthetemperatureclassificationoftheequipment.JunctionboxesExeenclosuresthatcontainbareconductivepartsrequireaningressprotectionofIP54.Ifonlyinsulatedconductivepartsarefitted,IP44willsuffice.Inpractice,however,usersrequireenclosureswithaningressprotectionofIP65or66.Enclosuresmaybeprovidedwithdrainholesorventilationopeningstopreventtheaccumulationofcondensation. TheingressprotectionmaybereducedbutnolessthanIP44whenfittedwithbareconductivepartsorIP24when fittedwithinsulatedconductiveparts.However,breatherdrainsmaintainingIP65or66areavailableonthemarket (seefigureattheendofthepage).Oneofthemainadvantagesofincreasedsafetyenclosuresistheavailabilityindifferentconstructionmaterialssuchas,stainless,mildsteel,aluminium,glassfibrereinforcedpolyester,polycarbonate,etc.ExamplesoftypicalExeenclosuresareshowninthefollowingfigures.ThebasicrequirementsforExeterminalsareinaccordancewithEN6094771andEN6094772.Foruseinhazardous areas,standardsEN50014andEN50019alsoapply.ExterminalsareclassifiedascomponentsinATEX95,which meansthattheyarenotCEmarked. Differenttypesofconnectionarenowpossible.TheWeidmllerclampingyoke,tensionclampandInsulationDisplacement Connection(IDC)clampingsystemprovideprotectionagainstselfloosening,andthedesignissuch thatstrandedcabledoesnothavetobecrimpedwithferrules.Thecrosssectionofthecableandotherconnection dataspecifiedintheselectiontablesareincludedintheECtypeexaminationcertificate.Thespecifiedvaluesof thecurrentcarryingcapacityarebasedonanambienttemperatureof40oC.Atratedcurrent(+10%),thesurface temperatureofthecurrentbaroftheterminalblockismaximum40K.Themaximumoperatingtemperatureinahazardous areaatmosphereoftheinsulatingmaterialWemidandMelamine(KRG)is100oC,and80oCforPolyamide(PA).TerminalblocksforintrinsicallysafecircuitsareconsideredsimpleapparatusthereforeExicertificationisnotrequired.SometerminalsareacolourvariantoftheExeterminals,hencetheyareExecertified.Theyarelightblueinaccordancewiththeindustrystandardforintrinsicsafety.WhencombinedwithnonIScircuits,theterminals shouldbeseparatedbyatleast50mmorwithapartition.Metalpartitionsmustbeearthed.AccessoriesthatcanbefittedtotheterminalsarealsolistedontheECtypeexaminationcertificate.Thelateststandardshavemadeitpossibletousepluggablecrossconnections.WhenusingtheWDU2.5fromWeidmller,itisevenpossibletofit3rowsofcrossconnectionsinparallel.Userscanfitcrossconnectionsonsite,buthavetofollowtheinstructionsprovidedbythemanufacturer.Fittingcrossconnectionsmightresultinlowervoltages.Exejunctionboxeshaveamaximumsurfacetemperaturewhichisnormallyinsidetheenclosure.Thisdefinesthetemperatureclassificationoftheenclosure.Thetemperatureisdeterminedbytestinganddependsontwofactors:NumberofterminalsandwiringinsideTemperatureriseofterminalsandwiringaboveambienttemperatureNormalambienttemperatureis20oCto+40oC.HigherambienttemperaturescouldmeanahigherTclassorreducing thecurrentthroughtheterminals. Enclosuresareallocatedamaximumdissipatedpowerfigure,whichisusedtocalculatethenumberofterminals thatcanbefitted.Basedontheratedcurrentandthetotalresistanceofcableandterminal,theuserormanufacturer calculatesthedissipatedpowerperterminal.Thisfiguremultipliedbythenumberofterminalsmustalwaysbelower thantheMDPfigureallocatedtotheenclosure.Alternatively,theusercanbeprovidedwithatableforeachenclosure size,indicatingthemaximumnumberofterminalsorconductorsbasedontheratedcurrentandcrosssection,i.e. the'definedarrangementmethod'.Forthesmallercrosssections,thepowerdissipationdependsonthecablesize, astheresistanceofaqualityterminalisnegligible.Therefore,thenumberinthetableisinfactthenumberofcable pairsthatcanbeconnectedintheenclosure,i.e.theusermightdecidetofitterminalswhichcanterminateacable sizeof4mm2butinsteaduses2.5mm2forthewiring.Inthatcase,itisnotthenumberof4mm2terminalsthat isimportantbutthenumberof2.5mm2cablepairsthatarebeingconnected.

Exedcontrolstations

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Allsparkingdevicessuchasswitches,contactors,lamps,thermalrelays,etc.are packagedindividuallyinaflameproofenclosure.Theelectricalconnectionismade viaExeterminalsincludedinthedesignorbymeansofanencapsulatedcable. ThesecomponentsaretheninstalledinanExeenclosure.CableentrydevicesCableglandsmustmaintainatleastIP54.Threadedentrieswithminimum6mm threadengagementdonotrequireanadditionalsealingwasher.However,to maintainhigherIPratingsasealingwasherisrecommended.Metalcableglands donotrequirecertificationbutshouldcomplywitharecognisedstandarde.g. EN50262.PlasticcableglandsrequireanECtypeexaminationcertificatebya notifiedbody.Unusedentriesmustbefittedwithsuitablestoppingplugs.Theplug mustrequiretheuseofatooltoremoveit.Somecountriesprefertheflexibilityof transitsystemsinenclosures.Thesystemcanbecertifiedaspartoftheenclosure orassemblycertification,orhaveitsowncomponentapproval.4.3.2.2Flameproof'd'BasicprinciplesFlameproofenclosuresareintendedforequipment,whichproducesarcs,sparksorhotsurfacesthatmaybeincendiveinnormaloperationorindustrialcomponentsthatcannototherwisebemadesuitableforuseinahazardous area.Thesurroundingexplosiveatmospherecanentertheenclosureandinternalexplosionsareexpectedduring thelifeoftheequipment.Theenclosurethereforehastobestrongenoughnottofractureordistortunderthepressuresgenerated.Anyconstructionaljointsintheenclosurearedimensionedsuchthattheydonottransmittheexplosionfromtheinsidetothesurroundingatmosphere.Thesearecalledflamepaths.TheequipmentisdesignedaccordingtoEN50018andissuitableforgasgroupsIandII,categories2GandM2.Typicalproductsareelectricmotorsandactuators,luminaries,loudspeakersandswitchgear.Thekeydesignfeaturesare:EnclosuresmustbesufficientlystrongtowithstandtheinternalexplosionJointsandgapshavecriticaldimensionsCovershavewarninglabelsiftheenclosurecontainspartsthatstoreenergyorachievetemperaturesinexcessofthetemperatureclassificationFastenersmustconformtodimensionalandstrengthrequirementsEnclosurematerialsmustbefullyspecified,andnonmetallicmaterialsmustbefullydefinedandhaveasuitablethermalindex(TI)CableandconduitentriesmustmeetconstructionalrequirementssothattheflameproofpropertiesaremaintainedFlamepaths,gaps,flangesandthreadedjointsAflamepathisanysmalljointorgapinaflameproofenclosurethroughwhichthehotgasesofaninternalexplosionmightpass.Whenescapingthroughthegaps,thehotgasesaresufficientlycooleddownsothattheydonotignitethesurroundingatmosphere.Thestandardspecifiesthemaximumpermissiblegapsforflanges,spigotsandothertypesofjointsbasedonexperimentaltesting.

Thetableonpage24showsthevaluesbasedonvolume,gassubdivision,andtypeofjoint.Cylindricalthreadsmust

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haveatleast5fullthreadsofengagement.Inpractice,6threadsareusuallyprovided.Ifthethreadhasanundercut,anondetachableandnoncompressiblewashershallbefittedtoensuretherightthreadengagement.Ifaninternalexplosiondoeshappen,someofthehotgaseswillpassthroughthegapsintheenclosures.Itisveryimportantthatthesegasespassfreelyintotheatmosphere.Therefore,aminimumdistanceisrequiredbetweenthegapandanysolidobstruction.CableentrydevicesThedesignofthecableentryshallbesuchthathotgasesarenotabletoignitethesurroundingatmospherefollowinganinternalexplosioneitherthroughtheglandorthroughthecable.Cableglandsalsohavetoconformtotherequirementsofthreadedjoints.5fullyengagedthreadsarerequired,but6areusuallyprovided.Cablesmaybebroughtintotheflameproofenclosuredirectlyviaacablegland.Thisiscalled'directentry'.Allcableentryholesmustbethreaded.IfthegasisIICorthecableisnotfilledproperly,asealingcompoundmustbeusedinthegland.Alternatively,themanufacturermightprovideaterminatingchamberandconnectthecomponentsintheflameproofenclosurewiththecomponentsintheterminatingchamberthroughbushings.Thisiscalled'indirectentry'.TheterminatingchamberisusuallyanExeenclosure.4.3.2.3Intrinsicsafety'i'BasicprinciplesIntrinsicsafetyisintendedforproductsinwhichthelevelofelectricalenergycirculatingorstoredintheproductisinsufficienttoigniteasurroundingexplosiveatmosphereevenunderfaultconditions.Becauseofthemethodbywhichintrinsicsafetyisachieved,itisnecessarytoensurethatnotonlytheelectricalapparatusexposedtothepotentiallyexplosiveatmospherebutalsootherelectricalapparatuswithwhichitisinterconnectedissuitablyconstructed.TheequipmentisdesignedaccordingtoEN50020andissuitableforgasgroupsIandII,categories1GorM1(ia)and2GorM2(ib).Typicalareasofusearecontrolandinstrumentationcircuitswithlowvoltageandcurrent.Dependingonthedesignandpurpose,apparatusaresubdividedintotwotypes:Intrinsicallysafeelectricalapparatusisapparatusinwhichallthecircuitsareintrinsicallysafe.Associatedelectricalapparatusisapparatusinwhichthecircuitsarenotallintrinsicallysafebutwhichcontaincircuitsthatcanaffectthesafetyofintrinsicallysafecircuitsconnectedtoit.Associatedelectricalapparatusmayeitherbe:Electricalapparatusthathasanalternativestandardtypeofprotectionsuitableforitsuseintheappropriatepotentiallyexplosiveatmosphere,orElectricalapparatusthatisnotprotectedandthereforecannotbeusedwithinapotentiallyexplosiveatmosphere.Thelimitingignitioncurvesforthedifferentsubdivisionsaredeterminedwiththehelpofasparktestapparatus.Thefigureaboveshowsthecurvesforaresistivecircuit.Also,thestoredenergyinacircuithastobetakeninto consideration,e.g.capacitanceorinductance.Intheeventofashortcircuit,thisenergycouldbereleasedinadditiontotheenergyfromtheassociatedapparatus.CategoriesIntrinsicallysafeapparatusandassociatedapparatusaredividedintotwogroups,'ia'and'ib'.Inthedeterminationofcategory'ia'or'b',failureofthecomponentsistobeconsidered.Category'ia'

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Intrinsicallysafecircuitsinelectricalapparatusofcategory'ia'mustnotbecapableofcausinganignitionduringnormaloperationwhentwofaultsoccur.Thefollowingsafetyfactorshavebeentakenintoconsideration:Safetyfactor1.5DuringnormaloperationandwithonefaultSafetyfactor1.0DuringnormaloperationandwithtwofaultsCategory'ib'Intrinsicallysafecircuitsinelectricalapparatusofcategory'ib'mustnotbecapableofcausinganignitionduringnormaloperationwhenonefaultoccurs.Thefollowingsafetyfactorshavebeentakenintoconsideration:Safetyfactor1.5DuringnormaloperationSafetyfactor1.0DuringnormaloperationandwithonefaultTypesofinterfaceTherearetwotypesofinterface,namelythezenerbarrierandthegalvanicisolator.ZenerbarrierThistypeofinterfacehasbeenaroundforalongtime.Thefigureontherightillustrateshowthebarrierisconstructed.Thefuserestrictsthefaultpower,thezenersrestrictthevoltageandtheresistorrestrictsthecurrent.Barriersareusuallydescribedbytheirsafetyparameters28V116mA240RwhereUo=28Vandthecurrentlimitingresistoris240R.Galvanicisolationinterface

Thefigureillustrateshowtheinterfaceisconstructed.Theactualpowerlimitationpartoftheisolator containsalltheelementsofthezenerbarrier.Thepowersupplyisviaatransformer,andthereturnsignalcanbe viaanoptocoupler,transformerorrelay.Thehazardousareacircuithaseffectivelybeenisolatedfromthesafearea circuit.Discussionsontheprosandconsofbothinterfacesareongoing.Earthingforazenerbarrierisessentialforittoremainsafe,unliketheisolatorwhereearthingisnotarequirement.Thetablebelowliststherelativemeritsofbarriersandisolators.Thesignificancedependsontheinstallation.

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Althoughbarriersareacceptedworldwide,thereareanumberofcountriesthathaveadditionalrequirements,e.g.Germanyinsistsonusinggalvanicisolatorsforcircuitsconnectedtozone0.SimpleelectricalapparatusandcomponentsSimpleelectricalapparatusandcomponents(e.g.thermocouples,photocells,junctionboxes,switches,plugsandsockets,resistors,LEDs)maybeusedinintrinsicallysafesystemswithoutcertification,providedthattheydonotgenerateorstoremorethan1.2V,0.1A,20Jand25mWintheintrinsicallysafesysteminthenormalorfaultconditionsofthesystemand,also,noneofthesecomponentslocatedinthehazardousareacandissipatemorethan1.3Wat40oCambienttemperature.Simpleelectricalapparatusandcomponentsshouldalsomeettheinsulation, creepageandclearanceandenclosurerequirementsspecified inEN50014,e.g.choiceofaluminiumalloyandsurfaceresistance oflessthan1G.Thetemperatureclassificationawardedto simpleelectricalapparatusandcomponentscomplyingwith theserequirements,isgenerallyT4(135C).Junctionboxesand switches,however,maybeawardedT6(85C)because,bytheir nature,theydonotcontainheatdissipatingcomponents.Awide varietyof'feedthrough'and'disconnect'terminalscanbefitted insimpleapparatusenclosures.Disconnectterminalsthatdonotrequiretheconductorstoberemovedfromtheterminalsfor testandcalibrationpurposesareparticularlyusefulduring operationalconditions.Examplesareshowninthefigureontheright.Itisimportantthattheexternalterminalconnectionsmaintain3mmclearancebetweenbaremetalpartsofthesameIScircuitand6mmbetweenbaremetalpartsofdifferentIScircuits.SomeuserspreferacertifiedjunctionboxforIScircuits.Anumberofmanufacturers cansupplyExiacertifiedenclosures.IntrinsicallysafeelectricalsystemsAnintrinsicallysafesystemconsistsofoneormoreinterfaces(zenerbarriersorisolators),oneormoreitemsoffieldequipment,andinterconnectingwiringinwhichanycircuitsintendedforuseinapotentiallyexplosiveatmosphere areintrinsicallysafecircuits.Whereacolourisusedinassociationwithintrinsicallysafeequipment,itshould preferablybelightblue.IndividualsystemsWheretheuserorinstallerbuysthecomponentsseparately,andbuildshisownsystem,hewillberesponsibleforensuringthatthecombinationofbarrierandhazardousareaequipmentissafe.The'systemdesignengineer'willberequiredtodocumentthecircuitwithitsinterfaces,fieldequipmentandcableparameters.AccordingtoATEX95,thistypeofassemblyisdefinedasaninstallation,andassuchdoesnotrequiringCEmark.Ifthefielddevice(s)onlyincludesimpleapparatus,theinformationneededtoconstructasafesystemisincludedinthecertificationofthebarrier.

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Wherethefielddeviceisacertifieditem,e.g.atemperaturetransmitterorasolenoidvalve,extrachecksarenecessary.Thecertificateofthefielddevicewillincludeitsmaximuminputparameters,whichwillspecifyoneormoreofthevaluesUi,LiandPi.Compatibilitymustbecheckedbyensuringthatthemaximuminputfiguresofthefielddevicearenotexceededbythemaximumoutputvaluesofthechosenbarrier.Ifthesystemincludesmorethanoneitemofcertifiedapparatus,compatibilitywiththebarriermustbecheckedseparately.Theadditionofsimpleapparatuswillnotaffectthecompatibility,exceptthatthesystemtemperaturemightbederatedtoT4.Thesystemwillbecategorisedaccordingtotheleastfavourablecomponentsofthebarriercategoryandtheapparatuscategory.Forexample,abarrierof[EExia]IICwithafielddeviceofEEXiaIICT6willcategorisethesystemasEExiaIICT6.TheadditionofapieceofsimpleapparatussuchasadiodeorresistorwillchangethesystemcategorytoEExiaIICT4.SystemcertificateInsomecases,thesupplierofthefielddevicemighthaveobtained,inadditiontotheapparatuscertificate,asystemcertificatethatdefinesanumberofbarriertypesandcableparametersofatypicalsysteminwhichthedevicemaybeused.Asystemcertificaterelievesthesystemdesignerofmuchoftheresponsibilityofchoosingtheindividualcomponents,providedthedefinedsystemissuitablefortheapplication.Ifthesystemcertificatedoesnotincludethedesiredarrangement,thisdoesnotmeanthatthearrangementisnotpossible,butsimplythatitwillneedtobeexaminedseparatelyasinthepreviousparagraph.ATEX95doesnotrequireasystemcertificate.However,ifitistheintentionofthemanufacturertoputthearrangement onthemarketasasingleunit,theassemblywillbeCEmarked.4.3.2.4Pressurisation'p'Pressurisedapparatusachievesseparationofignitionsourcesfromexplosiveatmospheresbypurgingtheatmosphereinsidetheapparatuswithairoraninertgasandthenmaintainingapositivepressureof0.5mbarinsidetheequipment topreventtheingressoftheexplosiveatmosphereduringoperation.Failureofthepressurisationleadstoanalarm operatingorthedisconnectionofthecomponentshavingignitioncapability.TheequipmentisdesignedaccordingtoEN50016andissuitableforgasgroupsIandII,categories2GandM2.Pressurised controlroomsarenotcoveredbythisstandard,astheyhavetheirownspecificstandard.Typicalproductsareelectric motors,controlcabinetsandgasanalyzers.

Therearethreetypesofpressurization:StaticpressurizationPressurizationwithcontinuousflowofprotectivegasPressurizationwithleakagecompensationStaticpressurisationinvolvesthechargingoftheequipmentwithprotectivegasinanonhazardousareaandmaintained onlybythesealingoftheenclosure.Thereisnoprotectivegassupplyinthehazardousarea.Whentheoverpressure dropsbelowasetvalue,analarmisraisedortheequipmentisswitchedoff.Theapparatuscanonlyberechargedin thenonhazardousarea.Pressurisationwithcontinuousflowofprotectivegasinvolvesaninitialpurgecyclefollowedbyacontinuousflowofprotectivegasthroughtheenclosurewhilemaintainingapositivepressure.Thesystemcanbeusedwherecoolingisrequiredordilutionofaninternalgasrelease.Pressurisationwithleakagecompensationinvolvesaninitialhighpurgewithprotectivegasthroughtheenclosure,afterwhichtheoutletapertureissealedandtheprotectivegassupplyismaintainedtocompensateforleakagefromtheenclosure.Theminimumnumberofairchangesbeforeenergisationisusually5.Pressurisedairshouldbedrawnfromagasfreeareaandneverfromzone0or1.Ifitisnotfeasibletoductairfrompurgedequipmentintoasafearea, asparkandflamearrestormayberequiredintheoutletairduct.

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4.3.2.5Zone0apparatusEN50284specifiesthe'Specialrequirementsfortheconstruction,testingandmarkingofelectricalapparatusofequipment groupII,category1G'.Ascategory1ismountedinazone0environment,theapparatusrequiresaveryhighlevelof safety.ThestandardsupplementstherequirementsofEN50014,EN50020andEN50028.Thestandardalsoappliestoapparatusmountedacrosstheboundarybetweenhazardousandlesshazardousareaswherecategory1andcategory2equipmentwouldnormallybeinstalled.Italsoincludesrequirementsforapparatusinstalledoutsidethehazardousareabutelectricallyconnectedtoapparatus ofcategory1insidethehazardousarea(e.g.associatedapparatus).Topreventignitionhazardsbytheelectricalcircuitsoftheapparatus,theveryhighlevelofsafetyrequiredcanbeobtainedby:Singleapparatus,whichremainssafewithtwofaultsoccurringindependentlyfromeachotherTwoindependentmeansofprotection.Intheeventthatoneprotectionfails,anindependentsecondoneisstillAvailableIndividualconceptssuitableforcategory1are:ApparatuscomplyingwiththerequirementsofEN50020,type'ia'ApparatusprotectedbyencapsulationinaccordancewithEN50028andsupplementedbytherequirementsofthisstandardTwoindependenttypesofprotectionElectricalapparatusshallmeettherequirementsoftwoofthestandardsintheseriesEN50015toEN50020(ib),plusEN50028.Thecombinedtypesofprotectionmustdependondifferentprotectionprinciples,whichcanbecheckedindividually.Bothtypesofprotectionwillbeassessedundertheassumptionofthemostarduousfaultoftheothertype ofprotection.Therethecombinedprotectionconceptreliesonanenclosure,twoenclosuresshouldbeused.Ifonlyoneenclosureisused,boththeenclosureandthecableentrieshavetowithstandanimpacttestof20J.Examples:TorchlightwithExdandExehousingandExibcircuitElectricmotorcomplyingbothwithEN50018,flameproofExd,EN50019,increasedsafetyExeMeasuringtransducerwithintrinsicallysafecircuittype'ib'andflameproofenclosureExdPressurisedapparatusExpwithincreasedsafetyenclosureExe.ApparatusmountedacrosstheboundarywallWhereapparatusaremountedacrosstheboundarybutarenotintrinsicallysafetype'ia',theymustcontainamechanical separationelementinsidetheapparatusandcomplywithameansofprotection.Thetablebelowillustratesthepossiblecombinationsofseparationelementsandtypesofprotection.

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Apparatusforuseinzone0mustbebuiltinsuchawaythatignitionsourcesduetoimpactandfrictionareexcluded.Ignitionhazardsduetodangerouselectrostaticchargesshouldalsobeavoided.MarkingTheequipmentmustbemarkedaccordingtoEN50014forequipmentgroupII,category1,andtherespectiveproduct standards.Specialmarkingisrequiredforsomeoftheconceptscoveredinthisstandard.Intrinsicsafety

Intrinsicallysafeapparatus II1G EExiaIICT4Associatedapparatus II(1)G (EExia)IIC

Specialencapsulation II1G EExmaUi=Ii=Pi=

Twomethodsofprotection II1G EExdIICT4/EExmeIIT4Apparatusacrossboundary, II1/2G EExd[ia]IICT4e.g.sensors

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4.3.2.6 Zone2apparatusApparatusforzone2aredesignedtocomplywithcategory3GequipmentaccordingtoATEX95.Theyhaveanormallevelofsafetyandaresuitablefornormaloperation.Apparatuscomplyingwithcategory0and1canalsobeusedinzone2.Therequirementsforcategory3canbemetbyusingtheharmonisedstandardEN50021,typeofprotection'n'.Othertechnicalstandards,e.g.nationalstandards,couldbeusedaslongastheEssentialHealthandSafetyRequirementsinATEX95arecompliedwith.Category3equipmentdoesnothavetobetestedbyanotifiedbodysuchasBASEEFA,PTB,KEMA,etc.butthemanufacturermustbeabletoprovideevidencethattheproductissafe.ControlboxesmayhousecomponentswithindividualECtypeexaminationcertificates,butnooverallcertification.Themanufacturermustestablishthemaximumsurfacetemperatureandprovidethenecessarydocumentation.TheExnstandardmakesadistinctionbetweenapparatusthatdoesnotproducearcs,sparksorhotsurface'nonsparkingapparatus',anapparatusthatproducesarcs,sparksorhotsurfaceinnormaloperation'sparkingapparatus'.NonsparkingapparatusTheriskoftheoccurrenceofarcs,sparksorhotsurfacesduringnormaloperationhasbeenminimisedbyconstructionalmeans.Theequipmentismarkedwith'nA'.Examplesofapparatusaremotors,luminaries,junctionboxesandcontrolboxes.Fuseterminalsareconsideredtobenonsparking,providedtheyarenotopenedunderload.Fusesmustbenonrewirable.WhenmountedinanenclosureandbuilttoprotectiontypeEExnAIIthemanufacturermustensuretheinternalorexternalsurfacetemperatureiswithintheTclassification.SparkingapparatusInthiscase,arcs,sparksorhotsurfacesdooccurduringnormaloperation.Thefollowingprotectionconceptsareallowed:Apparatuswithprotectedcontacts'nC'Theseincludeenclosedbreakdevices,nonincendivecomponents;hermeticallysealeddevicesandsealedorencapsulateddevices.Energylimitedapparatusandcircuits'nL'Essentiallyanintrinsicallysafesystemthatissafewithnofaultsandnounityfactorofsafetyontheignitioncurves.Therequirementsfordesignanddocumentationareverysimilartointrinsicsafety.Restrictedbreathingenclosures'nR'TheseenclosuresmeetatleastIP54andaninternalpressureof3mbartakesatleast80secondstodropto1.5mbar.Thetypeofprotectionmaybeappliedtoenclosurescontainingsparkingcontactsbutwithalimitationindissipatedpowersuchthattheaverageairtemperatureinsidetheenclosuredoesnotexceedtheexternalambienttemperaturebymorethan10K.Whenappliedtoenclosureswithoutsparkingcontacts,theonlylimitationistheoutsidetemperature.Restrictedbreathingenclosures,withouttheprovisionforcarryingoutchecksafterinstallation,mustbetyptestedbythemanufacturerwiththecableglandsinplace.Simplifiedpressurisation'nP'ThisconceptisbasedonanenclosurewithatleastIP54(couldberestrictedbreathingenclosure)thatonlyrequiresaminimalairflowtocoverleakagelosses.SimplifiedpressurisationiscurrentlynotcoveredbyEN50021,butthetechnicalrequirementswillbebasedonIEC600792,typeofprotection'pz'.CableentrydevicesGlandsmustbeconstructedandmountedsuchthattheymaintainthetypeofprotectionoftheapparatus.StandardindustrialglandstoEN50262canbefitted.Ofcourse,certifiedcableglandscanalsobeused.4.3.2.7Powderfilling'q'Protectionisprovidedbyimmersingtheignitioncapablepartsinafinepowder,usuallyquartz.Thearcisquenchedbeforeitcanignitethesurroundinggas.Currentislimitedtoasafelevel.TheequipmentisdesignedaccordingtoEN50017,andissuitableforgasgroupsII,categories2G.4.3.2.8Oilimmersion'o'Protectionisprovidedbyimmersingtheapparatusinoilsothatanexplosiveatmospherecannotbeignitedbythearcsandsparksgeneratedundertheoil.TheequipmentisdesignedaccordingtoEN50015,andissuitableforgasgroupsII,categories2G.4.3.2.9Encapsulation'm'Protectionisprovidedbyencapsulatinganyhotorsparkingcomponentswithamaterialthatpreventstheingressofexplosivegasandcoolsanyheatproducedbythecomponents.TheequipmentisdesignedaccordingtoEN50028,andissuitableforgasgroupsII,categories2G.

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4.4InstallationThestandardfor'Electricalinstallationsinhazardousareas'isEN6007914.IntheUK,thestandardreplacesBS5345.AllnewinstallationsshouldcomplywiththeEuropeanstandard,butoldinstallationscanstilluseBS5345.Nevertheless,electricalinstallationsinhazardousareasshallalsocomplywiththeappropriaterequirementsforinstallationsinnonhazardousareas.4.4.1SelectionofelectricalapparatusInordertoselecttheappropriateapparatusforanexplosiveatmosphere,thefollowinginformationisrequired:ClassificationofhazardousareasTemperatureclassorignitiontemperatureofthegasorvapourinvolvedGasorvapourclassificationinrelationtothegrouporsubgroup(applicableforprotection'd','i'andcertainapparatuswithprotection'n')ExternalinfluencesandambienttemperatureThetablebelowshowstherelationshipbetweenthegas/vapoursubdivisionandtheapparatussubgroup:

4.4.2ProtectionagainstdangerousincendivesparkingInordertoavoidtheformationofsparksliabletoignitetheexplosiveatmosphere,anycontactwithbarelivepartsotherthanintrinsicallysafepartsmustbeprevented.Usually,IP54isspecifiedasaminimumdegreeofprotection.Whereintrinsicallysafeandnonintrinsicallysafecircuitsaretogetherinanenclosure,thenonintrinsicallysafecircuitsmaybeprotectedwithanIP30cover.Thebasicprinciplesonwhichsafetydependsarethelimitationofearthfaultcurrents(magnitudeand/orduration)inframeworksorenclosures,andthepreventionofelevatedpotentialsonequipotentialbondingconductors.Forelectricalsupplysystemsotherthanintrinsicallysafecircuitsforuseinzones1and2upto1000Va.c./1500Vd.c.thefollowingapplies:TNsystemIfatypeTNpowersystemisused,itmustbethetypeTNS(withseparateneutralNandprotectiveconductorPE)inthehazardousarea,i.e.theneutralandtheprotectiveconductormustnotbeconnectedtogether,orcombinedinasingleconductor,inthehazardousarea.AtanypointoftransitionfromTNCtoTNS,theprotectiveconductormustbeconnectedtotheequipotentialbondingsysteminthenonhazardousarea.TTsystemsIfaTTsystemisusedinzone1,ithastobeprotectedbyaresidualcurrentdevice.ITsystemsIfanITsystemisused,aninsulationmonitoringdevicemustbeprovidedtoindicatethefirstearthfault.EquipotentialbondingPotentialequalisationisrequiredforinstallationsinhazardousareas.ForTN,TTandITsystems,allexposedandextraneousconductivepartsmustbeconnectedtotheequipotentialbondingsystem.Itisalsoadvisabletoconnectmetalconstructions,metalconduitsandmetalcablesheathstothesystem.Connectionsmustbepermanentandsecureagainstselfloosening.Exposedconductivepartsneednotbeseparatelyconnectedtotheequipotentialbondingsystemiftheyarefirmlysecuredtoandinmetalliccontactwithstructuralpartsorpipingwhichareconnectedtotheequipotentialbondingsystem.Metallicenclosuresofintrinsicallysafeapparatusdonothavetobeconnectedtotheequipotentialbondingsystemunlessrequiredbytheapparatusdocumentation.StaticelectricityThestandardEN50014specifiesthebasicrequirements,andtheproductstandardsEN50284(zone0)andEN50021listtherequirementstobemetbyelectricalequipment.Unlikeearlierprovisions,thesestandardsspecifythesurfaceresistancesandthemaximumadmissiblesizesofplasticssurfacesforzone2.LightningprotectionBecausenointernationallyharmonisedstandardsexistforlightningprotection,nationalstandardshavetobeapplied.

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Inanycase,stepsmustbetakentoreducetheeffectsoflightningtoasafelevel.

4.4.3ElectricalprotectionTheelectricalequipmentandthewiringmustbeprotectedagainstoverloadandtheharmfuleffectsofshortcircuitsandearthfaults.Specialprotectivemeasuresarerequiredinthecaseofrotatingelectricalmachinery.Theoverloadprotectivedevicestobeusedare:Acurrentdependent,timelagdeviceforallthreephases,setatnomorethanthemachinesratedcurrent.Thedevicemusttripwithin2hoursat1.2timesthesetcurrentbutmustnottripwithin2hoursat1.05timesthesetcurrent.Embeddedtemperaturesensorsprovidingdirecttemperaturemonitoringofthemachine.Innocaseshouldtheautomaticswitchoffresultinanincreasedsafetyrisk.Whereitmight,alarmingisanacceptablealternativetoautomaticdisconnectionifthealarmleadstoimmediateremedialaction.4.4.4WiringsystemsCablesystemsmustbeinstalledsuchthattheyareprotectedagainstmechanicaldamageandcorrosionorchemicalinfluences.Theeffectsofheatshouldalsobeavoided.Ducts,pipesandtrenchesaredesignedsuchthatgasescannotcollectinthem.Wherecircuitscrossthehazardousarea,thewiringsystemmustcomplywiththerelevantzone.Openingsinwallsorceilingsforcablesandconduitsmustbeadequatelysealed.Cablerunsinhazardousareasshouldbeuninterrupted.Whereconnectionsaremade,thecorrecttypeofprotectionmustbeused,e.g.Exejunctionbox.Unusedcoresshouldbeterminatedinappropriateterminals.Theyshouldbebondedtoearthatonepoint,preferablyinthesafearea.Multistrandedand,inparticular,finestrandedconductorsmustbeprotectedagainstseparationofthestrandsbymeansofferrules,lugsorthetypeofterminal, Ingeneral,onlyoneconductorperterminalclampispermitted.Sometypesofterminalsareabletoaccommodatemorethanoneconductor, Wherealuminumisusedastheconductormaterial,thecrosssectionalareamustbeatleast16mm2,withtheexceptionofintrinsicallysafecircuits.Overheadlinesshouldbeterminatedinthenonhazardousareaandtheservicecontinuedintothehazardousareawithcableorconduit.Suitablesurgeprotectionshouldbefittedatornearthisterminalpoint.Cablesforfixedwiringmusthaveflamepropagationcharacteristics.Conduitsystemsmustbefittedwithsealingfittings:WhereitentersorleavesahazardousareaWithin450mmofallenclosurescontainingasourceofignitioninnormaloperationAtanyenclosurecontainingtaps,splices,jointsorterminationswheretheconduitdiameterismorethan50mmThetotalcrosssectionalareaofthecables,includinginsulation,mustnotbemorethan40%ofthecrosssectionalareaoftheconduit.Tomeetthedegreeofprotectionofanenclosure,itmaybenecessarytosealbetweentheconduitandtheenclosureorbetweentheconductorsandtheconduit.Unusedcableentriesshouldbefittedwithstoppingplugsappropriateforthetypeofprotection.Exceptforintrinsicsafety,theyshouldonlyberemovedwiththeaidofatool.4.4.5Additionalrequirementsforflameproofenclosures'd'Flameproofjointsmustbeprotectedagainstcorrosion.Theuseofgasketsisonlypermittedwhenspecifiedinthedocumentation.Nonsettinggreaseoranticorrosiveagentscanbeapplied.Nonhardeninggreasebearingtextiletapemayalsobeemployedoutsideofthejoint,butonlyinconjunctionwithgasesallocatedtogroupIIA.Thetapeshouldberestrictedtoonelayersurroundingallpartsofthejointswithashortoverlap.Therearethreecableentrysystems:DirectentryIndirectentryvia,e.g.ExeenclosureConduit

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Fordirectentry,thecableglandselectionmustbemadeaccordingtoappendix.Tomaintaintheintegrityofthetypeofprotection,glandsandconduitsshouldhaveatleast5threadsofengagement.Clearanceholesarenotallowedinflameproofenclosures.Whenmineralinsulatedcableisselected(withorwithoutplasticoutercovering),thecableglandassemblyand'sealingpot'mustbeEEx'd'certifiedandinstalledstrictlyinaccordancewiththemanufacturersinstruction.Thistypeofcableisoftenusedforfireandgasprotectionsystemsduetoitshighresistancetotemperatureandintegrityduringafire.Conduitsystemsmustbeofthetype:Screwedheavygauge,soliddrawnorseamweldedFlexibleconduitofmetalorcompositematerialconstructionMotorssuppliedatvaryingfrequencyandvoltagerequireeither:Meansfordirecttemperaturecontrolbyembeddedtemperaturesensorsspecifiedinthemotordocumentation.Theactionoftheprotectivedevicewillbetodisconnectthemotor.Inthiscase,themotorandconvertercombinationdoesnothavetobetestedtogether.Themotorhasbeentypetestedforthisdutyasaunitinassociationwiththeconverterspecifiedinthedescriptivedocuments.4.4.6Additionalrequirementsforincreasedsafety'e'CableentrydevicesmustmaintainatleastIP54.Threadedentriesinenclosureswithawallthicknessofatleast6mmdonotrequireasealingwashertomaintaintheminimumIPrating.However,inpracticeenclosuresarenormallyIP65orIP66.Therefore,asealingwasherisrecommended.Thevariousmethodsofentryformetallicenclosuresandforthickwallplasticenclosuresaredetailedinthenextfigure.Whencastalloyenclosuresareselected,specialcareisnecessarytoavoidthedangerfrombimetalliccorrosionwithdissimilarmetals.Thisisparticularlyprevalentwithalloyenclosuresfittedwithbrasscableglands.Theoptionstoovercomethisproblemare,nickelplatedbrass,stainlesssteel,plasticorglandsmadefromacompatiblealloy.PlasticenclosuresdonotpresentthesameearthandbondingproblemsinGermanyandotherContinentalEuropeancountriesastheydointheUK.Whenarmouredcablesareusedthearmourmustbeeffectivelybondedtothemainearthconnectionontheenclosure.Therearecommonlytwomethodsusedtoachievethenecessaryearthingrequirementsasshowninthwfollowingfigurei.e.eitheraninternalmetalcruciformplate,oralternativelyathickbrassplatewhichisnormallysuppliedwithathreadedentry.Duetotheoverallwallthicknessofmanynonmetallicenclosures,plustheneedforsealingandpossiblyanantivibrationwasher,itisoftennecessarytouseacableglandwithanextralongcableglandentrythread(e.g.20mm).Concernhasbeenexpressedbyvariouscertificationbodiesregardingthepotentialdangerofselflooseningofcableglands,duetothermaleffectsinnonmetallicenclosures.EN50019includesanewtestrequirementforplasticenclosuresthatteststhethermalstabilityoftheenclosurematerial.Ifthematerialpassesthetest,theearthcontinuityshouldbesecureevenwithouttheserratedwasher.Ifitfailsthetest,theonlywaytosecurelymaintaintheearthcontinuityisbysandwichingthebrassplatebetweentwolocknuts.Motorssuppliedatvaryingfrequencyandvoltagebyaconvertermustbetypetestedforthisdutyasaunitinassociationwiththeconverterspecifiedwiththedescriptivedocuments.4.5Inspectionandmaintenance4.5.1GeneralrequirementsElectricalinstallationsinhazardousareashavefeaturesspecificallydesignedtomakethemsuitableforuseinsuchatmospheres.ATEX137stipulatesthatitistheoperatorsresponsibilitytomaintaintheintegrityofthosespecialfeatures.Theoperatormustensurethatelectricalequipmentis:InstalledandoperatedcorrectlyMonitoredonaregularbasisMaintainedwithdueregardtosafetyThemainstandardfortheinspectionandmaintenancerequirementsisEN6007917/IEC6007917:Electricalapparatusforexplosivegasatmospheres,'Inspectionandmaintenanceofelectricalinstallationsinhazardousareas(otherthanmines)'.Dependingonthecountryandindustry,e.g.offshoreorpetrolstations,additionalnationalstandardsmighthavetobecompliedwith.

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4.5.1.1DocumentationUptodateinformationonthefollowingitemsmustbemadeavailable:SitedrawingsoutliningthezoneclassificationListandlocationoftheapparatusApparatusgroupandtemperatureclassSpecialconditionsforsafeuseofelectricalapparatuswithcertificatenumbers,whichhavethesuffix'X'.The'instructions'ofATEXcertifiedequipmentmusthaveallrelevantinformationlistedDescriptivesystemdocumentfortheintrinsicallysafesystemSpareslist4.5.1.2QualificationofpersonnelTheinspectionandmaintenanceofinstallationsshouldonlybecarriedoutbyexperiencedpersonnelwhosetraininghasincludedinstructiononthevarioustypesofprotectionandinstallationpractices,therelevantrulesandregulations,andonthegeneralprinciplesofareaclassification.Appropriatecontinuingtrainingshouldbeundertakenonaregularbasis.4.5.1.3PermittoworkApermittoworksystemisaformalwrittensystemusedtocontrolcertaintypesofworkthatarepotentiallyhazardous.Apermittoworkisadocumentwhichspecifiestheworktobedoneandtheprecautionstobetaken.Permitstoworkformanessentialpartofsafesystemsofworkformanyinspectionandmaintenanceactivities.Theyallowworktostartonlyaftersafeprocedureshavebeendefined,andtheyprovideaclearrecordthatallforeseeablehazardshavebeenconsidered.Apermitisneededwheninspectionormaintenanceworkcanonlybecarriedoutifnormalsafeguardsaredropped,orwhennewhazardsareintroducedbythework.Examplesareentryintovessels,hotworkandpipelinebreaking.Thepreciseformatofaworkpermitwillvaryfromsitetosite.4.5.2Inspections4.5.2.1GeneralBeforeaplantisbroughtintoserviceforthefirsttime,itmustbegivenaninitialinspection.Thisworkcanbedonebytheoperatororanoutsidecompany(thirdparty).Toensurethattheinstallationismaintainedinasatisfactorycondition,itisnecessarytocarryouteither:Regularperiodicinspections,orContinuoussupervisionbyskilledpersonneland,wherenecessary,maintenancemustbecarriedout.4.5.2.2Typesofinspectiona. Initialinspectionsareusedtocheckthattheselectedtypeofprotectionanditsinstallationareappropriate.Examplechecklistsareshownintables1,2and3(seeAppendixVII).b. Periodicinspectionsarecarriedoutonaroutinebasis.Theymaybevisualorclose(seetables1,2and3inAppendixVII)butcouldleadtoafurtherdetailedinspection.Thetypeofequipment,manufacturersguidance,deteriorationoftheapparatus,zoneofuse,andtheresultofpreviousinspectionsdeterminethegradeandtheintervalbetweenperiodicinspections.Theintervalbetweenperiodicinspectionsshouldnotexceedthreeyearswithoutseekingexpertadviceortheuseofextensiveinspectiondata.Movableelectricalapparatusareparticularlypronetodamageormisuseandthereforetheintervalbetweeninspectionsshouldbesetaccordingly.c.Sampleinspectionscanbevisual,closeordetailed.Thesizeandcompositionofallsamplesdependsonthepurposeoftheinspection.d.Continuoussupervisionisbasedonthefrequentattendance,inspection,service,careandmaintenanceofthe

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electricalinstallationbyskilledpersonnelwhohaveexperienceinthespecificinstallationanditsenvironment,inordertomaintaintheexplosionprotectionfeaturesoftheinstallationinsatisfactorycondition.Wheretheinstallationfallsoutsidethecapabilityofcontinuoussupervision,itwillbesubjecttoperiodicinspection.4.5.2.3Gradesofinspectiona.Visualinspectionsidentify,withouttheuseofladdersorhandtools,thosedefectswhichareapparenttotheeye,e.g.missingboltsb.Closeinspectionsincludethoseaspectscoveredbyvisualinspectionsand,inaddition,identifythosedefects,whichareonlyapparentbytheuseofaccessequipmentandtools,e.g.loosebolts.Closeinspectionsdonotnorma