EM 385 ARC Welding and Cutting.pdfVIP专享VIP免费原创优质

WeldingandCuttingConstructionSafetyandHealthOutreachProgramU.S.DepartmentofLaborOSHAOfficeofTrainingandEducationMay1996ARCWELDINGANDCUTTING­'1926.351ManualElectrodeHoldersOnlymanualelectrodeholderswhicharespecificallydesignedforarcweldingandcutting,andareofacapacitycapableofsafelyhandlingthemaximumratedcurrentrequiredbytheelectrodes,shallbeused.Anycurrent­carryingpartspassingthroughtheportionoftheholderwhichthearcwelderorcuttergripsinhishand,andtheoutersurfacesofthejawsoftheholder,shallbefullyinsulatedagainstthemaximumvoltageencounteredtoground.WeldingCablesandConnectorsAllarcweldingandcuttingcablesshallbeofthecompletely,insulated,flexibletype,capableofhandlingthemaximumcurrentrequirementsoftheworkinprogress,takingintoaccountthedutycycleunderwhichthearcwelderorcutterisworking.Onlycablefreefromrepairorsplicesforaminimumdistanceof10feetfromthecableendtowhichtheelectrodeholderisconnectedshallbeused,exceptthatcableswithstandardinsulatedconnectorsorwithspliceswhoseinsulatingqualityisequaltothatofthecablearepermitted.Cablesinneedofrepairshallnotbeused.Whenacable,otherthanthecableleadreferredtoabove,becomesworntotheextentofexposingbareconductors,theportionthusexposedshallbeprotectedbymeansofrubberandfrictiontapeorotherequivalentinsulation.Whenitbecomesnecessarytoconnectorsplicelengthsofcableonetoanother,substantialinsulatedconnectorsofacapacityatleastequivalenttothatofthecableshallbeused.Ifconnectionsareeffectedbymeansofcablelugs,theyshallbesecurelyfastenedtogethertogivegoodelectricalcontact,andtheexposedmetalpartsofthelugsshallbecompletelyinsulated.GroundReturnsandMachineGroundingAgroundreturncableshallhaveasafecurrent­carryingcapacityequaltoorexceedingthespecifiedmaximumoutputcapacityofthearcweldingorcuttingunitwhichitservices.Whenasinglegroundreturncableservicesmorethanoneunit,itssafecurrent­carryingshallexceedthetotalspecifiedmaximumoutputcapacitiesofthealltheunitswhichitservices.Pipelinescontaininggasesorflammableliquids,orconduitscontainingelectricalcircuits,shallnotbeusedasagroundreturn.Whenastructureorpipelineisemployedasagroundreturncircuit,itshallbedeterminedthattherequiredelectricalcontactexistsatalljoints.Thegenerationofanarc,sparks,orheatatanypointshallcauserejectionofthestructuresasagroundcircuit.Whenastructureorpipelineiscontinuouslyemployedasagroundreturncircuit,alljointsshallbebonded,andperiodicinspectionsshallbeconductedtoensurethatnoconditionofelectrolysisorfirehazardexistsbyvirtueofsuchuse.Theframesofallarcweldingandcuttingmachinesshallbegroundedeitherthroughathirdwireinthecablecontainingthecircuitconductororthroughaseparatewirewhichisgroundedatthesourceofthecurrent.Groundingcircuits,otherthanbymeansofthestructure,shallbecheckedtoensurethatthecircuitbetweenthegroundandthegroundedpowerconductorhasresistancelowenoughtopermitsufficientcurrenttoflowtocausethefuseorcircuitbreakertointerruptthecurrent.Allgroundconnectionsshallbeinspectedtoensurethattheyaremechanicallystrongandelectricallyadequatefortherequiredcurrent.OperatingInstructionsEmployersshallinstructemployeesinthesafemeansofarcweldingandcuttingasfollows:�Whenelectrodeholdersaretobeleftunattended,theelectrodesshallberemovedandtheholdersshallbesoplacedorprotectedthattheycannotmakeelectricalcontactwithemployeesorconductingobjects.�Hotelectrodeholdersshallnotbedippedinwater;todosomayexposethearcwelderorcuttertoelectricshock.�Whenthearcwelderorcutterhasoccasiontoleavehisworkortostopworkforanyappreciablelengthoftime,orwhenthearcweldingorcuttingmachineistobemoved,thepowersupplyswitchtotheequipmentshallbeopened.�Anyfaultyordefectiveequipmentshallbereportedtothesupervisor.�Adisconnectingmeansshallbeprovidedinthesupplycircuitforeachmotorgeneratedarcwelder,andforeachACtransformerandDCrectifierarcwelderwhichisnotequippedwithadisconnectmountedasanintegralpartofthewelder.�Aswitchorcircuitbreakershallbeprovidedbywhicheachresistancewelderanditscontrolequipmentcanbeisolatedfromthesupplycircuit.Theampereratingofthisdisconnectingmeansshallnotbelessthanthesupplyconductorampacity.ShieldingWheneverpracticable,allarcweldingandcuttingoperationsshallbeshieldedbynoncombustibleorflameproofscreenwhichwillprotectemployeesandotherpersonsworkinginthevicinityfromthedirectraysofthearc.