655OccupationalSafetyandHealthAdmin.,Labor§1910.218Anacceptablemethodforinterlockingsupplementalguardsasrequiredbypara-graph(h)(6)(xiii)wouldbetoincorporatethesupplementalguardandthePSDIpresencesensingdeviceintoahingedarrangementinwhichthealignmentofthepresencesensingdeviceserves,ineffect,astheinterlock.Ifthesupplementalguardsaremoved,thepresencesensingdevicewouldbecomemis-alignedandthepresscontrolwouldbede-activated.Noextramicroswitchesorinter-lockingsensorswouldberequired.Paragraph(h)(6)(xv)ofthestandardre-quiresthatthecontrolsystemhaveprovi-sionsforan‘‘inch’’operatingmeans;thatdie-settingnotbedoneinthePSDImode;andthatproductionnotbedoneinthe‘‘inch’’mode.Itshouldbenotedthatthesensingdevicewouldbeby-passedinthe‘‘inch’’mode.Forthatreason,theprohibi-tionsagainstdie-settinginthePSDImode,andagainstproductioninthe‘‘inch’’modearecitedtoemphasizethat‘‘inch’’operationisofreducedsafetyandisnotcompatiblewithPSDIorotherproductionmodes.7.EnvironmentalRequirementsItistheintentofparagraph(h)(7)thatcontrolcomponentsbeprovidedwithinher-entdesignprotectionagainstoperatingstressesandenvironmentalfactorsaffectingsafetyandreliability.8.SafetysystemThesafetysystemprovisioncontinuestheconceptofparagraph(b)(13)thattheprob-abilityoftwoindependentfailuresinthelengthoftimerequiredtomakeonepresscycleissoremoteastobeanegligibleriskfactorinthetotalarrayofequipmentandhumanfactors.Theemphasisisonaninte-gratedtotalsystemincludingallelementsaffectingpointofoperationsafety.Itshouldbenotedthatthisdoesnotre-quireredundancyforpresscomponentssuchasstructuralelements,clutch/brakemecha-nisms,plates,etc.,forwhichadequatereli-abilitymaybeachievedbyproperdesign,maintenance,andinspection.9.SafeguardingthePointofOperationTheintentofparagraph(h)(9)(iii)istopro-hibituseofmirrorsto‘‘bend’’asinglelightcurtainsensingfieldaroundcornerstocovermorethanonesideofapress.Thisprohibi-tionisneededtoincreasethereliabilityofthepresencesensingdeviceininitiatingastrokeonlywhenthedesiredworkmotionhasbeencompleted.Objectsensitivitydescribesthecapabilityofapresencesensingdevicetodetectanobjectinthesensingfield,expressedasthelinearmeasurementofthesmallestinterruptionwhichcanbedetectedatanypointinthefield.Minimumobjectsensitivitydescribesthelargestacceptablesizeoftheinterrup-tioninthesensingfield.Aminimumobjectsensitivityofoneandone-fourthinches(31.75mm)meansthataoneandone-fourthinch(31.75mm)diameterobjectwillbecon-tinuouslydetectedatalllocationsinthesensingfield.Inderivingthesafetydistancerequiredinparagraph(h)(9)(v),allstoppingtimemeas-urementsshouldbemadewithclutch/brakeairpressureregulatedtothepressmanufac-turer’srecommendedvalueforfullclutchtorquecapability.Thestoppingtimemeas-urementsshouldbemadewiththeheaviestupperdiethatisplannedforuseinthepress.Ifthepresshasaslidecounterbalancesys-tem,itisimportantthatthecounterbalancebeadjustedcorrectlyforupperdieweightac-cordingtothemanufacturer’sinstructions.Whilethebrakemonitorsettingisbasedonthestoppingtimeitactuallymeasures,i.e.,thenormalstoppingtimeatthetopofthestroke,itisimportantthatthesafetydis-tancebecomputedfromthelongeststoppingtimemeasuredatanyoftheindicatedthreedownstrokestoppingpositionslistedintheexplanationofTs.Theuseintheformulaoftwicethestoppingtimeincrease,Tm,al-lowedbythebrakemonitorforbrakewearallowsforgreaterincreasesinthedown-strokestoppingti...
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