What's the difference between PL and SIL machine safety ...

Although the methods for performing risk assessment are different, both machine safety standards, EN ISO 13849-1 and EN 62061, achieve the ... SkiptoprimarynavigationSkiptomaincontentSkiptoprimarysidebarSkiptofooter Youarehere:Home/FAQs+basics/What’sthedifferencebetweenPLandSILmachinesafetystandards?Machinesafetyisgovernedbytwostandards:EN/ISO13849-1andEN/IEC62061.BothstandardsareharmonizedtotheEUMachineryDirective2006/42/EC,whichdefinestheEssentialHealthandSafetyRequirements(EHSR)formachinery.Althoughtheirmethodsforperformingriskassessmentaredifferent,bothstandards—ENISO13849-1andEN62061—whencorrectlyapplied,achievethesameresult. TheEUMachineryDirectiverequiresthatmachinemanufacturerseliminateorminimizehazardsasmuchasreasonable,applynecessaryprotectivemeasuresagainsthazardsthatcannotbeeliminated,andinformusersoftherisksthatremainandrequirementsfortrainingorpersonalprotectiveequipment.AlthoughthisdirectiveisspecifictotheEuropeanUnion(EU),itisrecognizedandfollowedinotherregionsaroundtheworld,tobetterfacilitateequipmentshipmentsoutsidetheEU. TheEN/ISO13849-1machinesafetystandardusesaqualitativeriskgraph,orflowchart,toassignaperformancelevel(PL),basedonthreecriteria: severityofinjury frequencyand/orexposuretimetothehazard possibilityofavoidingthehazardorlimitingtheharm Theperformancelevel(PL)isdesignatedbyanalphabeticcharacter,athrue,withPLebeingthehighestrisklevel. EN/ISO13849-1assignsaperformancelevel(PL)ratingfromatoe,withPLebeingthehighestrisk.Imagecredit:TUV Oncetheperformancelevelhasbeendetermined,thearchitecturethatfacilitatesthedefinedperformancelevelisclassifiedintooneofsixcategories(“B”and1thru5,withBbeingtheleastsafeand5beingthemostsafe).Thearchitecturecategoryisdeterminedbycombiningtheperformancelevel(PL)withquantitativemeasuresofdiagnosticcoverage(DC)andmeantimetodangerousfailure(MTTFd). ThischartshowstherelationshipbetweenCategory,DiagnosticCoverage,andMeanTimetoDangerousFailureforPLlevelsunderEN/ISO13849-1.Notealsothecorrelationwithprobabilityofdangerousfailureperhour(PFHd)rates.Imagecredit:ABB TheEN/IEC62061machinesafetystandard(oftenwrittenasjustEN62061)assignsasafetyintegritylevel(SIL)toeachfunctionbasedontheseverityofthepotentialharm(Se)andtheprobabilityoftheharmoccurring. Theseverityofpotentialharmisgivenascorefrom1to4,with4beingthemostsevere.Theprobabilityofharmoccurringisbrokendownintothreeparameters: frequencyanddurationofexposure(Fr) probabilityofaneventoccurring(Pr) probabilityofavoidingorlimitingtheharm(Av) EN62061assignsasafetyintegritylevel(SIL)from1to3basedontheseverityofpotentialharmandtheprobabilityoftheharmoccurring.Imagecredit:TUV Eachoftheseparametersisscoredfrom1to5,with5beingthe“worst,”orleastsafesituation,andtheirscoresaresummedtodetermineaclass(Cl).TheSILratingisthenchosenfromamatrixthatplotstheseverityscores(Se)andclasses(Cl). SILratingsaredeterminedbyamatrixthatrankstheseverityofinjuryandtheinjuryclassification. Oncethesafetyintegritylevel(SIL)hasbeenassigned,thesystemisbrokenintosubsystems,whosearchitecturesareclassifiedasA,B,C,orD,withDbeingthe“highest,”orsafest. Eacharchitectureisassociatedwithaformulatodeterminetheprobabilityofdangerousfailureperhour(PFHd)ofthesubsystem. Notethatperformancelevel(PL)ratingsunderEN/ISO13849-1arealsocorrelatedwithprobabilityofdangerousfailuresperhour(PFHd)values,sodirectcomparisonscanbemadebetweenEN/ISO13849-1performancelevelsandEN62061safetyintegritylevels. Thereisnostrictguidelineregarding theuseofmachinesafetystandardsforparticularapplications,butthechoicemaybeinfluencedby: Priorexperiencewithonestandardorriskassessmentmethodology Theuseofsafety-relatedcontrolsthatarenotbasedonelectrical,electronic,orprogrammableelectronicsystems(useEN/ISO13849-1) ArequirementtouseSILratingstodemonstratesafetyintegrity(useIEC62061) Useofequipmentinprocessindustrieswhereothersafety-relatedsystemsarecharacterizedintermsofSIL(useIEC62061) Youmayalsolike: Whichdrive-basedsafetyfunctionscanIuseforacontrolled… HowdoSTOinputsaffectSIL3/PLeconformityforACdrives? HowtogetFunctionalSafetycertificationbyusingencoderson… Whataretypicaldrive-basedsafetyfunctions? Whatarefunctionalsafetystandardsforservodrives? 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