2.4.1 EN ISO 13849-1, Part 1: General principles for design

Like EN 954-1, it incorporates the safety-related parts of control systems (SRP/CS) in its area of application and all types of machines, regardless of the ... Startpage Solutions Applicationknow-how/topics Safetyatwork 2.MachineSafetyintheEU 2.4.1ENISO13849-1,Part1:Generalprinciplesfordesign 2.4.1ENISO13849‑1"Safetyofmachinery–Safety-relatedpartsofcontrolsystems–Part1:Basicprinciples" InOctober2006ENISO13849-1wasofficiallyadoptedasthesuccessorstandardtoEN954-1.LikeEN954-1,itincorporatesthesafety-relatedpartsofcontrolsystems(SRP/CS)initsareaofapplicationandalltypesofmachines,regardlessofthetechnologyandenergyformused(electric,hydraulic,pneumatic,mechanical,etc.).ItfocusesontheestablishedcategoriesofEN954-1andcontainsspecialrequirementsforSRP/CSwithprogrammableelectronicsystems.ENISO13849-1goesbeyondthequalitativeapproachofEN954-1toincludeaquantitativeassessmentofthesafetyfunctions.Performancelevels(PL)aredefinedinENISO13849-1toclassifydifferentsafety-relatedcapacitiesintotheirrespectivecategories.ThefivePLs(a,b,c,d,e)representdifferentaverageprobabilityvaluesofafailuretodangerperhour. Performancelevels(PL)inaccordancewithENISO13849-1 Performancelevel(PL)Averageprobabilityofafailuretodangerperhour(1/h)a≥10-5to<10-4b≥3x10-6to<10-5c≥10-6to3x10-6d≥10-7to<10-6e≥10-8to<10-7 DeterminingtherequiredperformancelevelPLrAriskassessmentmustbeperformedanddocumentedinordertodefinetherequiredPLrforeachsafetyfunctionofthesafety-relatedcontrolsystem.TheinformativeAnnexAofthestandardpresentsaqualitativeprocedureforassessingtheriskandfordeterminingthePLr. Riskparameters: SSeriousnessofinjuryS1Minor(usuallyreversible)injuryS2Serious(usuallyirreversibleinjuryincludingdeath)FrFrequencyand/ordurationoftheexposuretothehazardF1Seldomtonotveryfrequentand/orexposuretohazardisbriefF2Frequenttocontinuousand/orexposuretohazardislongPPossibilityofpreventingthehazardorlimitingtheharmP1PossibleundercertainconditionsP2Notreallypossible Fig.2.4.2-1:RiskgraphfordeterminingthePLrforeachsafetyfunction(source:ENISO13849‑1) Legend StartPointatwhichtheevaluationoftherequiredcontributionofthesafetydevicetotheriskminimizationbeginsLLowcontributiontoriskminimizationHHighcontributiontoriskminimizationPLrRequiredperformancelevel DeterminationoftheperformancelevelreachedThefollowingsafety-relatedparametersarerequiredfordeterminingtheperformancelevelofcomponents/devices: ENISO13849‑1parametersMeaningCat.Category(B,1,2,3,4),structuralsetupasthebasisfordeterminingaspecificPLPLPerformancelevel(a,b,c,d,e)MTTFdMeantimetodangerousfailureB10dNumberofcycleswithwhich10%ofarandomselectionoftheconsideredabrasion-pronepneumaticorelectro-mechanicalcomponentshaveafailuretodanger.DCDiagnosticcoverageCCFCommoncausefailureTMServicelife,intendedusagetime(missiontime) Furtherparameterstobeconsideredaretheinfluencethatoperationalfactorssuchasrequestrateand/orthetestrateofthesafetyfunctioncanhaveontheresultingPL.NoteTheSISTEMAPCsoftwareoftheInstitutfürArbeitsschutz(IFA)isusedforthecalculationandevaluationofthefunctionalsafetyofcontrolsystemsinaccordancewithENISO13849‑1.ItisanidealcomplementtoSafexpertandcanbedownloadedasfreewarefromwww.leuze.com/sistema.FormoreinformationseechapterSISTEMA,page66.Fig.2.4.2-3showsasimplifiedmethodfordeterminingtheachievedPL.ItillustratesagraphicalmethodforroughlyestimatingthePLusingthestatedsafety-relatedcharacteristicparametersofthecomponents(ENISO13849‑1).ThecombinationofcategoryandDCavgdetermineswhichcolumnistobeselected.TherespectiveshadedareaisthendeterminedinthecolumninaccordancewiththeMTTFdofeachchannel.TheresultingPLcannowbereadontheverticalaxis. Fig.2.4.2-3:Relationbetweenthecategories,DCavg,MTTFdofeachchannelandtheresultingPL(source:ENISO13849‑1) MTTFdinyears MTTFdofeachchannel=low3