Basics 17 - PFH (Probability of Failure on Demand per Hour)

PFH (The Probability of Failure on Demand per Hour) is the probability that a system will fail dangerously, and not be able to perform its ... BacktoBasics17-PFH(ProbabilityofFailureonDemandperHour)|exida ContactUs Careers Store CertifiedProducts About Aboutexida CompanyNews ContactUs Locations ChannelPartners Leadership Careers Certification Overview FunctionalSafety(IEC61508) Cybersecurity(IEC62443) Automotive(ISO26262) Machine&RobotSafety Personnel ListofCertifiedProducts Services Overview FunctionalSafety ProcessIndustry Automotive RobotandMachine IACSCybersecurity Overview WastewaterSolutions AlarmManagement Products SystemEngineeringTools(exSILentia) DeviceEngineeringTools(OEMx) ReferenceMaterials Templates IEC61508DevelopmentProcess IEC61511 IEC62443 Training CourseOfferings PublicCourseSchedule OnlineTraining Resources EducationalContent Blog Webinars Videos Seminars WhitePapers&eBooks CaseStudies Glossary Brochures RelatedWebSites SAELSafety/SecurityAutomationEquipmentList SILSafeData SiteSafetyIndex(SSI) RISISecurityIncidents Programs Safety&CyberAwards CFSE/CFSP CACE/CACS PersonnelCertificatePrograms Store Germany Singapore Australia Japan SouthAfrica India UnitedKingdom Latinoamérica–España Canada Ireland exidaexplainsBlog exida Blog BacktoBasics17-PFH(ProbabilityofFailureonDemandperHour) BacktoBasics17-PFH(ProbabilityofFailureonDemandperHour) LorenStewart,CFSE Tuesday,November19,2019 PFH(TheProbabilityofFailureonDemandperHour) istheprobabilitythatasystemwillfaildangerously,andnotbeabletoperformitssafetyfunctionwhenrequired.PFHcanbedeterminedasaprobabilityormaximumprobabilityoveratimeperiodofanhour.IEC61508andIEC61511usePFHasthesystemmetricuponwhichthe SILisdefined.EachSILratinghasanassociatedPFHwhichincreasesanorderofmagnitudeforeachincreaseinSILrating. ThePFHisbasedonthe dangerousfailurerate,andautomaticdiagnostics.  IfAutomaticDiagnosticsareeffective: IfAutomaticDiagnosticsare NOTeffective: Hereyouareassumeyourautomaticdiagnosticswillnotfindthefailurebeforeademand. PFHcalculationisanextremelyimportantpartofsafetyengineeringinhighandcontinuousdemandapplicationsasitisprobablythemostdifficultofthe threebarriers tomeetifrealisticassumptionsaremadeandifrealisticfailureratesareused(likefailureratesfromwww.SILSafeData.com).  Funfacts: PFHisdefinedforhighorcontinuousdemandmodeofoperation(forlowdemandmodesee PFDavg) TargetlevelsforPFHaredefinedinIEC61508foreachofthe4levelsofSIL It’soneofthe3designbarriersthatmustbemetforcertification RelatedItems BacktoBasics01-FunctionalSafety BacktoBasics02-SafetyIntegrityLevel(SIL) BacktoBasics03-SafetyInstrumentedFunction(SIF) BacktoBasics04-SafetyInstrumentedSystem(SIS) BacktoBasics05-WhatisaSafetyFunction? BacktoBasics06–IEC61508 BacktoBasics07–SafetyLifecycle–IEC61508 BacktoBasics08–IEC61511 BacktoBasics09–SafetyLifecycle–IEC61511 BacktoBasics10–HowDoesaProductGetaSIL? BacktoBasics11–HowisSILUsedbyanEndUser? BacktoBasics12–WhatisIEC61508Certification? BacktoBasics13-HowDoIStartIEC61508Certification? BacktoBasics14-SystematicCapability BacktoBasics15-ArchitecturalConstraints BacktoBasics16-PFDavg Taggedas:    silsafe    SIL    PFH    LorenStewart    IEC61511    IEC61508    dangerousfailurerate    backtobasics   OtherBlogPostsByLorenStewart BacktoBasics:FailureRates-λS BacktoBasics:FailureRates-λDD BacktoBasics:FailureRates-λDU BacktoBasics:FailureRates-λD BacktoBasics:FailureRates-λ