Probability of Failure on Demand in IEC 61508
This paper presents a new and explicit approach for estimation of average Probability of Failure to perform its design function on Demand (PFD), based on the expectations of fault duration / repair time in accordance with IEC 61508. From a practical viewpoint, the formula for estimation of PFD of the negligible Mean Time To Repair (MTTR) configuration Safety-Related System (SRS) operated in low and short duration demand mode is feasible for the non-negligible MTTR configuration SRS with no self-diagnostic function.
KeywordsRepair Time Repair Rate Practical Viewpoint International Electrotechnical Commission Fault Duration
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- 1.IEC 61508: Functional safety of electricalIelectronicIprogrammable electronic safety-related systems. IEC, Geneva, 1998-2000.Google Scholar
- 2.Y. Misumi and Y. Sato, Estimation of average hazardous-event-frequency for allocation of safety-integrity levels, Reliability Engineering and System Safety 1999; 80: 133–141.Google Scholar
- 3.E. Kato and Y. Sato: Safety Integrity Levels Model for IEC 61508: Procs. PSAM5. Universal Academy Press, 2000, pp 2787-2793.Google Scholar
- 4.T. Zhang, W. Long and Y. Sato, Availability of systems with self-diagnostic components — applying Markov model to IEC 61508-6, Reliability Engineering and System Safety 2003; 66: 135–144.Google Scholar