How are the values in the reliability block diagram for PFD calculation determined in SIL verification?
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I’m seeking help from experts: Guidelines for verifying the Safety Integrity Level (SIL) of Safety Instrumented Functions (SIF); PFD calculation: Data from the reliability block diagram – Sensor section: MTTFDU=30; PFDS=0.017; Proportion: 53%； Where do the data for the same logic solver and final components come from? ISATR84.00.02 also does not specify exactly how the data is obtained I earnestly beg the experts for their guidance; thank you.
In the SIL verification of safety instrumented systems, the reliability parameters for calculating PFD (Probability of Failure Rate), such as the sensor’s MTTFD (Mean Time To Failure) and PFDS (Probability of Failure Rate of the sensor), are typically derived from data provided by the equipment manufacturers or from industry standards. The proportion of each component is determined based on its importance and contribution within the entire system. If the manufacturer does not provide such information, relevant international standards can be referred to, such as IEC 61508, IEC 61511, or ISA TR84.00.02. These standard documents contain failure rate data for typical devices that can be used as a reference. The specific values need to be determined based on the actual circumstances and application context. Sometimes field tests and historical data collection are also required to obtain these parameters. .
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Teacher, this is our company’s verification report. The MTTFS after verification is 36.25 years. How was this figure obtained?