Proceedings of the Eighth International Conference on Probabilistic Safety Assessment & Management (PSAM)
304 Evaluation of the Analytical Bottom-Up SIL Proof by Statistical Top-Down Methods (PSAM-0242)
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According to the IEC 61511 a Safety Integrity Level (SIL) has to be assigned to all new safety instrumented loops in chemical and pharmaceutical industrial plants. An important SIL criterion is represented by the probability of failure on demand (PFD) defined as a probability interval for each different SIL. The PFD can be calculated based on the individual loop structure and the failure rates of all the loop components. Commercial software tools are available to assist the calculation. But, as a rule, these bottom-up methods need many assumptions and suffer from uncertain data, especially for inline components like...