SIL-D. Definition of SIL. Assignment of the Safety Integrity Level, preliminary (pSIL) or definitive (SIL), to a system in safety during planning and realization. The SIL is determined on the basis of the Risk Evaluation and Acceptance review (REA); in particular it is attributed according to the risk category (QRC-A), the frequency of hazardous events (FHE) and the hazard severity levels (HSL). For example the occurrence of frequent events involving catastrophic level hazards is intolerable “category”, therefore a system that can find itself in such conditions must have SIL 4. See Preliminary Hazard Analysis and Hazard Analysis
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