Safety integrity level analysis phase

Phases 1 to 5 deal with concept and analysis—risk assessments to discover the Safety Instrumented Functions (SIF) and assign an appropriate Safety Integrity Level (SIL) rating. 

The reliability performance of the SIS is referred to as safety integrity in the lEC-standards. This is the probability that the SIS satisfactorily performs the required SIFs, under stated conditions and for a stated period of time (lEC 61511 2003). In an early design phase, a hazards and risk analysis is performed to establish the required level of safety integrity of each SIF that is performed by the SIS, and in design and operation, it is necessary to demonstrate that this level of safety integrity is met. 

There are, however, many definitions of V V. In one of the most commonly used safety standards, lEC 61508, the objective of safety verification is ""...to demonstrate, for each phase of the overall, E/E/PE and software safety lifecycles (by review, analysis and/or tests), that the outputs meet in all respects the objectives and requirements specified for the phase [7]. The objective of safety validation is to. . validate that the E/E/PE safety-related systems meet the specification for the overall safety requirements in terms of the overall safety functions requirements and overall safety integrity requirements... [7]. These definitions differ in level of detail, but they can be summarized as verification is to answer the question are we building the system right While validation is to answer the question are we building the right system ... 

Pre-use Analysis When a site is considering new equipment, chemicals, facilities, or significantly different operations or procedures, the safety and health impact to the employees must be reviewed. The level of detail of the analysis should be commensurate with the perceived risk and number of employees affected. This practice should be integrated in the procurement/design phase to maximize the opportunity for proactive hazard controls. (Section 2.d)... 

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