SIS safety life-cycle overview

Safety life-cycle phase or activity Objectives Require- ments Inputs Outputs 

1 Hazard and risk assessment To determine the hazards and hazardous events of the process and associated equipment, the sequence of events leading to the hazardous event, the process risks associated with the hazardous event, the requirements for risk reduction and the safety functions required to achieve the necessary risk reduction 8 Process design, layout, manning arrangements, safety targets A description of the hazards, of the required safety function(s) and of the associated risk reduction 

2 Allocation of safety functions to protection layers Allocation of safety functions to protection layers and for each safety instrumented function, the associated safety Integrity level 9 A description of the required safety instrumented function(s) and associated safety integrity requirements Description of allocation of safety requirements (see Clause 9) 

3 SIS safety requirements specification To specify the requirements for each SIS, in terms of the required safety instrumented functions and their associated safety integrity, in order to achieve the required functional safety 10 Description of allocation of safety requirements (see clause 9) SIS safety requirements software safety requirements 

6 SIS operation and maintenance To ensure that the functional safety of the SIS is maintained during operation and maintenance 16 SIS requirements SIS design Plan for SIS operation and maintenance Results of the operation and maintenance activities 

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Table 1 - SIS safety life-cycle overview (modified ANSI/ISA-84.00.01-1 Table 2)...

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