Phase 3

Safety Requirements Specification


The Safety Requirements Specification (SRS) is fundamental to the design and validation of the safety-instrumented system.  The SRS is developed during phase 3 of the Functional Safety lifecycle, and must be available throughout the lifecycle.

The SRS specifies the integrity and functional requirements for each Safety Instrument Function (SIF) required to achieve the target risk reduction.


The SRS is firstly used as a single source location to record all relevant information from the PH&RA, SIL Allocation, P&IDs required to design the SIF for a given hazard scenario so that it meets its required safety integrity and required functional safety and the applicable IEC 61511 Clause 10 & 12 requirements.  However the SRS does not stop there, this document must be updated as a controlled document for the entire life of the SIF.  The SIF is validated and proofed against the SRS and therefore it is fundamental that the SRS is maintained through the SIF lifecycle to reflect any modifications, changes in equipment or circumstances until the SIF is taken permanently out of service.


ProSalus has assisted a number of our clients in either the development of the SRS’s or conducting verification of suitability of their SRS’s.