The Safety Requirements Specification (SRS) is one of the key documents for delivering functional safety.
Below is a list of the other lifecycle phases that depend materially on the availability and quality of the SRS:
The SRS would also be a typical input into any Modification (what are we changing in the specification?) and any review of a SIFSafety Instrumented Function demand (did it work as it was supposed to?).
The SRS also provides a signpost to other key documents related to the SIS. The SRS should reference “down” to the tags of the SIF components and “up” to the Hazard and Risk Assessment documentation. It should be possible to use the instrument tag to locate the particular SRS that describes the need for that particular instrument. And from the SRS you should be able to find the LOPA scenario that concluded a SIF with a given RRFRisk Reduction Factor was needed. And from the detail in the SRS you should be able to find the lines in the HazOp worksheet that identified the initiating events that could bring about the harmful event that the SIF is protecting against.
It is very likely (despite what the idealised safety lifecycle might suggest) that the SRS will be updated through the SIS design process (as the design and the specification of the design evolve together. And the SRS will be updated again, once the instrument tags are known (towards the end of the design process) and following Modifications, re-validation of Hazard and Risk Analysis documentation and re-visiting other lifecycle activities.
The Safety Requirements Specification could be considered to have 4 main sections:
Project to develop SRS documents for four Safety Instrumented Functions (SIFs). The four SIFs, comprised nine device / element types, some of which were common to multiple SIF.
Industry: Mining / Metal / CementVerification of Safety Requirements Specifications for distilling application.
Industry: Brewing and DistillingProject to review a client's Functional Safety Specification for Process Operations & Machinery, which detailed basic BPCS and SIS design requirements for reactors with processes that have potentially exothermic reactions.
Industry: ChemicalProject to develop x22 Safety Requirements Specifications.
Industry: Oil and Gas OnshoreSupport to systems integrator working on anaerobic digester project
Industry: PowerE: support@methodfs.com. T: 44 (0)1462 713313. W: www.methodfs.com