IEC61511 does not specify if the SIS safety requirements specification is a single document or a collection of several documents.
According to IEC61511 the requirements regarding the SRS documentation may be developed by the Hazard and Risk Assessment team or the project team.
It is important that the documentation covers all safety aspects to be addressed during the safety lifecycle. The need of documentation depends on the complexity of the application.
Typically, a SIS safety requirements specification includes requirements for:
- design and architecture
- reliability (nuisance trip rate)
- availability (SIL)
- support systems
- installation, testing and maintenance
- hardware specification
- software development, Security