In order to fulfil the requirements of the standard IEC 61511 a Safety Requirement Specification, SRS, is needed.
Most companies must develop their own format of SRS, this document provides a guideline on how to write a SRS. In order to fulfil the requirements the standard IEC 61511 has to be used.
The main purpose with the safety requirement specification is to identify and present the safety requirements for the Safety Instrumented Functions.
The definition of the SRS is given in the standard IEC 61511:
“specification that contains all the requirements of the safety instrumented functions that have to be performed by the safety instrumented systems”
The objective for the SRS is stated in the standard IEC 61511:
The SRS shall specify all requirements of safety instrumented systems, SIS, needed for detailed engineering and process safety information purposes.
The development of the SRS is one of the more important activities during the design of safety instrumented systems. If important information regarding safety issues is missing the design of the SIS may not be performed in a safe way.