How do you conduct a functional safety audit of an existing SIS installation?

Functional safety audit methodology: review lifecycle documentation (SRS, design documents, V&V records) for completeness and compliance with IEC 61511, verify SIL calculations with current failure rate data and actual proof test intervals, inspect physical installation against design (correct devices, proper installation, adequate separation), review proof test records (tests performed on schedule, documented properly, failures addressed), assess competency records of personnel, evaluate management of change process (changes properly assessed and documented), review bypass logs and incident records, verify software configuration matches approved version, and interview operations and maintenance personnel. Document findings with severity classification and corrective action requirements.