What is IEC 61511 and how does it relate to IEC 61508?

IEC 61511 is the process industry-specific standard for safety instrumented systems, derived from IEC 61508. It provides practical guidance for implementing SIS in process industries (oil and gas, chemical, pharmaceutical). Key aspects: Safety Lifecycle phases (analysis, realization, operation), SIL determination methods (LOPA, risk graph), requirements for SIS design, operation, and maintenance, and competency requirements. IEC 61511 allows use of proven-in-use equipment and simplified approaches compared to IEC 61508's more rigorous requirements. ANSI/ISA 84 is the US version.