Prior Use & Proven In Use
IEC 61511 requires devices that make up a Safety Instrumented Function (SIF) to be either, assessed against the requirements of IEC 61508 or against the requirements of “Prior-Use”. Many facilities utilise equipment that is used in both Safety and Control functions and the operator has gained experience and confidence in these devices. In these circumstances, Prior Use may be considered a more suitable (and logical) alternative to replacing these devices for IEC 61508 assessed items of which the operator has no experience.