Operator Actions Within a Safety Instrumented Function

This paper presents an overview of the factors that should be considered when crediting operator action for performing a safety function or being a part of the process of enabling a safety function. Criteria for evaluating operator action, such as required time response and operator training among others, are discussed. The paper will address these and other factors that should be considered when determining the reliability of the operator to respond and perform his/her part of the safety function. The entire safety function includes the operator and the reliability of the instrumented system that provides the alarm or indication, the final control element, and support systems. The integration of the operator performance with the hardware safety availability, including the effects of the supporting systems is discussed. The analysis of these factors will provide the justification for the amount of risk reduction or safety integrity level that can be credited for the Safety Instrumented Function (SIF), including operator action