Management of factors that influence common cause failures of safety instrumented system in the operational phase

Common Cause Failures (CCFs) represent a serious threat to the reliability of safety instrumented systems. In quantitative reliability analyses, the effects of CCFs are often accounted for by using the beta-factor model. Causes of CCFs may be introduced in all phases of the system life cycle, as a result of inadequate decisions and actions. This paper focuses on CCFs causes that are related to actual human interactions and human errors, and the underlying organizational factors that may affect human performance. A model that relates CCFs to human and organizational factors is proposed. The model may be used for management of defenses against CCFs, but also as basis for finding a more realistic (and updated) estimate of the beta-factor in the operational phase. Some final recommendations and ideas are suggested for how human and organizational factors can be incorporated into the beta-factor model.