Additional Uses of Bow Ties

This chapter outlines some important additional uses of bow ties. Bow ties provide support for important operational uses such as for activity decisions and for incident investigation. Bow ties provide important assistance to the task of building Manual of Permitted Operations (MOPO)/Summary of Operational Boundaries (SOOB) matrices as they have identified all the barriers related to relevant top events, including many important degradation controls. Bow tie chaining or linking is an advanced feature of the diagram used to display multiple top events in an event sequence. Other safety studies such as process hazard analysis (PHA) generally, and hazard and operability studies (HAZOP), layer of protection analysis (LOPA) and safety integrity levels (SIL) assessments specifically, also document barriers therefore, it is useful to show how bow tie barrier analysis links to these other studies. Dashboards are a means to display the status of safety barriers in a high level overview of overall facility safety status.