Common Bow Tie Errors and How the CCPS Concept Book Rectifies

Abstract

The bow tie risk analysis method is growing in its application as it is a powerful tool for visually communicating major accident risks and the barriers deployed to prevent or mitigate these. The ease of communication can mislead users to think that bow tie creation is also easy. A new CCPS Concept Book, Bow Ties in Risk Management, thoroughly reviews how to create bow ties and provides detailed guidance on how to avoid errors. This paper provides several examples of common errors seen in the current bow ties. These cover structural errors, such as degradation factors and controls are misplaced onto main pathways, barriers that do not comply with guidance on required barrier core attributes, and incorrect hazards, top events, and consequences. The paper also covers a better means to treat human error. A final part of the paper presents a novel multi-level approach to bow ties that can be helpful for human error and mechanical integrity applications where deeper degradation controls are important to display.