Consequence analysis, layer of protection analysis, and bow‐tie as strategies to prevent accidents

Abstract This article discusses some accidents and uses consequence analysis as well as layer of protection analysis (LOPA) and bow‐tie to establish the best approach for safely controlling the process to avoid loss of containment due to overfilling. Four accidents and their aftermaths are examined, considering current investigations. Consequence analysis was used with 12 products to demonstrate how to determine the level of protection of the systems to reduce the likelihood of containment loss due to overflow. Finally, LOPA and bow‐tie were used to ensure that the systems have adequate protection at an acceptable level of risk tolerance and will be correctly maintained throughout their life cycle. The analyses indicated that an independent layer of protection with safety integrity level 2 was required to achieve the risk tolerance requirement of <10 −4 /year, which is a known and widely accepted frequency when an accident has the potential to result in a fatality. Furthermore, a study of degradation factors and controls was performed to enhance the reliability of all the components that interfere with the frequency of the top event. This will improve process safety throughout the system's lifecycle, and the results will also be input for safeguards audits.