Layer of protection analysis: Generating scenarios automatically from HAZOP data

• Published in: Plant/operations progress 2005-03, Vol.24 (1), p.38-44
• Main Authors: Dowell III, Arthur M. (Art), Williams, Tom R.
• Format: Article
• Language: English
• Subjects: HAZOP; linking; LOPA; risk assessment tools
• ISSN: 1066-8527; 0278-4513; 1547-5913
• DOI: 10.1002/prs.10061

This paper details the concept of automatically generating layer of protection analysis (LOPA) scenarios from a process hazard analysis (PHA) conducted using the hazard and operability (HAZOP) methodology. Specialized software selects consequences that meet severity criteria or risk criteria. It then takes each end consequence, follows each link path to an initiating cause, and presents each rolled‐up link path as a single LOPA scenario, complete with all the safeguards (that is, candidate protection layers) found along the link path. The scenarios can be presented in database or spreadsheet format. The rolled‐up LOPA spreadsheet allows the analyst(s) to identify safeguards that are independent protection layers and assign appropriate values to each independent protection layer. The spreadsheet calculates the resultant mitigated risk (or mitigated likelihood or frequency) in real time. This makes it easy for the analyst(s) to determine which independent protection layer or group of independent protection layers provides the most effective means for reaching or maintaining a target risk threshold. The concept (demonstrated using ABS Consulting's HazardReview LEADER™ software) makes the process of going from PHA results to LOPA results a lot less time consuming. It avoids retyping and reduces the risk of overlooking scenarios. The paper will present lessons learned from applying the tools in real PHA/LOPA applications. © 2005 American Institute of Chemical Engineers Process Saf Prog, 2005