The Endless “Do Loop” of LOPA: How LOPA Could be Dragging You Down

While a handful of companies were individually evaluating risk using early versions of what later became known as Layer of Protection Analysis (LOPA), the 2001 CCPS’ book “Layer of Protection Analysis” provided industry the first standardized method for conducting LOPAs. Over the 20 years since its publication, both the application and method have evolved to improve efficiency, reliability, and accuracy; however, in some ways, industry has come to over-rely on LOPA. This overreliance takes several forms including overapplication to scenarios identified during a qualitative assessment, and overconfidence in the process (i.e. “let’s use LOPA so we know for sure”). This has created significant inefficiencies and unnecessary confusion while conducting risk assessments, not to mention a potential false sense of security in the results.

The CCPS book describes two major situations where LOPA may be useful: (1) when a qualitative assessment team believes a scenario is too complex for the team to make a reasonable risk judgement and (2) when the consequences are too severe to rely solely on qualitative risk judgement. It was often used to bridge the gap between a qualitative assessment and a more rigorous quantitative risk assessment (QRA), when the consequences could be catastrophic. As part of a spectrum of tools used for risk-based decision making, the book estimated that only 10-20% of identified scenarios would require some type of simplified quantitative analysis (e.g. the Dow Fire & Explosion Index, Human Reliability Analysis and LOPA). The authors clearly stated that if a team can make a reasonable risk decision using only qualitative methods, LOPA may be overkill.

Companies that are over reliant on LOPA use the tool for scenarios in which a reasonable qualitative assessment can be made, for non-complex scenarios, and where the consequences are less than worst case. This can result from a number of sources including scenario selection based on Risk instead of Severity, the belief that LOPA provides “more correct” answers, and the narrow view that LOPA is the only tool available before QRA. Companies have reached the point of diminishing returns in the use of LOPA, resulting in overly complicated, inefficient, and less valuable risk assessments.

The authors will present specific examples of LOPA overuse in industry, along with alternatives and remedies. Implementing these strategies will improve the efficiency, understanding, and effectiveness of future risk assessments, producing results that are both reliable and more useful.