More issues with layer of protection analysis-From the originators

Layer of protection analysis (LOPA) has now been around for more 25 years and in general use for now 20 years, starting with the initial textbook being officially published in 2001. Two companion books have been published on the topics of Enabling Events and Conditional Modifiers (2013) and on Initiating Events and Independent Protection Layers (2015). Many papers have been published in the past 20 years on LOPA. This paper shares observations and lessons learned from two originators of LOPA and provides further guidance on how to and how Not to use LOPA. The paper provides specific examples of best practices, some of which are not covered well enough in or are omitted from the textbooks on the topic. The originators of LOPA hope you will use this paper as an expansion on the concepts in the first LOPA textbook, and as an addendum to all three textbooks on the topic.