The Chemical Process Industry (CPI) has long recognized the necessity of periodically revalidating Process Hazard Analyses (PHAs), such as Hazard and Operability Studies and What-if analyses. CCPS has published a book which describes this work process titled Revalidating Process Hazard Analyses. However there is limited guidance for revalidating supplemental risk analyses, such as Layer of Protection Analyses (LOPAs), Quantitative Risk Assessments (QRAs), and Fault-Tree Analyses (FTAs). The objectives of performing periodic revalidations are to address the cumulative changes in risk that occur over time and to continuously improve our understanding of that risk. Ultimately the goal is to avoid incidents.
An objective revalidation is focused primarily on safety while a project review focuses on many other aspects beyond safety, such as productivity and efficiency. The revalidation is generally more effective at reviewing the external factors that impact the results of an assessment. By revalidating a risk analysis, the team takes a holistic approach to analyzing factors that affect risk to surrounding people or the environment imposed by the continued operation of the facility. Particular focus is placed on changes that impacted the analysis, but may not have been recognized or fully addressed in the Management of Change (MOC) review. Some of these external factors include population changes, culture and organizational changes, changes and improvements in the risk analysis methodology, and discovery of conflicting data.
This paper introduces a work process for revalidating various types of risk analyses, and discusses many of the factors that need to be considered. This can improve the quality of the revalidation while reducing the overall effort expended. The primary discussion will center on revalidating LOPAs, but other types of studies will be discussed as well. Case studies and experiences from actual revalidation efforts will be incorporated into the discussion.
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