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Keywords:

  • revalidation;
  • risk analysis;
  • LOPA;
  • QRA

Abstract

The chemical process industry has long recognized the necessity of periodically revalidating process hazard analyses (PHAs), such as hazard and operability studies and What-if analyses. Center for Chemical Process Safety (CCPS) has published a book which describes this work process titled Revalidating PHAs [1]. 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. 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, whereas 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 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 article introduces a work process for revalidating various types of risk analyses and discusses many of the factors that need to be considered. This improves the quality of the revalidation while reducing the overall effort expended. The primary discussion centers on revalidating LOPAs, but other types of studies are discussed as well. Case studies and experiences from actual revalidation efforts are incorporated into the discussion. © 2011 American Institute of Chemical Engineers Process Saf Prog, 2011