The Most Effective Approach to Updating PHAs: Revalidation Vs Redo (The Good, The Bad and the Ugly)

When used correctly, PHA revalidation is an effective method to maximize the value of the PHA team’s time and keep the risk analysis consistent with previous teams’ work. However, challenges that are commonly encountered during a revalidation PHA study are:

• The tendency for revalidation sessions to either become a mind-numbing exercise in blind agreement with the previous PHA, or;
• So much needs to be changed due to insufficient description of hazards, safeguards, or risk ranking;
• Complication of including design or process modifications made since the last PHA, incidents or near-misses that occurred;
• The time and pressure caused by the expectation that a revalidation should be significantly faster than a baseline PHA, and the misconception that a good revalidation can “fix” a bad PHA.

In many cases, revalidation can still be the best choice, as long as some effort is made before and during the session to account for these challenges and manage the expectation of the PHA team and management. However, without consideration of these challenges, many revalidation studies are set up for failure before they even begin.

On the other hand, redoing a PHA can be a more effective and efficient approach, by using the previous version of the study for reference as required. Despite the constant debate on whether PHA redo can achieve the consistent risk assessment from the original PHA findings, redo session can be proven to use the best of the PHA team time, if the following considerations are taken:

• The quality of the original PHA;
• The availability of MOC records, past incident records since the original PHA study;
• The consistency of PHA team’s expertise and experience.

This paper will discuss when a revalidation is most effective and when a redo should be considered, the key threats and opportunities for each method, and strategies to ensure the success of the PHA session whether a revalidation or redo is chosen.