PHA revalidation is a key requirement within a company’s site or corporate procedures and risk management processes. Revalidating previous PHA studies (HAZID, HAZOP, LOPA etc.) every 4-5 years is becoming the norm.

As the PHA’s form the backbone of your overall Safety Assessment, this revalidation process is a crucial step in continuously managing risk on your facility through re-assessing the previously identified hazards, potential consequences, controls in place to reduce likelihood of these events, and assurance that the controls will operate as intended.

Some of the challenges faced in the build-up to this Revalidation process are:

• Most or all of the team who did the previous studies are no longer available
• Due to the subjectivity and reliance on team knowledge/experience during hazard reviews, incomplete or non-specific minutes will lead a new team to, rightly or wrongly, question the quality and credibility of the previous PHAs, leaning towards a complete “Redo”
• Lack of discipline in maintaining records of key Safety Management System (SMS) elements such as Management of Change and Incident Management

Probably even more relevant in the practical world is that all this is easier said than done when you are limited by budget and/or manpower!

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There are many great papers and articles that have been or are being published on the approach or methodology to use to go about the Revalidation process, but I find that Operators are at various levels of maturity of their site PHAs and systems that support it, and it is difficult to decide on the best approach to follow. There are however common requirements across most of them which would be a good starting point:

1. A review of the previous PHA reports and status of action completion
2. Assessment of the MOC’s that have been completed since the previous HAZOP, specifically:
   1. Plant changes as a result of the last HAZOP failure
   2. Implementation of new or changes to existing safeguards previously identified
   3. Operating changes – decommissions, operating envelope changes, more or less frequent modes of operation (start-up / shutdown)
3. A thorough review of incidents on your site that have occurred over the years since the last PHAs which may impact on its validity
   1. Incidents related to causes or initiating events previously identified
   2. Incidents related to safeguards previously identified
   3. Incidents related to human error causes previously identified
4. Consideration of incidents in similar industry local and global over the years since the last PHAs
5. Changes or updates to local regulations
6. If budget and resources is a concern, prioritization of higher risk hazards as a starting point

There are three typical phases to revalidation: planning, workshop and reporting. I have seen that the total revalidation effort would take about 60-70% of the time of the original site PHA, of which about 30-40% should be spent on the planning phase. The effort put into the planning phase by only a select few experienced and technical people would improve efficiency and focus during the workshop phase which involves a small team with specific and relevant areas of expertise. In an ideal world you would like to be keeping your PHA status current rather than through a Revalidation after every 5 years, but it would probably take dedicated resource and a few cycles of conventional Revalidation to get you to that point.

I like reading articles and papers on how to do things as much as the next person, but I prefer incorporating lessons from how it was actually done. If you have lessons to share from your experiences with Revalidations, then please feel free to reach out. This is a topic that our industry will greatly benefit from considering the revalidation cycle is fast approaching for many Operators.