Periodic Review of Unchanged Relief Systems
Periodic Review of Unchanged Relief Systems
(OP)
Most of our processes get changed over time. More capacity is needed, new chemicals come along, process condition changes are recommended by R&D, etc.
In parallel, relief calculation methods improve and standards change.
The wheels of progress keep turning on all fronts as time goes on. Some turn fast and others turn slow.
When we have a process change, we review existing reliefs and design new reliefs, if needed, using the best relief sizing technology we have at that time.
I would guestimate that 80% of the reliefs in our plants get a review because of a change every 5-10 years. Our processes are batch with hundreds of products. Many new products get introduced every year. Things may be different in a commodity chemical plant.
Is there a requirement, either regulatory or your company policy, to periodically review unchanged relief systems? How frequently? Must relief sizing methodology be updated at that time, or is the old methodology grandfathered?
In parallel, relief calculation methods improve and standards change.
The wheels of progress keep turning on all fronts as time goes on. Some turn fast and others turn slow.
When we have a process change, we review existing reliefs and design new reliefs, if needed, using the best relief sizing technology we have at that time.
I would guestimate that 80% of the reliefs in our plants get a review because of a change every 5-10 years. Our processes are batch with hundreds of products. Many new products get introduced every year. Things may be different in a commodity chemical plant.
Is there a requirement, either regulatory or your company policy, to periodically review unchanged relief systems? How frequently? Must relief sizing methodology be updated at that time, or is the old methodology grandfathered?
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.





RE: Periodic Review of Unchanged Relief Systems
Being done first time calculation is never done again. Many of PSV are "as is" and have no calculation record.
RE: Periodic Review of Unchanged Relief Systems
There are a lot of engineering consulting companies that make a lot of their money performing PSV revalidations. Naturally, they'll say that PSA revalidation means revalidating each PSV. That's an interpretation that they're free to make, but that's not the only interpretation of the reg. Many companies have a practice similar to yours. PSV revalidation occurs naturally due to plant changes and re-designs that automatically cause a re-analysis of the relief devices within the scope of those projects.
RE: Periodic Review of Unchanged Relief Systems
And since I'm in pharma, any deep dive into PSVs would definitely go to a contractor
RE: Periodic Review of Unchanged Relief Systems
RE: Periodic Review of Unchanged Relief Systems
Reviews of safe operating limits are recommended every 2-3 years, even if there are no changes to the system - reviews not specifically related to relief systems only but for all elements that are a part of the Loss of Containment risk management system, or technical integrity management system. I don't know if PRV/PSV reviews and the corresponding sizing methodologies are defined as a separate PSM requirement, but this is something that an efficient PSM system would definitely capture - the case(s) when the changes in calculation/sizing principles are significant and may lead to the finding that some of the overpressure protection devices are ineffective. Your question is actually a great litmus that can show how effective and thorough is PSM system in any operating entity.
Dejan IVANOVIC
Process Engineer, MSChE
RE: Periodic Review of Unchanged Relief Systems