Relief valves and Deficiencies
Relief valves and Deficiencies
(OP)
Would like to know if anybody had to develop plan to address PRD deficiencies?
I am currently working on a list of PSVs with the following deficiencies: incorrect setpoint, Inlet/Outlet Piping issues, orifice/valve sizing issues, oversized, undersized.
The way I thought about prioritizing them was to have the ones in hazardous chemicals on the top of the list, together with the ones that are Safety Critical. The next level should probably be based on cost.
Is there a better approach? Am I in correct the way I am prioritizing them?
Can I have some ideas on how to prioritize the remaining ones?
I am currently working on a list of PSVs with the following deficiencies: incorrect setpoint, Inlet/Outlet Piping issues, orifice/valve sizing issues, oversized, undersized.
The way I thought about prioritizing them was to have the ones in hazardous chemicals on the top of the list, together with the ones that are Safety Critical. The next level should probably be based on cost.
Is there a better approach? Am I in correct the way I am prioritizing them?
Can I have some ideas on how to prioritize the remaining ones?





RE: Relief valves and Deficiencies
Furthermore, are you interested in process applications only. spring operated or pilot operated SRV ?
Per ISO, only the term Safety Valve is used regardless of application or design.
RE: Relief valves and Deficiencies
I was just wondering if anyone had had to prioritize relief valve deficiencies?
RE: Relief valves and Deficiencies
It would be great if you can also factor the likelihood of failure (something like the chance that a relief might be required from a PSV during "normal" operation - some systems are simply closer to this point than others, e.g. live process vs. storage). But even without frequency, the consequence ranking should do.
Dejan IVANOVIC
Process Engineer, MSChE
RE: Relief valves and Deficiencies
RE: Relief valves and Deficiencies
Once you have those buckets filled I would go with.
1. Incorrect orifice (I'm assuming this takes care of undersized/oversized).
2. Incorrect setpoint.
3. Incorrect inlet/outlet lines.
RE: Relief valves and Deficiencies
High/Emergency
- Resulting overpressure > 3x MAWP (if you ever find one of these, triple check your calculations, and make sure it is a single jeopardy scenario. I have yet to find a PSV this grossly undersized)
Medium- Resulting overpressure is 1.5-3x MAWP
- Inlet or outlet lines are smaller than PSV nominal body size (i.e., a 2J3 PSV has 1.5" inlet piping)
- Inlet line losses > 7% of set pressure, for a non-pilot PSV, at rated capacity
Low- Resulting overpressure < 1.5x MAWP
- Minor set pressure adjustments
- Inlet/outlet line losses are slightly above allowable per code/plant standards.
- Thermal relief valve issues (i.e., a 3/4"x1" PSV)
Most PSV defiencies are going to be in the "Low" priority and fixing them within 5 years or next turnaround is appropriate. "Medium" priority findings should be fixed within a year ideally. For a "High/Emergency" priority finding, a senior engineer once told me they would push to shut the refinery down and fix it immediately.RE: Relief valves and Deficiencies
a) Whether there is a lower level high pressure trip loop to isolate the source of the overpressure, and how dependable is this trip loop?
b) Whether you have sufficient process safety time (PST) to prevent the PSV lifting - what is the additional pressure rise that would occur upon activation of the instrumented trip loop, given the flow through the SDV as it tends to close.
In recent times, it has become good engineering practice (but not mandatory) to ensure that all penultimate trip loops are engineered such that the PST is adequate to keep the max accumulated pressure within the limits of activation of the higher level PSV.