PSV relief case

[wannaza]

Hi,

I'm currently doing PSV failure consequence assessment on an oil platform and I have a question on a PSV downstream of an accumulator (refer to attached sketch). I have found few cases like this but I am not sure what is the relief scenario for the PSV. What is the PSV for?

Thank you.

 

[Latexman]

That's not much to go on, so I'm guessing.

Closed valve and overpressure from PD pump?
Closed valve and thermal expansion?
Fire exposure on vessel?

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[EmmanuelTop]

It looks like a part of the Hydraulic Power Unit loop, but as Latex says it is impossible to figure out the relief scenario based on the sketch only. What is written on the P&ID, next to the PSV symbol?

Dejan IVANOVIC
Process Engineer, MSChE

 

[wannaza]

I've attached a bit more detail drawing. The first PSV after the pump I think for blocked outlet case, but not sure about the second PSV after the accumulator, maybe blocked outlet also I guess.

 

[EmmanuelTop]

It is still unclear. Can you dig into PSV Sizing Report or HAZOP, and identify the function and the scenario for this PSV?

Dejan IVANOVIC
Process Engineer, MSChE

 

[georgeverghese]

This is probably a firecase PSV dedicated to the accumulator / bladder - the designer believes the bladder is to be treated as a pressure vessel.

If you want a firecase PSV to operate only for firecase, then its setpoint should be some what higher than than the blocked discharge PSV.

Depending on which country this HPU is located in, you may have this firecase PSV setpoint set at 1.05x 228barg, or 1.1x 228barg. So this setpoint needs to be corrected. Also check the local codes for max permissible relieving pressure used in the calculation for deriving the firecase load.