Need help determining PRV Set pressure 2

[POL23]

I'm replacing 2 PRV's(3/4" by 1 1/2" Stainless Steel) on Jet A-1 fuel storage tank inlet 8" and outlet 5" pipeline. MAWP based on the highest operating pressure reasonably expected to be encountered is 96 PSIG (Pump deadhead pressure 87 PSIG plus 10%)

Questions:

- At what pressure setting should the PRV's be set to open

- What factors must be use to determine PRV set pressure

- What Code/standard governs PRV pressure setting

Any help would be greatly appreciated!!

 

[JimCasey]

You can legally use a PRV set at up to the pressure stamped on the nameplate of your coded vessel for unfired pressure vessels as governed by ASME section III. 10% overpressure at relief, 21% overpressure during fire, and 50% overpressure (valve gagged) for Hydro-test are all addressed in the ASME rating of the vessel.

You are not going to want to set the valves at less than 106.7 psi because once you pop a valve it is allowed to blow down to 10% below the setpoint. You want your operating point to be less than this or you could pop the valve and it would stay open. Your max operating point is 96. 96/.9 is 106.7.

 

[POL23]

Thanks, would you suggest that the PRV's on both the inlet and outlet pipeline be set above 107 psi ?

 

[TD2K]

what are you protecting with these PSVs and what is the basis for their sizing?

The storage tank is not going to be designed for 97 psig (your suggested MAWP) so I would suspect the PRVs are there to protect the piping. 3/4" by 1 1/2" is a little large on the outlet for a thermal relief PSV but it's possible.

My suggestions would be to identify the the relief case these PSVs were originally identified for. Then determine for the system (piping and/or equipment) they are protecting what the minimum design pressure of all components are. Set the PSV at the minimum pressure would be reasonable. Depending on the piping code that the system was designed under, that could also affect where you set your PSV.

 

[POL23]

Thanks TD2K...You're correct the PRVs are there to protect the piping not the tank