Fire PSV for PHE' s
Fire PSV for PHE' s
(OP)
Does anyone have any thoughts on the following...???
For a new offshore project we are providing gasketted plate type heat exchangers for the oil train.
My thoughts are that installing a PSV on the hot side for fire (the cold side is provided with a PSV for thermal relief) is pointless as the gaskets are likely to disintegrate/leak, and thus 'feed the fire', before the relief valve has even had a chance to lift.
Secondly, we are also required to provide SAFE charts as per API 14C. The HX section in 14C is primarily concerned with S&T HX's. If I leave the PSV out on the PHE's hot side, how can I justify this in my SAFE chart??
For a new offshore project we are providing gasketted plate type heat exchangers for the oil train.
My thoughts are that installing a PSV on the hot side for fire (the cold side is provided with a PSV for thermal relief) is pointless as the gaskets are likely to disintegrate/leak, and thus 'feed the fire', before the relief valve has even had a chance to lift.
Secondly, we are also required to provide SAFE charts as per API 14C. The HX section in 14C is primarily concerned with S&T HX's. If I leave the PSV out on the PHE's hot side, how can I justify this in my SAFE chart??





RE: Fire PSV for PHE' s
Normal flow piping can provide an escape route for some contingencies, including fire. Check for delta P and overpressure potential.
You have to specify HE design pressure based on the worst process condition, like pump shutoff pressure, etc. Possibly no PR device is needed.
For the case of the cold side, of course you must consider liquid expansion as a contingency. Preventive measures for overpressure could be as simple as avoid unnecessary block valves, or specify car-seal open. Every particular case must be analyzed in detail.
Also, code requirement (for S&Ts) says about 2/3 rule. Design pressure of the low pressure side must be no lower than 2/3 of the high pressure side.
Regarding fire contingency, this has much to do with your fire fighting facilities, rather than mechanical design. Fireproofing might be considered.
Sorry not having API 14C with me right now... not sure what is it.
RE: Fire PSV for PHE' s
Good luck,
Latexman
RE: Fire PSV for PHE' s
PR devices have nothing to do with gasket selection.
To mention: Important consideration in plant design is equipment spacing. It has to do with fire events.
Oil industries have their standards regarding equipment spacing, stack arrangement, and so on.
I would invite you to learn more about NFPA (National Fire Protection Agency) regulations.
RE: Fire PSV for PHE' s
RE: Fire PSV for PHE' s
As the plates will leak and prevent a catastrophe, I see no reason to add relief protection for fire. There may be other cases that might require a safety device and you will undoubtedly uncover these duiring a HAZOP.
RE: Fire PSV for PHE' s
My first post was a spoof, playing on this knowledge. Why would one rely on a gasket to blow out at the right moment by chance if they could scientifically calculate a relief device when someone's life may depend on it? I just don't understand the logic.
Good luck,
Latexman
RE: Fire PSV for PHE' s
Plate and frame heat exchangers with MAWP > 15 psig have ASME stamps.
Good luck,
Latexman