Lube Oil Cooler PSV required?

[Barhp]

Hi Guys,

I am working verifying if a PSV is required for fire case in a lube oil cooler (oil side). The exchanger is a plate and frame type with a thermal PSV in the water side. The heat exchanger is very small with 2" inlet and outlet lines for water and lube oil.

Any advice will be appreaciated

Regards

 

[Latexman]

Usually a PSV is required. If not for oil/liquid expansion, then boiling. And, given fire scenario is credible for the entire HX, not just one side, I’m surprised thermal expansion is the controlling case on the water side and not boiling. Or was that overlooked? But maybe that PSV is big enough for either case. We have no details.

Good Luck,
Latexman

 

[georgeverghese]

My previous company standards indicate fire case relief by means of a PSV is not required in gasketed plate frame heat exchangers - too many leak points to enable containment of built up pressure, especially during a fire. Essentially both sides are self relieving.

 

[Latexman]

Previous assumptions that the gaskets will fail on fire exposure if the exchanger is not water-sprayed and pressure will relieve through the gasketed joints are no longer considered valid. Industry fire tests on newer designs showed that the gaskets can remain intact for a significant period of time. Whether the heat exchanger is watersprayed or not, relief should be provided for both sides of new heat exchangers.

Good Luck,
Latexman

 

[georgeverghese]

Another case where firecase relief may be excluded, in my previous company standard, is when the HX total fluid volume is <500litres. Am assuming this HX is built to TEMA / ASME BPVC or equivalent i.e. it is a coded pressure vessel.
Guess that when you have contradictions in your Company or other industry practices, is to tabulate the risk and consequences of loss of containment in such a scenario, then run this tabulation and conclusion on to a process safety engineer for review. To me, if the lube oil contains significant quantities of dissolved flammable or toxic low boiling point components, I would recommend a firecase RV on the oil side.