Filter vessel - Thermal relief valve or normal relief valve 3

[EngCutie]

Hi, I have attached a drawing to help me explain.

Filter vessel - MAWP is 20Barg, I have a normal relief valve sized for when the pressure goes above the MAWP pressure, but my client wants a thermal relief valve. I’m a little confused, does that mean the pressure inside the vessel would never actually exceed the MAWP pressure without thermal effects? I read that thermal relief valves normally have smaller orifice size. Is it possible to have a relief valve that will relieve due to thermal effects as well as when the pressure exceeds the MAWP?

Upstream of the inlet is a pump, but it’s outside of our scope, so I’m not sure exactly what else is there.

Please help, thanks.


Cutie


Thank you, EngTips

 

[jrwchem]

Tickle,

I have to disagree that thermal expansion, or fire are the only two ways to exceed the MAWP. Blocked discharge can cause overpressurization if the shut off head on the pump is higher than the MAWP, and there are non-locked-open block valves down stream of the filter.

Jon

 

[tickle]

Sorry jon but I did say "can be", there are other methods as you state, but they are not always present or are mitigated by other means (eg PSV at the pump).

 

[EngCutie]

Thanks, when I told a vendor I wanted a ‘thermal’ instead, he said ‘D’ orifice would be sufficient. I did the orifice sizing calculation (using equation in Crosby pressure relief valve handbook), I know the SG, set pressure, and the back pressure is 0, it looks like all I need to know is flow rate when thermal expansion happens. But I don’t know the formula to do the calculate.

Cutie


Thank you, EngTips

 

[EngCutie]

calculation*

Cutie


Thank you, EngTips

 

[pleckner]

Do, if you have settled on the fact that thermal relief is the controlling scenario, don't be concerned about the flow rate. It will be so small that it won't matter.

I hope you at least have a copy of Perry's Handbook because if you really want to calculate it, I believe you can find the equation for thermal expansion there.

 

[EngCutie]

Thanks, a friend once recommended that book, I think I have a copy.

I don’t know if thermal is the worst case, but my boss is getting annoyed with me for questioning the client spec, because our client is one of the biggest oil company in the world, he thinks they know what they are doing, so I have no choice but get a ‘thermal’.

Cutie


Thank you, EngTips

 

[EngCutie]

and my request for buying API standards has been rejected, because "we don't know how often we are going to use them, too expensive, don't want to waste money"

Cutie


Thank you, EngTips

 

[786392]

Dear Hello/Good Evening,

At our previous we faced serious problems as we shifted our Jet A-1 Filter water separator to downstream of a pipeline segment around 1.2KM length

(the segment was made above ground) with filter/water separator moved from its upstream side location.

The vessel was subjected to thermal high pressures beyond capability and the glass differential pressure gauge frequently broke.

We had no option except to provide thermal relief valve taking care of solar radiant heat input in blocked-out non-pumping state;thereby we made the system safe functioning

Hope this practical info proves helpful.

Best Regards
Qalander(Chem)