Pump discharge PSV/TSV specifications

[curve3104]

I have noticed relief valves in refining plants (not sure exactly which type of relief device) installed on piping from process units to storage tank farms, and on the discharge side of product pump stations, sending product to truck/barge loading, etc.
Are these pressure relief valves, or temperature relief? I can't think of why you would put a PRV on a pumped system, unless your pump was sized such that the shut-off head could breach piping design conditions. Is this under an API code? I can't recall this being covered in ASME B31, unless I missed it.
Would appreciate some feedback.
Thanks
CB

 

[KANN]

I see either pressure or temperature could be the reason. As you state, if the deadhead pressure of the pumping system could result in overpressure, then pressure relief is necessary for protection. Also, if solar loads on the piping could heat trapped fluid, causing fluid expansion, then this could be the reason also.

Not knowing more about the fluid and the piping specifics, those may be reasons for the relief valves you observe.

 

[MJCronin]

curve,

Another reason to put a relief device on pump discharge piping is to ensure that the pump will pass the "minimum flow" required to prevent damage/overheating.

There have been cases where "high energy" mulitistage pumps can vaporize fluids if the dischrge is completely blocked (shut-off conditions). If the pump casing is cast iron, it can fail.

Thus it may be the pump itself (not the piping) that requires protection.


-MJC

 

[curve3104]

Thanks MJC. I agree with you 100%. Not only is there a SRV on the discharge header in my case, we have a small recirc line to divert flow when we run up the curve.
The issue here is thermal fluid expansion. Long pipe runs that can be isolated need to be relieved. With most fluids, the pressure rise does not endanger the pipe or fittings, but when you try to open the valve, it's almost like being welded shut.
I have heard of these devices, and they are called out in B31.3, but no details are provided for how they are sized, specified, etc. I'm not sure if you just call a Consolidated, Kunkle or other and tell them you need a TRV and they specify...

 

[Ashereng]

Thermal relieve valve in liquid pipeline service have been covered in this forum I believe.

Safety Relief Valve engineering (PSV) Forum
(498 members)
forum1203

Take a search through it.

I think the answer is, due to the nature of pressure relieve with liquids, only a 1" x 1" PRV would be needed, for themal expansion relieve, which you call TSV.

I am not sure what you mean by SRV.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[psvdesign]

Can anybody help me out, is there any standard that says about safety relief valve can not be installed on pressure vessel inlet line.
If vessel overhead nozzle & disharge line are smaller than PSV required orifice size, can that PSV be installed on vessel inlet line which is of higher size.
thanks,