internal relief valve gear pump

[frankieh]

For a lube oil pump (gear type) of a compressor only an internal pressure relief valve is in place. I am sure that there should also be an external relief valve as there are some valves in pump discharge. Can somebody tell me where I can find this requirement. The pump will serve on a plant located in the UK so european guidelines are mandatory.

thx

 

[don1980]

There is no such requirement.

 

[Latexman]

I don't follow your logic, maybe a system P&ID or sketch would clarify it for me.

Good luck,
Latexman

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[LittleInch]

As far as I know, the requirement is simply for a pressure relief somewhere between the pump discharge and the first isolating valve. If this is the internal pump relief, then so long as it will relieve at the right pressure for the downstream piping and handle full flow then it should be Ok. The internal reliefs though are not intended for any long term pressure relief as the temperature would increase so it depends on what other warning / shutdown systems are in place to protect the pump.

There are other posts on gear pumps so if you search for gear pumps you'll find more discussion.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[jamesbanda]

Your requirement is to ensure your downstream system is adequatly protected from an over pressure event. And, that you suitably maintain and managed your relief valve.

I've seen systems that are unsuitable for Pressure reliefs on positive displacement pumps becuase they are carrying solids. And, the level of high pressure trip we installed depending if the stream being processed was flammable, toxic etc..

Your duty as a process engineer is to ensure that you have access the consquences of over pressure.

 

[maddocks]

In general, the pump internal reliefs do not qualify as registered relief valves because they are (of course) not registered, and you can't take them off and bench set them to a prescribed bench criteria. We've usually been forced to install another external ASME registered relief valve to protect these systems. The internal relief usualy does the work and the external helps us pass the inspection.

 

[silebi66]

Dear frankieh
The relief valve installed downstream positive displacement pump is only for the block outlet case.