centrifugal relief valve

[Lekoso]

Hello All,

I need a little clarification.
Is it necessary to place a Relief Valve at pump discharge.
If not, at what occassions would an exception be considered?

Regards

'Lekan

 

[TenPenny]

For a given speed, there is a maximum head that a centrifugal pump will develop.

You need to determine what the system maximum suction pressure could be, add to that the maximum shut off head of the pump, and then look at your downstream system to determine if you need a relief valve, based on this potential maximum pressure.

 

[Lekoso]

M. TenPenny,

From my understanding, and more often than not, the pump shut-off pressure is always less than the Allowable Stress of the Pipe Material - in the case of Steel Pipes (defined by ASME B31.3).

Consequently, the reason for using Relief Valves for in Centrifugal Pump arrangement is to protect the pump.

My question remains, when is is necessary to install these Releif Valves to protect the pumps, because I find that, some installations do not use it.

Regards

'Lekan

 

[BigInch]

It is not required that pipe max pressure must be greater than pump shutoff pressure, but if it is the safe way to handle that situation is to place a relief valve with a set pressure not higher than the maximum pressure allowed within the piping under such circumstances. Installations that have maximum allowable pipe pressures greater than the pump shutoff pressure would not need such a relief valve under normal circumstances, provided that any possible transient pressures (waterhammer pressures) are also under pipe pressure limits.

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

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[Artisi]

I would suggest that there are millions of installations round the world running successfully without PRV fitted. If a PRV is fitted it is usually there so as the pump doesn't have to run against a closed head which can introduces a multitude of problems or for the condition described by BigInch. Fitting of PRV's is an engineering decision influenced by a multitude of reasons, this means that there is no hard and fast overall rule to use or not to use PRV.