Pump flowrate reduction
Pump flowrate reduction
(OP)
I have an issue with a pump flowrate. We have a situation where we require a pump to perform a suction lift of 2m, then discharge through 25m of 25mm i/d pipework. Problem is, we have a maximum discharge flowrate requirement of 1 l/min and the closest pump we can find capable of performing the lift delivers 2.5l/min at 60m max head. I realise that by installing a PRV we can drop the pressure in the line and for us, pressure is not really an issue as long as it doesn't drop below 2 bar, however, will this also reduce the flowrate? Or will it increase the velocity and maintain the flowrate? Could we install a length of smaller diameter pipework in the line to reduce the flow? Alternatively, is there any other way to be able to reduce the flow and quantify the reduction? Any help would be greatly appreciated as this has been driving me insane.





RE: Pump flowrate reduction
Any restriction will reduce flow... a smaller diameter pipe, a valve, or an orifice plate for example, to get a higher discharge pressure, up to pump shutoff discharge pressure, and a lower flow.
Alternately you could drop the pump speed to get a reduced discharge pressure and a flow reduction.
Alternately you could recirculate some flow to suction to accomplish basically the same thing.
If you know a little about hydraulics, you can easily model and quantify any of the above.
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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) http://virtualpipeline.spaces.live.com/
RE: Pump flowrate reduction
If you put a throttle valve (see link) on the outlet of the pump you can reduce the flow rate based on your pump curve. Be sure not to go below the minimum allowed flow rate of the pump.
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RE: Pump flowrate reduction
If you have a PD pump then introducing a restriction should not change your flowrate since inprinciple a PD pump has a vertical head/flow curve. Here only speed modification will help you.
Best regards
Morten