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# centrifugal pump

Question asked by Shaheen Mongam in #Coffee Room on Jun 16, 2016
Shaheen Mongam · Jun 16, 2016
Rank D3 - MASTER
what will happen if a centrifugal pump is used for taking water into a level below its center line (certain flow rate is required). Usually performance curve is available only for positive differential heads. so how we will calculate discharge flow rate Posted in: #Coffee Room
Ramani Aswath · Jun 16, 2016
Rank A1 - PRO
If the suction level is below discharge level it is still a positive head. You have to add the frictional drop from intake to output to get the total operating head. If the discharge point is below the water level, why do you need a pump at all?
Shaheen Mongam · Jun 16, 2016
Rank D3 - MASTER
Discharge is below water level. Water will flow due to gravity. But I need a particular flow rate which is possible only with a pump( assume a case where gravity flow will be very less and hence I need something to boost)
Ramani Aswath · Jun 16, 2016
Rank A1 - PRO
It depends on the area available for flow. In a river the head available is very small but the area for flow is large. Hence flow is large.
As said above the pressure drop in the pipeline will also come into the picture. You can add a flow control valve on the delivery side to add as much resistance as you want.

For a project in Nilgiris we designed a gravity flow system to get process water from a stream nearby by tapping the stream a few meters above the factory.
Shaheen Mongam · Jun 17, 2016
Rank D3 - MASTER
U didn't get my question. I need to transfer certain amount of water which is higher than what gravity can transfer( given- increasing the pipe size is not feasible). So providing a pump is the only option to increase its velocity. So a centrifugal pump is an option? How to get its characteristics then since the differential head will be negative
Shaheen Mongam · Jun 17, 2016
Rank D3 - MASTER
U didn't get my question. I need to transfer certain amount of water which is higher than what gravity can transfer( given- increasing the pipe size is not feasible). So providing a pump is the only option to increase its velocity. So a centrifugal pump is an option? How to get its characteristics then since the differential head will be negative
Ramani Aswath · Jun 17, 2016
Rank A1 - PRO
Please go through the reply. By putting a flow control valve on the outlet one can get any positive differential head one wants.
A centrifugal pump is eminently suitable.

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