Travis_King

I assume you mean if you "incrementally" close the valve. Centrifugal pumps ride on curves (just type in pump curve and you'll see) which vary such that as head increases, capacity decreases. So if the pump must overcome 100 psi, the capacity will be at a low of, say 50 gpm. But, if the valve is opened and the resistence (effective head pressure) is reduced, you will get higher capacity.

Type in "pump handbook" into google. it should be a 1.5 Mb pdf and it is very informative.

hi thanks for answering my doubts.I asked about the valves thing.
can u tell me wat will happen if we close the discharge valve of a centrifugal compressor??
i feel since the system resistance is increased now the pump will pump at a higher head but lower capacity and vice versa.
is this true..??
can u please give me the link of some good articles on fluid flow.
i feel very frustrated due to my weak concepts.