Question

g A pump is required to deliver 100 gpm at a head of 100 ft, but the pump rated capacity is 150 gpm at a head of 100 ft. If the pump speed is constant, what will be the effect of valving the pump discharge to reduce flow

Answer 1

Answer: valving the pump discharge to reduce the flow will only result in an increase in the water velocity according to the laws of continuity of flow.

Q = AV = constant.

The pump speed of 150 gpm is, and will remain constant. Valving simply reduces flow area A, which is balanced out by increased velocity V of water through the pipe.

This does not affect the pump speed Q (flow rate) and hence it remains the same.