What happens when a discharge valve is closed at a station with centrifugal pumps?

When the discharge valve is closed at a station with centrifugal pumps, the discharge pressure will increase suddenly. This is because closing the valve restricts the flow of water, causing the pump to build pressure against the closed valve. In centrifugal pumps, when the flow is obstructed, the kinetic energy imparted to the fluid by the pump is converted into pressure energy, resulting in an increase in the discharge pressure.

It is important to note that while this increase in pressure can initially seem beneficial, it can lead to hazardous conditions, such as pump damage or cavitation if the pressure exceeds the pump's design limits. Thus, operators must monitor the system closely to avoid potential failure.

The other options do not correctly describe the effects of closing the discharge valve. A sudden drop in pressure would not occur; in fact, the opposite is true. An increase in flow rate is also inaccurate since restricting flow does not allow for an increase; rather, flow will decrease as the valve closes. Finally, while some might think that closing the valve could improve efficiency, it often results in inefficiencies and risks, particularly if the system experiences excessive pressure or cavitation as a consequence.