A centrifugal pump discharging at a reduced rate may indicate the condition of a jam in the impeller.

• A. Jam in impeller
• B. Low suction head
• C. Overheating
• D. Electrical fault

Answer: (A)

When a centrifugal pump runs, the rate at which it delivers fluid is set by how effectively the impeller can move that fluid. If something jams the impeller, the flow path becomes obstructed and the cross-sectional area available for flow shrinks. That direct obstruction reduces the volume of fluid the pump can discharge per unit time, even though the motor may still be turning. You might also notice the load on the motor increasing and the pump vibrating more as it struggles with the blockage, and if the jam persists, overheating could follow as the driver fights the higher torque.

Other causes like low suction head would affect the pump’s ability to draw fluid and could lead to cavitation or a drop in suction-side pressures rather than a direct impeller blockage. An overheating condition or an electrical fault changes the operating behavior more broadly (shutoffs, faults, or abnormal speeds) and doesn’t specifically explain a reduced discharge rate due to a physical blockage.