Centrifugal Pump/Motor Set Faults: Indications and Causes
(a) Five Indications of a Fault:
- Reduced Flow Rate: The pump delivers a noticeably lower flow rate than expected at the system’s operating pressure.
- Increased Vibration: The pump and/or motor vibrate excessively during operation.
- Unusual Noises: Abnormal noises like grinding, rattling, or cavitation sounds are heard from the pump or motor.
- Loss of Prime: The pump loses its prime and fails to deliver any fluid, even after attempting to reprime.
- Overheating: The pump motor or bearings experience excessive temperature rise during operation.
(b) Possible Causes for Each Fault:
- Reduced Flow Rate:
- Cause: Clogged impeller, worn-out wear ring or casing, blocked suction or discharge line, incorrect pump selection for the application (insufficient capacity).
- Increased Vibration:
- Cause: Bent shaft, worn bearings, loose coupling between pump and motor, cavitation due to insufficient NPSH (Net Positive Suction Head) available, foreign object lodged within the pump.
- Unusual Noises:
- Cause: Cavitation, worn bearings, damaged gears (if gear-driven pump), loose components within the pump, air leak in the suction line.
- Loss of Prime:
- Cause: Air leak in the suction line, faulty check valve on the suction side not holding pressure, insufficient liquid level in the suction reservoir.
- Overheating:
- Cause: Running the pump dry (no liquid to cool it), excessive load on the motor due to high system pressure or blocked discharge, malfunctioning bearings causing friction, failing motor windings.
Note: These are just some possible causes, and the actual cause of a fault can vary depending on the specific pump/motor set and operating conditions. Consulting a qualified pump technician is recommended for proper diagnosis and repair of any faults.