After using dozens of pumps, I figured out the patterns behind their failures!

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During operation, potential faults of the pump can be predicted by observing or monitoring aspects such as its flow rate, sound, vibration, temperature, current, tripping of electrical protection components, and controller alarms. The fault prediction and handling for pumps should follow the principle of first predicting, then confirming on-site, and finally taking action. 1. Traffic prediction ①: Significant decrease in traffic. If the pump’s flow rate decreases significantly (by more than 20% below the normal value), the following checks should be carried out one by one, and appropriate measures taken. a) The valve on the pump discharge pipe is not open or is blocked: The valve can be opened or the pipe can be cleared. b) The pump’s suction height exceeds the limit: Lower the pump’s installation height or replace it with a pump that has a greater suction range. c) Air leakage in the suction pipe and foot valve: Repair or replace the suction pipe and foot valve. d) Insufficient submersion depth of the bottom valve: The submersion depth of the bottom valve should be more than 1.5 times the diameter of the water inlet pipe; if it is insufficient, the depth of water immersion should be increased. e) Volute cavitation or erosion perforation: Replace the volute. f) Clogged impeller or worn seal ring: Clean the clogged impeller or replace the worn impeller seal ring. g) Wear or detachment of the wear ring at the water inlet: The wear ring should be replaced if the wear exceeds the requirements specified in the manual; if it has detached, it must be reinstalled. h) Severe corrosion of the pump shaft, bearings, and leakage reduction rings: Replace the severely corroded components. i) Incorrect impeller rotation: Adjust the motor wiring. j) Motor brush wear: Replace the bearings or the motor. k) Failure of the parallel pump check valve: Replace the check valve. ②: No traffic. 1. Check whether the power supply is connected; if it isn’t, reconnect it. 2. Check whether the relays and contactors can operate properly; if they cannot, replace the damaged relays or contactors. When the power supply is normal but the pump cannot be restarted, the pump should be moved to the maintenance area, and the issues should be checked one by one as follows, with appropriate actions taken. a) Excessively tight packing or clogged impeller: Loosen the packing or clear the water inlet channel. b) The impeller, bearings, and leak reduction rings are stuck or rusted: Disassemble the pump casing to remove debris or carry out rust removal. c) Bent pump shaft: Remove the pump shaft for correction or replace it. d) Damaged waterproof cable: Cut off the damaged section of the cable and reconnect it or replace the damaged cable. e) Poor sealing or water resistance at the power cable connections: Re-seal them after repairing or replacing components affected by water ingress. f) Severe wear of the mechanical seal: Replace the mechanical seal after repairing or replacing the components affected by water ingress. g) Severe wear of the O-ring: Replace the O-ring after repairing or replacing the components affected by water ingress. h) Bolts at the seals are not tightened: Re-tighten the bolts after repairing or replacing the components affected by water ingress. i) Excessively low motor insulation resistance: When the insulation resistance does not meet the requirements, dry the motor, re-apply insulating paint, rewind the motor coils, or replace the motor. j) Faults in the three-phase power wiring of a three-phase pump: Inspection and rewiring can be carried out as follows: 1) Check whether the cables have poor contact ； 2) Check whether there is any phase loss in the power supply and motor ； 3) Check the balance of voltage and current across the three phases of the power supply. 3. If the power supply is normal and the pump can be restarted but no flow is still present, the pump should be moved to the maintenance area for systematic inspection according to the following steps, and appropriate measures should be taken. a) The pump body and suction pipe are not filled with the conveying medium: Fix the bottom valve issue and fill the conveying medium. b) The operating water level is below the pump’s inlet pipe: Lower the pump’s installation height or raise the operating water level, and then start the pump once the operating water level is above the inlet pipe. c) Broken suction pipe: Repair or replace the suction pipe. d) Fault in the check valve of the parallel pump: Replace the check valve. 2. Sound prediction: In case of noise or abnormal sounds during the pump’s operation, the pump should be moved to a maintenance area, where each potential cause should be checked one by one, and appropriate measures taken accordingly. a) Damaged or stuck motor ball bearings: Replace the motor ball bearings. b) Damaged pump bearings or stuck impeller: Replace the bearings or clean out any debris from the impeller. c) The pump shaft is bent, or it is not aligned or parallel to the motor shaft: Correct the bent pump shaft or adjust the relative position of the pump and the motor. d) Improper installation or the pump being installed too high: Adjust the pump or lower its installation height. e) Low liquid level in the inlet well: Adjust the inlet liquid level. f) Suction port blockage: Clear foreign objects from the pump’s suction port. 3. Vibration prediction 1. The causes of abnormal pump body vibration can be mainly divided into mechanical and hydraulic factors. 2. Mechanical causes can be checked item by item as follows, and corresponding measures can be taken. a) Foreign objects are stuck in the pump impeller or bearings: Remove the foreign objects. b) The mass distribution of the pump impeller or motor rotor is uneven: the impeller or motor should be replaced. c) Deviation between the pump shaft and the motor shaft: Align the pump shaft and the motor shaft to be concentric. d) The bolt spacing of the coupling is not satisfactory: Adjust the gap between the couplings. e) The spindle speed is close to the critical speed: Adjust the spindle speed. f) The pump shaft bends, causing the rotating part to come into contact with the bushings and bearing shells, which results in the shaft deflecting: Replace the faulty components. g) The base is not sturdy or the bolts are not tight: Reinforce the base and the bolts. h) Resonance occurs when the vibration frequency of the pump is close to that of the pipeline: the pipeline can be reinforced. 3. Hydraulic-related issues can be checked item by item as follows, and corresponding measures can be taken. a) Cavitation-induced vibration: A pump with a higher suction lift can be used. b) Vibration caused by water flow hitting the baffle and the leading edge of the guide vanes: Adjust the distance between the impeller outlet and the baffle of the pump volute or the leading edge of the guide vanes. c) Low water level in the well or blockage at the pump’s suction inlet: Adjust the water level or remove any obstructions from the pump’s suction inlet. d) Surge phenomenon: Handle it in accordance with the pump’s manual instructions. 4. Temperature prediction: If the pump temperature is too high, conduct inspections according to the items listed below and take appropriate measures. a) Bearing wear or jamming: Add lubricant or replace the bearing. b) Bearing or motor overload: Reduce operating power or replace with a pump of higher capacity. c) Lack of conveying medium: Ensure the valves before and after the pump are open to maintain an adequate level of the conveying medium. 5. Current prediction: When there is an abnormal current, the pump should be moved to the maintenance area, and inspections should be carried out step by step as follows, with corresponding measures taken. a) Abnormal operating conditions: Verify the on-site operating conditions and replace or adjust facilities that are not suitable for those conditions. b) Bearing malfunction: Inspect, repair, or replace the bearing. c) Speed exceeds the rated speed: Check the circuit voltage and reduce the pump speed. d) The coupling is out of alignment or the pump shaft is bent: Correct or replace the pump shaft. e) Obstruction by debris: Clear the debris. f) Damaged ball bearings in the motor: Replace the ball bearings of the motor. g) Improper selection of the water pump head: Replace it with a pump having an appropriate head. 6. Prediction of tripping of electrical protection components 1. Tripping of electrical protection components includes tripping due to the operation of thermal relays, tripping due to the operation of air switches, and tripping due to the operation of AC contactors. 2. If the thermal relay trips due to protection activation, conduct inspections step by step as follows and take corresponding measures. a) Poor contacts of the thermal relay: Replace the thermal relay. b) The current setting value is too low: Increase the current setting value. c) Overload operation: Reduce the operating power; if the fault cannot be resolved, the motor should be replaced. d) The impeller is blocked or stuck: Clear the water inlet channel. e) Operation of a three-phase motor with one phase missing: Reconnect the wiring or replace the motor. f) Damage or breakage of the winding temperature control cable: Replace the damaged component. 3. If the air switch trips due to protection activation, conduct inspections step by step as follows and take appropriate measures. a) The air switch selected is not compatible with the load: Replace the air switch. b) Soft starter or inverter failure: Replace the damaged components. c) Short circuit in the power circuit: Reconnect the wires. d) There are short circuits between phases, between turns, and to ground in the motor windings: Replace the motor. e) Pump operating under overload: Reduce the operating power; if the fault cannot be resolved, the motor should be replaced. 4. If the AC contactor trips due to protection activation, conduct inspections step by step as follows and take corresponding measures. a) AC contactor coil failure: Replace the AC contactor coil. b) Abnormality of the auxiliary contacts of the AC contactor: Adjust or replace the auxiliary contacts of the AC contactor. c) Abnormal intermediate relay: Replace the intermediate relay. d) There are short circuits between phases, between turns, and to ground in the motor windings: Replace the motor. 7. Controller alarm prediction 1. Oil chamber leakage alarm: If a leakage alarm is triggered by the controller, it can be checked step by step as follows, and corresponding measures can be taken. a) Fake signal: Press the reset button. b) Sensor malfunction: Disconnect the wires, inspect the sensor, and replace the faulty component. c) Water inlet to the cooling oil chamber: Drain and clean the cooling oil chamber, and replace the sealing components. d) Pump body and base perforations: Replace the pump. 2. Bearing temperature alarm: If a bearing temperature alarm is triggered, check each item as follows and take corresponding measures. a) Fake signal: Press the reset button. b) Pump controller malfunction: Press the reset button; if it does not work, open the unit to inspect the controller and replace the faulty component. c) Sensor malfunction: Replace the sensor. d) Faults such as bearing displacement or damage: The pump should be moved to a maintenance area to inspect the bearings; if there is a fault with the bearings, they should be repaired or replaced. 3. Motor winding alarm: If there is an alarm related to the motor windings, it is possible to check each item as follows and take appropriate measures. a) Spurious signal: The reset button should be pressed. b) Temperature control switch circuit open: Close the circuit. c) Motor overload: Reduce the motor’s operating frequency or close the outlet valve; if the fault cannot be resolved, the motor should be replaced. d) Abnormal motor insulation resistance or inter-phase/inter-turn insulation: Replace the motor. e) Damage or breakage of the winding temperature control cable: Replace the damaged component. f) Operation of a three-phase motor with one phase missing: Reconnect