Common faults of water pumps and their solutions

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If it cannot be started, the power supply should be checked first: ensure that the connections are secure； Are the switch contacts tight? ； Is the fuse blown? ； Check whether there is a phase imbalance in the three-phase power supply. In the event of an open circuit, poor contact, blown fuse, or missing phase, the cause should be identified and repaired promptly. Next, check for mechanical faults in the water pump itself. Cause: The packing is too tight, or debris has gotten stuck between the impeller and the pump casing, causing a blockage ； The pump shaft, bearings, and leak reduction rings are rusted ； Severe bending of the pump shaft, etc. Exclusion method: Relax the filler and clear the water diversion channel ； Disassemble the pump body to remove debris and rust ； Remove the pump shaft to correct it or replace it with a new one. (II) Causes of water pump overheating: damaged bearings ； The clearance between the rolling bearing or bracket cover is too small ； The pump shaft is bent or the two shafts are not aligned ； The tape is too tight ； Lack of oil or poor oil quality ； The balance holes on the impeller are blocked, causing the impeller to lose its balance and increasing the thrust in one direction. Exclusion method: Replace the bearing ； Remove the rear cover and insert shims between the bracket and the bearing housing ； Inspect the pump shaft or adjust the concentricity of the two shafts ； Adjust the tape tension appropriately ； Fill with clean butter, with the butter occupying about 60% of the space within the bearing ； Remove the blockages from the balance hole. (III) Insufficient flow is caused by an inappropriate motor speed or belt slippage, resulting in a low rotation speed ； The installation angle of the axial flow pump blades is too small ； Insufficient head, too long piping, or piping with right-angle bends ； The suction lift is too high ； Local blockage of the bottom valve, pipelines, and impeller, or damage to the impeller ； The water outlet pipe is leaking severely. Exclusion methods: Restore the rated speed, remove oil buildup from the belt, and adjust the belt tension properly ； Adjust the blade angle, lower the installation height of the water pump, shorten the pipes or change their curvature ； Seal the leak in the water pump by compressing the packing ； Remove the blockage and replace the impeller ； Replace the leak-reducing ring to seal the leak. (IV) Reasons for inability to draw in water: air inside the pump or air accumulation in the water inlet pipe, inadequate filling of water due to a poorly sealed bottom valve, severe leakage in the vacuum pump’s packing, or poorly sealed gate valves or check valves. Exclusion method: First increase the water pressure, then fill the pump body with water, and finally turn it on. At the same time, check whether the check valve is airtight and whether there are any air leaks in the pipes and connections; if leaks are found, disassemble them, apply lubricant or sealant to the connections, and tighten the screws. Inspect the oil seal ring of the water pump shaft; if it is severely worn, replace it with a new one. The pipeline is leaking fluid or air. The nut might not have been tightened properly during installation. If the leakage is not severe, cement can be applied to the area where air or water is leaking, or a cement paste mixed with asphalt oil can be used. For temporary repairs, some wet mud or soft soap can be applied. If water leaks at the joint, the nut can be tightened using a wrench; if the leakage is severe, the assembly must be disassembled again and the cracked pipe replaced ； Reduce the head by submerging the pump outlet 0.5m underwater. (5) Cause of severe vibration: Unbalanced electric rotor ； Poor coupling fit ； Bearing wear and bending ； The parts of the rotating mechanism are loose or cracked ； Reasons such as loose pipeline supports. Exclusion methods: Adjustments, repairs, reinforcement, straightening, replacement, and other methods can be employed separately. The above situations are common causes of pump failures, but they are not the only ones. When dealing with such failures in practice, one should follow the principle of starting with the external aspects before moving on to the internal ones, and avoid acting blindly. (VI) Overheating of the auxiliary drive motor: One reason is related to the power supply – either the voltage is too high or too low. Under certain loads, if the voltage deviates beyond the range of +10% to -5% of the rated value, it can cause the motor to overheat ； If the three-phase voltage of the power supply is asymmetric, with an imbalance between the phase voltages exceeding 5%, it can cause the windings to overheat ； Operation with a missing phase. Exclusion method: Over 85% of cases of burned agricultural motors are caused by operation under a missing phase condition; therefore, phase-loss protection devices should be installed on the motors. The second reason is related to the water pump: an inappropriate power level is used, meaning a motor that is not strong enough for the task is employed; as a result, the motor operates under overload conditions for extended periods, causing its temperature to rise excessively ； Motors that are started too frequently, or those designed for short-duration or intermittent operation, are forced to work continuously. Exclusion methods: The number of starts should be limited, appropriate thermal protection should be selected, and the motor should be used according to the rated specifications indicated on it. Third is a problem with the motor itself: an incorrect wiring method, where a delta connection was mistakenly used in place of a star connection, causing the motor’s temperature to rise rapidly ； The stator windings may suffer from inter-phase short circuits, turn-to-turn short circuits, or local grounding; in mild cases this causes localized overheating of the motor, while in severe cases it leads to insulation damage ； The squirrel-cage rotor has broken bars or defects; after the motor operates for 1 to 2 hours, the core temperature rises rapidly ； The ventilation system has failed. Exclusion method: Check whether the fan is damaged, whether its rotation direction is correct, and whether the ventilation channels are blocked ； Bearing wear and rotor eccentricity cause the stator and rotor cores to rub against each other, generating metallic knocking sounds; the temperature of the cores rises rapidly, and in severe cases the motor starts to smoke or even the windings get burned out. Fourth is the issue related to the working environment: the motor windings become damp, or dust, oil, and other substances accumulate on them, resulting in reduced insulation. The insulation resistance of the motor should be measured, and it should be cleaned and dried ； The ambient temperature is too high. When the ambient temperature exceeds 35°C, the high inlet air temperature can cause the motor to overheat. Exclusion method: Efforts should be made to improve their working environment. Such as setting up shelters for shade, etc. Note: In the event of a fault caused by electrical issues, it should be repaired by an electrician with professional qualifications; those with only limited knowledge should not attempt repairs, to prevent accidents that could cause injury. (7) If a deep well submersible pump does not draw water or draws only a small amount of water, first check how much the current flowing through the pump at this time differs from the current during normal operation. If it is lower than normal operating levels (basically 2/3 of the usual current), then there may be issues such as impeller wear or a clogged check valve on the pump head*. If the current is as high as during normal operation, then there may be problems such as leakage at the pipe gasket, leakage in the pipes, or leakage in the pump body. If the current is higher than normal during operation, it can basically be determined that it is a problem caused by wear and tear of the vulnerable components. As an additional point, if the cable is damaged, the water flow will remain the same as usual, but the current will increase. The current for the 3×380V motors is generally 2.2A.