Six Common Faults and Solutions of Water Pump

Figure 1: Water pump.

Unable to Start

What you need to do first is to check the power supply: whether the joint is firmly connected, the switch contacts tightly, the fuse is blown, three-phase power supply is equal. If there are broken circuit, poor contact, blown fuse and phase loss, identify the reasons and repair immediately.

Then you should check whether there are mechanical faults in water pump itself. Common reasons are: fill too tightly or between the impeller and pump body and the plug was stuck debris or shaft, bearings, minus leakage ring rust to live, or severe bending shaft.

Solutions

Loosen the packing, dredge the water channel; disassemble the pump body to remove debris and rust; take off the pump shaft for calibration or replace it with a new one.

Supporting Power Motor Overheating

There are four reasons accounting for this problem.

First, the power supply: the voltage is too high or too low. If the voltage variation range is beyond between positive 10% of rated value and negative 5% of the rated value, under a specific load, the motor will overheat.
The three-phase voltage of the power supply is asymmetric, and the phase-to- phase imbalance of the three-phase voltage of the power supply exceeds 5%, which will lead to overheating of the winding.
Experience shows that more than 85% of the burned agricultural motors are caused by phase loss operation, thus, phase loss protection devices shall be installed on motors.

Second, water pump: the power is not matched, and the motor runs overload for a long time, which makes the temperature too high.
The motor is started too frequently or that is rated as short-time or intermittent working system works continuously. The number of starts shall be limited, the thermal protection shall be selected correctly and used according to the rated value on the motor.

Figure 2: Water pump unit.

Third, motor itself: the connection method is wrong, and the O-shape is wrongly connected to the Y-shape, which makes the temperature of the motor sharply rise.
The stator winding has phase-to-phase short circuit, turn-to-turn short circuit or local ground. The motor is overheated locally in not serious condition, and the insulation is burnt out in severe condition.

The squirrel cage rotor is broken or defective. When the motor runs for 1 to 2 hours, the iron core temperature rises rapidly.
If the ventilation system fails, check whether the fan is damaged, the rotation direction is correct, and the ventilation duct is blocked.
Bearing is seriously worn and rotor eccentric bore sweeping make the stator and rotor iron cores rub against each other and produce metal impact sound. The iron core temperature rises rapidly. In serious cases, the motor smokes and even the coil is burned.

Forth, working environment: motor winding is affected with damp or dust and grease dirt are attached to the winding, resulting in low insulation. Insulation resistance of motor shall be measured, cleaned and dried; the ambient temperature is too high.

Solutions

When environment temperature exceeds 35 Celsius degrees, the high air inlet temperature will make the motor temperature too high, so what should be done foremost is to try to improve its working environment. For example, putting up a shed for sunshade.

Note: if a fault occurs due to electrical reasons, it should be repaired by an electrician with a professional qualification certificate. People with a little knowledge should not repair blindly to prevent personal injury accidents.

Overheating

Figure 3: Bearing failure of water pump.

Reasons: broken bearing; small clearance between rolling bearing and bracket cover. The pump shaft is bent or the two shafts are not concentric; too tight tape; shortage of oil or poor oil quality; the balance hole on the impeller is blocked, and the impeller loses balance, increasing the thrust to one side.

Solutions

Replace bearing; remove the rear cover and install a gasket between the bracket and the bearing seat; investigate the pump shaft or adjust the concentricity of the two shafts; properly loosen the tightness of belt; add clean grease, which accounts for about 60% of the clearance in the bearing; remove the blockage in the balance hole.

Insufficient Flow

Reasons: the power speed is not matched or the belt slips, resulting in low speed; axial flow pump blade installation angle is too small; insufficient head, and the pipeline is too long or the pipeline has a right-angle bend; high suction lift; bottom valve, pipeline and impeller are partially blocked or the impeller is damaged; serious water leakage of outlet pipe.

Solutions

Restore the rated speed, remove the belt oil dirt, and adjust the tightness of belt; adjust the blade angle, lower the installation position of the water pump, shorten the pipeline or change the bending of the pipeline; seal the air leakage of the water pump and tighten the packing; remove the blockage and replace the impeller; replace the minus leakage ring and plug the water leakage.

Figure 4: Water pump overhauling.

Unable to Pump Water

The reason is that there is air in the pump body or gas accumulated in water inlet pipe, or the bottom valve is not closed tightly, the filling water is insufficient, the vacuum pump packing is seriously leaking, and the sluice valve or flap valve is not closed tightly.

Solutions

First lift the water, then fill the pump body with water, and then start the pump. At the same time, check whether the check valve is tight and the pipeline and joint have air leakage. If air leakage is found, apply lubricating oil or ready-mixed paint on the joint after disassembly, and tighten the screws.

Check the oil sealing ring of the water pump shaft. If it is worn seriously, replace it with a new one. If there is air or water leakage in pipeline, the chances are that the nut is not tightened during installation. If the leakage is not serious, cement can be applied at the place where the air or water leaks, or cement slurry mixed with asphalt oil can be applied. For temporary repairs, apply some wet mud or soft soap.

If there is water leakage at the joint, the nut can be tightened with a wrench. If the water leakage is serious, it must be reassembled again and the cracked pipe must be replaced; lower the head and press the nozzle of the water pump into the water surface below 0.5 meters.

Fierce Vibration

Main reasons are as follows: imbalanced electric rotor; poor connection of coupling; worn and bending bearing; loose and cracked parts of rotating parts; infirm pipeline support, etc.

Solutions

Respective measures are adjustment, repair, reinforcement, straightening and replacement, etc.

Related Info