Precautions for use and maintenance of submersible pumps

Submersible pumps are prone to various problems during daily operation. In order to extend their service life and ensure the normal operation of the submersible pump and related systems, comprehensive maintenance and upkeep of the submersible pump and its control system should be carried out at least once a year.

Today we will learn about some of the main factors that affect the operation of submersible pumps, key points for daily maintenance and upkeep of submersible pumps, as well as common faults and troubleshooting methods.

1. The main factors affecting the operation of submersible pumps

In general, the main factors that affect the normal operation of submersible pumps are as follows:

1. Leakage problem.

A submersible pump, as the name suggests, is a machine pump that operates underwater, so leakage is one of the important factors affecting the normal operation of the submersible pump.

2. Locked rotor.

When the submersible pump is blocked, a blocking current of 5-7 times the normal full load current will be generated in the stator winding. Without corresponding protective measures, the submersible pump will quickly burn out. There are many reasons for the blockage of submersible pumps, such as impeller jamming, mechanical seal fragments jamming the shaft, and entanglement of dirt.

3. The power supply voltage is too low or the frequency is too low.

4. Wear and corrosion.

Wear and tear will greatly reduce the performance of the electric pump, resulting in a decrease in flow rate, head, and efficiency. Rust on the impeller and pump cover will also cause rotor blockage. The corrosion of submersible pump parts not only affects the performance of the pump, but also shortens its service life.

5. Cable breakage or breakage. Cable breakage and breakage not only easily cause electric shock accidents, but also the water pump is likely to be in a two-phase working state during operation, which not only does not discharge water but also easily damages the motor.

2. Preparation work before using submersible pumps

1. Check if the cable is broken or broken.

Before use, both observe the appearance of the cable and use a multimeter or megohmmeter to check if the cable is connected. There should be no leakage at the cable outlet.

Before using a new pump or starting a standby pump that has been left for a long time, a megohmmeter should be used to measure the insulation between the stator and the casing, which should not be less than 1 megaohm. Otherwise, the motor winding should be dried to improve the insulation level.

3. Check if the submersible pump is leaking oil.

The possible sources of oil leakage in submersible electric pumps include cable connections, sealing at the oil screw in the sealing chamber, and O-ring seals at the sealing points.

When checking, it is necessary to determine whether there is really oil leakage. The reason for the oil leakage at the refueling screw is that the screw is not tightened or the oil resistant rubber pad under the screw is damaged.

If it is determined that there is oil leakage at the O-ring seal, it is mostly due to the failure of the O-ring seal. At this time, it is necessary to disassemble the electric pump and replace the sealing ring.

Before reusing a submersible pump that has been out of service for a long time, the impeller should be turned before starting to prevent rusting of the components and failure to produce water, which may damage the motor winding.

3. Precautions during the operation of submersible pumps:

When the submersible sewage pump is tested without water, the operating time must not exceed the rated time.

The volume of the suction tank can ensure that the water level is high when the submersible sewage pump is started and during operation, to ensure the cooling effect of the motor and avoid frequent starting and stopping caused by large water level fluctuations. The frequent starting of large and medium-sized submersible sewage pumps has a significant impact on the performance of the pump.

2. When the humidity sensor or temperature sensor emits an alarm, or when the pump body vibrates or makes noise during operation and the output line is abnormal;

When the output water volume, water pressure drops, and electrical energy consumption significantly increases, the submersible sewage pump should be immediately shut down for maintenance.

3. When some poorly sealed submersible pumps are immersed in water for a long time, even if they are not used, the insulation value will gradually decrease and eventually cannot be put into use. Even in a shorter period of time than the continuous operation of submersible sewage pumps in water, insulation will disappear.

Therefore, sometimes the standby function of a submersible pump in the suction pool cannot be achieved. If conditions permit, it can be used as a dry standby outside the pool. When a running submersible pump fails, it should be immediately stopped and lifted up, and then the standby pump can be put down again.

4. The submersible pump should not be started or stopped too frequently, otherwise it will affect the service life of the submersible pump.

When the submersible pump stops, the water in the pipeline flows back. If it is restarted immediately, it will cause the load of the electric pump to be too heavy and bear unnecessary impact loads;

In addition, frequent starting and stopping of submersible pumps will damage components with poor impact resistance and cause damage to the entire electric pump.

5. After shutdown, the motor cannot be restarted until it has completely stopped running.

When checking the electric pump, the power must be cut off.

7. When the submersible pump is working, do not wash items, swim or let livestock enter the water nearby to avoid electric shock accidents when the pump leaks electricity.

4. Maintenance and upkeep of submersible pumps

1. Regularly refuel and change the oil regularly.

The sealed oil of the submersible pump must be replaced every 1000 hours of operation, and the oil inside the motor must be replaced once a year.

Regular replacement of the upper and lower end caps, skeleton oil seals in the bearing chamber, and lithium based lubricating oil is required for the water filled submersible pump to ensure good lubrication.

For small submersible pumps with mechanical seals, it is necessary to frequently open the sealing chamber and fill the oil screw hole with lubricating oil to ensure that the mechanical seal is in a good lubrication state and its working life is fully guaranteed.

2. Replace the sealing box in a timely manner

If a significant amount of water is found leaking into the interior of the electric pump (normal leakage rate is 0.1mL/h), the sealing box should be replaced in a timely manner, and the insulation resistance value of the motor winding should be measured.

If the insulation resistance is less than 0.5 megaohms, drying treatment is required, using the same method as drying the winding of a general electric motor.

When replacing the sealing box, attention should be paid to the integrity of the outer diameter and O-ring seal in the shaft hole, otherwise a large amount of water will leak into the interior of the submersible pump and damage the motor winding.

3. Regularly measure the insulation resistance value.

Measure the insulation resistance value of the stator winding of the electric pump to the casing using a 500V or 1000V megohmmeter. Only those with a resistance of 1 megohm or more (minimum not less than 0.5 megohm) can be used. Otherwise, the winding should be repaired or dried to ensure safety during use.

4. Reasonable storage

When not in use for a long time, the submersible sewage pump should not be immersed in water for a long time and should be stored in a dry and ventilated room.

When storing the rubber cables of submersible pumps, it is important to avoid exposure to sunlight, as they may age and crack on the surface. In severe cases, this can lead to a decrease in insulation resistance or allow water to enter the outlet box of the submersible pump through the cable sheath, resulting in serious consequences such as short circuits between power lines or zero insulation resistance of the winding to ground.

5. Timely carry out rust prevention treatment on the surface of the submersible pump.

After one year of use, the submersible pump should be coated with rust prevention treatment in a timely manner based on the corrosion condition of the surface of the submersible pump.

The internal paint rust prevention should depend on the pump type and corrosion situation. In general, when the interior is filled with oil, it will not rust, and there is no need to paint the interior at this time.