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What is the appropriate installation height of the water pump and precautions when using a submersible pump

Feb 08, 2023
The key to the installation technology of centrifugal pumps is to determine the installation height of the pump. This height refers to the vertical distance from the water surface of the water source to the centerline of the impeller of the pump. It cannot be confused with the allowable suction vacuum height. The allowable suction vacuum height marked on the pump nameplate or product manual refers to the vacuum value on the water inlet section of the pump, and It is measured under the condition of 1 standard atmospheric pressure and water temperature of 20 degrees Celsius. It does not consider the water flow conditions after the suction pipe is matched. The installation height of the water pump should be the remaining value after deducting the loss lift of the suction pipe from the suction vacuum height, which should overcome the actual topographical suction height. The installation height of the water pump cannot exceed the calculated value, otherwise, the water pump will not be able to pump water. In addition, the influence on the calculated value is the resistance loss head of the suction pipe. Therefore, it is advisable to adopt the shortest pipeline layout and install as few fittings as possible. It may also be considered to properly equip water pipes with larger diameters to reduce the flow rate in the pipes.

It should be pointed out that when the elevation and water temperature of the pump installation site are different from the test conditions, for example, the local altitude is above 300 meters or the temperature of the water being pumped exceeds 20 degrees Celsius, the calculated value should be corrected. That is, the atmospheric pressure at different altitudes and the saturated vapor pressure when the water temperature is higher than 20 degrees Celsius. However, when the water temperature is below 20 degrees Celsius, the saturated vapor pressure is negligible.

From the perspective of pipeline installation technology, the water suction pipeline must be strictly sealed and must not leak air or water. Otherwise, the vacuum degree at the water inlet of the water pump will be destroyed, the water output of the water pump will be reduced, and even the water cannot be pumped in severe cases. Therefore, it is necessary to do a good job in the interface work of the pipeline to ensure the construction quality of the pipeline connection.

     The submersible pump works underwater. It has a compact structure and light weight. It does not pump water from the well and does not need a long drive shaft. Therefore, submersible pumps are very suitable for rural well water irrigation, and QW type submersible pumps are more widely used. This kind of submersible pump adopts waterproof measures such as mechanical seal or air seal to keep the inside of the motor dry and free from water intrusion. Pay attention to the following points when using it:
   (1) Check whether the air vent, water vent, oil drain hole and the seal of the cable joint of the submersible pump are loose, and must be tightened if loose.
   (2) Use a 500 volt meter to check the insulation resistance. It should not be less than 0.5 megohms. If it is lower than this value, open the water and vent holes for drying or drying.
   (3) Check the cable of the submersible pump. If it is cracked or broken, it should be replaced to avoid leakage.
    (4) Before starting the submersible pump, check all the circuits and switches to see if the wiring is correct and secure, then idle on the ground for 3 to 5 minutes (the time should not be too long, so as not to damage the parts or burn out the motor windings), and check the motor Whether the direction of rotation is correct, if there is no problem with the above, it can be put into water for use.
   (5) When the submersible pump is used in water, the cable must not be stressed, and it should be tied to the wooden frame at the wellhead with ropes. The maximum depth of the electric pump into the water is 3 meters, and the minimum depth is 0.5 meters (calculated from the center of the impeller).
    (6) During the operation of the submersible pump, the change of the water level in the well should be observed frequently. The motor must not be exposed to the water surface or sink into the mud, so as not to affect the heat dissipation of the motor and burn out the winding. The electric pump should be raised and lowered at any time with the change of the water level in the well. If the water volume decreases or is interrupted, the cause should be found out immediately or stopped for inspection. The cable should not rub against the well wall, so as to prevent the well water from penetrating into the motor along the cable core after the cable is worn out.
    (7) For submersible pumps with new or newly replaced integral sealing boxes, check whether the sealing is good after 50 hours of use, and then check once a month, and check whether the shielding sleeve between the motor rotor and stator is well sealed.
    (8) After one year of use, the corrosion of the submersible pump should be checked, and the rust should be removed and painted. If the submersible pump is not used for a long time, it should be carefully checked and stored in a dry and ventilated house.

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