What causes high current in horizontal multi-stage water pumps?

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Among the various faults that can occur in horizontal multi-stage water pumps, high current in the associated motor is a relatively typical one. Troubleshooting this issue involves many factors, and it is quite difficult and complicated to resolve. The following is a summary of several common faults: 1. High current in horizontal multi-stage pumps caused by improper selection: As fluid machinery, the two most important parameters for horizontal multi-stage pumps are flow rate and head. During operation, the flow rate and head parameters of a horizontal multi-stage pump do not remain constant; that is, when the actual head does not reach the rated head, the head margin of the horizontal multi-stage pump is automatically converted into flow rate. Often, designers from design institutes and similar entities take into account factors such as increased pipe losses and reduced efficiency due to wear of the pump when selecting horizontal multi-stage pumps, and thus increase the head margin. In cases where the head margin is particularly large, it is easy for the water pump to operate at a flow rate far exceeding its rated value. If the motor power is not sufficient, this can lead to overcurrent in the motor, and horizontal multi-stage water pumps may also experience problems such as cavitation and vibration. 2. Horizontal multi-stage pumps experience high current levels due to mechanical friction. The resistance generated by this mechanical friction leads to higher current demands on the motor driving it. There are various factors contributing to this: 1) The shaft of the horizontal multi-stage pump may be bent, or there may be excessive radial play in different parts of the rotor. During rotation, the pump shaft or its bushings come into contact with the guide vane sleeves, and the impeller rubs against the sealing rings, all of which result in increased operating loads. 2) The tilt of the balance disk in ordinary horizontal multi-stage water pumps is too large; this is mainly due to excessive axial movement of the balance disk. During operation, certain parts of the balance disk frequently rub against the balance plate, thereby increasing the power consumption of the motor. 3) An uneven distance between the impellers indicates poor assembly quality of the water pump; in multi-stage centrifugal pumps, the uneven distances between the impellers in different stages cause some of these impellers to rub against the intermediate section or the sealing rings, thereby increasing the load on the motor. 4) The packing gland is tightened too much. When filling the packing, over-tightening the gland increases the friction between the packing and the pump shaft sleeve, thereby increasing the load on the motor. 5) In ordinary horizontal multi-stage water pumps, a balance pipe connects the balance chamber to the suction section; if this balance pipe becomes blocked, it prevents the balance disc from opening, resulting in an unbalanced axial thrust. This leads to direct friction between the balance disc and the balance plate, causing high load on the motor, and in some cases preventing it from starting at all. 6) Excessive wear of the balance disk and balance plates in ordinary horizontal multi-stage water pumps: When these components are severely worn, the axial suction side of the horizontal multi-stage water pump shifts, causing the impeller to come into contact with and rub against the mouth ring. This results in a significant increase in load, rapid damage to the impeller, and reduced efficiency of the water pump (due to misalignment between the impeller and the guide vanes); in severe cases, the water pump may not be able to start at all. 7) The clearance between the couplings is too small; when the balance discs and plates are severely worn, the water pump moves towards the axial water intake side, which causes the coupling of the water pump to collide with that of the motor, thereby increasing the load on the motor. 8) In horizontal multi-stage water pumps, bearing jamming occurs due to lack of oil or other reasons, resulting in high load on the motor. 3. The high current in horizontal multi-stage water pumps is caused by insufficient voltage; due to low voltage in the power grid, the current increases while the power output remains unchanged, resulting in overcurrent ； Furthermore, in some cases where variable frequency drives are used for speed control, since some of these drives adjust the frequency by changing the voltage, the current level becomes excessive at low frequencies.