Failure Analysis of Mini DC Water Pump
Definition of 12v miniature DC pump:
Generally, the machines that lift liquids, transport liquids, or increase the pressure of liquids, which convert the mechanical energy of the prime mover into liquid energy to achieve the purpose of pumping liquids are collectively called pumps.
(1) The magnetic pump shaft is broken. The material used for the pump shaft of the CQB magnetic pump is 99% alumina porcelain. The main reason for the pump shaft breaking is that the shaft is twisted due to the dry running of the pump and the dry grinding of the bearings. When the pump is disassembled and inspected, it can be seen that the bearings have been severely worn. The main way to prevent the pump from breaking is to avoid the dry running of the pump.
(2) The bearing of the magnetic pump is damaged. The bearing material of CQB magnetic pump is high-density carbon. If the pump is cut off or there are impurities in the pump, the bearing will be damaged. If the coaxiality between the inner and outer magnetic rotors of the cylindrical coupling is not guaranteed, it will directly affect the life of the bearing.
(3) The magnetic pump cannot pump liquid. The failure of the magnetic pump to pump liquid is the most common failure of the pump, and there are many reasons for it. Firstly, check whether the suction pipe of the pump is leaking, check whether the air in the suction pipe is discharged, whether the amount of liquid filled in the magnetic pump is sufficient, whether there is debris in the suction pipe, and whether the pump is reversed. (Especially after the motor is changed or the power supply line is overhauled), also pay attention to whether the suction height of the pump is too high. If the problem still cannot be solved through the above inspection, the pump can be disassembled and checked to see if the pump shaft is broken. It should also be checked whether the moving ring and static ring of the pump are intact, and whether the entire rotor can move slightly axially. If the axial movement is difficult, check whether the carbon bearing is too tightly combined with the pump shaft.
It is worth noting that the magnetic drive pump has been repaired several times and no problems can be found, and attention should be paid to whether the magnetic coupling is working properly. Bearings, inner magnetic rotors and spacers all generate heat during operation, which will increase the operating temperature, on the one hand, reduce the transmitted power, on the other hand, it will cause a lot of trouble for the magnetic pump that transports easily vaporized liquid. The power transmitted by the magnetic steel is a continuous decline curve with the increase of temperature. Generally, below the working limit temperature of the magnetic steel, the reduction of its transmission capacity is reversible, and it is irreversible above the limit temperature, that is, the magnetic steel is cooled. Later, the lost delivery capacity can no longer be restored. Under special circumstances, when the magnetic coupling slips (out of step), the eddy current heat in the spacer will increase sharply and the temperature will rise sharply. If it is not handled in time, it will cause the magnetic steel to demagnetize and cause the magnetic coupling to fail. Therefore, the magnetic pump should be designed with a reliable cooling system. For the medium that is not easy to vaporize, the cooling circulation system usually draws the liquid flow from the outlet of the impeller or the pump, and returns to the suction port through the bearing and the magnetic transmission part. For the medium that is easy to vaporize, a heat exchanger should be added or the liquid flow should be led out of the pump. The storage tank should avoid heat returning to the suction port. For media with solid or ferromagnetic impurities, consider filtering, and for high temperature media, consider cooling to ensure that the magnetic coupling does not exceed the operating limit temperature.
When considering whether the rotation speed is sufficient, first check whether the rotation speed of the motor itself is normal, which can be measured with a tachometer. When the rotation speed of the motor is normal, consider whether the magnetic coupling slips.
(4) Insufficient head. The reasons for this failure are: there is air in the conveying medium, the impeller is damaged, the speed is not enough, the specific gravity of the conveying liquid is too large, and the flow is too large.
(5) Insufficient flow. The main reasons for insufficient flow are: impeller damage, insufficient rotation speed, excessive lift, and clogging of debris in the pipe.
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