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Solutions to the high temperature of the motor bearing of the pump motor in addition to the salt water in the power plant

12 Apr 2021Email

A power plant desalinated water station has 5 external desalinated water pumps, which are responsible for the desalinated water supply of the whole plant. The motor drive of the 5 water pumps: model Y3315M-2WTH; power 132KW. However, the temperature of the bearings of these 5 motors remains high (up to 90℃) in the hot summer weather. After many times of motor disassembly and inspection, bearing replacement and grease brand debugging, they still do not get better. Every summer during the high temperature period, operators and maintenance personnel are required to conduct special inspections of these 5 motors, which brings a great workload to the production operation and also brings greater pressure to the stability of the demineralized water pipe network of the whole plant. risk.

 

Analysis on the Causes of High Temperature of Motor Bearings for Desalting Pump

Because this series of motors are simply housing and bearing temperature is high, and the vibration of the motor body and the bearings at both ends, motor sound, current, etc. are all within the normal range, so it can be ruled out due to loose anchor bolts, unbalanced motor rotors, and coupling. The temperature rise caused by poor shaft alignment and other factors.

(1) High ambient temperature: For motors, especially pumps exposed on site, high temperature weather and direct sunlight have a particularly significant impact on the temperature of motor bearings on site, especially from 3 to 5 in the afternoon, when the temperature of motor bearings almost reaches The peak temperature of the day was about 10°C higher than that at night.

(2) The external load fluctuates greatly: when the external supply demineralized water pump is operating normally, three pumps are running. When the external load suddenly increases, the pressure of the demineralized water pipe network will decrease, and the pump output will increase, causing the motor to run overloaded and the casing temperature. The increase causes the bearing temperature to be higher.

(3) Unreasonable grease filling: Insufficient or excessive grease filling of the motor will cause the temperature of the bearing to be higher, and the filling of grease is not like the lubricating oil, which can intuitively read the liquid level. Operate based on the experience of maintenance personnel, which makes it difficult to grasp the amount of grease each time. Or the grease is not filled in time when the specified time is reached, and the long-term operation will cause the grease to emulsify and deteriorate, which will not provide good lubrication and cooling.

(4) The temperature of the motor itself is high: Considering that the temperature of the front end cover is generally higher than the temperature of the bearing at the drive end of the motor when the motor is running, and the motor maintenance unit Zhongke Electromechanical has evaluated this series of motors, the inspection result is that the internal structure of this batch of motors exists The problem is that the heat from the inner stator and rotor cores cannot be dissipated well. At the same time, this batch of motors has been running continuously since the desalination station was put into operation, and the operating life is long, coil aging, poor heat dissipation, etc. will also cause the temperature of the motor itself to rise.

 

Solution to high temperature of motor bearing of pump motor except salt water

(1) Motor repair: Check the motor stator windings. If there is scan boring, slight scan boring, motor coil aging or unqualified insulation, the motor stator winding needs to be replaced; check whether the motor rotor dynamic balance meets the standard, and if it does not meet the requirements, it needs to be renewed. Counterweight to make the dynamic balance reach the standard; check the motor shaft to see if there is any bending of the shaft center; check whether the drive end of the motor and the non-drive bearing chamber are worn, whether the bearing runs out of the outer ring or the inner ring; replace the two motors 2 end 6317/C3 bearings, back-loaded for trial shipment.

(2) Motor transformation: After the above-mentioned repairs, the trial operation results of this series of motors were not satisfactory. The motor was disintegrated and found that the motor heats from the stator and rotor cores inside the motor. The detected rotor temperature is 70°C and the stator temperature is 72°C. Since the stator and rotor cores and internal cooling have been finalized during the design of the motor, the status quo cannot be changed through maintenance. After communicating with the equipment center and the electrical professional group to obtain agreement, it was decided to replace the cooling fan and the fan cover to drill holes to increase the air intake to cool the motor stator. At the same time, the drive end cover adds a draft hood to provide ventilation and cooling for the drive end bearing. The results of the no-load test again are as follows: the ambient temperature is 35°C, the measured stator temperature is 55°C, and the drive end bearing temperature is 52°C. After reinstallation, the maximum motor drive end bearing temperature is 60°C. The cooling effect is obvious, and the test operation results show that the highest bearing temperature at the drive end of the motor is 60°C.

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