Analysis and modification of bearing failure of medium-sized motor

In the auxiliary equipment of the power plant, the electric motor is used as the main power source to complete and ensure the normal operation of the unit, so the loss caused by the failure of the motor is also quite large, especially the medium-sized motor, which can seriously affect the safety of the unit. run. According to our statistics on motor faults, the bearing is damaged or the motor is faulty due to bearing damage, accounting for more than 60% of all motor faults. Therefore, solving the damage of the motor bearing is also an important problem to solve the motor fault. According to analysis, medium-sized motors are mostly "end-cap sliding bearing type" structures and "end cap rolling bearing type" structures. After our summary and analysis of various medium-sized motor maintenance experience, we believe that there are the following problems:

1. End cap sliding bearing type: Most of these motors have the phenomenon of bearing bush heating and oil leakage, which causes corrosion of the stator coil of the motor, and causes excessive oil and ash accumulation inside the motor, resulting in poor ventilation. The motor temperature is too high and is damaged.

2. Box-type high-voltage motor: This motor is a new type of motor produced in China in recent years. Its performance and shape are superior to the "JS series" motor. However, some of the motors produced by some manufacturers have some defects in the design of the bearings, resulting in more bearing failures in the running of the motor. The structure of these motors is such that a grease damper with a small gap from the bearing is placed on the outside of the bearing, so that the grease inside the bearing can be kept sufficient, but this structure has the following disadvantages:

(1) It is not conducive to the heat dissipation of the bearing and the circulation of the grease, so that the temperature of the bearing rises during operation, the performance of the grease is lowered, and the vicious cycle of the temperature rises again, causing the bearing to be damaged.

(2) Due to the existence of the bearing oil retaining plate, the motor can not be inspected when the motor is under minor repair. When the motor is overhauled, the oil retaining disk can not be cleaned and the bearing can not be cleaned. Only the replacement causes unnecessary Waste.

(3) Due to the need to remove the oil retaining disc and the replacement of the bearing during repeated inspections, the loosening of the hole between the oil retaining disc and the shaft causes the oil retaining disc to escape from the shaft during operation, causing malfunction.

3. Double-bearing motor: Some medium-sized motors produced in China now use a double-bearing structure on the load side. Although this increases the radial load carrying capacity on the load side, it also brings difficulty in maintenance. In the overhaul of the motor, the bearing cannot be cleaned and inspected and must be replaced. Otherwise, the quality of the inspection cannot be guaranteed, resulting in an increase in maintenance costs. In addition, most of the motors of this structure have higher temperatures during operation, which reduces the service life of the bearings and damages them.

4. Structural problems of bearing accessories: At present, most of the bearing accessories of China's motors are internal and external oil cap structures. The shortcoming of this structure is that the sealing effect is poor, the dust inside and outside the motor is easily sucked into the bearing, and the wear of the bearing is accelerated and damaged; then the structure of the bearing accessory heats, cools and circulates the grease. Does not work, so the bearing's operating temperature is higher, the life is reduced, causing the motor to fail to reach an overhaul cycle. According to our analysis of the imported medium-sized motor structure, firstly, all the sealing devices are installed on both sides of the bearing to ensure the cleaning inside the bearing; secondly, the positioning and cooling device are installed on the outer side of the bearing, and the oil chamber space of the bearing is compared. Large, this greatly reduces the temperature in the bearing operation, and obtains good lubrication, extending the service life of the bearing.

5, bearing selection problem: According to our analysis and calculation of the motor bearing, bearing failure and bearing selection have a great relationship. From the comparison of China's motor and imported motor, the load side bearing of domestic medium-sized motor is generally selected as "medium-sized roller bearing". The radial load carrying capacity of the bearing greatly exceeds the calculated value, but the allowable rotational speed is very different from the actual rotational speed of the motor, resulting in the bearing not reaching the rated service life. However, the bearings on the load side of the imported medium-sized motor are generally selected from the larger "light ball bearings", while the no-load side is the "light roller bearings" that are smaller than the load side, which not only ensures the bearing capacity of the bearings, but also the bearings. The allowable speed greatly exceeds the actual speed of the motor, so it can reach or exceed the service life of the bearing.

Transformation process and method:

After our analysis of the above various motors, we have carried out the transformation of the motor bearings in our factory for many years and received good results. Our factory was built and put into production in 1958. In the early 1970s, we carried out the transformation of bearings for the problem of "end cap sliding bearing" motors, and accumulated a lot of experience. In the 1980s, the factory introduced and imported the imported boilers and all the auxiliary equipment. After years of operation and several overhauls, we found out the advantages of the structural design of the imported medium-sized motor, and further modified it in combination with the actual structure of the domestically produced motor.

In the transformation of the motor bearing, we first demonstrated the selection of the bearing and found that the above problems existed, that is, the bearing was recalculated, designed and selected. The transformation plan is based on the actual structural size of the motor, and the structure of the imported motor bearing and accessories is used as much as possible. After the calculation of the motor operation after the transformation, the service life of the bearing has been more than doubled, which solves the problem of frequent damage of most medium-sized motor bearings, and provides a reliable guarantee for the safe operation of the unit.