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When the imported bearing rotates, the raceway surfaces of the inner ring and outer ring of the imported bearing are in rolling contact with the rolling element, so the running track is a dark surface.
The running track attached to the raceway surface is not abnormal, so the load conditions can be known. Therefore, when removing the imported bearing, please pay close attention to and observe the running track of the raceway surface.
If you carefully observe the running track, you will know that it only bears radial load, large axial load, moment load, or extreme uneven rigidity on the bearing housing.
It can be checked whether the unexpected load is added to the Running Track bearing and whether the installation error is Guoda, which will become a clue to investigate the cause of bearing damage.
Premature aging of rolling bearings will cause equipment shutdown. Combined with the author’s motor maintenance practice, this paper introduces the experience of Running Track preventing premature aging of rolling bearings.
The reasons for premature aging of rolling bearings are: too tight fit, poor lubrication, misaligned installation, Running Track strong vibration, material fatigue, pollution and corrosion, etc.
1. Too tight fit
When the bearing inner ring is forcibly sleeved into the journal, the light one will produce a severely worn annular track at the bottom of the raceway, Running Track and the heavy one will have cracks or peeling on the inner, outer ring and ball of the raceway.
Cause: the clearance between the ball and the slideway is too small, the torque increases, the friction increases, and the working Running Track temperature of the bearing is too high, which aggravates the wear and fatigue of the bearing and leads to failure.
Prevention method: restore the radial clearance of the bearing and reduce Running Track the interference.
There are two inspection methods for bearing assembly quality:
Visual inspection method: when the bearing is installed in the bearing chamber of the motor end cover and the end cover is rotated by hand, if the bearing rotates freely and flexibly Running Track without vibration and shaking up and down, it is regarded as qualified.
Feeler gauge inspection method: assemble the motor end cover with bearing on the base stop, and use a 0.03mm thick feeler gauge to check the radial clearance around the bearing.
If the large clearance position is just above the center (horizontal installation of motor), the assembly is correct and reliable, otherwise, the installation is poor. The position of the end cap shall be properly adjusted and reassembled until it is qualified.
The reason is a serious lack of grease or dry aging of grease. Due to the friction heat generated by the high-speed operation of the motor, the bearing temperature is too high and oxidation discoloration occurs, which is manifested in that the ball, cage, inner ring and Journal of the bearing turn brown or blue.
Prevention method: determine the oil replenishment and oil change time according to the four factors of motor operation time, ambient temperature, load condition and quality of lubricating grease.
In general, the oil shall be replenished once when the motor runs for 6000 ~ 10000h; The oil shall be changed once after 10000 ~ 20000 h operation. The oil change of motors with 2 poles or more shall be 1 / 2 ~ 2 / 3 of the volume of bearing chamber, and high-quality lithium base grease (code ZL-2) shall be used.
3. The installation is not centered
If the installation is not centered, there are not only bead marks on the bearing slide, but also uneven wear marks of the ball and deflection. When checking the radial clearance on both sides of the bearing with a feeler gauge, it will be unequal and the difference is large.
The reason may be that the iron hammer has directly knocked on the outer ring of the bearing; The drive belt is pulled too tight (gear engagement); Make the center lines of the driving wheel and the driven wheel not parallel. When the deflection is greater than 1 / 1000,
the bearing operating temperature will be too high, the slideway and ball will be seriously worn, the rotating shaft will be bent and the pressing surface of the end cover bolt is not perpendicular to the bolt axis.
Correct installation method: use a steel pipe sleeve with smooth and flat end face and almost the same thickness as the inner ring of the bearing to press the bearing at the correct position of the clean journal. The force shall be uniform and not too strong. Then check the allowable runout value of shaft end radial according to different motor speeds.
4. Strong vibration
When the motor core fails, the bearing will vibrate strongly. The reasons are: the iron core is deformed by heating; Motor bearing aging; The bending deformation of the rotating shaft is large; The tightening bolts at the end cover stop are loose due to vibration; Weak foundation causes bearing vibration.
Prevention method: turn the iron core into a small one and soak the surface of silicon steel sheet and the opened gap with silicon organic varnish 1052; Replace new bearings of the same model;
Withdraw the rotor core and straighten the bending part of the rotating shaft; 180 ° symmetry method is adopted; Tighten the end cap stop bolts; Reinforce the foundation and tighten the anchor bolts.
5. Material fatigue
Due to the fatigue of metal materials and the irregular fragments falling off the bearing raceway and ball surface, if mixed in the grease, the working noise will increase, the ball will be in a sliding state,
resulting in the increase of the radial clearance of the bearing and the allowable radial runout value of the shaft end will increase by 2 ~ 3 times. The determinants of bearing fatigue include: motor load, speed, air gap, end cover type, material toughness, grease quality and grease addition.
Prevention method: according to the motor operation records, when the light load working current is more than 60% of the rated value and runs to 2000 ~ 25000h,
the medium load working current is 60% ~ 80% of the rated value and runs to 15000 ~ 20000 h, and the heavy load working current is 80% ~ 100% of the rated value and runs to 10000 ~ 15000 h, the normal fatigue of bearing materials shall be considered and new bearings of the same model shall be replaced.
6. Pollution and corrosion
At this time, red and brown spotted corrosion appears on the surface of raceway and ball, and the working noise increases compared with the sound of new bearing.
The reason is that the assembly site is not clean, such as water gas, acid, alkali and toxic gas; Contamination of tools and hands; Poor quality lubricating fingers are used.
Prevention method: keep the environment, tools and clean when assembling the bearing; Clean the bearing thoroughly; Replace high-quality lithium grease.