Why does your bearing always have a shorter service life than others?
These points are critical!
Bearings are an indispensable and important part of machinery, and their service life has attracted more and more attention. However, in daily use, we can clearly observe that under the same working conditions, bearings with the same appearance and model have very different actual life. Why is this? Beware of the following!
Tight fit 01
When the bearing inner ring is forced into the journal, the lighter one will produce a severely worn annular track at the bottom of the raceway, and the heavy one will have cracks or peeling on the slideway, outer ring and balls.
The gap between the ball and the slideway is too small, the torque increases, the friction increases, and the bearing operating temperature is too high, which makes the bearing wear and fatigue worse and fail.
Restore the radial clearance of the bearing and reduce the amount of interference.
There are two ways to check the quality of bearing assembly:
Visual inspection method: After the bearing is installed in the bearing chamber of the motor end cover, when the end cover is rotated by hand, if the bearing rotates freely, flexibly, without vibration and shaking up and down, it is deemed qualified.
Feeler gauge inspection method: Assemble the end cover of the motor with bearing on the machine base, use a 0.03mm thick feeler gauge to check the radial clearance of the bearing. If the maximum clearance position is just above the center (horizontal installation of the motor) ), it means the assembly is correct and reliable, otherwise, it is a poor installation. The position of the end cover should be adjusted appropriately and reassembled until it is qualified.
Poor lubrication 02
The reason is a severe lack of grease or dry and aging grease. Due to the friction and heat generated by the motor running at high speed, the bearing temperature is too high and oxidizes and discolors. The bearing balls, cage, inner ring and their journals turn brown or blue.
According to 4 factors such as the running time of the motor, the ambient temperature, the load condition, and the quality of the lubricating grease, determine its oil supplement and oil change time. Under normal circumstances, the motor should be replenished once for 6000~10000h; the oil should be changed once for 10000~20000h, and the oil change should be 1/2~2/3 of the volume of the bearing chamber, and high-quality lithium grease should be used.
Installation is not centered 03
If the installation is not centered, not only will there be bead marks on the bearing slide, but also the ball wear marks will be uneven, and deflection will occur. When the radial clearance on both sides of the bearing is checked with a feeler gauge, the difference will be large.
It may be directly hitting the outer ring of the bearing with an iron hammer; the transmission belt is pulled too tightly (gear engagement); the center lines of the driving wheel and the driven wheel are not parallel. When the deflection is greater than 1/1000, the bearing operating temperature will be too high, the slideway and balls will be severely worn, the rotating shaft will be bent and the end cover bolt pressing surface will not be perpendicular to the bolt axis.
Correct installation method
Use a steel tube sleeve with a smooth end surface and almost the same thickness as the inner ring of the bearing to press the bearing on the correct position of the clean journal. The pressing force should be even and not too strong. Then check the allowable deflection value of the shaft end according to the different speeds of the motor.
Strong vibration 04
The iron core is heated and deformed; the motor bearing is aging; the rotating shaft is bent and deformed; the bolts tightened on the end cover are loose due to vibration; the foundation is not strong and the bearing vibrates.
Make the iron core car small, soak the surface of the silicon steel sheet and open the gap with silicon organic varnish 1052; replace the new bearing of the same model; exit the rotor core to straighten the bent part of the shaft; adopt the 180° symmetry method; tighten the end cap bolts; reinforcement Foundation, tighten the anchor bolts.
Material fatigue 05
Due to the fatigue of the metal material, the irregular fragments of the bearing raceway and the surface of the ball, if mixed in the grease, it will increase the operating noise and the ball will slide, resulting in an increase in the radial clearance of the bearing and the allowable diameter of the shaft end. Increase the yaw value by 2~3 times.
The determinants of the degree of bearing fatigue include: motor load, speed, air gap, end cover type, material toughness, grease quality, and grease loading volume.
According to the motor operation record, when the light load working current is more than 60% of the rated value, it runs to 2000~25000h, the medium load working current is 60% to 80% of the rated value, and the heavy load working current is the rated value. After 80%~100% of the bearing is operated for 10000~15000h, the normal fatigue of the bearing material should be considered, and a new bearing of the same model should be replaced.
Pollution corrosion 06
At this time, red and brown spot-like corrosion appears on the surfaces of the raceways and balls, and the operating noise is increased compared to the noise of a new bearing.
The assembly site is not clean, such as moisture, acid, alkali and toxic gas; tools and hands are contaminated; low-quality lubricating fingers are used.
When assembling bearings, keep the environment, tools and hands clean; clean the bearings thoroughly; replace with high-quality lithium-based grease.
For more bearing knowledge communication or discussion, freely contact the bearing specialist.