The maintenance of the ball mill main bearing is very important to ensure the stable operation of the ball mill. According to the cement plant's many years of maintenance and repair experience, main bearing failure accounts for a relatively high proportion of transmission system failures. In view of this, this article will share some experience and opinions on the maintenance of the ball mill main bearing.
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1. Application of static and static main bearings
Since ball mills usually need to be started at full load, especially after long-term shutdown, the lubricating oil film between the hollow shaft neck and the bearing shell will gradually become thinner or even disappear due to extrusion. At this time, if the ball mill is started directly, it may cause a large starting torque and starting current, increase the load of the transmission system, and may damage the bearing alloy on the surface of the bearing shell. Using static and hydrostatic main bearings can establish a stable hydrostatic oil film before starting, ensuring that the shaft neck and the bearing shell are in a state of sufficient liquid friction, thereby avoiding damage at the moment of starting.
2. Effect of Radius Clearance on Lubricating Oil Film
The radius clearance between the ball bearing and the hollow journal is very important for the formation of the lubricating oil film. A reasonable radius clearance can improve the load-bearing capacity and reduce the friction power consumption. However, too small a clearance is not conducive to the formation of the lubricating oil film, and too large a clearance may cause the oil to flow along both sides of the bearing edge, affecting the stability of the oil film. Therefore, it is necessary to determine the appropriate radius clearance.
3. Influence of contact angle
The contact angle between the ball bearing and the hollow journal directly affects the formation of the oil film. Although a larger envelope angle helps to improve the load-bearing capacity, it is not conducive to the formation of the oil film. Using a small contact angle can ensure that the lubricating oil enters the contact area smoothly, which is conducive to the formation of the oil film and helps the heat dissipation of the hollow journal and the ball bearing. In actual operation, the contact angle should be less than 35°.
4. The influence of ball bearing on oil tank
Opening the oil groove on the ball bearing may cause the oil film to rupture, reduce the effective contact area, and be detrimental to the formation of the oil film. In fact, even if many ball bearings do not open the oil tank, there will be no abnormal phenomenon after long-term operation. For bearings that are started by high-pressure oil pumps, the opening of the oil groove should be carefully considered.
5. Processing of hollow journal
The polishing of hollow journals should be done carefully. Manual polishing may damage the roundness of the journal and is not conducive to the formation of oil film. Hollow journals that have been running for a long time usually have reached the ideal roundness state and do not need large-area polishing.
6. Scratching treatment of ball bricks
After a period of running-in between the ball bearing and the hollow journal, the contact angle usually does not increase significantly. Due to the uncertainty of dynamic loads during operation, the contact angle is automatically limited to a certain range. Therefore, for ball bearings in normal use, it is not necessary to perform frequent scraping.
7. Surface contact of spherical bearings
When scraping the ball tile, the surface should be kept smooth so that there is no obvious boundary between the points and non-points. In fact, after long-term operation, the surface of the ball tile is close to a smooth whole, which is conducive to the formation of oil film. When scraping, pay attention to maintaining the smoothness of the surface.
8. Matching of spherical tiles and tile bases
The match between the ball bearing and the bearing seat should ensure that the ball bearing has enough freedom to follow up flexibly during operation. The ball radius of the ball bearing should be smaller than the ball radius of the bearing seat to achieve point contact. Correct match can avoid the occurrence of bearing burnout accidents.
Through the above measures, the stability and service life of the ball mill main bearing can be effectively improved, ensuring the efficient operation of the ball mill.
