Bearing wear is one of the common faults of ball mills. The main bearing is one of the core components of the main bearing. The bearing is spherical and installed on the concave spherical surface at the bottom of the bearing. It is generally made of lead-based bearing alloy. During the operation of the equipment, the weight of the ball mill cylinder is all concentrated on the bearing, so the wear rate of the bearing is high. So when the bearing fails, where should we look for the cause?

1. Bearing itself

Some ball mill bearings contact the bearing surface with a Babbitt alloy layer of graphite nails, which has a lubricating effect, but the Babbitt alloy layer has a high hardness and poor ductility. After the bearing is ground for a long time, the bearing produces local high temperature points and local ablation, and the journal is also prone to scratches and annular grooves.

During the pouring process, the Babbitt alloy layer will have problems such as fine cracks, pores, and rough surface. During the operation of the machine, due to the dynamic load, it reaches its fatigue strength, reducing the service life of the ball mill contact bearing, causing damage to the ball mill contact bearing; in addition, the ball mill contact bearing belongs to the cast iron matrix, and its surface and interior are prone to defects such as pores. During operation, cooling water is easy to flow along these defective positions onto the working surface of the contact bearing, causing the journal to rust or even burn the bearing; when the ball mill is running, the contact bearing position will produce a local temperature rise due to long-term friction, which makes the coal mill work. The contact bearing and the hollow journal cannot produce excellent lubrication effect with the help of lubricating grease, causing serious wear of the contact bearing.

2. The surface of the bearing is rough and uneven

In order to ensure good contact between the hollow journal and the contact bearing of the ball mill, before installing the contact bearing, the contact surface of the contact bearing and the middle journal must be scraped and polished to form an oil film between the hollow journal and the contact bearing to prevent excessive dry friction.

However, in the actual equipment installation, the scraping quality of the contact bearing of the ball mill is not strictly controlled, resulting in rough bearing surface, insufficient number of contact spots and uneven distribution, resulting in poor contact between the two. During the operation of the ball mill, local temperature rise will occur, which not only aggravates the wear of the contact bearing, but also causes the contact bearing to burn out in severe cases.

3. The outer spherical surface of the bearing seat and the bearing are not tightly matched

If there is a large deviation in the matching of the ball mill bearing seat and the contact bearing, it will cause uneven distribution of the force on the contact bearing, resulting in the cylinder pressure on the contact bearing being concentrated in the annular strip position close to the cylinder side, and the lubricating oil cannot enter its interior to produce a lubricating oil film. Over time, it will cause local wear and overheating of the contact bearing. In severe cases, the Babbitt alloy layer will be burned and melted, causing the ball mill to fail.

4. The ball mill has a bad seal. 

The grinding material will enter the contact bearing through two main ways. If the ball mill feed port leaks, it will cause material accumulation at the hollow shaft. Over time, when the height of the accumulated material is greater than the height of the hollow shaft neck sealing felt, the material can easily enter the contact bearing, causing wear and damage to the lubrication between the hollow shaft neck and the contact bearing. In addition, if the ball mill is in a very harsh environment, the floating dust will enter the contact bearing chamber through the observation hole of the contact bearing, destroying the lubricating oil film between the hollow shaft neck and the contact bearing, which will cause the contact bearing to fail.