In the past, the main bearing is sealed with fine wool felt ring in the traditional vertical roller mill structure, which is easy to wear. Moreover, the dust particles will enter into the main bearing after the cracks between the wool felt ring and hollow shaft after the wear.

This method is also the key reason for abrasive wear and oil blockage of spherical bearing shells. Therefore, during the maintenance, the wear of sealing ring should be checked timely. If the degree is serious, it should be replaced and updated, which will block the dust.

Many manufacturers have also improved and optimized on this basis. In order to avoid oil leakage, the main bearing adopts more advanced piston seal.