To achieve satisfactory operation, tapered roller thrust bearings, like all ball and roller bearings, must always be subjected to a given minimum load, particularly if they are to operate at high speeds or are subjected to high accelerations or rapid changes in the direction of load. Under such conditions the inertia forces of the rollers and cages, and the friction in the lubricant, can have a detrimental influence on the rolling conditions in the bearing arrangement and can cause damaging sliding movements to occur between the rollers and raceways.
The minimum axial load to be applied to single direction tapered roller thrust bearings can be estimated using
|Fam||=||minimum axial load [kN]|
|A||=||minimum load factor (→ contact SKF)|
|n||=||rotational speed [r/min]|
When starting up at low temperatures or when the lubricant is highly viscous, even greater loads may be required. The weights of the components supported by the bearing, together with the external forces, generally exceed the requisite minimum load. If this is not the case, the single direction tapered roller thrust bearing must be subjected to an additional axial load.
It is not necessary to check the minimum axial load for screw-down bearings as these are preloaded via O-rings or, in reversing mills, by springs. When using O-rings to produce the preload, the preload force should compress the diameter of the O-ring by some 20%.
When the bearing is preloaded by springs, the minimum load is dependent on the weight of the associated components. Appropriate values will be supplied on request by the SKF application engineering service.