Comparison of Position Preload and Constant-Pressure Preload

Position preload and constant-pressure preload may be compared as follows:

1. When both of the preloads are equal, the position preload provides greater bearing rigidity. In other words, the deflection due to external loads is less for bearings with a position preload.
2. In the case of a position preload, the preload varies depending on such factors as a difference in axial expansion due to a temperature difference between the shaft and housing, a difference in radial expansion due to a temperature difference between the inner and outer rings, and deflection due to load. In the case of a constant-pressure preload, it is possible to minimize any change in the preload because the variation of the spring load with shaft expansion and contraction is negligible.

From the foregoing explanation, it is seen that position preloads are generally preferred for increasing rigidity while constant-pressure preloads are more suitable for high-speed applications, prevention of axial vibration, or use with thrust bearings on horizontal shafts.