The type and quality of the shaft bearing exerts a decisive influence on a mechanical seal's proper functioning and service life. Positioning the bearing directly adjacent to the sealing point and with the biggest possible bearing span makes for good smooth running of the shaft and the mechanical seal, especially in the case of shafts with a long free end affected by forces of varying magnitude and direction (e. g. agitator shafts). Shaft bearings are built mostly in a "locating/ non-locating" arrangement (see figure). In this case the locating bearing is the one guiding the shaft in both directions. It is possible to use all types of bearings that absorb radial and axial forces in both directions. The non-aligning bearing is the one compensating the axial shaft movements. Cylindrical-roller bearings and needle bearings are considered to be ideal non-aligning bearings because they enable differences in length to be compensated in the bearing itself. With separable bearings such as deep-groove ball bearings and self-aligning roller bearings, one of the two raceways is loosely fitted to allow it to move on its seat.

Shaft bearing arrangement – locating/non-locating