Vertical shaft mounting for bearings

Once again three different zones can be identified. In Zone 1 the inner ring is cooled by the very cold shaft. Clearance then increases. The inner ring with the shaft and gear moves axially downwards. In Zone 2 the warm gear has heated the shaft, and the warm shaft now warms the inner ring. The inner ring then expands. Clearance decreases. The inner ring with the shaft and gear moves upwards. Zone 3 indicates that real motion between rollers and raceway has probably stopped. It is likely that the measurements have included temperature-related dimensional changes of the complete stand. The measurements highlight that there may be two “stick-slip” occasions (marked by red circles).

In this case, the appearance of the lower inner ring raceway in the test bearing was studied after dismounting the test bearing. Thin axially oriented marks were visible.

However, not all roller contacts left such marks. Under the microscope, the thin axially oriented marks showed to partially consist of smeared material.

This damage will copy due to the overrolling and develop into surface distress/wear.

To avoid mounting-initiated damages there are three factors to work on. Firstly, it is important to reduce or eliminate the bearing load during the mounting sequence. The logical path is to avoid vertical mounting and/or to counteract gravity. If this is not possible, mount vertically, but then tilt horizontally to reduce the axial loading during cooling. Try to release friction by rotating to release and avoid motion by centring axially during cooling. Above all, awareness is key, as being aware of the potential damage during mounting helps reduce risk.

SKF has considerable strengths in bearing mounting, and its BearingAssist app can help with mounting issues. SKF can also support with training fitters on best practice as well as help to review machine design and bearing mounting procedures for all types of equipment.