Fan bearings id other factors which play an important part in the choice of beadngs include thermal expansion and heat losses. Any fan when it operates will experience a temperature rise and this can give different amounts of expansion between the stator and rotor which in turn may impose additional forces on the bearings or a requirement to design the overall bearing system to compensate for such events.

Fan bearings, Ventilation

The load may in some cases contribute to the problem by its own shaft expansion. All bearings have some frictional losses which appear as heat and may require some bearing cooling. Lubrication plays an important part in maintaining bearing temperatures at an acceptable level and in some cases cooling of the lubricant may be essential.

Wherever there is rotating machinery there will be a need for bearings i.e. those components whereby forces are transmitted between solids which are moving relative to each other. It is at such interfaces that friction takes place, accounting in its turn for significant amounts of energy to be added to that required for the air power provided by a fan impeller. It is also at these interfaces that wear occurs, with a consequential risk of malfunctioning and/or overcoming the effects of wear, not only on the impeller and stationary parts, but often more importantly on the fan bearings and shatt.

Fan bearings id other factors which play an important part in the choice of beadngs include thermal expansion and  heat losses.
The change of lubrication from an empirical art to an exact science, now dignified with the title “Tribology” grew out of the studies of Beauchamp Tower. He reported to an Institution of Mechanical Engineers committee set up in 1879. Osborne Reynolds, that giant of Victorian engineers, analysed these results and in 1886 showed that in certain circumstances, the relative motion and convergent geometry could generate sufficient pressure to overcome the loads applied to a bearing and prevent the two surfaces from making physical contact.

There is a wide variety of bearing types used for fans of which plain and rolling element bearings are by far the most numerous and form the main part. More exotic bearings, for example air bearings and magnetic bearings, may be used for some very special applications and are briefly discussed. Although the bearings essentially support and position the impeller, they may be called upon to withstand some of the other forces imposed by the driven load.

The rotor weight will always act downwards whatever the motor attitude but the forces arising from the load, where applicable, may be in any direction and even vary according to the load conditions.

The type of bearing selected will depend upon these conditions in addition to any limitations imposed by the environment. There is clearly a difference in the type of bearing used for impellers running horizontally or vertically. Except for some very small fans and fans intended to run with the shaft in any direction, particular attention may need to be paid to the choice of bearings.

Other factors which play an important part in the choice of bearings include thermal expansion and heat losses. Any fan, when it operates, will experience a temperature rise, or indeed may handle hot gases.

This can give different amounts of expansion between the fan casing and bearing support structure, which in turn may impose additional forces on the bearings or a requirement to design the overall bearing system to compensate for such events. The fan may in some cases contribute to the problem by its own shaft expansion. All bearings have some frictional losses which appear as heat and may require some bearing cooling. Lubrication plays an important part in maintaining bearing temperatures at an acceptable level and in some cases cooling of the lubricant maybe essential.

The fan attitude, forces from the driven load, air or gas temperatures and site ambient conditions all affect the bearing reliability and life. In turn the maintenance requirements are determined by these factors and the type of bearing selected. Generally the manufacturer will fit bearings suitable for the specified requirements but customers may have a preference for a particular bearing type. For example, sometimes rolling element or plain bearings may be suitable and the customer has a preference based on his experiences.