5.1 Calculating Bearing Requirements

Lubricant delivery system manufacturers have devised basic calculations for bearing surface lubrication requirements that act as starting points for setting up lubricant delivery schedules. These values are then fine tuned according to the environmental or physical conditions. These outside variables are termed service factors, and are shown in Figure 5.1a.

When lubricating a bearing, the object is not to fill the void areas of the bearing, but rather replenish and sustain a lubricant film. (Filling the entire bearing cavity, or over lubricating, basically causes the bearing to draw on more power to overcome the fluid friction.) The film thickness replacement rate varies, dependent on whether the lubricant is oil or grease, manually applied or automatically delivered see Figure 5.1b.

For example, when an automatic terminating grease system is employed, under normal conditions a .001 (.025mm) grease film thickness, applied every 4 hours to the total bearing surface is all that is required to provide adequate lubrication.

Lubricant must be replenished on a...