There are many nuances to lubrication. Applying a lubricant is not as simple as it is often made out to be. This is especially true when working with industrial grease. Lubricating using grease requires a certain amount of precision with regards to the amount of the lubricant being applied. Too little grease and lubricant starvation can happen. Too much grease and the movement of the mechanical components can be hindered, resulting to increased power requirement and higher heat generation.
A general rule for applying industrial grease on bearings is to not put too much lubricant that the external seals are beginning to be pushed out. However, there are equipments with care and lubrication instructions that might state otherwise.
It is not uncommon to encounter equipment with bearings that instruct applying as much grease as possible, as long as the speed of the bearing allows it. The reason behind this practice to create a continuous slight leakage from the bearing which provides a good protection against the entrance of foreign material or contaminants. However, this practice only applies to bearings with shield and lip seals that allow for discharge of excess grease without damaging the outer edge of the seal.
Sealed bearings which are the common type of bearings found in most equipment are not designed to handle excessive greasing. Applying too much grease can cause the seals to rupture.