Foreign scholars have conducted extensive research on the lubrication mechanism of bearing grease, proving that:
After a complex flow, the lubricating grease inside the rolling bearing enters a stable distribution state. The very small amount of fluid lubricating grease left in the friction area plays the main lubricating role, while the lubricating grease left in the outer casing does not flow itself, that is, does not have a direct lubricating effect. However, the bearing grease left inside the outer casing acts as a seal to prevent the flow of fluid grease left in the friction area from escaping.
Experimental results have shown that if the lubricating grease inside the outer casing is removed after 50 hours of bearing operation, the wear of the bearing will increase. At the same time, due to the effects of heat, vibration, and other factors, the base oil separated from the static state of the bearing grease inside and outside will enter the friction surface and also act as a lubricant.
Obviously, excessive lubricating grease in the bearing is unnecessary. Due to the weak repair ability of the grease film and other reasons, the lubrication state of the bearing will deteriorate. Therefore, it is important to determine the appropriate filling amount of lubricating grease in the bearing. It can be seen that excessive or insufficient filling of lubricating grease can cause an increase in bearing temperature, which cannot guarantee the continuous optimal operation of the bearing.
Adding too much lubricating grease can have several hazards:
During operation, the temperature rises, causing sealing problems and increased energy consumption. In addition, it is not good for the lubricating grease itself. For example, adding lubricating grease to the motor can increase power consumption and, in severe cases, cause motor failure.
Taking bearings as an example, excessive lubricating grease vigorously stirs inside the bearing chamber, increasing the bearing's rotational resistance, temperature, and energy consumption. The temperature rise can also accelerate the oxidation rate of the lubricating grease (premature deterioration, shortened service life), and the temperature rise can accelerate the precipitation of the base oil contained in the lubricating grease - and lubricating grease can play a lubricating role mainly because of the oil contained inside.
After the base oil is lost from the lubricating grease, only thickening agent is left, which dries and hardens, causing the newly added lubricating grease to not flow fully to the bearing core, resulting in poor lubrication, bearing wear, and even failure. In addition, dry and hard lumps of lubricating grease may also fall off, break, and be carried into the bearing.
Excessive greasing can also cause sealing problems, with increased pressure on the seals leading to seal rupture and failure, resulting in poor sealing, introduction of impurities, water leakage, and damage to the bearings.
When using a grease gun to add grease, attention should be paid to the pressure that the seal can withstand. Some grease guns can reach a pressure of 15000psi, while general lip seals can withstand around 500psi. Therefore, when adding grease, the pressure of the grease gun should be reasonably controlled.
For motors, the harm of adding too much grease is similar to that of bearings, but there is also a possible consequence of excessive grease leaking onto the motor windings, causing dry knots on the surface and poor heat dissipation of the windings.
The following principles should be followed for filling lubricating grease in rolling bearings:
(1) Generally, the bearing should not be filled with lubricating grease, and it should be filled to 1/2-3/4 of the entire space inside the bearing cavity;
(2) Horizontal bearings fill 2/3-3/4 of the internal cavity space;
(3) Vertically installed bearings fill 1/2 (upper side) and 3/4 (lower side) of the cavity space;
(4) In environments prone to pollution, for low-speed or medium speed bearings, the entire space inside the bearing and bearing box should be filled;
(5) Before grease installation, high-speed bearings should be soaked in high-quality lubricating oil, usually the base oil of the bearing grease to be filled, to avoid bearing burnout caused by insufficient lubricating grease on the friction surface during start-up.
The addition of lubricating grease should be appropriate
How to prevent excessive use of lubricating grease? Firstly, the reasonable amount of lubricating grease should be determined. In addition, operating standards for the amount of lubricating grease added should be formulated. After adding or replacing lubricating grease, attention should be paid to temperature, noise, vibration, and whether there is oil leakage. For important equipment, specialized monitoring tools can also be used. Specify the reasonable amount of lubricating grease:
The amount of grease added to the bearing can refer to this formula:
G = 0.005 DB
here
G=Fated weight, grams
D=outer diameter of the bearing, in millimeters
B=Bearing width, millimeters
perhaps
G = 0.114 DB
Here, D and B are measured in inches.
If using a grease gun to add lubricating grease, calculate how much grease the grease gun can dispense each time. You can use an electronic scale to calibrate the grease gun and calculate how many times it needs to be dispensed.
How to prevent excessive addition of lubricating grease?
In addition to having a clear idea of the amount of grease added, certain methods can also help prevent over greasing:
When adding fat, if you feel difficulty, obstruction, or begin to feel a significant reaction force, you should stop adding fat.
When adding grease, the outlet of the lubricating grease should be kept unobstructed to prevent dry grease from blocking the holes.
If necessary, using some small accessories can also have a very convenient effect, such as a grease gun pressure gauge, a grease nozzle with pressure relief function, and so on.
Slowly adding grease, too aggressively or too quickly, can easily cause sealing problems and is not conducive to the uniform distribution of lubricating grease in the bearing.

• Previous：How to deal with the inexplicable overflow of bearing grease?
• Next：4 specific ways to deal with high temperature in deep groove ball bearings