Scholars have conducted extensive research on the lubrication mechanism of bearing grease and have proven that the grease in the rolling bearing enters a stable distribution state after a complex flow at the beginning. The very small amount of fluid grease left in the friction part plays an important role. The grease itself does not flow, that is, it has no direct lubrication effect. However, the bearing grease left in the outer cover acts as a seal to prevent the fluid grease left in the friction parts from flowing out.
Experiments have shown that if the grease in the outer cover is removed after 50 hours of operation of the bearing, the bearing wear will increase. At the same time, due to the influence of heat, vibration, etc., the base oil separated from the static bearing grease inside and outside the bearing will be lost again. Entering the friction surface also acts as lubrication. Obviously, too much grease in the bearing is unnecessary. Due to reasons such as poor repairability of the grease film, the lubrication condition of the bearing will deteriorate. Therefore, it is important to determine the appropriate filling amount of grease in the bearing. It can be seen that excessive or insufficient grease filling will cause the bearing temperature to rise, which cannot ensure the continuous optimal operation of the bearing.
Adding too much grease has the following hazards: the temperature rises during operation, causing sealing problems, increased energy consumption, and is not good for the grease itself. For example, if too much grease is added to the motor, the power consumption will increase, and in severe cases, it may cause motor failure.
Taking bearings as an example, too much grease stirs violently in the bearing cavity, increasing the rotational resistance of the bearing, increasing the temperature and energy consumption, and the increase in temperature will also cause the grease to accelerate oxidation (premature deterioration, shortened service life), The increase in temperature causes the base oil contained in the grease to accelerate the precipitation - and the grease can provide lubrication mainly because of the oil contained in it. After the base oil is lost from the grease, the thickener is left, which dries and hardens, causing the newly added grease to not fully flow into the bearing core, resulting in poor lubrication, bearing wear and even failure. In addition, dry grease lumps may fall off, break and be brought into the bearing.
For motors, the harm of adding too much grease is similar to that of bearings, but another possible consequence is that too much grease leaks to the motor windings and dries on the surface, causing poor heat dissipation of the windings.
Rolling bearings filled with grease refer to the following principles:
(1) Generally, the bearing should not be filled with grease, only 1/2-3/4 of the total space in the bearing cavity can be filled;
(2) The horizontal bearing fills 2/3-3/4 of the inner cavity space;
(3) Vertically installed bearings fill 1/2 (upper side) and 3/4 (lower side) of the space in the cavity;
(4) In an environment that is easily polluted, for low-speed or medium-speed bearings, all spaces in the bearing and bearing box must be filled;
(5) Before loading high-speed bearings with grease, the bearings should be placed in high-quality lubricating oil, usually soaked in the base oil of the bearing grease to be filled, to avoid bearing burnout due to insufficient grease on the friction surface during startup. .
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