Foreign scholars have done a lot of research on the lubrication mechanism of bearing grease, which has proved that:...
Foreign scholars have done a lot of research on the lubrication mechanism of bearing grease, which has proved that:
The lubricating grease in the rolling bearing enters the stable distribution state after the complex flow at the beginning. The very small amount of flowing lubricating grease left in the friction part plays a major role in lubrication, while the lubricating grease left in the outer cover does not flow, that is, it does not play a direct role in lubrication. However, the bearing grease left in the outer cover acts as a seal to prevent the flowing grease left in the friction part from flowing out.
The experiment shows that if the grease in the outer cover is removed after 50 hours of bearing operation, the bearing wear will increase. At the same time, the base oil separated from the static bearing grease inside and outside the bearing will enter the friction surface for lubrication due to heat, vibration and other effects.
Obviously, too much grease in the bearing is unnecessary. Due to the poor oil film repair of the grease, the lubrication state 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 can not guarantee the continuous and optimal operation of the bearing.
Too much grease can cause the following hazards:
The temperature rise during operation causes sealing problems, increases energy consumption and is not good for the lubricating grease itself. For example, if the motor is greased, the power consumption will increase, and even cause motor failure.
Take the bearing as an example, excessive grease churns violently in the bearing cavity, increases the bearing rotation resistance, increases the temperature and energy consumption, and the temperature rise will also cause the oxidation speed of the grease to accelerate (deterioration in advance, shorten the service life), and the temperature rise will lead to the accelerated precipitation of the base oil contained in the grease - and the grease can play a lubricating role, mainly because of the oil contained in it.
After the base oil is lost from the lubricating grease, the thickener will be left, which will dry and harden, resulting in that the newly added lubricating grease cannot fully flow to the inner core of the bearing, resulting in poor lubrication, bearing wear and even failure. In addition, the dry grease hard block may fall off, break and then be brought into the bearing.
Excessive greasing will also cause sealing problems. The pressure on the sealing element will increase, resulting in seal cracking and failure, resulting in loose sealing, introducing impurities and water permeability, and causing damage to the bearing.
When using the grease gun for greasing, pay attention to the pressure of the seal. Some grease guns can reach 15000 psi, while the general lip seal can withstand about 500 psi. Therefore, the pressure of the grease gun should be properly controlled.
For motors, the harm of adding too much lubricating grease is similar to that of bearings, but there is also a possible consequence that too much lubricating grease will leak onto the motor winding and dry on the surface, resulting in poor heat dissipation of the winding.
Refer to the following principles for lubricating grease filling of rolling bearings:
(1) Generally, the bearing should not be filled with lubricating grease, which should be filled to 1/2-3/4 of the total space in the bearing cavity;
(2) The horizontal bearing fills 2/3-3/4 of the inner cavity space;
(3) The vertically installed bearing fills 1/2 (upper side) and 3/4 (lower side) of the cavity space;
(4) In the environment prone to pollution, for low-speed or medium-speed bearings, all the space in the bearing and bearing box should be filled;
(5) Before greasing the high-speed bearing, put the bearing in high-quality lubricating oil. Generally, soak it in the base oil of the bearing grease to be filled to avoid burning the bearing due to insufficient lubricating grease on the friction surface during startup.
Add proper amount of lubricating grease
How to prevent excessive grease? First of all, determine the reasonable amount of lubricating grease. In addition, formulate the operation specification for the amount of lubricating grease. After adding and replacing lubricating grease, pay attention to temperature, noise, vibration, etc., and pay attention to oil leakage. For important equipment, some special monitoring tools can also be used. Specify the reasonable amount of lubricating grease:
The grease amount of bearing can refer to this formula:
G = 0.005 DB
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G=weight of greasing, g
D=outer diameter of bearing, mm
B=bearing width, mm
perhaps
G = 0.114 DB
Here, D and B use inch units.
If you use a grease gun to add grease, you should calculate how much grease the grease gun can produce each time. You can use an electronic scale to calibrate the grease gun and calculate how many times you need to use it.
How to prevent excessive grease addition?
In addition to keeping the amount of grease in mind, some methods can also help to prevent excessive greasing:
When adding grease, if you feel it is difficult, blocked or begin to feel a large reaction force, you should stop adding grease.
During greasing, the oil outlet of the grease should be kept smooth to prevent the dry grease from blocking the orifice.
If necessary, some small accessories can also play a very convenient role, such as grease gun pressure gauge, grease nozzle with pressure relief function, etc.
Slow greasing, too fast or too fast, can easily cause sealing problems, and is not conducive to the uniform distribution of grease in the bearing.
