Too much bearing grease may cause a fire?
Bearing is an important part of contemporary machinery and equipment. Its main function is to support the mechanical rotating body, reduce the friction coefficient during its movement, and ensure its rotation accuracy, almost all rotating machinery will use bearings.
01 - Type of lubrication for rolling bearings
1) Grease lubrication of rolling bearings
The rolling bearing uses grease as the lubrication medium, which has the advantage that the fluidity of the grease is small, it is not easy to leak, the oil film formed is good, and it is more conducive to the sealing use of the rolling bearing. At the same time, the grease lubrication of rolling bearings can also extend the lubrication maintenance time, making bearing maintenance easier. Rolling bearings lubricated with grease also have disadvantages. Compared with lubricating oil, the friction torque of lubricating grease is larger, and the applicability of rolling bearings requiring high-speed operation is low. In addition, the cooling performance of grease lubrication is poor, if too much grease is added to rolling bearings, it will also cause overheating of rolling bearings due to stirring lubricants.
2) Oil lubrication of rolling bearings
Rolling bearings are lubricated by oil lubrication, which can achieve a good cooling and cooling effect, especially for rolling bearings with relatively high working temperature. The lubricating oil viscosity used in rolling bearings is about 0.12 to 0.2cm/s, if the rolling bearing load is high, the working temperature is high, the lubricant with high viscosity is selected, and the rolling bearing with fast speed is suitable for the lubricating oil with low viscosity. The disadvantage of using oil lubrication for rolling bearings is that oil lubrication requires that bearings must be kept in a good sealed state to avoid leakage of lubricating oil. In addition, oil lubrication requires a more complex oil supply device, which is not as convenient as grease in operation and use, and increases the maintenance workload of rolling bearings
02 - What is the effect of too much bearing grease
When the rolling bearing uses grease lubrication, the amount of grease applied must be properly controlled, some people think that the more grease coated the better, this is a common wrong concept, too much grease in the bearing and bearing room will cause excessive stirring of the grease, resulting in extremely high temperature, when the oil temperature rises, the Base Oil in the grease will precipitate, that is, it will become a liquid oil that can flow. The liquid oil will soon seep out of the bearing end cap or seal. Bearing roller to bottom due to base oil precipitation. Does not provide effective lubrication. Gradually appear more serious wear, the temperature of the bearing will rise higher, so as to form a vicious cycle, and even make the inner ring and shaft locked, higher temperatures make the foundation of oil and gas, and sometimes even cause fire
03 - Case of fire caused by too much grease in bearings
In the background software of a wind farm, a unit was found to stop reporting "generator overspeed", and then triggered multiple failures such as "generator bearing temperature is too high" and "generator bearing temperature is too high". After the accident, it was found that the coupling and the coupling cover were completely burned. The unit was successfully connected to the grid after replacing the generator, coupling, coupling cover, burned part of the line and sensor. Due to the small number of burning parts of the accident unit, the collection and processing of the master control and data were not jeopardized, and the power failure of the unit was late, and the master control data obtained after the accident was relatively complete and the site remained intact, which brought great convenience to the accident analysis
Later, it was found that because the generator bearing was coated with too much lubricating ester, the bearing temperature rose sharply in normal operation, and then caused a fire.
04 - How much bearing grease should be applied?
Bearing grease, in addition to the performance of the grease and the applicability of the motor working conditions, as well as the cooperation relationship with the bearing associated parts, a very important factor is the control of the amount of grease during the bearing operation, the amount of grease, as long as it can ensure the normal operation of the bearing
The general filling amount of grease in rolling bearings can be referred to the following principles:
1, the general bearing should not be filled with grease, in order to install the bearing cavity of the total space of 1/2~3/4 can be;
2, horizontal bearings fill the inner cavity space 2/3~3/4;
3, vertically mounted bearing filled cavity space 1/2 (upper side), 3/4 (lower side);
4, in an easily polluted environment, for low or medium speed bearings, to fill all the space in the bearing and bearing box;
5, high-speed bearings should be placed in high-quality lubricating oil before loading grease, generally soaked in the base oil of the installed grease, so as not to cause the bearing to burn out due to insufficient friction surface grease when starting
If excessive filling, including grease drainage is not smooth, it will lead to excessive oil accumulation in the bearing, so that when the motor is running, it will heat up due to friction, resulting in oil degradation failure and loss, and then make the bearing run in a non-lubricated state, in a very short time, the bearing will appear to fall apart and hold the shaft.
