Bearing maintenance 3

               
Update: 06-12-2019
               
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3. Inspection and troubleshooting during operation The […]

3. Inspection and troubleshooting during operation
The inspection items during operation include the rolling noise, vibration, temperature, and lubrication status of the bearing. Among them, the rolling noise, vibration, and temperature of the bearing are as described above. The lubrication here is as follows:
3.1 The role of bearing lubrication
Lubrication has a significant impact on the fatigue life and friction, wear, temperature rise, vibration, etc. of rolling bearings. Without normal lubrication, bearings cannot work. Analysis of the causes of bearing damage shows that about 40% of bearing damage is related to poor lubrication. Therefore, good bearing lubrication is an effective measure to reduce bearing friction and wear. In addition, the bearing lubrication also has various functions such as heat dissipation, rust prevention, sealing, and shock mitigation. The role of bearing lubrication can be briefly explained as follows:
a. An oil film is formed between the two rolling or sliding surfaces in contact with each other to separate the two surfaces, reducing friction and wear of the contact surfaces.
b. When oil lubrication is used, especially when circulating oil lubrication, oil mist lubrication and oil injection lubrication are used, the lubricant can take away most of the frictional heat inside the bearing and play an effective role in heat dissipation.
c. When grease lubrication is used, foreign matter such as external dust can be prevented from entering the bearing, which acts as a seal.
d. Lubricants can prevent metal corrosion.
e. Extend the fatigue life of the bearing.
3.2 Grease lubrication
Grease is a lubricant composed of base oil, thickener and additives. When selecting, you should choose a grease that is very suitable for the conditions of bearing use. Due to different trademarks, there will be great differences in performance, so you must pay attention when selecting. Bearing commonly used greases are calcium-based grease, sodium-based grease, calcium-sodium-based grease, lithium-based grease, aluminum-based grease, and molybdenum disulfide grease. The amount of grease in the bearing is suitable to fill 1 / 2-1 / 3 of the internal space of the bearing. It should be reduced to 1/3 at high speed. Too much grease raises the temperature.
3.3 Selection of grease
When selecting grease according to operating temperature, the main indicators should be the dropping point, oxidation stability and low temperature performance. The dropping point can generally be used to evaluate high temperature performance. The actual operating temperature of the bearing should be 10-20 ° C lower than the dropping point. The operating temperature of synthetic grease should be 20-30 ℃ below the dropping point. When selecting the grease according to the bearing load, select a grease with a small penetration for heavy loads. When working under high pressure, in addition to the small penetration, it also needs to have high oil film strength and extreme pressure performance. When selecting grease according to environmental conditions, calcium-based grease is not easily soluble in water and is suitable for dry and low-moisture environments.
3.4 Lubricant replenishment and replacement
Due to mechanical action, aging and pollution increase, the lubricating base filled in the bearing arrangement will gradually lose its lubricating performance. Therefore, the lubrication rank needs to be continuously supplemented and updated. Lubricant replenishment intervals vary depending on bearing formation, size, and rotation speed. Approximate intervals between replenishment of grease depending on operating time. In addition, when the bearing temperature exceeds 70 ° C, the replenishment interval using grease is reduced by half for every 15 ° C increase in bearing temperature. Double-sided closed bearings are already filled with grease at the time of manufacture. "HRB" uses standard grease in these products. The total operating temperature range and other properties are suitable for the specified occasions. The service life of grease can generally exceed the service life of bearings. Except for special occasions, no additional grease is required.
3.5 Bearing damage and countermeasures
It is not possible to observe the bearing directly during operation, but the abnormality of the bearing can be detected by the conditions of noise, vibration, temperature, and lubricant. The following table is a representative example of bearing damage.

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