1. Regular inspection
In order for the bearing to fully exert its performance and maintain its performance for a long time, regular maintenance (regular inspection) must be carried out. Through appropriate regular inspections, it is very important to detect faults early and prevent accidents before they occur, which is very important for improving productivity and economy.
The main methods are as follows:
1.1 How to identify bearing faults: It is possible to identify or predict whether a running bearing has faults without disassembly and inspection. The main identification methods are as follows:
a. Recognition by voice: Recognition by voice requires extensive experience. Sufficient training is required to be able to distinguish bearing sounds from non-bearing sounds. For this reason, this work should be carried out by dedicated personnel whenever possible. Use a listening device or listening stick to the shell to clearly hear the sound of the bearing.
b. Identification by operating temperature: This method is a comparative identification method and is limited to situations where the operating status does not change much. For this purpose, continuous recording of the temperature is necessary. When a fault occurs, not only does the temperature increase, but also irregular changes occur.
c. Identification by the status of the lubricant: Sampling and analyzing the lubricant, and judging whether it is contaminated with foreign matter or metal powder, etc. This method is particularly effective for bearings or large bearings that cannot be observed closely.

1.2 Inspection of bearings. During regular equipment maintenance, operation inspection and replacement of peripheral parts, the disassembled bearings should be inspected to determine whether the usage is good or bad and whether the bearing can continue to be used. After sampling, clean the bearings well, check the condition of the raceway surface, rolling surface and mating surface, as well as the wear status of the cage, and determine whether there is any damage or abnormality. Precautions for bearing cleaning: When disassembling the bearing for inspection, it is necessary to take photos and record the appearance. In addition, confirm the amount of remaining lubricant and sample the lubricant before cleaning the bearings. The commonly used cleaning agents are neutral non-aqueous diesel or kerosene, and warm alkali solution is sometimes used as needed. No matter which cleaning agent you use, filter it frequently to keep it clean. After cleaning, immediately apply anti-rust oil or anti-rust grease to the bearings.

1.3 To determine whether a bearing can be used again, the decision should be made after considering the degree of bearing damage, machine performance, importance, operating conditions, inspection cycle, etc. If damage or abnormality is found in the bearing, it is necessary to find out the cause and formulate countermeasures. If the following defects are found during inspection, the bearing can no longer be used and needs to be replaced with a new one.
a. There are cracks and fragments in any of the inner and outer rings, rolling elements, and cages.
b. Any of the inner and outer rings or rolling elements is peeled off.
c. The raceway surface, ribs, and rolling elements are obviously jammed.
d. The cage is severely worn or the rivets are loose.
e. The raceway surface and rolling elements are rusty and scratched.
f. There are obvious indentations and scratches on the rolling surfaces and rolling elements.
g. There is creep on the inner diameter surface of the inner ring or the outer diameter of the outer ring.
h. Severe discoloration due to overheating.
i. The sealing ring and dust cover of the sealed bearing are seriously damaged.

2. Inspection and troubleshooting during operation
Inspection items during operation include rolling sound, vibration, temperature, lubrication status of the bearing, etc. Here we focus on lubrication as follows:
2.1 The role of bearing lubrication: Lubrication has an important impact on the fatigue life, 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 lubrication of bearings is an effective measure to reduce bearing friction and wear. In addition, bearing lubrication also has many functions such as heat dissipation, rust prevention, sealing, impact mitigation, etc., as follows:
a. An oil film is formed between the two rolling surfaces or sliding surfaces that are in contact with each other to separate the two surfaces and reduce the friction and wear of the contact surfaces.
b. When using oil lubrication, especially circulating oil lubrication, oil mist lubrication and oil injection lubrication, the lubricating oil can take away most of the friction heat inside the bearing and play an effective heat dissipation role.
c. When using grease lubrication, it can prevent external dust and other foreign matter from entering the bearing and act as a seal.
d. Lubricants have the function of preventing metal corrosion.
e. Extend the fatigue life of bearings.

2.2 Grease lubrication: Grease is a lubricant composed of base oil, thickener and additives. Different brands of grease will also have great differences in performance, and the specific selection needs to be based on the use conditions of the bearing. Commonly used greases for bearings include calcium-based grease, sodium-based grease, calcium-sodium-based grease, lithium-based grease, aluminum-based grease and molybdenum disulfide grease.

2.3 Selection of grease: When selecting grease according to the 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 service temperature of synthetic grease should be 20-30°C below the dropping point. When selecting grease according to bearing load, grease with small penetration should be selected for heavy loads. When working under high pressure, in addition to small penetration, it must also 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 less moisture-rich environments.

2.4 The filling amount of grease: it is appropriate to fill 1/2-1/3 of the internal space of the bearing. It should be reduced to 1/3 at high speed. Excessive grease will increase the temperature.

2.5 Replenishment and replacement of lubricant: Due to mechanical action, aging and increase in pollution, the lubricant in the bearing will gradually lose its lubrication performance. Therefore, lubricants need to be constantly replenished and updated. The interval for lubricant replenishment varies depending on the structure, size and speed of the bearing. The approximate interval for lubricant replenishment can be judged based on the operating time. In addition, when the bearing temperature exceeds 70°C, the lubricant replenishment interval needs to be reduced by half for every 15°C increase in bearing temperature. Double-sided sealed bearings have been filled with grease during manufacture. Generally, the service life of the grease can exceed the life of the bearing, so there is no need to replenish the grease except for special occasions.