The inspection items during operation include the rolling sound, vibration, temperature, lubrication status of the bearing, etc. The specific conditions are as follows:

1. Rolling sound of the bearing

Use a sound meter to check the size and sound quality of the rolling sound of the running bearing. Even if the bearing has slight damage such as peeling, it will emit abnormal and irregular sounds, which can be distinguished by a sound meter.

2. Vibration of the bearing

Bearing vibration is very sensitive to bearing damage. For example, peeling, indentation, rust, cracks, wear, etc. will be reflected in the bearing vibration measurement. Therefore, by using a special bearing vibration measuring device (frequency analyzer, etc.), the size of the vibration can be measured, and the specific situation of the abnormality can be inferred through frequency analysis. The measured values ​​vary depending on the use conditions of the bearing or the installation position of the sensor, so it is necessary to analyze and compare the measured values ​​of each machine in advance to determine the judgment standard.

3. Bearing temperature

The bearing temperature can generally be inferred from the temperature outside the bearing chamber. If the oil hole can be used to directly measure the bearing outer ring temperature, it is more appropriate. Normally, the temperature of the bearing rises slowly as the operation begins, and reaches a stable state after 1-2 hours. The normal temperature of the bearing varies depending on the heat capacity, heat dissipation, speed and load of the machine. If the lubrication and installation are appropriate, the bearing temperature will rise sharply and abnormally high temperature will appear. At this time, the operation must be stopped and necessary precautions must be taken.

4. Lubrication

4.1 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, the bearing 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 the bearing 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, and impact mitigation. The role of bearing lubrication can be briefly described as follows:

a. Form an oil film between the two rolling surfaces or sliding surfaces in contact with each other to separate the two surfaces and reduce the friction and wear of the contact surface. b. When oil lubrication is used, especially when circulating oil lubrication, oil mist lubrication and oil spray lubrication are used, the lubricating oil can take away most of the friction heat inside the bearing and play an effective heat dissipation role. c. When grease lubrication is used, it can prevent external dust and other foreign matter from entering the bearing and play a sealing role. d. Lubricants have the function of preventing metal corrosion. e. Extend the fatigue life of the bearing. 4.2 Comparison of grease lubrication and oil lubrication The lubrication methods of bearings are roughly divided into grease lubrication and oil lubrication. In order to give full play to the function of the bearing, it is important to use the lubrication method according to the use conditions and purpose. 4.3 Grease lubrication: Grease is a lubricant composed of base oil, thickener and additives. When choosing, you should choose a grease that is very suitable for the use conditions of the bearing. Due to different brands, there will be great differences in performance, so you must pay attention when choosing. Commonly used greases for bearings include calcium-based greases, sodium-based greases, calcium-sodium-based greases, lithium-based greases, aluminum-based greases and molybdenum disulfide greases. The amount of grease filled 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 will increase the temperature.

4.4 Selection of grease: When selecting grease according to the working temperature, the main indicators should be dropping point, oxidation stability and low temperature performance. The dropping point can generally be used to evaluate the high temperature performance. The actual working temperature of the bearing should be 10-20℃ lower than the dropping point. The operating temperature of synthetic grease should be 20-30℃ lower than the dropping point. When selecting grease according to the bearing load, grease with small needle penetration should be selected for heavy loads. In addition to small needle penetration, it must also have high oil film strength and extreme pressure performance when working under high pressure. When selecting grease according to environmental conditions, calcium-based grease is not easily soluble in water and is suitable for dry and less water-rich environments.

4.5 Oil lubrication: Under high-speed and high-temperature conditions, oil lubrication can be used when grease lubrication is no longer suitable. A lot of heat can be taken away through the circulation of lubricating oil. Viscosity is an important characteristic of lubricating oil. The viscosity directly affects the fluidity of lubricating oil and the thickness of oil film formed between friction surfaces. The viscosity of lubricating oil at bearing working temperature is generally 12-15cst. ​​The higher the speed, the lower the viscosity should be, and the heavier the load, the higher the viscosity should be. Commonly used lubricating oils include mechanical oil, high-speed mechanical oil, turbine oil, compressor oil, transformer oil, cylinder oil, etc.

Oil lubrication methods include:

a. Oil bath lubrication: Oil bath lubrication is the most common lubrication method, suitable for lubrication of low and medium speed bearings. A part of the bearing is immersed in the oil tank. The lubricating oil is carried by the rotating bearing parts and then flows back to the oil tank. The oil level should be slightly lower than the center of the lowest rolling element.

b. Oil drip lubrication: Oil drip lubrication is suitable for bearing parts that require quantitative supply of lubricating oil. The amount of oil dripped is generally one drop every 3-8 seconds. Excessive oil will cause the bearing temperature to increase.

c. Circulating oil lubrication: Use an oil pump to transport the filtered oil to the bearing parts. The lubricating oil after passing through the bearing is filtered and cooled before use. Since the circulating oil can take away a certain amount of heat and cool the bearing, this method is suitable for bearing parts with higher speed.

d. Spray lubrication: Use dry compressed air to mix with lubricating oil through a sprayer to form oil mist, and spray it into the bearing. The airflow can effectively cool the bearing and prevent impurities from invading. This method is suitable for the lubrication of high-speed and high-temperature bearing parts.

e. Spray lubrication: Use an oil pump to spray high-pressure oil into the bearing through a nozzle, and the oil injected into the bearing flows into the oil tank through the other end of the bearing. When the bearing rotates at high speed, the rolling elements and the cage also rotate at a relatively high speed to form airflow around the air. It is difficult to send the lubricating oil to the bearing using general lubrication methods. At this time, the lubricating oil must be sprayed into the bearing by high-pressure spraying. The nozzle should be placed between the inner ring and the center of the cage.