What kind of lubrication products need to be selected for high-load bearings?

Lubrication has an important influence on the fatigue life of rolling bearings and friction, wear, temperature, vibration, etc. Without normal lubrication, the bearings cannot work. Analysis of the cause of bearing damage indicates that about 40% of bearing damage is associated with poor lubrication. Therefore, good lubrication of the bearings is an effective measure to reduce bearing friction and wear. In addition, the lubrication of the bearing also has various functions such as heat dissipation, rust prevention, sealing, and mitigation of impact. The effect of bearing lubrication can be briefly explained as follows:
a. Forming an oil film between the two rolling surfaces or sliding surfaces that contact each other to separate the two surfaces, reducing friction and wear on the contact surfaces.
b. When using oil lubrication, especially when using circulating oil lubrication, oil mist lubrication and fuel injection lubrication, the lubricating oil can take away most of the friction heat inside the bearing and effectively dissipate heat.
c. When grease lubrication is used, foreign matter such as dust can be prevented from entering the bearing and sealing.
d. Lubricants have the effect of preventing metal corrosion.
e. Extend the fatigue life of the bearing.
Grease is a lubricant consisting of a base oil, a thickener and an additive. When selecting, you should choose a grease that is very suitable for the conditions of use of the bearing. Due to the different trademarks, there will be a big difference 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 preferably 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 rise.
When selecting the grease according to the working temperature, the main indicators should be the 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 lower than the dropping point of 10-20 °C. Synthetic grease should be used at a temperature below the drop point of 20-30 °C.
When selecting grease according to SKF bearing load, grease with a small penetration should be selected for heavy load. When working under high pressure, in addition to the small penetration, it also has higher 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 drying and low moisture environments.
Under high-speed and high-temperature conditions, oil lubrication can be used when grease lubrication is not suitable. A large amount of heat can be taken away by the circulation of the lubricating oil. Viscosity is an important characteristic of lubricating oil. The viscosity directly affects the fluidity of the lubricating oil and the thickness of the oil film formed between the friction surfaces. The viscosity of the lubricating oil at the working temperature of the bearing is generally 12-15 cst. The higher the speed, the lower the viscosity. The heavier the load, the higher the viscosity. Commonly used lubricating oils include mechanical oil, high-speed mechanical oil, turbine oil, compressor oil, transformer oil, cylinder oil, and the like.
The oil lubrication methods for bearings include:
a. Oil bath lubrication
Oil bath lubrication is the most common lubrication method. It is suitable for the lubrication of low and medium speed bearings. Part of the bearing is immersed in the groove. The lubricating oil is brought up by the rotating bearing parts and then flows back to the oil groove. The oil level should be slightly lower than the minimum. The center of the rolling element.
b. drip lubrication
Drip lubrication is suitable for bearing parts that need to supply lubricating oil quantitatively. The amount of dripping is generally one drop per 3-8 seconds. Excessive oil quantity will cause the bearing temperature to increase.
c. Circulating oil lubrication
The filtered oil is delivered to the bearing components by an oil pump, filtered through the lubricating oil after the bearings, and then cooled and used. Since the circulating oil can take a certain amount of heat to cool the bearing, this method is suitable for bearing parts with higher rotational speed.
d. Spray lubrication
The dry compressed air is mixed with the lubricating oil through a sprayer to form an oil mist. In the jet bearing, the air flow can effectively cool the bearing and prevent the intrusion of impurities. This method is suitable for the lubrication of high speed, high temperature bearing components.
e. Injection lubrication
The high-pressure oil is injected into the bearing through the nozzle by the oil pump, and the oil injected into the bearing flows into the oil groove through the other end of the bearing. When the bearing rotates at high speed, the rolling elements and the cage also form a gas flow at the relatively high rotation speed of the surrounding air. It is difficult to send the lubricating oil to the bearing by the general lubrication method. At this time, the lubricating oil must be sprayed by the high-pressure injection method. In the bearing, the position of the nozzle should be placed between the inner ring and the center of the cage.