Published at:2012-07-13 View:183
First, the role of bearing lubrication Lubrication has a significant impact on the fatigue life of rolling bearings and friction, wear, temperature, vibration, etc., without normal lubrication, the bearing can not 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 shock mitigation.
The effect of bearing lubrication can be briefly explained as follows:
Second, grease lubrication and oil lubrication comparison of bearing lubrication methods are roughly divided into grease lubrication and oil lubrication.
In order to fully utilize the function of the bearing, it is important to use a lubrication method depending on the purpose of use reduction and use. 3. Grease Lubricating Grease is a lubricant composed 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 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 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.
Fourth. Selection of grease
When selecting grease according to working temperature, the main indicators should be dropping point, oxidation stability and low temperature performance. The dropping point can generally be used to evaluate 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 the grease according to the bearing load, the grease with a small penetration should be selected for the 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.
Fifth. Oil lubrication Under the conditions of high speed and high temperature, 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, and 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. Oil lubrication methods include:
Sixth. Solid Lubrication Solid Lubrication Under some special conditions, a small amount of solid lubricant is added to the grease. For example, adding 3 to 5% of Molybdenum Disulfide No. 1 can reduce wear and improve resistance to pressure and heat. For high temperature and elegance. Special conditions such as high vacuum, corrosion resistance, radiation resistance, and extremely low temperature. Adding solid lubricants to engineering plastics or powder metallurgy materials can produce bearing parts with self-lubricating properties, such as solid lubricants with binders. Bonded to the raceway, cage and rolling elements to form a lubricating film that has a certain effect on reducing friction and wear.
Seventh.Replenishment and replacement of lubricants a. Replenishment interval of grease Due to mechanical action, aging and pollution increase, the lubricating base filled in the bearing configuration will gradually lose its lubricating performance. Therefore, the lubrication rank needs to be continuously supplemented and updated. The interval between lubricant replenishment will vary depending on the formation, size, and rotational speed of the bearing. Figure 4-1 shows the approximate interval between refilling the grease based on the operating time. In addition, when the bearing temperature exceeds 70 ° C, for every 15 ° C rise in the bearing temperature, the supplemental interval of the grease is reduced by half. Double-sided closed bearings have been filled with grease at the time of manufacture. “HRB” uses standard greases in these products. The total operating temperature range and other properties are suitable for the specified conditions, and the amount of grease is also corresponding to the bearing size. The service life of the grease can generally exceed the bearing life. Except for special occasions, no grease needs to be replenished. b. Lubricating oil replacement cycle The replacement period of the lubricating oil varies depending on the conditions of use and the amount of oil. Under normal circumstances, when the operating temperature is below 50 ° C and the dust is used in a good environment, it is replaced once a year. When it reaches 100 °C, it should be replaced in 3 months or less.