Which grease is best for bearing？
Lubricants used in bearings are mainly divided into two types: grease lubrication and oil lubrication. Solid lubricants can also be used under special working conditions. In theory, choosing lubricating oil or grease as the lubrication of the bearing can meet the lubrication needs of the bearing. . When lubricating, it is enough to ensure that there is a lubricant that can form an oil film on the moving contact surface and reach the ideal working temperature.
The choice of bearing grease is directly related to the stable operation of the equipment. In order to better exert the best condition of the bearing, the bearing will generate heat after long-term high-speed operation, and it will be in a high-heat operation process for a long time, so the purchased Grease must be resistant to high temperature, and the higher the speed, the higher the temperature, and the higher the temperature resistance requirements for the bearing grease .
In the actual selection of lubricants, it can be comprehensively considered according to factors such as the structure of the machine, the operating conditions of the bearing, the structure of the components adjacent to the bearing, the lubrication method, and maintenance. Therefore, the following aspects must be considered:
The seal is a necessary barrier to protect the bearing and lubricant from external contamination. During the operation of the bearing, no debris or moisture can penetrate into the bearing to prevent damage to it. Correct installation and maintenance is an important factor for the longest service life of the bearing. At the same time, we must pay attention to the cleanliness of the bearing, the correctness of the bearing selection and the selection of appropriate installation and maintenance tools. In addition, the bearings must be protected from contaminants and moisture, and they must be installed and lubricated correctly. Therefore, the design of the bearing arrangement, the condition of the oil seal, the type of lubricant and the lubrication cycle, and even the special maintenance all play the same and important role.
2. Mechanical stability:
Grease will soften during machining, causing leakage. During normal operation, grease will be thrown into the bearing from the bearing housing. If the mechanical stability of the grease is not enough, the soap structure of the grease will be mechanically disintegrated during operation, causing the grease to be destroyed and thus losing its lubricating effect.
3. Anti-rust performance:
The grease used in the bearing must have an anti-rust effect, and the anti-rust agent should preferably be insoluble in water. Grease should have good adhesion and can form an oil film on the surface of the steel to protect the bearing.
4. Mixed grease:
Never mix incompatible greases unless it is necessary. If two incompatible greases are mixed, the consistency will usually become softer, and the bearing may be damaged due to the easy loss of grease in the end. If you don't know which kind of grease the bearing originally used, you must thoroughly remove the old grease inside and outside the bearing before adding new grease.
When choosing which kind of grease to use for a bearing, not only the factors of the grease must be considered, but also the factors of the bearing, such as the structure of the bearing, the speed, the way of filling the grease, and the type of the bearing.
1. Bearing structure factors:
Ball bearings: Grease with high consistency
Cylindrical and tapered roller bearings: low-consistency grease
Needle roller bearings: grease with high adhesion
2. Speed factor:
Ball bearing: (inner diameter less than 65mm)
Grease for dn value<300000; Lubricant for dn value>300000
Roller bearing: (inner diameter less than 50mm)
Grease for dn value <150000; Lubricant for dn value> 150000
3.Speed and load factors:
High speed: low base oil viscosity, high consistency grease
Low speed: grease with high base oil viscosity and low consistency
Heavy load: grease with high base oil viscosity and extreme pressure anti-wear properties.
Low load: low base oil viscosity, high consistency grease.
4.Factors of grease injection method
Centralized lubrication: grease with appropriate base oil viscosity and low consistency
Non-centralized lubrication: Grease with unlimited base oil viscosity and high consistency
Grease for sliding bearings:
Peripheral speed is less than 2m/s, intermittent movement and requirements have a sealing effect on pollutants and moisture
Factors to consider when choosing lubricating grease
The dropping point of grease should be 30~50℃ higher than the working temperature of the equipment
Water resistance and adhesion of grease
When the load is large, use extreme pressure grease with high base oil viscosity and low consistency
When the sleeve is made of non-ferrous metal, the grease must not contain active elements such as S and Cl.
Data expansion: Which grease is best for gear?
The effect of grease on gears is also very large, but the selection of grease is slightly different than that of bearing grease. For example:
1. Open gears and chains
Use grease with high base oil viscosity and strong adhesion.
Outdoor equipment should be considered for the water resistance and low temperature performance of the grease.
Centralized lubrication equipment uses semi-fluid grease.
Equipment operating at high temperatures should consider the high temperature performance of the grease
Heavy-duty equipment uses extreme pressure grease.
2. Selection of grease for gearbox
Splash gear reducer can be lubricated with grease
Use 00 extreme pressure grease when the center distance is 400mm and below
When the center distance is above 400mm, use 0# extreme pressure grease
Determine the water resistance of the grease according to the use environment of the equipment
The amount of grease injected should be higher than the amount of lubricating oil used.
3. Planetary cycloid reducer
Non-circulating lubricated planetary cycloid reducer can be lubricated with extreme pressure semi-fluid
4. Worm gear reducer
Generally, high-viscosity lubricating oil is used. Under special conditions, lubricating grease with high base oil viscosity and oily agent can be used. If the worm gear is made of bronze or other non-ferrous materials, the grease is not allowed to contain strong active elements such as S and Cl.
In conclusion, bearing grease should be determined according to the bearing speed, operating temperature, load and other working conditions. If there is no special requirement, there will be no problem in purchasing grease of up to standard quality. If you don't know what the bearing speed load and temperature requirements are, it is recommended to use fully synthetic high temperature and high speed bearing grease. If there are special requirements, such as high temperature resistance, low temperature resistance, high load, high speed, high load, synthetic grease is recommended. The synthetic lubricating grease process is complicated and there are fewer manufacturers. Therefore, when choosing a product, you need to pay attention to the product quality, not just the price of the product.