1. Bearing type
Need to distinguish between point contact (NTN ball bearings) and line contact (NTN needle roller bearings and NTN cylindrical bearings).
For NTN ball bearings, the contact area for ball movement is relatively small, and grease with a base oil viscosity of ISO VG 68 to 100 is usually sufficient.
NTN bearings with line contact have higher requirements for grease. Not only because the contact surface requires more grease, but also because of sliding and friction. This is not conducive to the formation of a lubricating film, which easily leads to wear. Grease with higher base oil viscosity (ISO VG 150 to 460 or higher) should be selected.
The grease should match the speed parameters of the NTN bearing. And this mainly depends on the type and proportion of thickener and base oil. The speed parameter of the grease is not a material parameter, but depends on the type of bearing and the shortest running time required. Generally speaking, high speed or low starting torque rolling bearings need to choose a higher speed parameter grease. For low-speed rolling bearings, it is recommended to choose a grease with a lower speed parameter.
In order to obtain a good lubrication effect and a longer working life, it is usually recommended to select the grease according to the temperature of the bearing in the standard operating range. The working temperature range and high temperature stability of grease depend on the type and proportion of thickener and base oil, production quality and production process.
Other factors that need to be considered include the maximum applicable temperature, the dropping point (the temperature at which the grease is heated under specified conditions to achieve a certain fluidity, called the dropping point), and the minimum applicable temperature. NTN 4T-LM12749-LM12711 bearings online , pls click here :
Since the penetration of the grease is related to the load that it can withstand during use, the grease with a small penetration (larger consistency) should be selected for the heavy load; if it is both subjected to heavy load and impact load, it should be selected containing extreme Pressure additive grease, such as grease containing molybdenum disulfide.
5. Environmental humidity
If the working environment is humid, water vapor can easily invade NTN bearings. If the temperature is suddenly cold and hot, the water is also easy to condense. This problem is particularly prominent when there are large cavities in the bearing or housing.
Water may cause serious damage to grease or bearings, usually caused by aging, hydrolysis, lubricating film failure and corrosion. Compound barium and compound calcium grease can provide good waterproof performance, which has been certified in practice. The anti-corrosion effect of grease is also affected by additives.
6. Oscillation, shock and vibration
Oscillating load can have a great impact on the structure of the thickener in the grease. If the mechanical stability of the grease is not high, the lubricating effect will be affected. This leads to softening, degreasing, or hardening of the grease, which reduces the lubricating ability. Therefore, it is recommended to choose a grease whose mechanical stability has been tested accordingly.
If hard particles penetrate into the NTN bearing, it will not only increase the noise, but also cause wear. Proper sealing of the bearing can prevent this from happening. The grease can enhance the sealing effect by adding a layer of protection to the seal. In this case, a stronger grease type should be selected.
8. Installation location and adjacent parts
Even if the axis of rotation is vertical or inclined, the lubricant must remain at the lubrication point. In addition to proper sealing, choosing a more viscous grease can also prevent it from running away.
If there are multiple lubrication points close to each other, accidental contact between greases may occur. Therefore, attention must be paid to the compatibility of greases with each other. However, when possible, the best solution is to use only one type of grease, which should also be compatible with the sealing material.
9. Regulations and environmental protection
Different industrial sectors should also consider legal and environmental factors when choosing grease. For example, in the food processing industry, greases with relevant authorizations are specified.
Correct lubrication and maintenance are very important, and correct installation and use are indispensable. During assembly or installation, if the internal clearance of NTN bearings is too large or too small, or in some cases, the preload is too high, which may cause early damage and shorten the bearing life. In addition to causing downtime and expensive maintenance, improper bearing assembly and installation may also have more negative effects, such as affecting the operation of other parts and shortening their service life.