The seven principles that should be followed when selecting lubricating grease for bearings are:
1. Environmental conditions: When bearings operate under humid, corrosive gas, low temperature, dust, and strong radiation conditions, lubricating oil is prone to contamination and deterioration. In this case, lubricating oil with water resistance, wear resistance, corrosion resistance, cold resistance, and strong radiation resistance should be selected. In areas with flowing water splashing, emulsion spraying, humid air, or severe dust particles, it is generally not advisable to use lubricating oil, but rather lubricating grease.
2. Bearing accuracy: When the friction surface of the bearing is rough, it is generally suitable to use oil with high viscosity to withstand local large pressure caused by poor contact. However, when the friction surface accuracy is high, low viscosity lubricating grease should be selected to reduce unnecessary energy loss and temperature rise.
3. Working temperature: Working temperature affects the viscosity change and lubrication effect of lubricating oil. Therefore, when the working temperature is low, lubricating grease with lower viscosity should be selected; When the working temperature is very high, lubricating grease with high viscosity or appropriate additives should be selected. When it is above, solid lubricants can generally be considered. The viscosity of the selected lubricating grease should also vary depending on the ambient temperature. For example, when lubricating the same bearing, in the north or winter of China, lower viscosity lubricating grease should be selected compared to the south or summer. When the working temperature often changes, lubricating grease with excellent viscosity temperature characteristics should also be selected, that is, the viscosity of the lubricating grease used does not change much with the increase or decrease of the working temperature, to ensure that the oil film thickness is stable within a certain range.
4. Movement speed: The higher the rotational speed, the lower the viscosity of lubricating grease should be selected to avoid increasing movement resistance and generating too much heat; On the contrary, in low-speed situations, lubricating grease with higher viscosity should be used to improve load-bearing capacity.
5. Sports properties: There are impacts, vibrations, frequent load changes, variable speeds, and starting during movement. Frequent parking, reverse rotation, and reciprocating or intermittent movements are not conducive to the formation of oil film, so lubricating grease with higher viscosity should be selected. Sometimes it is preferable to use lubricating grease or even solid lubricants to ensure reliable lubrication.
6. Working load: The larger the load the rolling bearing bears, the higher the viscosity of the lubricating oil should be selected, and it should have good oiliness and extreme pressure to prevent the lubricating oil from being squeezed out of the friction pair or causing direct contact between metals. The smaller the radial clearance of rolling bearings, the higher the machining accuracy of friction surfaces, and the lower the viscosity of lubricating grease.
7. Bearing hardness: When the friction surface hardness of the bearing is low, lubricating grease with high viscosity should be selected, and the oil amount should be sufficient; On the contrary, the viscosity of lubricating grease can be reduced.
