To fully utilize and maintain the expected performance of bearings in the long term, it is necessary to carry out related operations such as cleaning, maintenance, lubrication, etc. Especially, the lubrication of bearings plays a very important role in bearing operation. Generally, lubricating grease is mainly used in bearings for lubrication. Suitable lubricating grease can not only reduce the friction force of bearings during operation, but also extend the service life of bearings to a certain extent. So, how to choose lubricating grease for bearings?
1、 Selection method of lubricating grease
1. Understand one's own needs
(1) Bearing operating temperature. For machine bearings used indoors, such as machine tools, manual tools, precision machinery, and intermittent starting motors, the general operating temperature range is 10-50 ℃. For mechanical bearings used in outdoor work such as transportation machinery, construction machinery, and agricultural machinery, the general operating temperature will definitely vary with changes in atmospheric temperature. In most areas of China, the atmospheric temperature changes from -40 to 40 ℃. Factors such as increasing load, speeding up speed, rising ambient temperature, overfilling of lubricating grease, and long-term continuous operation all cause the temperature of rolling bearings to rise. For the wheel bearings of heavy-duty trucks traveling along the main road, the temperature can reach 40-80 ℃. Large generator bearings can reach temperatures of 80-90 ℃, while rolling bearings for aircraft landing gear and high-temperature motors can reach temperatures of 150-200 ℃ or higher.
(2) Bearing working environment. Bearings working in humid environments should use lubricating grease with good anti-corrosion performance. When machinery works in a humid environment and needs to stay for a long time, condensation water will form on the bearing surface due to cooling. To prevent rusting, non absorbent calcium based grease should be selected. When there is a lot of dust around the bearing and a curved seal is used, it is hoped that the lubricating grease will also have a sealing effect. Lubricating grease with lower penetration should be selected. When the bearing medium has strong chemical reactions, lubricating grease with anti-corrosion additives should be selected.
(3) Bearing motion performance. When bearings lubricated with grease require particularly low friction or low starting friction torque at low temperatures, lubricating grease composed of synthetic base oil with similar low viscosity and high penetration should be selected. For small motor bearings that require low noise, filtered hard oil or high viscosity base oil lubricating grease should be selected to reduce bearing noise.
2. Understand lubricating grease
Once you have determined the type of lubricant you need, you can start choosing a lubricant. However, there are many different types of lubricants on the market. What kind of lubricant is good and how should you judge its quality? Let's take a look at the selection method of bearing grease together.
(1) Check the production date. In general, the storage time of lubricating grease should not be too long. Users should choose grease with a shelf life of no more than one year. Lubricating grease with a shelf life of more than one year should be inspected and qualified before use. If it exceeds one year or is not within its shelf life, it cannot be selected. Even if such lubricating grease is chosen, its effect will not be significant, and it may even damage the bearing.
(2) Look at the appearance. Different types of lubricating grease have different colors, but regardless of the color of the grease, it should be a uniformly viscous paste. If the color of the grease is uneven or the skin hardens, there is a lot of floating oil or a significant decrease in viscosity on the surface of the grease, or if the surface of the grease emulsifies and turns white due to the mixing of water, these phenomena indicate that the lubricating grease has deteriorated and cannot be used.
(3) Smell the scent. If you smell a clear odor of grease and acid decay when opening the packaging, it indicates that the lubricating grease has deteriorated. The deteriorated lubricating grease cannot be used. If you insist on using it, it will not only have no effect but also damage the bearings.
(4) Hand twisting. When twisting lubricating grease without fillers by hand, the feel is smooth and there is no rough texture; Otherwise, it may be due to uneven dispersion of thickening agents or impurities mixed in, which will increase the resistance of bearing operation and cannot be used. However, lubricating grease containing filler powder has a slightly uncomfortable feel, so everyone needs to pay attention to distinguishing it.
(5) Use fire. Lift a piece of lubricating grease with a wire and burn it with a lighter. If the lubricating grease softens and drips, it indicates that it is a low-quality lubricating grease with a low drip point and cannot be used. It should be noted that this method can only identify low-quality lubricating grease with low drop points, as the temperature of the lighter flame does not exceed 120-130 ℃, and most lubricating greases have drop points above this temperature, so they will not drip even when burned with a lighter.
(6) Sunlight exposure. Take a piece of lubricating grease and place it in a cup in the sun for one or two days. If there is a significant change in the grease body, such as oil separation or discoloration, it indicates that the performance of the grease is unstable and cannot be used. If there is no significant change in the grease after a period of sun exposure, it indicates that the performance of the lubricating grease is still relatively stable and can be considered for use.
(7) Water addition method. Take a small amount of lubricating grease and place it in a cup. Add a few drops of water on top of it and stir with a glass rod. If turbidity or whitening occurs, it indicates that the grease is easily emulsified and not water-resistant. If there is no significant change after adding water, it indicates that the water resistance of the lubricating grease is still acceptable and can be considered for use.
3. Look at the manufacturer
(1) Production scale. It is recommended that you choose manufacturers with larger production scales and longer production periods, as such manufacturers generally have more experience and guaranteed quality. The important thing is that if the production period is longer, it proves that the manufacturer is still capable in the industry and good in innovation, otherwise it would have been eliminated long ago.
(2) Highly reputable. When choosing a lubricant manufacturer, it is important to choose one with a high reputation. This is a guarantee for us that there will be no fraudulent or substandard products. You can compare several options and choose the one with higher credibility under the same conditions.
(3) The quality is relatively good. Merely having a high reputation is not enough if the quality is not up to standard. Therefore, when evaluating the reputation, it is important to carefully examine the quality of the lubricating grease. This is also a noteworthy issue when choosing a manufacturer.
(4) Good service. The use of lubricating grease is not just about buying it back and filling it directly. There are certain requirements for its usage, so when choosing, you need to pay attention to the relevant services of the grease manufacturer. If you have any questions, you can consult and communicate at any time.
2、 Precautions for selecting lubricating grease
1. The selected lubricating grease should be suitable for its intended use. The specific selection of grease for lubrication should be based on the type of friction, operating conditions, working conditions, environmental conditions, and grease supply methods; For protective grease, it should be able to effectively protect metals from corrosion, such as protecting parts that come into contact with seawater. Aluminum based grease with strong adhesion and water resistance should be selected; Generally, protective grease can be made from solid hydrocarbon thickened high viscosity base oil. For sealing grease, attention should be paid to its resistance to the solvent of the sealed medium.
2. The selected lubricating grease should minimize the variety of grease and improve economic efficiency as much as possible. When meeting the requirements, try to use multi effect universal lubricating grease such as lithium based grease, composite soap based grease, polyurea grease, etc. In this way, the variety of fats is reduced, the management of fats is simplified, and the long service life of multi effect fats can reduce the cost of using fats and repair costs.
3. The selected lubricating grease should be compatible with the working state of the friction pair. When there is significant vibration, use grease with high viscosity, good adhesion, and vibration damping properties, such as composite soap based grease thickened with high viscosity cyclic or mixed base lubricating oil.

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