Principles for selecting bearing grease When selecting grease, it is mainly based on the working environment, operating temperature, load conditions, etc. of the bearing.

1. Working environment It mainly refers to the minimum and maximum temperature of the working environment, air humidity, whether it contains corrosive gases or excessive dust, etc. For example, when used outdoors in severe cold areas, lithium-based low-temperature grease should be used; calcium-based grease should be used in places with high humidity and water; in dry places with less water, sodium that is easily soluble in water should be used. base grease.

2. Working temperature One is the lowest temperature of the use environment, and the other is the highest temperature that may occur during operation. When the operating temperature is high, high-temperature grease with a higher dropping point should be selected. The actual maximum operating temperature should be 10-20°C lower than the grease dropping point (synthetic grease should be 20 ~ 30°C).

3. Load conditions For heavy loads, grease with smaller taper penetration should be used. When working under high pressure, in addition to requiring small cone penetration, it also requires high oil film strength and extrusion performance.

Injection method of bearing grease There are two types of grease injection tools for rolling bearings: manual grease injection and pressure grease injection, commonly known as oil guns; larger production, use and repair units may use special grease injection machines (cans or barrels) with metering devices.

Note: In the absence of the above special equipment, clean and burr-free bamboo boards or copper plates can be used. The use of angular steel tools should be prohibited.

The amount of grease injected into the bearing

1. The impact of grease injection amount on bearing use For sealed bearings, appropriate grease has been filled during production; for open bearings, although a sealing device is installed to prevent grease leakage, it will still gradually decrease due to a small amount of leakage and other reasons during use, and needs to be carried out. Keep replenishing.

Practice has proved that the amount of grease injected into the bearing will have a certain impact on its operation. Too little grease injection can easily lead to insufficient lubrication. In severe cases, it can lead to dry friction, generate high heat, and cause the bearing to be scrapped in a short period of time due to wear, which may have a serious impact on the entire equipment. Too much grease will cause the rolling resistance of the bearing rolling elements to be large, and the temperature of the grease in the bearing will be high. When it reaches its dropping point, it will turn into liquid and be lost. Finally, the above-mentioned serious consequences of too little grease will occur. In addition, Leaking grease causes waste and pollutes the environment.

2. Principles of fat injection amount The principle of grease injection: the less the better while ensuring sufficient lubrication of the bearing. Based on practical experience, the following principles are more appropriate. For open bearings, the appropriate amount of grease injection should depend on the cavity volume of the bearing chamber (after the two bearing caps and the bearing are installed, the part occupied by the air in the internal space contained by them, and the blank part except the bearing balls) The size and the speed of the bearing used (for AC motors, the number of poles can also be used instead of the speed) to simply calculate the amount of grease. For the bearing chamber structure with an oil retaining plate (also called an oil slinging plate), the first amount of grease should be appropriately increased, and no grease should be injected into the cavity of the bearing outer cover (this is to accept the “waste grease” that is thrown out “Trash can”, the grease in it will not enter the bearing for lubrication, so the newly injected grease will be wasted). With this structure, the grease in the bearing chamber will become less and less. If the grease is not added regularly as required, the lubrication effect will be reduced due to too little grease. Eventually, the grease will dry up due to overheating, causing the entire bearing to be damaged.

3. Things to note When adding grease, the site should be clean and the tools used should be cleaned with gasoline. After the grease is filled, other components should be assembled as soon as possible to prevent the grease entering the bearing from entraining dust and debris, especially sand and iron filings.

Grease injection of rolling bearings during operation For machines using open bearings, after running for a certain period of time, grease should be added to the bearing chamber. For those with an oil filling system, this can be done without dismantling the machine. Otherwise, the bearing cover should be disassembled and oil should be filled directly into the bearing chamber. Care should be taken to use the same brand of grease as the original grease to avoid harmful reactions of greases with different components that may reduce or even lose the lubrication effect, causing overheating damage to the bearing.

Note: If the original grease has deteriorated, it should be completely removed with solvents such as gasoline, and then refilled with new grease.

Time interval for replenishing grease during operation The expected life of a grease is affected by many factors. For example, the type of grease, the speed and temperature of the bearing, the amount of dust and corrosive gases in the working environment, the design and actual function of the sealing device, etc.

For sealed or smaller bearings, both the bearing itself and the grease in it determine the life of a set of bearings. There is no need or possibility to add or change grease midway.

According to experience, the effect of temperature on the grease replenishing interval is: when the temperature (temperature measured on the outer ring of the bearing) reaches above 40°C, the grease replenishing interval will be shortened by half for every 15°C increase.

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