The purpose of lubrication is to reduce friction and wear; Lubricating oil can also take away the heat generated by friction, thereby reducing the temperature of the friction surface and playing a cooling role. There are many varieties and specifications of electric motors, and the selection of lubricating grease for general electric motors depends on the type of bearings, speed and temperature, load, etc. Therefore, lubricating grease with different quality requirements must be selected according to the operating conditions of the mechanical equipment.

Types and properties of commonly used lubricating grease for motors

Calcium based grease is a calcium soap made from animal and vegetable oils and lime, thickened with medium viscosity lubricating oil. It is divided into five grades based on penetration: 1, 2, 3, 4, and 5. The larger the grade, the harder the grease, the smaller the penetration, and the higher the drip point. The characteristics are good water resistance, not easily emulsified and deteriorated when in contact with water, and able to work in humid environments or in contact with water, but poor heat resistance.

Sodium based grease is made from animal and vegetable oil sodium soap, thickened with medium viscosity lubricating oil, and is divided into three grades: 2, 3, and 4. The larger the grade, the harder the grease and the higher the drip point. The characteristic is good heat resistance but poor water resistance.

Calcium sodium based grease is made from a mixture of animal and vegetable oils, calcium sodium based soap, and thickened lubricating oil with medium viscosity. It is divided into two grades: 1 and 2. The characteristic is good heat resistance and water resistance. Water resistance is better than sodium based grease, and heat resistance is better than calcium based grease.

Graphite calcium based grease is made by thickening medium viscosity lubricating oil with animal and vegetable oil calcium soap and adding 10% flake graphite. The characteristic is good wear and pressure resistance, able to adapt to heavy loads, and has good water resistance, suitable for lubricating equipment that comes into contact with water or moisture. However, graphite contains a large amount of mechanical impurities and is not suitable for rolling bearings and precision parts.

Lithium based grease is made from 12 hydroxystearic acid or lithium stearate soap, thickened lubricating oil of medium viscosity, and added with antioxidants. Divided into four grades: 1, 2, 3, 4. It is a universal long-life grease that can replace calcium based, sodium based, and calcium sodium based greases. Widely used on components that come into contact with high temperature, high speed, and water, and can be used in environments around 120 ℃ for a long time. The characteristics are good water resistance, good mechanical and chemical stability, good heat resistance, and high drop point.

Composite calcium based grease is made by using calcium acetate as a composite agent to make calcium soap and thickening lubricating oil with medium viscosity. Divided into four grades: 1, 2, 3, 4, commonly used are grades 2 or 3. They are characterized by good heat resistance, high drop point, certain water resistance, and can work in humid environments or in contact with water. They have good mechanical and colloidal stability and can be used on high-speed rolling bearings.

Molybdenum disulfide grease is made by adding a certain amount of molybdenum disulfide to certain types of grease. Commonly used lubricants include molybdenum disulfide calcium based, composite calcium based, lithium based, etc., which are suitable for lubricating bearings with particularly heavy loads and high speeds.

Aluminum based grease is made from stearic acid aluminum soap and thickened lubricating oil with medium viscosity. The characteristics are good water resistance and protection, but poor heat resistance, low drop point, and a maximum operating temperature of 50 ℃.

Precautions for using lubricating grease

1. In order to prevent lubricant loss and external dust and moisture from entering the bearing, it is necessary to pay attention to sealing. Bearing seals are divided into two categories: contact seals and non-contact seals. Non contact clearance seals are commonly used for motor bearing seals.

2. Lubricating grease should not be added too much or too little, usually accounting for about 1/3 to 1/2 of the bearing chamber volume. Bearings with low speed and light load can be added more, while bearings with high speed and heavy load can be added less.

3. Different types of lubricating grease cannot be mixed, and the old grease must be cleaned before replacing the lubricating grease.

4. After running for 1000-1500 hours, the bearing should be lubricated once, and after running for 2500-3000 hours, the lubricating grease should be replaced.