Types of commonly used lubricating grease for motor bearings
Analysis of the causes of bearing damage shows that about 40% of bearing damage is related to poor lubrication. Therefore, good lubrication of bearings is an effective measure to reduce the friction and wear of bearings. In addition, the lubrication of bearings has many functions, such as heat dissipation, rust prevention, sealing, mitigation of impact and so on.
There are many kinds and specifications of motors. Generally, the selection of lubricating grease for motors depends on the type of bearings, number of revolutions, temperature, load, etc. Therefore, lubricating grease with different quality requirements must be selected according to the operating conditions of mechanical equipment.
Types and properties of lubricating grease commonly used in motors
Calcium base grease is made of calcium soap made of animal and vegetable oil and lime, and thickened medium viscosity lubricating oil. It is divided into five grades: 1, 2, 3, 4 and 5 according to penetration. The larger the number, the harder the grease, the smaller the penetration and the higher the drop point. It is characterized by good water resistance, not easy to emulsify and deteriorate in case of water, and can work in a humid environment or in contact with water, but poor heat resistance.
Sodium base grease is made of animal and vegetable oil sodium soap and thickened lubricating oil with medium viscosity. It is divided into three grades: 2, 3 and 4. The larger the number, the harder the grease and the higher the drop point. It is characterized by good heat resistance and poor water resistance.
Calcium sodium base grease is made of animal and vegetable oil calcium sodium base mixed soap and thickened lubricating oil with medium viscosity. It is divided into two grades: 1 and 2. It is characterized by good heat resistance and water resistance. Water resistance is better than sodium grease, and heat resistance is better than calcium grease.
Graphite calcium base grease is made of animal and vegetable oil calcium soap, thickening medium viscosity lubricating oil and adding 10% flake graphite. It is characterized by good wear resistance and pressure resistance, can adapt to heavy loads, and has good water resistance. It is suitable for lubricating equipment in contact with water or moisture. However, graphite contains a lot of mechanical impurities and is not suitable for rolling bearings and precision parts.
Lithium grease is made of 12 hydroxystearic acid or lithium stearate soap, thickened lubricating oil with medium viscosity and antioxidant. It is divided into four grades: 1, 2, 3, 4 and 4. It is a universal long-life grease, which can replace calcium, sodium and calcium sodium grease. It is widely used in high temperature, high speed and parts in contact with water, and can be used in the environment of about 120 ℃ for a long time. It is characterized by good water resistance, good mechanical stability and chemical stability, good heat resistance and high drop point.
Compound calcium base grease is made of calcium soap with calcium acetate as a compound agent and thickened with medium viscosity lubricating oil. It is divided into four grades: 1, 2, 3, 4 and 3. The commonly used ones are No. 2 or 3. It is characterized by good heat resistance, high drop point, certain water resistance, and can work in a humid environment or in contact with water. It has good mechanical stability and colloidal stability. It can be used on high-speed rolling bearings.
Molybdenum disulfide grease is made by adding a certain amount of molybdenum disulfide to some greases. Commonly used are molybdenum disulfide calcium base, composite calcium base, lithium base and other greases, which are suitable for bearing lubrication with particularly heavy load and high speed.
Aluminum base grease is made of aluminum stearate soap and thickened lubricating oil with medium viscosity. It is characterized by good water resistance and protection, but poor heat resistance, low drop point, and its maximum service temperature is 50 ℃.
Precautions for using grease
1. In order to prevent the loss of lubricant and the invasion of external dust and moisture into the bearing, attention must be paid to sealing. Bearing seals are divided into contact seals and non-contact seals. Motor bearing seals mostly adopt non-contact gap seals.
2. Grease should not be added too much or too little, generally accounting for about 1/3~1/2 of the volume of the bearing chamber. Bearings with low speed and light load can be added more, and bearings with high speed and heavy load can be added less.
3. Different types of grease cannot be mixed, and the old grease must be cleaned before replacing the grease.
4. The bearing should be lubricated once after 1000~1500 hours of operation, and the grease should be replaced after 2500~3000 hours of operation.