As we all know, grease is very important for motor bearings. Therefore, it is necessary to have a certain understanding of the grease.
First of all, let's look at the classification of grease. Grease is made from mineral oil or synthetic oil and thickener. Mineral oil or synthetic oil is a liquid lubricant. Thickener is usually a metal soap and a thickener, such as a polyurea soap. According to the use temperature, the grease can be divided into three categories.
High temperature grease: the general use of temperature is above 120 degrees centigrade.
Low temperature grease: the genral use of temperature is below -20 degrees centigrade.
High and low temperature grease: It can not only meet the high tempearture, but also meet the low temperature.
Grease also has advantages and disadvantages, compared with the lubricating oil, the grease has advantages as follows.
Good bearing capacity and damping capacity.
Good adhesion, not easy to drain.
Simplifying the design and maintenance of equipment.
And the grease also has disadvantages as follows.
Internal friction is big and it is not good for energy saving.
It is inconvenient to provide grease and replace grease.
Poor cooling and poor heat dissipation.
There are several important indicators for grease.
Cone penetration is an indicator of the consistency of grease and the degree of soft and hard. It refers to the depth of the cone faling into the specimen under the spcified load, time, and temperature. The unit of penetration is expressed in 0.1mm. The greater the penetration value, the more soft the grease is.
The ability of petroleum products to resist heat and oxidation and to maintain their properties without permanent change when used in long-term storage or under long-term high temperature is called oxidation stability.
The viscosity of the grease varies with the shear rate at a certain temperature, which is called similar viscosity. The unit is Pa·S.
Only between the low temperature performance limit and the high temperature performance limit can the grease function reliably. Whem the temperature is higher than the high temperature perfrmance limit, the aging and oxidation of the grease will speed up rapidly. on the contrary, the amount of oil in the grease will be reduced and the consistency increses, leading to the lubrication of the rolling body and the contact surface.
In a word, the grease is important for motor, we should have relative knowledge for the grease.