The seal of the bearing can be divided into two types: self-contained seal and external seal. The so-called bearing self-sealing is to manufacture the bearing itself into a device with sealing performance. Such as bearing with dust cover, sealing ring and so on. The sealing takes up little space, is easy to install and disassemble, and has a relatively low cost. The so-called bearing plus sealing performance device is a sealing device with various performances manufactured inside the installation end cover, etc. Bearing seals are divided into non-contact seals and contact seals. Among them, the non-contact seal is suitable for high-speed and high-temperature occasions, and has different structural forms such as gap type, labyrinth type and gasket type. Contact seals are suitable for medium and low speed working conditions, and commonly used structural forms such as felt seals and leather cup seals.

According to the working conditions of the bearing and the requirements of the working environment for the degree of sealing, various sealing forms are often used comprehensively in engineering design to achieve a better sealing effect. The following main factors should be considered in the selection of additional seals for bearings:

1. Bearing lubricants and types (grease and lubricating oil);

2. The working environment of the bearing and the size of the space occupied;

3. The advantages of the supporting structure of the shaft allow the angle deviation;

4. The peripheral speed of the sealing surface;

5. The working temperature of the bearing;

6. Manufacturing costs.