Basic terms and definitions：

Sealing: Refers to the fact that there is no leakage at the connection of the machine and equipment；

Leakage: The main causes of seal leakage caused by the transfer of sealed materials: 1. Surface defects of mechanical parts, dimensional processing errors and assembly gaps formed by assembly errors; 2. There is a pressure difference on both sides of the seal.Reducing or eliminating assembly gaps is the main way to prevent leakage；

Sealing force (or sealing load): The contact force acting on the seal of the contact seal；

Contact pressure: The force between the friction surfaces of the packing seal；

Packing: On equipment or machines, parts assembled between the movable rod and the hole through which it passes to seal the medium；

Compression packing: A packing with a soft texture and axial compression in the packing box, which produces radial elastic deformation to block the gap.；

Compression ratio: The compression deformation rate caused by the compression deformation of the sealing ring when it is loaded into the sealing groove and squeezed, and its cross-section is compressed and deformed.；

Static seal: A seal between relatively static mating surfaces. The function of the seal is to prevent leakage.；

Dynamic sealing: Refers to the sealing between moving parts in a machine or equipment；

Contact type sealing: The sealing force is used to make the seal and the mating surface compress or even embed each other to reduce or eliminate the gap between the sealing；

Packing seal: Packing is used as the seal of the seal；

Sealing gaskets: thin-section seals placed between the mating surfaces with geometries that meet the requirements. According to the material, they are divided into: rubber gaskets, metal gaskets, paper gaskets, asbestos gaskets, plastic gaskets, graphite gaskets, etc.；

Sealing ring: A ring used to prevent the medium from leaking from the sealing device, and to prevent external foreign objects and air from entering the sealing inside the sealing device.；