The moving ring can be divided into non-compensatory and compensatory types. In the stationary mechanical seal, the non-compensatory moving ring is used, which is fastened on the shaft (Figure 17), and some are pressed on the shaft with the shaft sleeve (Figure 3). Obviously, such moving ring cannot float.

　　The compensatory moving ring is widely used in rotary mechanical seals. After the sealing end surface is worn, the moving ring is automatically compensated under the action of elastic force, and the sealing mode of the moving ring and the shaft sleeve is realized by the auxiliary sealing ring. At present, the structure of moving ring is very different. According to the sealing method of moving ring and shaft sleeve, it can be summarized into three categories: moving ring with axial installation of auxiliary sealing ring, moving ring of auxiliary sealing ring and moving ring with bellows.

　　The moving ring installed by the auxiliary sealing ring (Figure 18) and the spring force to press the sealing ring. Spring force can be regarded as no change, reliable sealing, long service life, installation is more convenient, so as to be widely used.

　　The moving ring radially mounted by the auxiliary sealing ring (Figure 19) is sealed by the surplus and elasticity of the sealing ring, mostly made of PTFlon and synthetic rubber. With the extension of use time, these two materials appear cold flow deformation and aging and lose elasticity. It has been documented that 40% of the failure of this structure occurs in the auxiliary sealing ring.

　　The third kind of moving ring refers to the bellows type seal, the moving ring and bellows are made into a whole (Figure 8), so there is no moving ring sealing ring is needed.