According to the number of springs in the compensation mechanism can be divided into multiple spring and single spring mechanical seal. The seal with multiple springs in the compensation mechanism is called the multiple spring mechanical seal (Figure 5); the mechanical seal with only one spring in the compensation mechanism is called the single spring mechanical seal (Figure 6). Multi-spring mechanical seal, also known as small spring mechanical seal, the axial size of this structure is small, can be used to change the number of spring method to change the elastic force, the axial force is more uniform, suitable for high-speed mechanical seal, should not be used in corrosive media. Single spring mechanical seal, also known as large spring mechanical seal, the sealing structure is relatively simple. Some sealing types also use springs to transfer torque. Domestic sealing application of large spring more, but can not be used for high-speed.