The mechanical seal structure is mainly distinguished according to the number of friction pairs, the number of springs, whether the spring is in contact with the medium, the spring movement or stationary, the specific pressure caused by the medium on the sealing end face, the leakage direction of the medium, and the like. Each type of structure is suitable for certain working conditions. When selecting the mechanical seal structure, the type of medium, temperature, pressure, speed and shaft diameter should be considered, and manufacturing and disassembly are also considered.
The main structural form of the mechanical seal is as follows:
Balanced and unbalanced type The specific pressure (the force per unit area) of the end face of the friction pair and the pressure of the medium to be sealed can be divided into balanced and unbalanced types.
Non-equilibrium type: The effective area of the medium acting on the moving ring (the area where the offset pressure cancels each other) is equal to or greater than the contact area of the moving and static ring. The specific pressure of the end face increases or decreases proportionally with the pressure of the sealing medium, so that when the medium pressure is high, a large specific pressure is generated on the end surface, which accelerates the wear of the friction surface, generates heat, and destroys the liquid film on the end surface to form dry friction. Generally, the unbalanced medium pressure does not exceed 686 KPA.
Balanced type: When the medium pressure is high, it is necessary to try to eliminate the effect of a part of the pressure on the friction surface from the sealing structure. This type of seal is called a balanced mechanical seal. In this seal, the effective area B of the medium acting on the dynamic damage is smaller than the contact area A of the end face of the dynamic static ring. The specific pressure on the sealing end face can be controlled by itself, and the increase or decrease of the medium pressure has little effect on the specific pressure of the end face.
