The selection of mechanical seal structural type is an important step in the design process, and a preliminary investigation must be carried out: ① Operating parameters - medium pressure, temperature, shaft diameter, and rotational speed. ② Medium characteristics - concentration, viscosity, corrosiveness, presence or absence of solid particles and fibrous impurities, and whether it is prone to vaporization or crystallization. ③ Characteristics of the main unit's operation and environmental conditions - continuous or intermittent operation; whether the main unit is installed indoors or outdoors; nature of the surrounding atmosphere and temperature changes. ④ Requirements for allowable leakage, leakage direction (internal or external), and life and reliability requirements that the main unit has for the seal. ⑤ Restrictions on the size of the sealing structure imposed by the main unit. ⑥ Stability of operation and production processes.