The pressure between the liquid in the pump and the air outside the pump is not equal, and leakage occurs along the shaft. In order to provide a sealing device, it is called a shaft seal. When the pressure at the shaft seal of the pump is less than atmospheric pressure, the shaft seal is used to prevent air from entering the pump; when the pressure at the shaft seal of the pump is greater than atmospheric pressure, the shaft seal is used to prevent liquid leakage.
The types of shaft seals commonly used in pumps:
1) packing seal;
2) mechanical seals;
3) Floating seal
Sealing device requirements:
1) The seal is reliable and can run for a long time;
2) low power consumption;
3) Adapt to changes in pump operating conditions.
The sealing device should consider the performance of the liquid to be sealed (corrosive, abrasive wear, coagulability, permeability, volatility, toxic, igniting, odor, etc.), temperature (high temperature, normal temperature, low temperature, temperature variation range) and Pressure (high pressure, normal pressure, low pressure, vacuum, pressure variation range).
