An effective seal is required between the rotating shaft of the centrifugal pump and the fixed shell to ensure the normal operation of the centrifugal pump and the safe operation of the air separation unit. At present, there are two common sealing methods, bellows face seal and inflatable labyrinth seal. Bellows end face seal is a mechanical seal, which is mainly sealed by the friction pair composed of two sealing elements, static ring and moving ring. It is simple to operate and maintain, but the operation cycle is limited by the friction rate of friction materials and can not operate for a long time. The inflatable labyrinth seal needs to maintain a certain pressure of dry gas, with complex operation and maintenance and high manufacturing and installation requirements, but it can run for a long time.
