Summary According to the working nature of the water turbine main shaft seal, it can be divided into maintenance seal.
The main shaft seal of the water turbine is an important protection of the hydraulic turbine. It is installed under the water guide bearing to prevent pressure water from leaking into the pit from the main shaft and the top cover (or support cover), flooding the water guide bearing, and destroying the water guide bearing. Work affects the operation of the unit.
The maintenance seal is a kind of seal that works when the water turbine is being overhauled. It is a bearing seal required when shutting down or overhauling the water turbine 's working seal and water guide bearing. It prevents backfilling into the machine pit when the tail water level is high. The maintenance seals can be divided into air-belt type, mechanical type and lift-type maintenance seals according to their structural types. But in practice, most of them use air bands to repair and seal. It is mainly composed of a fixed ring and a rubber air band. When working, the air band is filled with an air pressure of 0.4-0.7Mpa to expand the rubber of the air band and tighten the main shaft to prevent water from entering. The compressed gas in the air shroud is eliminated to make it shrink, and the gap between the air shroud and the main shaft is maintained at 1.5 to 2 mm. The maintenance seal structure is simple, easy to operate, and has a good sealing effect. Most unit maintenance seals use this structure.
