What is the function of the gland sealing system in a steam turbine?

The gland sealing system in a steam turbine has two primary functions: preventing steam from leaking out of the turbine casing where the rotor shaft penetrates it, and preventing air from leaking into the turbine casing in the vacuum stages. Steam turbines operate with high internal pressures in the high-pressure stages and under vacuum in the low-pressure stages. Without effective sealing, steam would leak out, reducing efficiency and potentially causing burns or other hazards. Conversely, air leaking into the vacuum stages would increase the back pressure, reducing power output and potentially causing damage to the low-pressure blades. The gland sealing system typically uses a labyrinth seal arrangement. This consists of a series of fins or teeth that create a tortuous path for any leakage flow. Steam, usually low-pressure steam extracted from an intermediate stage of the turbine, is injected into the labyrinth seals to create a positive pressure barrier. This sealing steam prevents both outward leakage of high-pressure steam and inward leakage of air. The used sealing steam, along with any leakage, is then typically routed to a gland steam condenser where it is condensed and returned to the feedwater system. Maintaining the correct pressure and flow of sealing steam is crucial for ensuring the effective operation of the gland sealing system and the overall efficiency of the turbine.