Why gland sealing is provided in steam Turbines??

 Significance of steam Turbine gland sealing system

 

 

A turbine gland sealing system is an integral part of steam turbine operation, essential for maintaining efficiency, protecting critical components, and ensuring safe operation.

 

Functions of gland sealing system:

 

Preventing Steam Leakage: 

The primary function is to prevent steam from leaking out of the turbine casing at the points where the rotating shaft exits the casing. This ensures the turbine operates efficiently by maintaining steam pressure and preventing energy losses.

 

Protecting Bearings:

 

It prevents steam from entering the bearing housing, which could lead to lubrication issues and potential bearing damage.

 

Maintaining Vacuum:

In condensing turbines, it helps maintain the vacuum in the condenser by preventing air from leaking into the system.

 

What are the components of gland sealing system???

 

Labyrinth Seals: These are non-contacting seals that use a series of ridges and grooves to restrict steam flow. They are effective at high speeds and temperatures.

 

Carbon Ring Seals:These seals consist of segmented carbon rings that provide a tighter seal than labyrinth seals, often used in low-pressure applications.

 

Steam Seal Regulator: This component regulates the amount of sealing steam supplied to the seals, ensuring an optimal balance between sealing effectiveness and steam consumption.

 

Sealing Steam Supply and Exhaust System:This includes the piping and control systems that manage the flow of sealing steam to and from the turbine gland areas.

 

Operation of the Gland sealing system:

 

Sealing steam is typically extracted from an intermediate stage of the turbine or through PRDSH station. It is introduced into the gland areas at a controlled pressure around  0.1 to 0.2 kg/cm2.

 

At HP side sealing steam helps to seal the glands there by preventing leakage of steam from inside to outside, whereas in LP side it prevents the ingress of atmospheric air in gland sealing system.

 

Any leakage past the seals is collected and returned to the condenser or reintroduced into the steam cycle, minimizing waste.

 

Why do U loop is provided in Gland sealing steam condenser drain lines?

 

Generally gland seal condensate drains are left to condenser hot well. The pressure difference in the condenser & gland sealing is very less, in order to seal this a small U seal say around 500 mm to 2 meters is provided in gland steam condenser drains.The U-loop helps maintain the necessary pressure differential across the gland seal system. By trapping condensate, it creates a barrier that ensures the pressure in the gland seal system is properly managed, which is critical for the system's efficiency and performance

 

Also U loop performs following functions.

 

The U-loop acts as a water seal to prevent steam or air from the gland seal system from flowing back into the drain line, which could lead to inefficiencies or potential damage to the system.

 

In systems where the condenser operates under a vacuum, the U-loop acts as a barrier to prevent air from being drawn into the system. Air ingress can reduce the efficiency of the condenser and the overall steam cycle.

Read more>>>>Why do U loop is provided in 1^st stage ejector drain line and float trap in 2^nd stage ejector drain line???

 

The U-loop ensures that condensate is drained in a controlled manner, preventing sudden surges of water that could potentially cause damage to downstream components or lead to operational issues.

 

The U-loop provides some flexibility for thermal expansion and contraction of the drain line. This reduces the risk of mechanical stress and potential failure of the piping due to temperature changes.

 

Read more>>>>powerplant and calculations