Gland Steam Sealing System for Steam turbine

Summary

The script explains the process of sealing a steam turbine's shaft to prevent leaks and air ingress. It details how labyrinth seals, consisting of sharp, thin edges, minimize steam leakage by creating a tortuous path. The gland sealing system uses steam from the cold reheat line for shaft sealing during turbine operation. Steam leakages are collected and condensed via the gland steam condenser system. The process ensures efficient steam flow through high-pressure, intermediate-pressure, and low-pressure stages, preventing unwanted steam loss and ensuring optimal turbine performance.

Takeaways

• 🛠️ The labyrinth packing set plays a key role in reducing leakages along the turbine shaft and shell penetrations.
• 🌬️ Steam sealing is critical before steam enters the turbine for rolling, and leakoff steam is required to prevent air ingress into shaft glands.
• 🔥 Gland sealing steam is supplied from the main steam supply, specifically from the cold reheat line via the HP bypass valve.
• 🚿 A condensate spray is used to desuperheat the gland sealing steam for the low-pressure (LP) end of the turbine to reach an acceptable temperature.
• 🔩 Low-pressure packing is located at the condenser end of the turbine, near the number one journal bearing.
• 🌀 Labyrinth seals, with sharp raised edges, prevent steam leakage along the turbine shaft by creating a tortuous path for steam to travel.
• ⚙️ Intermediate stage packing is positioned at the reheat steam inlet, acting as a seal between the high-pressure and intermediate-pressure sections of the turbine.
• 🔧 High-pressure packing is located on the generator end of the turbine, ensuring steam does not leak from the high-pressure turbine section.
• 🌡️ Bleed-off steam from various valves is routed to the gland steam condenser, where it is condensed by cooling water and returned to the main condenser.
• 💨 The gland steam system manages leakoff steam from multiple steam valves, including main and reheat steam control valves, preventing excess steam from escaping.

Q & A

What is the purpose of the labyrinth packing set in a steam turbine?

The labyrinth packing set is designed to reduce leakages along the turbine shaft and shaft penetrations. It consists of steam seal areas that prevent air in-leakage and control steam leakage along the turbine shaft.

Why is a source of steam needed to seal turbine shaft penetrations during startup?

During startup, there is no leakoff steam available to seal the shaft glands. A source of steam is needed to prevent air from leaking into the turbine by sealing the shaft penetrations before steam is fully admitted for turbine rolling.

How is gland sealing steam supplied to the turbine?

Gland sealing steam is supplied from the cold reheat line by way of the high-pressure (HP) bypass valve. As the cold reheat steam line becomes pressurized, some steam is taken off to provide shaft sealing steam.

Why is the gland sealing steam to the low-pressure (LP) gland desuperheated?

The gland sealing steam to the LP gland is desuperheated to reduce its temperature to an acceptable level for use at the LP end of the turbine, ensuring it doesn’t damage the components.

Where is the low-pressure packing located on the steam turbine?

The low-pressure packing is located on the condenser end of the turbine rotor, near the number one journal bearing.

What function do the labyrinth seals perform on a steam turbine?

Labyrinth seals prevent steam leakage by creating a tortuous path through sharp, thin, raised edges that protrude toward the shaft and fit into machined ridges on the turbine shaft. This design slows or stops steam leakage along the shaft.

Where is the intermediate stage packing located, and what does it seal?

The intermediate stage packing is located at the reheat steam inlet and seals the interface between the high-pressure and intermediate-pressure sections of the turbine.

What is the role of the high-pressure packing in the steam turbine?

The high-pressure packing is located on the generator end of the turbine rotor. It helps prevent steam leakage as the main steam exits the high-pressure turbine.

What happens to the steam that bleeds through the packing in a steam turbine?

Some steam bleeds through the packing and is routed to pipes on the bottom of the turbine casing. This bleed-off steam goes to the gland steam condenser, where it is condensed and transferred to the main condenser.

What is the purpose of the gland steam condenser in the system?

The gland steam condenser is designed to condense the leakoff steam from the packing glands and the steam valve stems. The condensed steam is then transferred to the main condenser.

Outlines

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🔧 Shaft Sealing and Steam Leakage Prevention

This paragraph discusses the measures in place to reduce steam leakages along the turbine shaft. It explains that the labyrinth packing set consists of three main steam seal areas, designed to prevent air from leaking into the system before the steam is admitted to the steam turbine. Initially, a source of steam is required to seal the turbine shaft penetrations, preventing air ingress. The labyrinth seals are used to prevent steam leakage, and these seals feature sharp, thin edges that form a tortuous path to slow or stop the steam leakage along the turbine shaft.

💨 Gland Sealing Steam and Its Function

This section explains the need for gland sealing steam, particularly when there is no leak-off steam available during the initial stages of turbine operation. The steam is supplied from the main steam supply or the cold reheat line, using a condensate spray to desuperheat the steam to an appropriate temperature for the low-pressure (LP) end of the turbine. The low-pressure packing is positioned near the condenser and the number one journal bearing, and the gland sealing system ensures the prevention of air ingress at these critical points.

⚙️ Labyrinth Seals and Their Role

Labyrinth seals, which are machined into the turbine shaft and gland ring, play a crucial role in preventing steam leakage. The seals are designed with ridges and valleys that interlock, creating a tortuous path that restricts the flow of steam. This detailed design helps slow or stop steam leakage along the turbine shaft, contributing to the efficiency of the turbine's operation.

📐 Intermediate and High-Pressure Packing

This section describes the placement of intermediate stage packing at the reheat steam inlet, acting as a seal between the high-pressure and intermediate pressure sections of the turbine. The high-pressure packing is located near the generator end of the turbine. As the steam exits the high-pressure section, some steam travels through balance pipes to the intermediate pressure section, while the rest bleeds through the packing and exits through pipes located at the bottom of the casing.

🌡️ Gland Steam Condenser and System Overview

Here, the focus shifts to the gland steam system, which collects leak-off steam from various valves including the main steam stop valves, reheat steam stop valves, and intercept valves. This steam is routed to the gland steam condenser, which condenses the leak-off steam from the turbine's packing glands and valve stems. The condenser uses cooling water to condense the steam leakage that enters the turbine shell, which is then transferred to the main condenser.

Keywords

💡Labyrinth packing set

The labyrinth packing set is a type of seal used in steam turbines to reduce leakages along the shaft. It consists of multiple sharp, thin edges that create a tortuous path for steam, slowing or stopping its leakage. This sealing system is crucial in preventing steam from escaping, as mentioned when describing the steam seal areas.

💡Gland sealing steam

Gland sealing steam is the steam used to prevent air from entering or steam from leaking out of the turbine shaft penetrations. It is supplied from the cold reheat line through the HP bypass valve. This sealing mechanism ensures that the turbine operates efficiently without pressure loss.

💡Cold reheat line

The cold reheat line is a part of the steam flow system that helps pressurize the steam before it enters the turbine. It provides steam for the turbine shaft sealing, ensuring the turbine is sealed before rolling, preventing air from leaking into the system. The cold reheat line is mentioned in the context of steam supply for shaft sealing.

💡Desuperheated steam

Desuperheated steam refers to steam that has been cooled to a lower temperature without turning into water, making it suitable for use in lower pressure systems. In the script, desuperheated steam is provided to the low-pressure (LP) gland for sealing the LP end of the turbine, ensuring proper operation.

💡Low-pressure packing

The low-pressure packing is a seal located on the condenser end of the turbine rotor, near the number one journal bearing. It is designed to prevent steam leakage in the low-pressure areas of the turbine. This packing is critical for maintaining the efficiency of the turbine and preventing energy loss.

💡Intermediate stage packing

Intermediate stage packing is the seal located between the high-pressure and intermediate-pressure sections of the turbine. It prevents steam from leaking between these sections, maintaining the separation of different pressure zones in the turbine for optimal performance.

💡Balance pipes

Balance pipes are pipes through which some of the steam from the high-pressure turbine section is directed to the intermediate pressure section. These pipes help equalize the pressure within the turbine and ensure smooth transitions between pressure stages, preventing mechanical imbalances.

💡Gland steam condenser

The gland steam condenser is a system designed to condense leakoff steam from the packing glands and steam valve stems. It collects and condenses steam that leaks from various components, such as the main steam stop valves and reheat steam intercept valves, and transfers the condensed steam back into the main condensate system.

💡Leakoff steam

Leakoff steam refers to the steam that escapes from the turbine's packing glands and valve stems. Instead of wasting this steam, it is routed to the gland steam condenser, where it is condensed and returned to the system. This process ensures minimal energy loss while keeping the turbine system sealed.

💡Main condensate system

The main condensate system is responsible for collecting and recycling condensed steam from the turbine, including the leakoff steam collected by the gland steam condenser. It helps maintain the efficiency of the turbine by ensuring that no steam is wasted and that all condensed water is reused in the system.

Highlights

Leakages along the shaft are reduced by using labyrinth packing sets consisting of three major steam seal areas.

During initial turbine rolling, a steam source is required to seal turbine shaft penetrations and prevent air in-leakage.

Gland sealing steam is provided by the main steam supply via the cold reheat line and HP bypass valve.

The cold reheat steam line becomes pressurized and supplies steam to seal the turbine shaft.

A condensate spray is used to desuperheat gland sealing steam for the LP turbine gland.

The low-pressure packing is located near the condenser end of the turbine rotor by the number one journal bearing.

Labyrinth seals, designed to prevent steam leakage, have sharp thin raised edges protruding from the gland ring toward the shaft.

These labyrinth seals create a tortuous path that slows or stops steam leakage along the turbine shaft.

The intermediate stage packing seals between the high-pressure and intermediate-pressure sections of the turbine.

High-pressure packing is located on the generator end of the turbine rotor.

As the main steam exits the high-pressure turbine, some steam is directed to the intermediate pressure section through balance pipes.

Leakoff steam from the turbine casing is routed to the gland steam condenser for cooling and condensation.

The gland steam condenser condenses leakoff steam from various valves and packing glands.

Leakoff steam is also routed from main steam stop valves, control valves, reheat steam stop valves, and intercept valves.

The gland steam system accepts leakoff steam from valve stems and transfers the condensed steam to the main condenser.

Transcripts

is to reduce leakages along the shaft to

Shell

penetrations the Labyrinth packing set

consists of three major steam seal

areas before steam is admitted to the

steam turbine for Rolling there is no

leakoff steam available to seal the

shaft glands a source of steam is needed

to seal turban shaft penetrations to

prevent air in leakage gland sealing

steam supplied from the rapidly heating

main steam Supply is supplied from the

cold re heat line by way of the HP

bypass valve as the cold reheat steam

line becomes pressurized some of this

steam is taken off to provide turban

shaft sealing

steam using a condensate spray the gland

sealing steam to the lp gland is des

superheated to an acceptable temperature

for the lp end of the

turbine the low press packing is located

on the condenser end of the turbine

rotor near the number one Journal

bearing

steam turbine shafts have been designed

with a feature to prevent steam leakage

called Labyrinth

seals these seals are sharp thin raised

edges that protrude toward the shaft

from the gland ring and fit into ridges

and valleys machined into the turbine

shaft they are precisely machined to fit

very closely within one another to make

a labyrinth or tortuous path for steam

to travel thus slowing or stopping steam

leakage along the turbine shaft

the intermediate stage packing is

located at the reheat steam Inlet and is

a seal between the high pressure and

intermediate pressure sections of the

turbine the high-pressure packing is

located on the generator end of the

turbine

rotor as the main steam exits the high-

Press turbine some of that steam goes up

through the balance pipes to the

intermediate pressure

section More Steam bleeds through the

packing and goes out two pipes on the

bottom botom of the casing this

bleed-off steam goes to the gland steam

condenser the gland steam system also

accepts leakoff Steam from the main

steam stop valves main steam control

valves reheat steam stop Valves and the

reheat steam intercept valves this

leakoff steam is routed to the gland

steam

condenser the gland steam condenser is

provided to condense the leakoff steam

from the packing glands and the steam

valve stems

steam leakage from the turban packing

glands enters the shell and is condensed

by the cooling water and transferred to

the main condens