Barring Gear in Steam Turbines: How It Works and Best Practices

Barring gear is a mechanism used in steam turbines to rotate the rotor during certain operations.

Barring gear is a mechanism used in steam turbines to rotate the rotor during certain operations, before turbine startup or after turbine shutdown. The barring gear allows for controlled and gradual rotation of the rotor, reducing the risk of hogging & sagging or uneven wear when the turbine is not in operation.

It can be controlled remotely from a control panel or locally near the barring gear assembly.

Here’s a simplified explanation :

The barring gear can be started remotely by turning the key to the ‘ON’ position in the control panel or manually from a local panel.

For manual starting, follow these steps:

1. Open the wheel cover to access the barring gear.
2. Turn the wheel in a clockwise direction while pressing the hand lever. This engages the driving gear with the turbine rotor gear.
3. Close the wheel cover to protect the mechanism.
4. Switch on the electric motor to start the barring gear.

Remember:

1. Never allow a hot rotor to stand without rolling. It’s important to keep it rotating to prevent damage.
2. Before starting the barring gear, ensure that the lubricating oil system is on. Maintain the oil temperature between 40-50°C by regulating the water flow through the oil coolers.
3. Check the operation of the seal oil system before starting the barring gear.

During a short shutdown, keep the turbine on barring gear until it’s needed again. If the shutdown is indefinite, continue rolling the rotor until it has thoroughly cooled.

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“Barring Gear: A Closer Look at its Functionality and Operation in Steam Turbines”

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• The barring gear in a turbine serves the main purpose of preventing sagging and hogging of the rotor shaft.
• Sagging refers to the downward bending or curve in the middle of the shaft, while hogging refers to the upward bending or curve in the middle.
• These deformations can occur due to the weight of the rotor or external forces acting on the shaft.
• By utilizing the barring gear, the rotor is periodically rotated at a slower speed during stoppage periods.
• This rotation helps to distribute the weight more evenly along the shaft, minimizing the risk of sagging or hogging.
• By balancing the weight distribution and stress on the shaft, the structural integrity of the turbine is maintained.
• Preventing sagging and hogging ensures smooth and reliable operation of the turbine during startup and normal operation.
• The barring gear is an essential mechanism in turbine maintenance to preserve the long-term performance and lifespan of the rotor and associated components.

Exploring the Purposes and Functions of Turning Gears in Turbines

Other turning gears are primarily used for specific maintenance and operational purposes. as given

1. Maintenance: Turning gears are often employed during maintenance activities such as rotor inspections, blade inspections, or repairs. These gears allow the rotor to be slowly rotated, providing access to different sections of the turbine for inspection or maintenance tasks.
2. Alignment: Turning gears can also be used to align the turbine components during startup. As the turbine begins to rotate, the turning gears ensure that the various components, such as the rotor and the stationary blades, are properly aligned before the main drive is engaged. This alignment is important for the efficient operation and longevity of the turbine.
3. Cooling: In some cases, turning gears may be used for cooling purposes. After shutdown, if the turbine is still hot, rotating it slowly with the turning gears can facilitate the circulation of air or cooling water, helping to dissipate heat from the turbine components more effectively.

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