Turning gear operation

The turning gear operation is essential aspect of maintaining large rotating machinery, such as turbines or generators, during periods of extended shutdown or maintenance. The turning gear is a mechanism designed to slowly rotate the shaft of the equipment as a very low speed, typically around 1 to 5 revolutions per minute (RPM). This rotation serves several important purposes:

1.)   Preventing warping or bowing: During extended shutdown periods, the weight of the rotor and other components can cause distortion or warping due to uneven thermal expansion or gravitational effects. By continuously rotating the shaft at a slow speed, the turning gear helps distribute the weight evenly and prevents deformation of the shaft or bearings.

2.)   Equalizing temperature: Rotating the shaft helps to distribute heat evenly throughout the equipment, reducing the risk of temperature differentials that could lead to thermal stresses or distortion.

3.)   Maintaining lubrication: Continuous rotation ensures that lubricating oil is evenly distributed throughout the bearings and other moving parts, preventing dry starts and reducing the risk of damage due to inadequate lubrication.

4.)   Preventing seizure: The slow rotation of the shaft prevents the formation of stationary points where lubricating oil could stagnate and potentially lead to bearing seizure or other issues.

5.)   Reducing windage effects: In large rotating machinery, such as turbines or generators, windage effects caused by the movement of air around the stationary components can create additional loads on the shaft bearings. Continuous rotation with the turning gear helps mitigate these effects by maintaining a steady airflow around the rotating components.

6.)   Aiding alignment checks: When performing maintenance activities such as alignment checks or inspections, the slow rotation provided by the turning gear allows technicians to easily access different areas of the equipment without the need for manual rotation.

 The operation of the turning gear is typically controlled by a dedicated motor or drive system, which is activated during shutdown periods or when the equipment is not in use. Safety interlocks and monitoring systems are often incorporated to ensure proper operation and prevent damage in the event of abnormal conditions.

Typically, turning gear operations cuts in when turbine shutdown and below 400 rpm turbine speed. Turning gear can be shutdown then first stage metal temperature is below < 120 degree Celsius. Usually, turning gear is started prior to start up to check for turbine eccentricity (<50 mm).

Overall, the turning gear operations plays a crucial role in preserving the integrity and reliability of large rotating machinery, helping to extend the service life of critical components and minimize the risk of costly downtime or repairs.

 

 

Top of Form