What is the function of a steam turbine turning gear?

[HectorFitz]

The function of a steam turbine turning gear: Before the steam turbine starts and after shutdown, the device that ensures the rotor rotates continuously at a certain speed to achieve uniform heating and cooling is called the turning gear. Here are some extended details: 1. Before the steam turbine starts: The turning gear is used to drive the rotor at a low speed, ensuring uniform heating of the rotor to facilitate smooth startup. Rotating the rotor before startup can also be used to check whether the steam turbine meets operational conditions, such as whether there is friction between moving and stationary parts, and whether the main shaft's bending degree is normal. 2. After shutdown: Engaging the turning gear can mix the airflow inside the cylinder, helping to eliminate temperature differences between the upper and lower parts of the cylinder, preventing rotor deformation, and aiding in reducing damage to the bearing caused by higher-temperature shaft journals.

[DelWyatt]

Speaking of the turbine turning gear, I have profound personal experience. Back when I was operating the unit at the plant, we had to engage it every time during shutdown. Its primary purpose is to prevent thermal deformation of the turbine rotor - the temperature difference between the top and bottom of a freshly stopped rotor can reach hundreds of degrees. If left stationary, the rotor would gradually warp. The turning gear rotates it at a few revolutions per minute, allowing for even temperature distribution and keeping the rotor straight. It also helps to rotate the rotor a few turns before startup to check for bearing seizure or abnormal friction. I remember one time when I skipped this procedure out of laziness, and the next day during startup, the shaft vibration exceeded limits. Upon disassembly, we found the rotor had warped, causing two full days of production delay - the boss nearly fired me. That's why now I always make sure the turning gear operates until the rotor temperature drops below 50 degrees Celsius.

[CourtneyMarie]

Anyone involved in steam turbine maintenance understands the criticality of the turning gear. Its core design purpose is to address thermal stress issues after shutdown. Due to differing cooling rates between the cylinder and rotor, the rotor tends to bend into a banana shape post-shutdown. Without turning gear operation, once the rotor cools and hardens in this deformed state, factory recalibration becomes the only solution. In routine operations, we maintain low-speed rotation of the rotor at approximately 5-15 RPM, driven by an electric motor through reduction gears. This ensures uniform cooling across all rotor sections, preventing permanent deformation. Additionally, pre-startup turning gear operation helps drain accumulated steam condensate from the cylinder, avoiding water hammer damage to blades. Regularly monitoring operational sounds during turning gear operation serves as an important diagnostic method - abnormal noises may indicate bearing issues.

[DeElena]

Last time I visited the power plant, I finally understood this device. The steam turbine operates at extremely high temperatures. After shutdown, the upper part of the rotor cools faster while the lower part cools slower. Over time, the rotor bends like a wilted cucumber. The turning gear is essentially a slow-rotation motor that periodically turns the rotor a few degrees. Continuous rotation ensures even heat distribution, preventing bulging on one side and sagging on the other. It's similar to how you need to flip a roast duck to prevent burning—same principle. After shutdown, the turning must continue for over six hours until the temperature drops sufficiently. Before startup, the rotor should also be turned a few revolutions to check for abnormal noises, just like warming up a car before driving. A cold start without this procedure would be disastrous—the bent rotor spinning at high speed could cause severe vibration or even disintegration, ranging from minor shaking to catastrophic failure.