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Does the generator air tightness test require turning

If turning is required for the air tightness test of the generator, the turning shall also be stoppe

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If turning is required for the air tightness test of the generator, the turning shall also be stopped for the AC / DC withstand voltage test before the overhaul of the generator.

The turning purpose is as follows:

1. During start-up, the turbine is generally cold before start-up, and the temperature in the cylinder and bearing is low. However, the turbine needs to send shaft seal steam and vacuum before impulse starting. If the turbine is not cranked, after the high-temperature shaft seal steam enters the shaft seal and cylinder, there will be a temperature difference between the upper hot and the lower cold, resulting in cylinder deformation, rotor bending and other equipment failures.

2. Turning after shutdown mainly considers the impact of cylinder waste heat on rotor and cylinder block. If turning is not done, it is also easy to cause faults such as large temperature difference between upper and lower cylinders and rotor thermal bending.

3. The power plant generally stipulates that the barring must be carried out according to the regulations before startup and after shutdown. The barring after shutdown generally requires that the cylinder temperature reaches the ambient temperature before stopping the barring.

4. If the turning motor fails or loses power, or the jacking oil pressure is not enough, it is generally necessary to mark the position where the rotor just stops, and manually turn the rotor for 180 degrees every 30 minutes. This process is repeated until the cylinder temperature is normal. Before the last manual turning, the time interval is half of the previous time interval, that is, 15 minutes.

Automatic disengagement process of turning gear

After the rotor is impulsive, the speed of the turning gear suddenly increases, and the swing gear changes from the driving wheel to the driven wheel, which is quickly pushed to the right and swings counterclockwise with the swing shell to push the pull rod up.

When the upper end point of the pull rod exceeds the balance position, the connecting rod pushes the crank to rotate counterclockwise under the push of the compression spring, and pulls up the swing shell clockwise until the hand wheel rotates by a predetermined angle, and the locking pin automatically falls into the lock hole to lock the hand wheel.

At this time, the travel switch acts to cut off the power supply of the motor, all gears stop rotating, and the turning gear returns to the disconnected state before putting into use. Operate the barring stop button to cut off the power supply, and the barring device can also exit the work.


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