I know large turbines are using barring gear( turning gear) to slowly rotate the turbine until it gets cooled.

my question here: why do we have turning gear on gear Box for (motor, gear box and compressor) train? is it for the same purpose as for turbine, even it didnt get the same temp?

I kinda need more explaining on turning gear function. how it engage and disengage automatically?

quote:

turning gear

Some are used to prevent the shaft from warping. But I'm not sure if it's the case for train.

Pawl and ratchet mechanism is there for engagement and disengagement of the barring gear with the with the dreiven shaft. As the speed increases, the ring outside the shaft ratchet starts slipping overe the pawl. After a fixed increase in speed , the pawls due to centrifugal force go inwards and get disengaged. You may refer the drawinf to understand this .
Irshad