Does the turbine shaft move axially during barring? Is the shaft displacement changing?
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When the newly installed turbine is shut down, the shaft displacement and expansion difference remain constant; whereas when the turbine is turned by hand, these values are opposite to each other, as shown in the figure. Is this normal? If anyone here has relevant knowledge, please answer.
As long as there are no problems in actual use, it’s normal. Usually, there is a certain amount of play in the control of axial displacement, and as long as it remains within this range, it is considered normal. As for the inconsistency between the movement during cranking and that at idle speed, it may be due to the difference between the movement caused by the forces acting during cranking and the movement resulting from the constant deceleration at idle speed; this is provided for reference only.
My understanding is that during normal operation, the rotor is driven by steam, with the axial force acting from the high-pressure side to the low-pressure side; whereas when the rotor is turned, it is driven by a motor, and in this case the turbine functions like a blower, with the axial force acting from the low-pressure side to the high-pressure side