One of the IP rotor of two 150 MW units is in very bad condition.
The run- out measurement revealed the rotor curvature.
What we measured is showed on the chart above. The curve is the rotor's axis.
The rotor is bent and max run- out 0.23 mm is located behind 1 stage.
There are two most often applicable ways to get rid off curvature.
The first one is to machine the rotor and remove a "plus indications" so the rotor would be machined only at certain angle if material thickness to be removed was no more than 0.23 mm.
I have not seen such solution so far. The solution, we usually use is to define new rotor axis. In this particular case the new fix points sholud be a journal at IP-LP coupling and place when max run-out is measured. Next, the HP end of the rotor would be machined.
We have done such machinings but for the rotors which were not bent so much. At max indications ~ 0.15 mm. In fact the internal tensions are still present and can cause further axis deformation. We have noticed this process.
The right technical solution applied in this case is to perform thermal streightening and after this repair step to machine rotor.
The final decision will be taken shortly on the customer meeting.
The rotor curvature is not the only problem we found.
The rotor blade groove edges are cracked. Allways rotor cracks are very hard task to deal with.We have found different kinds of cracks.
1. The cracks inside the blade groove
2. The blade groove edges cracks.
