Vibro-Consult AG


Generator cracks

Initial situation

In a hydropower, cracks (spider) appeared on the generator rotor. This situation was critical and investigations had to be initiated immediately. As always in such cases, the cause had to be identified before any action could be taken.
It was necessary to determine the cause of these cracks by means of vibration and torsion measurements and to propose measures.


Measuring points were defined and installed on the machine at all critical locations. Of course, this was done at the guide bearings so that any possible repercussions on the machine could be analyzed.
As with a basic VC measurement, all possible operating conditions were run after the measurement equipment was completed in order to obtain as good a picture as possible of all machine situations. The result was surprising.


The machine vibrations were in a good to very good range in all operating conditions. Even the partial load operation, which normally has very high vibrations with this type of turbine, was surprisingly quiet.
But based on the strain measurements, it could be shown that the cracks were caused by manufacturing defects and therefore the supplier had to correct his delivery under warranty.
The rotor was then immediately removed and repaired.