Abstract
This article presents two experiences of applying a model-based fault-identification method to real machines. The first case presented is an unbalance identification in a 320 MW turbogenerator unit operating in a fossil power plant. In the second case, concerning a machine of the same size but from a different manufacturer, the turbine has been affected by a rub in the sealings. This time, the fault is modeled by local bows. The identification of the faults is performed by means of a model-based identification technique in a frequency domain, suitably modified in order to take into account simultaneous faults. The theoretical background of the applied method is briefly illustrated and some considerations are also presented about the best choice of the rotating speed set of the run-down transient to be used for an effective identification and about the appropriate weighting of vibration measurements at the machine bearings.