Affiliations: Department of Mechanics, Politecnico di Milano, Via La
Masa, 34, I-20156, Milano, Italy
Note: [] Corresponding author: P. Pennacchi, Department of Mechanics,
Politecnico di Milano, Via La Masa, 34, I-20156, Milano, Italy. Tel.: +39
0223998440; Fax: +39 0223998492; E-mail: paolo.pennacchi@polimi.it
Abstract: This paper is focused on the application of two different diagnostic
techniques aimed to identify the most important faults in rotating machinery as
well as on the simulation and prediction of the frequency response of rotating
machines. The application of the two diagnostics techniques, the orbit shape
analysis and the model based identification in the frequency domain, is
described by means of an experimental case study that concerns a gas
turbine-generator unit of a small power plant whose rotor-train was affected by
an angular misalignment in a flexible coupling, caused by a wrong machine
assembling. The fault type is identified by means of the orbit shape analysis,
then the equivalent bending moments, which enable the shaft experimental
vibrations to be simulated, have been identified using a model based
identification method. These excitations have been used to predict the machine
vibrations in a large rotating speed range inside which no monitoring data were
available. To the best of the authors' knowledge, this is the first case of
identification of coupling misalignment and prediction of the consequent
machine behaviour in an actual size rotating machinery. The successful results
obtained emphasise the usefulness of integrating common condition monitoring
techniques with diagnostic strategies.
