Some Examples of Incomplete Diagnostic Analyses of Industrial Machinery

Diagnostic tasks on industrial machinery can sometimes be dealt basing only on previous experience with successful model based identification techniques. This may be required when necessary time and resources for complete diagnostic analysis are not available. Some examples of machines affected by malfunctions that have been more or less successfully analyzed, often without resorting to machine specific models, are presented. Journal ovalisation in a HP-IP steam turbine was identified in the first example, the vibration changes in a LP steam turbine could be attributed to coupling misalignment and to a loose last stage blade of the shaft in the second example. Rubs and thermal bow combined to axial shaft expansion restriction could explain the severe vibrational behavior of a steam turbine that prevented its operation in a third example. The abnormal noise of a vertical shaft generator of a hydroelectric power plant was attributed to a structural resonance excited by electromagnetic forces in a third example, where the diagnostic process was completed by validating the complex excitation mechanisms with simulations.