Experimental Study on Vibration Analysis of Rotor-Stator Rub Defect in a Gas Turbine Generator Set

Monitoring turbomachines requires the pre-selection of several indicators used to process vibration signals. In this study, spectral analysis and orbital analysis were used to identify the nature of faults in a gas turbine generator set used to produce electricity. Using international vibration standards ISO 10816-4 and ISO 7919-4, vibration trend measurements, spectral analysis, and orbit analysis, it is possible to detect the severity of malfunctions and determine their nature, including unbalance, misalignment, rubbing, rotor bow, mechanical looseness, and shaft crack. According to this case study, the generator had a thermal imbalance which caused the rotor to bend, creating a complete annular rub between the shaft end cover and the fan of the excitation unit. Diagnostic features obtained by fast Fourier transform (FFT) related to mechanical imbalance have been explained. Also, orbit plots were effectively used to explain the unique nature of the fault.