Use of composite higher order spectra for faults diagnosis of rotating machines with different foundation flexibilities

• Machines’ dynamics often differ due to differences in foundation flexibilities.
• Composite spectra combine vibration signals measured from several locations.
• Proposed combined composite bi and tri-spectra gives better diagnosis features.
• The proposed approach is useful for machines with different foundation flexibilities.

It is commonly observed in practise that rotating machines installed at different plant locations often exhibit different dynamic behaviours, due to variations in the flexibilities of their supports. This often makes the faults diagnosis complex from one machine to another machine. In the current study, a similar scenario has been experimentally simulated on a rotating rig with different foundation flexibilities. Also, different faults were experimentally simulated at different machine speeds so as to develop a reliable diagnosis technique that will be suitable for different machine foundations. Recently developed data fusion methods for constructing composite spectrum (CS) and composite bispectrum (CB) for a machine are again applied for faults diagnosis here. In addition, the present study introduces the composite trispectrum (CT) as a new feature for diagnosis. The paper hereby presents the computational concepts of all composite spectra, rig details, data analysis and diagnosis.