Marscher W.

Evaluation of operationally-induced vibration is useful for machinery health diagnosis and prognosis. However, obtaining vibration at many locations required for adequate diagnostic information is time-consuming because of the need to move probes to locations that may be difficult to access, especially on large or hot machinery. In addition, measurement of structural vibration is dependent upon consistency of probe attachment integrity on typically rough uneven surfaces. The authors use a microphone pair in which the microphones are phase-matched to allow independent determination of sound pressure and acoustic particle velocity, such that sound intensity measurements can be made on all line-of-sight locations on a rotating machine surface, including exposed rotating components. This approach has been demonstrated useful even when the probes are located at a significant distance from the machine. Novel calibration and signal processing techniques allow the sound intensity spectra gathered at various locations to be used to determine local excitation forces as well as responses (displacement, velocity, and acceleration) within the machine. The forces and responses can be used in deterministic tribological and fatigue models to indicate impending problems, and to predict remaining useful life. This paper explains the authors’ procedure, and provides seeded fault case histories to illustrate successful application in the diagnosis and prognosis of a electric motor/ gear driven compressor rig in a reverberant environment.