Method and apparatus for analyzing rotating machines

Abstract

A vibration transducer (22) is mounted to a rotating machine (20) for sensing vibration thereof. An output electrical signal from the vibration transducer is analyzed to generate a level display (18) of vibrational displacement per unit time, a speed display (22) indicative of rotational speed, and a bearing condition display (20) indicative of bearing condition, all displays derived directly from the vibration transducer signal. The electrical signal is transformed (36) into a frequency spectrum that has an amplitude for each of a plurality of narrow frequency ranges or bins. Each frequency bin has a characteristic center frequency and a predefined width or band of frequencies. A speed analysis program (38) identifies a set of at least first, second and third order related frequency bins, i.e. frequency bins whose center frequencies are an even multiple of each other, that have a significantly high amplitude and provides the lowest bin center frequency as a control signal to the speed display. A bearing condition analysis program (40) eliminates the bins that are integer multiples of the running speed and lower frequency, e.g. less than third order, identifies sets of bins with relatively large amplitudes that are integer multiples of each other, and selects the set of bins with the largest amplitude as being controlling of bearing condition. After elimination of frequencies not indicative of bearing condition, the bearing defect frequency remains. The amplitude of this frequency is displayed on bearing condition readout (22). The amplitude indicating the severity of the bearing defect.