Hitachi, Ltd.

Masafumi Takechi

Nobuo Kurihara

Mitsuyo Nishikawa

Yoshitoshi Nagahashi

In a rotary machine mounted on a rotary shaft journaled in journal bearings, a source of unusual vibration of the rotary machine is identified on the basis of the results of the steps of (1) subjecting a shaft vibration signal to frequency analysis for analyzing its frequency distribution, and (2) analyzing the amplitude of the shaft vibration signal and the variation rate of a phase signal of a component related to the shaft rotation frequency among the frequency components of the shaft vibration signal. The present invention is usefully applicable to diagnosis of vibration of a rotary shaft of a large-size turbine or a generator in a power plant by continuously monitoring the shaft vibration for immediately automatically detecting unusual vibration of the rotary machine in the event of occurrence of such unusual vibration. The usefulness is more enhanced when the signal indicative of vibration of the rotary shaft is converted into a digital signal to be analyzed by a digital computer which identifies the source of unusual vibration.

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Hitachi, Japan

Masafumi Takechi