Method and apparatus for monitoring the shaft vibration of a rotary machine

Claim 1

A method of monitoring a shaft vibration of a rotary machine comprising the steps of: detecting the shaft vibration as a wave signal in proportion to a rotational frequency of the rotary machine; filtering the detected shaft vibration signal; sampling the filtered signal at a predetermined frequency, the predetermined frequency being selected by; (a) selecting the number of waves of the filtered signal to be included in an analyzing time interval determined by at least a minimum fractional harmonic of the rotational frequency which exists in a frequency range to be monitored, (b) selecting the number of samples to be sampled from the filtered signal in the analyzing time interval in accordance with a ratio of a maximum higher harmonic of the rotational frequency to the minimum fractional harmonic of the rotational frequency in the frequency range to be monitored, and (c) multiplying the rotational frequency by a ratio of the selected number of samples to the selected number of waves with the product thereof being the predetermined frequency; and analyzing the sampled data to obtain the vibration amplitude of frequency components within the frequency range to be monitored by digital processing so as to monitor the shaft of vibration state of the rotary machine.

Claim 2

A method of monitoring a shaft vibration of a rotary machine comprising the steps of: detecting the shaft vibration as a wave signal in proportion to a rotational frequency of the rotary machine; filtering the detected shaft vibration signal; sampling the filtered signal at a predetermined frequency, the predetermined frequency being selected by; (a) selecting the number of waves of the filtered signal to be included in an analyzing time interval determined by at least a minimum fractional harmonic of the rotational frequency which exists in a frequency range to be monitored, (b) selecting the number of samples to be sampled from the filtered signal in the analyzing time interval in accordance with a ratio of a maximum higher harmonic of the rotational frequency to the minimum fractional harmonic of the rotational frequency in the frequency range to be monitored, and (c) multiplying the rotational frequency by a ratio of the selected number of samples to the selected number of waves with the product thereof being the predetermined frequency; and analyzing the sampled data to obtain the vibration amplitude of frequency components within the frequency range to be monitored by digital processing so as to monitor the shaft of vibration state of the rotary machine.

Claim 6

An apparatus for monitoring a shaft vibration of a rotary machine comprising: shaft vibration transducer means for detecting shaft vibration and providing a shaft vibration signal; filtering means for filtering the shaft vibration signal; means for generating a present rotational phase signal which is a rotational phase reference signal of the rotating shaft of the rotary machine; means for generating a present synchronization pulse signal which is a predetermined number of pulses per revolution of the rotating shaft; synchronization means for receiving the synchronization pulse signal, the rotational phase reference signal and sample control data as input signals and for generating a sampling clock signal by effecting a phase synchronization in accordance with the rotational phase reference signal and the synchronization pulse signal during a starting-up period of the rotating shaft; timing signal generator means for receiving the sampling clock signal and the rotational phase reference signal as input signals and for generating a time control signal for sampling and holding; sampling means including analog-to-digital converter means responsive to the filtered shaft vibration signal and the time control signal for sampling the filtered shaft vibration signal at a predetermined frequency in accordance with the time control signal and for generating a digital signal in accordance therewith; and means for effecting a frequency analysis of the digital signal by digital signal processing so as to monitor the shaft vibration state of the rotary machine.

Claim 7

An apparatus for monitoring a shaft vibration of a rotary machine comprising: shaft vibration transducer means for detecting shaft vibration and providing a shaft vibration signal; filtering means for filtering the shaft vibration signal; means for generating a present rotational phase signal which is a rotational phase reference signal of the rotating shaft of the rotary machine; means for generating a present synchronization pulse signal which is a predetermined number of pulses per revolution of the rotating shaft; synchronization means for receiving the synchronization pulse signal, the rotational phase reference signal and sample control data as input signals and for generating a sampling clock signal by effecting a phase synchronization in accordance with the rotational phase reference signal and the synchronization pulse signal during a starting-up period of the rotating shaft; timing signal generator means for receiving the sampling clock signal and the rotational phase reference signal as input signals and for generating a time control signal for sampling and holding; sampling means including analog-to-digital converter means responsive to the filtered shaft vibration signal and the time control signal for sampling the filtered shaft vibration signal at a predetermined frequency in accordance with the time control signal and for generating a digital signal in accordance therewith; and means for effecting a frequency analysis of the digital signal by digital signal processing so as to monitor the shaft vibration state of the rotary machine.