Monitoring slow speed machinery using integrator and selective

Abstract

A method for nonintrusive monitoring of slow speed machinery incorporates a high sensitivity accelerometer capable of detecting low level mechanical vibrations, and a standard data collector/analyzer for processing the accelerometer output in accordance with a slow speed technology (SST) methodology that is implemented by firmware or software. To prevent the high frequency components from overwhelming the low frequency components of the accelerometer output as a result of dynamic range loss during processing of the accelerometer output by the data collector/analyzer, the SST methodology converts the accelerometer output from the acceleration domain to the velocity domain with an analog integrator that amplifies the low frequency components of the accelerometer output while attenuating the high frequency components. The analog integrator distorts the low frequency vibration components as well as the electrical noise introduced by the accelerometer. The distorted signal is then digitized by an A/D converter and transformed to the frequency domain by means of a fast Fourier transform. Within the frequency domain, mechanical vibrations (significant peaks) are separated from the noise and other non-vibration induced transients by fitting the transformed data set to a threshold noise floor that is calculated based on a statistical variance of a most probable noise floor of the accelerometer. All peaks/amplitudes greater than the threshold noise floor are considered significant and retained as indicative of mechanical vibrations occurring within the machinery, while all peaks below the threshold noise floor are considered insignificant and eliminated from further consideration.