Method of detecting and localizing partial rotor-stator rubbing during the operation of a turbine

A method of detecting and localizing partial rotor-stator rubbing during the operation of a turbine, in which the rotor of the turbine is monitored by means of at least one pair of sensors of rotor vibrations arranged in one plane of measuring perpendicular to the axis of the rotor and by at least one pair of sensors of absolute vibrations of the bearings, wherein, by synchronically digitalized signals of the sensors of rotor vibrations the arithmetic mean of their harmonic bands in full spectrum in the frequency domain is calculated, by which means the information about the subharmonic components and their multiples in full spectrum of these signals is transferred into the frequency band −1X to 1X, where X indicates the rotational frequency of the rotor, at the same time is by calculation of the median estimated the level of the signal noise, with which the individual frequency bands of the full spectrum are encumbered, and which is subtracted from the amplitudes in the individual frequency bands of full spectrum of the signals of the sensors, whereby, in normalized accumulated full spectrum of the signals of the sensors of rotor vibrations created in this manner, the amplitude of the predetermined subharmonic component/components of the signals of rotor vibrations is compared with the amplitudes of the frequency components in its proximity determined by the Fourier transform or by approximation with the help of the Fourier series, whereby on the basis of visual and/or automatic analysis is deduced to presence of the monitored subharmonic component of the signals of rotor vibrations in spectrum of these signals, on the ground of which subsequently on the occurrence of rotor-stator rubbing is presumed, and in case of its occurrence the place/places of the turbine where it occurs is/are further localized, whereby for axial localization sections of the signals of the sensors of the absolute vibrations of the bearings of the turbine are processed in the time of beginning of rotor-stator rubbing or during the rubbing in the time-frequency domain, in which the increases in broadband amplitude of these signals are identified and subsequently times of increase in broadband amplitudes of these signals above the signal noise are determined, and from the knowledge of these times and their time variances, as well as the distribution of the sensors of absolute vibrations of the bearings and the spreading speed of the impact in the material of the rotor/stator, the axial position of the place/places of the rotor-stator rubbing is determined by axial localization, and by comparison of the histogram of the absolute frequencies of these places with the drawing or the turbine axis the axial position of the place/places where the rotor-stator rubbing really occurs, and, for circumferential localization, increases in the amplitudes of the signals of the sensors of absolute bearing vibrations are visualized into the orbit of the first harmonic component of the rotational frequency of the rotor created from the signals of the sensors of rotor vibrations, by which means the angular position of the maximum of the increases in amplitudes caused by the rotor-stator rubbing is determined, whereby the angular position corresponds to that of the place/places where the rotor-stator rub occurs.