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Topical issues of formation of the system elements of diagnostic signs of malfunctions and defects of piston compressors are considered in the paper. Diagnostic signs are formed on the basis of parameters of vibroacoustic signal. Vibration sensors are installed on various units of the piston compressor. Usually sensors are installed on the cylinder in the axial direction, on the compressor valves, on the crosshead, on the main bearing. Today, there are effective ways to assess the condition of components and parts of piston compressors on the parameters of the vibroacoustic signal, which are developed by the authors of this work. Diagnostic signs are based on statistical parameters of vibroacoustic signal such as the root-mean-square value of vibroacoustic signal, quantile of instantaneous values of vibroacoustic signal, spectral invariants the vibrating acoustic signal envelope. The first two groups of diagnostic traits are formed on the basis of statistical processing of signals for different types of machines. Thus, these features can only be used for a certain type of piston compressors. The appearance of faults and the degree of their hazards are estimated by the spectral inversion of the envelope of vibroacoustic signal regardless of the type of the machine. To increase certainty and reliability of diagnostics in this work it is suggested to use the size of module characteristic function of instantaneous values of vibroacoustic signal at the specified parameter characteristic function. Given that the module of the characteristic function varies from 0 to 1, it can be assumed that the value of the characteristic will not depend on the absolute value of the signal and, accordingly, on the type of machine. In this case, the characteristic function of the vibroacoustic signal is used, which is obtained at certain intervals by the angle of rotation of the crankshaft of the piston compressor in the region of the lower and upper dead points. Using probabilistic-statistical decision-making methods and the probability density functions of the modulus of the characteristic function, which are determined for different states of compressor nodes, the boundary values of the modulus of the characteristic function are obtained. Thus, the authors managed to get a diagnostic sign of faults and defects, which does not depend on the absolute value of the vibration acoustic signal. Thus, it is possible for the authors to first obtain a diagnostic feature of faults and defects on the basis of probabilistic characteristics of the vibration-acoustic signal, which is independent of absolute value of vibroacoustic signal.

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Establishing patterns of the relationship of informative diagnostic parameters signals’s and test modes and operation of rolling bearings is an urgent task of technical diagnostics. The determining factor in the use of certain methods for assessing the condition and bearings faults, as well as the use of certain informative diagnostic parameters, is their sensitivity to changes in the condition of the bearing or to the size and degree of the defect development. The paper presents the results of the dependence study of the rolling bearings vibration parameters on the test and operation conditions: the rotation frequency of the inner ring, axial and radial loads. Numerical values of the listed factors are obtained that are optimal for testing bearings at the input control according to the sensitivity criterion. The study was conducted in accordance with the provisions of the experiment planning theory. It has been established that the magnitude of the vibration parameters and the level of components at the frequencies of bearing defects depend on the speed of rotation in direct proportion and increase with the deterioration of the technical condition of the bearings. It was experimentally confirmed that axial and radial loads significantly affect the values of the controlled vibration parameters only when defects appear in the tested bearings.