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This study explores the potential application of the wavelet analysis to the assessment of the working condition of compact ropes (qualitative assessment). The assessment procedure is a key aspect in the decision-making during the non-destructive testing. This is the first study on diagnostics of the new-design ropes, summarising the results of the analysis of signals from novel compact ropes, based on the defect models. Selection of the wavelet type and of the decomposition detail is a key element of the diagnostic procedure. A major step in the assessment procedure involves the replicas of the rope's surface. The data provided in this paper will be useful in developing new specialist equipment for magnetic inspection of compact ropes.Keywords: magnetic inspection of wire ropes, wavelet analysis, diagnostics W artykule przedstawiono możliwości oceny stanu technicznego (analiza jakościowa) lin kompaktowanych przy zastosowaniu analizy falkowej, która stanowi ważny element wspomagający proces decyzyjny w trakcie badań nieniszczących. Jest to pierwsza informacja związana z problematyką diagnozowania lin nowej konstrukcji. Omówiono w niej wyniki analizy sygnału zarejestrowanego na nowej linie kompaktowanej z zamodelowanymi uszkodzeniami. Dobór typu falki i wybór detalu dekompozycji niosącego informację o symptomach zużycia jak również dobór częstotliwości rejestracji jest ważnym elementem procesu diagnostycznego. Pomocnym elementem oceny stanu technicznego stały się repliki z powierzchni badanej liny. Informacje zawarte w artykule pozwolą na opracowanie nowej, specjalistycznej aparatury do badań magnetycznych lin kompaktowanych.Słowa kluczowe: badania magnetyczne lin stalowych, analiza falkowa, diagnostyka

SUMMARYThis paper presents the application of a Self-exited Acoustical System (SAS) for monitoring stress changes in the cement plant. The change in the speed of wave propagation, which is associated with a change in the resonance frequency in the system is caused by the deformation of the examined material. The SAS system is based on this phenomenon and can be used for the indirect measurement of the stress changes in the material.

The magnetic field created by technical devices is a source of information. This information could be used in contactless diagnostics and predictive maintenance or for resolving problems along with standard NDT (nondestructive testing) methods, especially if we consider large, slow-speed devices, such as electromotors, transmissions, or generators. Identification of causalities of device failure processes with near magnetic field is one of the suitable NDT methods improving sustainability of systems. The measurements presented in the article were performed with the VEMA 04 fluxgate vector magnetometer with the DC-250 Hz bandwidth and 2 nT sensitivity. Postprocessing of the results was performed in the means of standard methods of discrete Fourier Transform, spectrogram creation and Wavelet Transform. The article presents data gathered during the measurement of a pair of extraction fans with power of 140 kW each and maximum revolutions up to 740 rev/min controlled by frequency converters and a single semi-Kaplan water power plant with 400 kW peak power at 1005 rev/min maximum generator speed. The measurements were performed before and after repairs of one of the ventilators in the ventilation system at 60% and 100% of maximal output power. The rotating magnetic fields of the fan electromotor stator, fan rotor revolutions, rotor slip frequency and ball-bearing frequencies were identified in frequency spectrums in the distance of 700 mm from fan electromotor axis in both cases. During the measurements on the semi-Kaplan turbine, the changes in states of mechanical and electrical components of the machine were monitored in the magnetic fields with increase of the power in the range of 0–95%, before and after phasing to the electrical grid. Standard processing methods, Discrete Fourier Transform, spectrograms and Discrete Wavelet Transform were used. In the spectrograms of the measured magnetic fields, the 1st–4th harmonics of the turbine shaft, generator shaft and also their side frequencies were identified. Significant changes of magnetic fields in time were identified in the area of 60–95% power. With the help of the Wavelet, transform intervals were identified where it is desirable to operate the turbine. The analyses of magnetic fields measurements performed on the power plant were compared with vibro-diagnostic principles.