Condition monitoring of Kaplan turbine bearings using vibro-diagnostics

Vibration diagnostics is an indispensable method to evaluate the technical condition of machinery. If the conditions of machines are regularly monitored, the problems can be corrected even before they arise. The most often overloaded components of the turbine are bearings that similarly like other machinery are subject to degradation wear. The article deals with the bearingś condition of the Kaplan turbine. Within the research, the frequencies at which maximum accelerations were achieved and their impact on plant operation were observed. Time records were converted to the frequency domain by means of Fast Fourier Transformation and the records were processed by means of filters. Acceleration peaks have determined the frequencies responsible for the outer and inner ring damages, but based on an evaluation of the operating state of the bearing using Root Mean Square (RMS) values could be concluded that that damage to any part of the bearing is not demonstrable and the turbine is operability. © 2020 Int. J. Mech. Eng. Rob. Res

Study of a tap failure at the internal threads machining

The article aims to study a tap failure during the internal threads making. Within the research, the synergic effects of cutting speed and helix angle on the durability of selected taps have been investigated including detection of the types tool wear that occurred during the machining. The C45 steel has been selected for the study as a standard machined material used at the long-term durability tests. Three types of taps for M12 thread making with three different helix angles ω = 0° 15° and 35° all with cutting cone type C, were used during the experiments. The experimental study was carried out in several steps. At the beginning, the preliminary tests were done to be verified the input parameters related to both machined material and tool geometry. In the main phase of the experiments, tool life was investigated at the cutting speed recommended by the tool supplier and after that also at the higher cutting speeds. Within the research, the equations that describe the dependencies of tool durability and threaded length on both observed parameters have been developed based on the experimentally obtained data. The vibro-diagnostic of the taps was carried out because of process stability monitoring and the possibility to predict the tool behavior at the machining with early identification a tool failure. The results have shown that the intensity of tool wear is affected not only by cutting speed but also by the pitch angle of the tap. Next findings confirmed that the tap failure can appear in various forms and that it is possible to identify the presence of tap wear by means of vibro-diagnostics. © 2019 Elsevier LtdMinistry of Education, Science, Research and Sport of Slovak Republic [KEGA 007TUKE-4/2018, VEGA 1/0795/19