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Shock and Vibration
Volume 2015, Article ID 960349, 11 pages
http://dx.doi.org/10.1155/2015/960349
Research Article

Application of Control Charts and Hidden Markov Models in Condition-Based Maintenance at Thermoelectric Power Plants

1School of Electrical Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade, Serbia
2School of Electrical Engineering and Computer Science of Applied Studies, Vojvode Stepe 283, 11000 Belgrade, Serbia

Received 10 February 2015; Revised 20 May 2015; Accepted 24 May 2015

Academic Editor: Yaguo Lei

Copyright © 2015 Emilija Kisić et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An innovative approach to condition-based maintenance of coal grinding subsystems at thermoelectric power plants is proposed in the paper. Coal mill grinding tables become worn over time and need to be replaced through time-based maintenance, after a certain number of service hours. At times such replacement is necessary earlier or later than prescribed, depending on the quality of the coal and of the grinding table itself. Considerable financial losses are incurred when the entire coal grinding subsystem is shut down and the grinding table found to not actually require replacement. The only way to determine whether replacement is necessary is to shut down and open the entire subsystem for visual inspection. The proposed algorithm supports condition-based maintenance and involves the application of control charts to distinct acoustic signal parameters in the frequency domain and the construction of Hidden Markov Models whose observations are coded samples from the control charts. In the present research, the acoustic signals were collected by coal mill monitoring at the thermoelectric power plant “Kostolac” in Serbia. The proposed approach provides information about the current condition of the grinding table.