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Proceedings Paper

Fluorescence spectroscopy: a promising tool for gear-oil condition monitoring
Author(s): Daniel D. Dorigo; Benjamin R. Wiesent; Özlem Simsek; A. Pérez Grassi; Alexander W. Koch
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Paper Abstract

Wind power is one of the most promising green energy sources, especially when produced in offshore power plants. Corrective operations in wind turbines cause a considerable part of the maintenance costs of such plants. One preventive action for reducing such operations is the periodic off-line control of oil samples from the wind turbines. The time delay between sampling and availability of the results is a major disadvantage of this kind of controlling. In-situ condition monitoring is a solution to this problem. In-situ monitoring allows real time detection of random, time discrete events, thus enabling a better scheduling of preventive actions and reducing costs and downtime. Fluorescence spectroscopy is a complementary technique to absorption spectroscopy. Due to absorption of UV or visible light, the electrons of specific molecules are excited from a ground electronic state to a vibrational state of higher energy. By collision with other molecules, the excited electron looses a part of the acquired energy and relaxes to a lower vibrational state. The remaining acquired energy is emitted during the electron's transition to the ground state. The resulting frequency shift between excitation and emission energy, known as Stokes shift, is unique and characteristic for each active molecule. In this paper gear-oil condition monitoring based on fluorescence spectroscopy is proposed. Three typical commercial gear-oils for wind turbines were studied. The spectra gained by UV excitation of the samples were analyzed by means of partial least square (PLS) regression. Good prediction results were obtained for the total acid number (TAN). The latter is a measure for the oil acidity and is considered to be a proxy variable for oil age. Other parameters delivering information about gear-oil additive depletion and the related oil aging condition, like phosphor, sulfur and molybdenum concentration, were also analyzed.

Paper Details

Date Published: 9 May 2012
PDF: 10 pages
Proc. SPIE 8439, Optical Sensing and Detection II, 84391B (9 May 2012); doi: 10.1117/12.922628
Show Author Affiliations
Daniel D. Dorigo, Technische Univ. München (Germany)
Benjamin R. Wiesent, Technische Univ. München (Germany)
Özlem Simsek, Technische Univ. München (Germany)
A. Pérez Grassi, Technische Univ. München (Germany)
Alexander W. Koch, Technische Univ. München (Germany)

Published in SPIE Proceedings Vol. 8439:
Optical Sensing and Detection II
Francis Berghmans; Anna Grazia Mignani; Piet De Moor, Editor(s)

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