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Oil film measurement in polytetrafluoroethylene-faced thrust pad bearings for hydrogenerator applications

Dwyer-Joyce, R.S., Harper, P., Pritchard, J. and Drinkwater, B.W. (2006) Oil film measurement in polytetrafluoroethylene-faced thrust pad bearings for hydrogenerator applications. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 220 (6). pp. 619-628. ISSN 0957-6509

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Abstract

There is a growing trend in the replacement of the babbit facing in thrust pad bearings with a composite polytetrafluoroethylene (PTFE) surface layer. The PTFE-faced bearings have been shown to allow a greater specific pressure, reduce thermal crowning, and, in some cases, negate the need for an oil-lift (jacking) system. These designs of bearing require new methods for the measurement of oil film thickness both to assist in their development and for plant condition monitoring. In this work, an ultrasonic method of oil film measurement is evaluated for this purpose. An ultrasonic transducer is mounted on the back face of the thrust pad. Pulses are generated and transmitted through the pad material, bonding interlayer, and PTFE surface layer. The proportion of the wave that reflects back from the oil film layer is determined. This is then related to the oil film thickness using a series of calibration experiments and a spring stiffness model. In practice, the reflected signal is difficult to distinguish, in the time domain, from other internal reflections from the pad. Signals are compared with reflections when no oil film is present and processing is carried out in the frequency domain. Experiments have been performed on a full size PTFE-faced thrust pad destined for a hydroelectric power station turbine. The instrumented pad was installed in a test facility and subjected to a range of loading conditions both with and without oil lift. Although there were some problems with the robustness of the experimental procedure, oil films were successfully measured and used to study the effect of the oil-lift system on film formation. © IMechE 2006.

Item Type: Article
Copyright, Publisher and Additional Information: Copyright (c) 2006 Professional Engineering Publishing. This is an author produced version of a paper published in ' Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy'. Uploaded in accordance with the publisher's self-archiving policy.
Keywords: Film thickness Fluid film bearings Lubrication Oil film measurement Polytetrafluoroethylene (PTFE)-faced bearings Thrust pad bearings Tilting pad bearings Ultrasound Films Frequency domain analysis Hydroelectric power plants Lubricating oils Polytetrafluoroethylenes Time domain analysis Ultrasonic measurement Ultrasonic reflection Ultrasonic transducers Thrust pad bearing Bearing pads
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Mechanical Engineering (Sheffield)
Depositing User: Mr Christopher Hardwick
Date Deposited: 18 Aug 2009 17:27
Last Modified: 08 Feb 2013 16:58
Published Version: http://dx.doi.org/10.1243/09576509jpe264
Status: Published
Publisher: Professional Engineering Publishing
Refereed: Yes
Identification Number: 10.1243/09576509jpe264
URI: http://eprints.whiterose.ac.uk/id/eprint/9176

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