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Lubricant Film Thickness Measurement

Tribosonics Ltd has the capability to measure thin films, solid or liquid, as low as 50 nanometres with no upper limit. These layers are commonly used in lubricating applications such as bearings, piston rings, seals and artificial hip joints. In these components thickness measurement of the lubricating oil film is essential information for performance monitoring and control.

Other examples of measurable layers include free surface films used in thermal cooling applications and solid layers used in adhesive applications and component separation.

To perform these measurements Tribosonics Ltd. uses patented technology jointly developed at the University of Sheffield and the University of Bristol for the measurement of thin layers using ultrasonic reflection. As such Tribosonics Ltd. is the only company worldwide performing such measurements.

To facilitate this Tribosonics Ltd. have developed a range of bespoke hardware and software for this purpose. See below for some of the different measurement applciations.

Lubricant Film Measurement and Monitoring Hardware

Journal Bearings

Journal bearing lubricant film measurements can be made from either sensors mounted behind the bearing shell or from shaft mounted sensors. Measurements from behind the bearing shell result in single point measurement per sensor. Shaft mounted sensors result in a full 360° swept profile.

Journal Bearing Lubricant Film Measurement

Journal Bearing Lubricant Film Measurement

Hydrodynamic Thrust Bearings

Hydrodynamic bearings are used in wide range of engineering applications to support an axial or thrust load from a rotating shaft. Once again the lubricant film thickness is crucial to operation. Tribosonics Ltd's sensors are ideal tools for monitoring these bearings.

Piston Ring / Liner

Sensors can be mounted on the external liner wall and measure the lubricant film as the piston ring passes. This can be done in real-time and piston ring lubricant film information can be output for instantanious parameter adjustment.

Piston Ring Liner Lubricant Film Measurement

Piston Ring Liner Lubricant Film Measurement

Mechanical Seals

Mechanical seals are used to retain a high pressure liquid inside a chamber at a shaft entry point. There are usually a minimum of two active components – the stationary seal and the rotating seal. Between these two parts there is a thin layer of liquid – either the process fluid or some other flushing fluid. If the thin layer is two thin then the surfaces come into contact and the seal fails. If the layer is too thick then there is excessive leakage from the seal.

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Reciprocating Seals

Reciprocating seals such as hydraulic cylinders and pistons depend on the seal or piston ring for operation and efficiency. Tribosonics Ltd's technologies have been applied to this application to give an understanding of the effect of pressure and sliding speed on film thickness.

Artificial joint measurement and monitoring

Artificial Joints

Our sensors are ideally suited for looking inside artificial joints such at hip and knee. Measuring the film thickness and surface separation can give vital information for the development of these joints. Our technology also allows the effect of different biological fluids to be examined.

Publications

Publications where at least one of the authors is now working for Tribosonics Ltd:

A. Hunter, R. Dwyer-Joyce & P. Harper (2012) 'Calibration and validation of ultrasonic reflection methods for thin-film measurement in tribology' Meas. Sci. Technol. 23 doi:10.1088/0957-0233/23/10/105605

Brockett, C. L., Harper, P., Williams, S., Isaac, G. H., Dwyer-Joyce, R. S., Jin, Z., and Fisher, J., (2008), ‘The influence of clearance on friction, lubrication and squeaking in large diameter metal-on-metal hip replacements.’, J Mater Sci: Mater Med. Vol. 19, pp. 1575–1579.

Harper, P. B., (2007), ‘Measurement of Film Thickness in a Piston Ring using Ultrasonic Reflection.’, Proceedings of IMechE, Seminar on Reciprocating Seals, 25th June 2008.

Harper, P. B., (2007), ‘Monitoring Mechanical Seals.’, Proceedings of IMechE Seminar on Mechanical Sealing Technology, 18th April 2007.

Reddyhoff, T., Dwyer-Joyce, R.S., and Harper, P., (2006) ‘A New Approach for the Measurement of Film Thickness in Liquid Face Seals’, Tribology Transactions. Vol. 51, No. 2, pp. 140 - 149.

Reddyhoff, T., Dwyer-Joyce, R.S., and Harper, P., (2006), ‘Ultrasonic measurement of film thickness in mechanical seals’, Sealing Technology, Volume 2006, Issue 7, July 2006, pp.  7-11.

Dwyer-Joyce, R.S., Green, D.A., Balakrishnan, S., Harper, P., Lewis, R., King, P., Rahnejat, H., (2006), ‘The Measurement of Liner-Piston Skirt Oil Film Thickness by Ultrasonic Means’, SAE Paper 2006-01-0648 (presented at the Society of Automotive Engineers International Congress, Detroit, April 4-6 2006), in SP 2013, pp127-132 (ISBN 13 978 076801 748 9), in press Transactions of the SAE.

P. Harper, R.S. Dwyer-Joyce, U. Sjödin, U. Olofsson, (2005) ‘Evaluation of an Ultrasonic Method for Measurement of Oil Film Thickness in a Hydraulic Motor Piston Ring’, Proceedings of the 31th Leeds-Lyon Symposium on Tribology, “Life Cycle Tribology”, eds. D.Dowson, M.Priest, G.Dalmaz, A.A.Lubrecht, Elsevier Tribology Series No. 48, pp. 305-312, (ISBN 0-444-51687-5).

Dwyer-Joyce, R.S., Harper, P., and Drinkwater, B., (2004), ‘A Method for the Measurement of Hydrodynamic Oil Films Using Ultrasonic Reflection’, Tribology Letters, Vol. 17, pp. 337-348.

Harper, P., Dwyer-Joyce, R. S., (2004), ‘Measuring Oil Film Thickness with Ultrasound’, Lubrication Excellence Conference Proceedings, March 23rd-25th, pp 425-428.

Drinkwater, B. W., Dwyer-Joyce, R. S., and Harper, P., (2004), ‘On-Line Measurement of Lubricant Film Thickness Using Ultrasonic Reflection Coefficients’, AIP Conference Proceedings, February 26, Volume 700, Issue 1, pp. 984-991

Dwyer-Joyce, R.S., Harper, P., and Drinkwater, B., (2004), ‘Evaluation of an ultrasonic oil film measurement technique for PTFE faced thrust pad bearings’, Proceedings of the ASME/STLE International Joint Tribology Conference, IJTC 2004, 2004, p 697-710.

Harper, P., Hollingsworth, B., Dwyer-Joyce, R.S., and Drinkwater, B.W., (2004), ‘Journal Bearing Oil Film Measurement Using Ultrasonic Reflection’, Proceedings of the 29th Leeds-Lyon Symposium on Tribology, Elsevier Tribology Series No. 41, pp. 469-476, (ISBN 0-444-51243-8).

Dwyer-Joyce, R.S., Harper, P., and Drinkwater, B., (2003), ‘Oil Film Measurement in PTFE Faced Thrust Pad Bearings for Hydrogenerator Applications’, Proc IMechE part A, Journal of Power & Energy, Vol. 220, pp. 619 – 628.