Development of an optical sensing system for the detection of lubricity conditions on the rail gage face

A novel optical sensing device that uses laser-induced fluorescence to detect the lubricity condition of the rail gage-face is evaluated. By analysing the fluorescence properties of eight commonly used gage-face greases used by the U.S. Class I railroads, we observed that the emitted fluorescence of the grease when exposed to ultraviolet (UV) light of different wavelengths can be used for detecting their presence. This observation is used to develop a non-contacting optical sensing device that uses two 405 nm lasers, a fluorescence detector, and a fluorescent bandpass filter, which are optimized for the fluorescence spectra of the greases. Two sensing devices are installed on a robotic rail cart, one on each side, to simultaneously detect the lubricity conditions on the rails over extended distances. After extensive evaluations using both laboratory and field testing, it is confirmed that the optical sensing system can accurately detect the presence of the gage-face grease through the fluorescence intensity or intensity variance, even when there are small quantities of grease in relatively thin layers. Furthermore, the test results indicate a high level of repeatability and efficiency in detecting the spatial distribution of grease along the rail.