Development of Laser/LED-Based Instrument for Optical Detection of Railroad Top-of-Rail (ToR) Friction Modifiers and Lubricity Conditions

This study provides the results of research for obtaining track lubricity conditions through using laser/LED-based, optical sensors while onboard a push-cart. The resulting sensors are intended to be able to identify the lubricity condition of a rail network while moving onboard either a track metrology car or a Hy-rail vehicle. U.S. railroads invest a large sum of money and resources applying friction modifying material and flange lubricants to their rails to reduce rolling resistance in curves in an effort to reduce curving forces, reduce wheel and rail wear, and improve fuel efficiency. There exists, however, no effective ways of measuring the amount, adequacy, or even presence of top of rail (ToR) friction modifiers over continuous, extended distances of track except through quasi-empirical visual inspections that can be subject to a high amount of errors due to the very small layer thicknesses of ToR material (commonly, a few microns). This effort intends to bridge this gap by evaluating the application of laser/LED-based instruments in detecting the presence of ToR friction modifiers and flange lubricants on the rail. Specifically, the reflective and scattering properties of a laser beam directed against the rail surface are used to provide a qualitative “gloss”-based assessment of the presence of ToR friction modifiers. Additionally, a UV fluorescence sensor (LED source) is used to detect the presence of flange grease which has migrated to the top of rail by taking advantage of the grease’s fluorescence properties. The results of both laboratory and field testing of a prototype system with embedded laser and LED fluorescence sensors and supporting peripheral sensors are presented. The details of the instruments and their working principle are explained. The conditions for laboratory testing and field testing on revenue service tracks are detailed. The test results indicate that the laser/LED system is capable of successfully detecting the presence of ToR friction modifier and flange grease contamination on the rail.