Lubrication, How Much Is Enought

Although no single method is superior, rail friction reduction, energy savings, and improvements to curving can be achieved by using a variety of lubrication practices.

Historically, lubrication has been shown to increase wheel and rail life, reduce energy consumption of trains, reduce lateral curving loads, and control noise emissions. However, it has also been shown that too much, or improperly applied, lubrication may negatively affect truck curving, train handling, and rail fatigue.

To examine the pluses and minuses of various lubrication methods, Transportation Technology Center, Inc., has conducted several lubrication studies over the years. The results show that rail friction reduction, energy savings, and improvements to curving can be achieved by using a variety of lubrication practices.

Currently, the Association of American Railroads is sponsoring research by TTCI engineers that will recommend target friction levels that field personnel can use for adjusting lubrication. Last year, AAR's NUCARS computer simulation model evaluated lubrication methods and their effectiveness as influenced by variations in track curvature, wheel/rail profile pairings, truck conditions, and train speed. Modeling data was supplemented with data from on-track testing at the Transportation Technology Center, Pueblo, Colo. These data were analyzed to develop best practices for lubrication (rail-friction guidelines) and to evaluate top-of-rail (TOR) lubrication effectiveness. They show that an effective, consistent wheel/rail lubrication application method reduces many of the negative effects of wheel/rail forces.

An optimum level of friction exists for each wheel/rail interface location (top-of-rail and flange face for both high and low rails). Although such optimal conditions may not be achieved everywhere, useful target friction values are important for reduced fuel usage and wear. This study was performed to analyze data (primarily from NUCARS) that represents as many related performance differences as possible. From the data, optimum levels of friction can be suggested, and through the use of automated high speed tribometers (or other means of friction-coefficient measurement), lubrication system effectiveness can be measured and managed.

Although NUCARS modeling indicated that wheel/rail profile pairing can overpower the effects of lubrication on energy and lateral load performance, the purpose of this study was to determine optimum lubrication effects. NUCARS also showed that the lowest curving resistance was achieved when friction levels were lowest on both gauge face and TOR locations. Also, high lateral forces and/or large L/V ratios can be induced by large friction differentials. From these results, optimum friction coefficients for the TOR and gauge-face locations were specified.

Track lubrication is traditionally applied by stationary wayside lubricators that apply a set amount of lubricant when