Models for the Residual Life of Railroad Bearing Grease in Laboratory and Industry Applications

Adequate lubrication in railroad bearings is crucial to the safe operation of these components. An investigation of the residual life of railroad bearing grease was conducted in a laboratory setting. The data was collected using a split-split-plot design of experiments. The Oxidation Induction Time (OIT), which is the time required for the remaining antioxidants in a sample of grease to be consumed in a test, is the response variable for this study. Low values of OIT indicate small remaining amounts of antioxidants in the grease and thus small remaining residual life in the grease. OIT measurements were made using differential scanning calorimetry. Laboratory testing was performed utilizing a specialized dynamic test rig that allowed four rail-road bearings of the same class, mounted on a test axle, to be subjected to varying operating conditions. The independent factors manipulated in this study were total service mileage, miles at load, average speed, mounted lateral spacing, and average temperature at three locations within each bearing. Additional information was recorded for each axle tested that includes axle number, bearing location within the test axle, grease location within each bearing and the presence or absence of a small sprall on the bearing surface. Regression analysis was employed to fit mixed effects models using JMP software. The first modeling effort was to develop the best possible model for laboratory usage. A second modeling effort was conducted to develop a model for industry usage without several variables available only in the laboratory setting. Web-based applications are provided for users to investigate the residual life of railroad bearing grease in both laboratory and industry settings.