Acoustic Detection of Distressed Freight Car Roller Bearings

Trackside Acoustic Detection System (TADS^®) development spearheaded implementation of an acoustic freight car roller bearing detector whose purpose is to prevent in-service bearing failures (burned off journals and hot bearing detector train stops). The means of accomplishing this goal is by providing the user with a warning of internal bearing defects or degradation with component involvement and severity information. The Transportation Technology Center, Inc. (TTCI) began the TADS^® development process in 1994 with basic research into bearing defect acoustic emissions. Subsequently, TTCI conducted prototype testing on a North American railroad, constructed and installed of several international beta test systems, and finally has sold production systems in North America and internationally. There are currently about 40 TADS^® sites in operation world-wide with 2.0 or more systems scheduled for installation in 2007. The original mission for TADS^® in North America was an early warning of bearing degradation to allow for scheduled maintenance, but after initial evaluation, this mission enlarged to include notification of potentially high risk bearings. The high risk bearing is defined as one with fairly large areas of internal damage and at an increased risk of overheating or failing in service. The high risk bearing has a different acoustic signature, dissimilar to that of smaller defects. This paper will outline the change in mission for this detector and describe the development of an improved capability for detecting these high risk bearings.