Bearing temperature trending is an ongoing problem that is receiving considerable attention in the railroad industry. Currently, bearings that display this phenomenon are removed from service since a trended bearing exhibits similar behavior to a burn-off bearing at the end of its life. The removal and replacement of these bearings is a costly process, in addition to causing undesirable time delays. Even though this topic has received ample attention, to date, research efforts have been unable to identify the mechanism(s), or the root cause(s), of this troubling phenomenon. Motivated by the latter, the study presented here focuses on identifying the root cause of the bearing temperature trending seen in service. To this effect, eight laboratory experiments were performed using three bearings that had been removed from service due to temperature trending, along with their mates. Laboratory experiments were performed on a test rig that accommodates four Class F bearings simultaneously rotating at a speed of 536 rpm, which corresponds to a train traveling with a velocity of approximately 57 mph (91.7 km/h). The laboratory study was successful in duplicating the bearing temperature trending phenomenon seen in service, and consequently identifying the main source of this problem. Data presented will include both temperature and vibration profiles measured during normal and trending phases, along with inspection results.

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