Interface - The Journal of Wheel/Rail Interaction

FRICTION MODIFICATION

Top of Rail Friction Modification in Tough Terrain (continued)

Figure 6 shows a typical wayside application system used to apply KELTRACK® Trackside Freight on NS. This Portec solar-powered, dual-track unit includes a digital control system and two TOR-XLTM applicator bars mounted to the field side of each rail. As shown in Figure 7, the applicator bars deposit a bead of the water-based friction modifier, which dries to establish dry, thin-film friction control. The wheels of passing trains produce a capillary effect that draws the product into the contact area to establish effective friction control at the wheel / rail interface.

Test Program and Objectives
NS was primarily interested in deploying wayside TOR friction management to reduce lateral forces and associated problems in the high-stress, heavy-haul operating environment. Since the benefits associated with TOR friction management had already been demonstrated in less challenging territories, the objective of this test was to evaluate wayside friction control in heavy grade conditions. On descending grades (Test 1), the goal was to determine the effectiveness of wayside TOR friction control in reducing lateral loads in the presence of air braking (i.e. the impact of the abrasive action and heat generated by brakes on the TOR film on the tread). On ascending grades (Test 2), the goal was to determine the effectiveness of wayside TOR friction control in reducing lateral loads under the conditions of heavy sanding and locomotive pusher service.

NS realized that because of the constraints that bi-directional traffic placed on track geometry, loaded coal trains on ascending grades were traveling well below balance speed. As such, the effects of train handling and superelevation on lateral forces were evaluated as part of this study. Though not addressed in this article, the effects of wheel and rail profiles were also considered.

Test Area 1: Descending Grades
In December 2003, NS installed 28 (single-track) wayside TOR systems at 14 sites on the double-track mainline coal route between Bluefield, West Virginia and Narrows, Virginia. The test area is characterized by a descending grade greater than 1% in the loaded HAL (eastbound) direction. As this was one of the earliest wayside TOR implementations, the initial 1-mile spacing between units was relatively conservative. (More recent studies have shown that 2- to 2.5-mile spacing is feasible in river grade territories.)

Initial track geometry data indicated that the TOR systems were successful in reducing loaded gauge widening. To verify the results, two lateral/vertical force measurement sites were installed in back-to-back reverse 6.3- and 6.8-degree curves. Data collected from these force sites, established in conjunction with the Transportation Technology Center Inc.'s Eastern HAL (Heavy Axle Load) Mega Site monitoring program, indicated that the lateral force reductions were less substantial than the loaded gauge widening results had indicated (1).

In early 2005, NS, TTCI, Portec Rail and Kelsan Technologies initiated a collaborative effort to better understand the performance of TOR friction control in the Bluefield-Narrows test zone. In addition to lateral force reductions, the group also studied:

• Wayside product transfer/pick-up.

• Application rates.

• Impacts of tread braking on friction modifier effectiveness.

• Multi-unit (i.e. wheel conditioning) effects.

• Impacts of applicator “wet zone” geometry on performance.

• Directional effects (ascending grade versus descending grade traffic).

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