Controlling Top-of-Rail Friction
Friction control has been shown to produce significant
benefits over the years. Effective gauge-face and top-of-rail (TOR) friction
control can reduce energy
consumption by 7% - 25% and lateral curving forces by 25% - 50%. Proper management
can also reduce wheel/rail wear.
Overall, these benefits can add up to significant savings. North American railroads
spend about $3.6 billion per year in fuel costs, tie and fastener maintenance,
rail and wheel wear, and derailments. "An effective friction management
program that addresses these areas can reduce overall costs by 5% - 20% and produce
annual savings of $240 million," Rich Reiff, principle engineer at the Transportation
Technology Center, Inc., told delegates at Advanced Rail Management / Interface
Journal's 2004 Rail/Wheel Interface Seminar. "In order to achieve these
savings, however, the application method must be reliable and the cost of the
products and maintenance must be less than the projected savings."
Friction control includes the use of grease-based lubricants and water-borne
friction modifiers. Though they are often used together, there are fundamental
differences between them. Traditionally, lubrication has been applied to the
gauge face of the rail and wheel flanges to reduce friction to 0.25µ or
less. Greases tend to migrate from the gauge face to the top of the rail, however.
While this is sometimes beneficial, it usually is detrimental, negatively affecting
truck steering and train braking.
Unlike grease, TOR friction modifiers control friction levels at 0.3µ to
0.35µ. Very little of this material, which is applied by wayside, hi-rail
or locomotive-mounted applicators, migrates from the top of rail to the gauge
face. Traditional gauge-face lubrication is generally used along with the TOR
material in sharp curves. While the primary benefit of TOR lubrication is a reduction
in curving forces, it can also reduce wear and energy requirements.
of Rail Cant on Wheel/Rail Forces and Derailment Potential"
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