Lightening lateral loading: tests performed by individual railroads and TTCI have shown that top-of-rail friction modifiers can reduce lateral loads and the stresses they generate by 50% without negatively affecting locomotive traction or train braking capabilities

Railway Age, April, 2004 by Bob Tuzik

It's a given that lateral forces accelerate wear and degradation of the track structure. High lateral forces, which are generated when a vehicle negotiates a curve, can lead to a host of problems such as plate cutting and reverse cant, broken fasteners, and excessive rail wear. When lateral forces are too high they can cause rail rollover derailments.

Railroads can address these forces by increasing the strength of the track structure or by reducing the forces applied to it. Ever mindful of the high costs associated with upgrading track structures, several major North American railroads have turned to the use of top-of-rail (TOR) friction modifiers to reduce lateral loads. Tests performed by individual railroads and the Transportation Technology, Center, Inc., have shown that TOR friction modifiers can reduce lateral loads and the stresses they generate by half.

"Top-of-rail friction management represents the most cost-effective way to reduce the lateral threes delivered to the track," says Mike Roney, CP Rail's general manager of track maintenance.

CP Rail will be installing wayside TOR friction modifier systems on a 50-mile segment of its rugged Thompson Subdivision--50% of which is in curves. Using Kelsan Technologies' KELTRACK[R] TOR friction modifier applied by Portec Rail PROTECTOR IV[R] Trackside Friction Management Systems, CP Rail has been able to maintain a constant 0.3 to 0.4 coefficient of friction (COF) on both the high and low rails in curves. This helps to reduce the trucks' angle of attack, and reduces the L/V ratio on the low rail by about half, Roney told the Transportation Research Board in January. "We are essentially making 10-degree curves into 6-degree curves by reducing lateral loads with top-of-rail friction modifiers."

The Kelsan-type friction modifier used in these and other applications is a water-based liquid material that can be applied by on-board locomotive, hi-rail, or wayside applicators. After the water evaporates, a thin, dry film remains on the rail providing an intermediate 0.30-0.35 COF. Unlike traditional grease-based lubricants, which have a low (0.15) COF that can create traction and braking problems, friction modifiers are not lubricants. They provide a COF that is low enough to reduce lateral loads by up to 50% without negatively affecting locomotive traction or train braking capabilities.

BC Rail, which was recently purchased by CN, began greasing the top surface of rails in curves to reduce lateral forces after a rash of rail rollover derailments and accelerated track component wear in locations with high curvature and steep grades. While greasing the rail reduced lateral loads, it compromised braking and tractive effort, particularly on BC Rail's many 2.2% grades. As a result, BC Rail opted to use a friction modifier with an intermediate 0.30-0.35 COF to reduce lateral loads without creating traction or braking problems.

Tests of Kelsan/Portec Rail Products, Inc. wayside and hi-rail delivery systems at an instrumented 12-degree main line curve showed consistent lateral force reductions of 30%-50%, Norm Hooper, BC Rail's vice president of maintenance and chief engineer, told the International Heavy Haul Association.

Wayside tests were done using Portec Rail PROTECTOR IV[R] electric TOR applicators with two special MC-4TR[R] TOR applicators installed on the field side of each rail.

The Portec Rail/Kelsan hi-rail application system directs an atomized spray of the friction modifier across the top surface of the rail. The material was applied at a rate of 0.5 liters per mile per rail through the test curve (and for 2,500 feet of track on either side of the curve). The water in the atomized spray evaporates quickly, leaving a thin, uniform film on the rail surface. (The equipment is winterized to permit operation at temperatures at or above minus 22 degrees F.) Tribometer readings showed an average COF of 0.32 following application of the friction modifier and an average COF of 0.39 after the passage of two trains. Based on these results, BC Rail implemented a hi-rail application program in 2001, and has begun testing a locomotive mounted delivery system.

While BC Rail did not adopt its program to reduce rail wear, Norm Hooper pointed out that gauge face and head-loss wear rates have been reduced by 60% to 75%, depending on the degree of curvature, since the introduction of its TOR friction modifier application program. Material was applied every second day or approximately every 3,500 axles. "The only thing we changed was to move from grease to the Kelsan product," Hooper said.

Like BC Rail, Norfolk Southern has tested various types of products and application methods. Among them was a locomotive-mounted low-COF (0.15) TOR lubrication system on a captive fleet operating on its Captina coal line in southeastern Ohio. While the system reduced lateral forces when it was turned on, because of its low COF it had to be switched off during braking applications. "Since air brakes are frequently used, we decided to go to a wayside delivery system on that line," said Bob Blank, NS director of Research and Tests.