Implementation of a flange bearing crossing diamond in revenue service: a performance update of a flange bearing frog crossing diamond at Shelby, Ohio

Railway Track and Structures, May, 2007 by David D. Davis, Rafael Jimenez, David Clark, Jim Beyerl

CSX Transportation has now operated 20 mgt over the flange bearing frog crossing diamond at Shelby, Ohio, at an allowable top speed of 40 mph. These first 20 mgt of operations have been successful with minimal maintenance required and no operating problems.

The FBF diamond, installed July 31, 2006, is the first one installed under the Association of American Railroads' waiver granted by the Federal Railroad Administration. A waiver of the FRA Track Safety Standards is needed to allow FBF operation above Class 1 track speeds. (1)

Train handling

At the Shelby FBF diamond, train handling and locomotive operations have not been adversely affected. CSXT trains can operate up to 40 mph and train crew comments indicated increased smoothness, reflecting the expected lower degradation and impact loads for these diamonds. The shortline cross-traffic is restricted to 10 mph for reasons not associated with the FBF diamond. As with other diamonds, the locomotive engineer on either railroad will notch down the throttle when the locomotives cross the diamond. This is done to prevent traction motor flashovers when crossing the transverse rails. With the FBF ramps, it helps by reducing the likelihood of wheel slip as the wheels transition from tread bearing to flange bearing. CSXT reports no train operating problems with the FBF crossing at Shelby. Additionally, there is no evidence of engine burns on the running surfaces of any of the diamonds.

Wheel performance

A fleet of 12 covered hoppers was pulled from storage and placed into service to support the FRA wheel/truck inspection requirements for the waiver. Inspections with truck roll-out are conducted on a 90-day cycle. Wheels and axles are examined with nondestructive evaluation methods and all major truck components are inspected visually. Figure 1 shows a truck inspection with ultrasonic inspection of the axle and dye penetrant inspection of the wheel flanges in process. Wheel tread profiles are taken during these inspections. From these profiles, tread and flange height loss (i.e., "wear" rates) are determined. The "inspection" cars are cycling between Indianapolis and Albany or Buffalo, New York. They are seeing about 10 FBF diamond passes and 5,000 miles of operation per month.

An important mechanical concern is the effect of flange bearing on wheel performance. Among the wheel concerns is the rate of flange height loss versus tread loss (i.e., will the flange wear away faster than the tread?).

Figure 2 shows the measured average flange heights versus FBF diamond passes for the 12 cars in the FBF test fleet. The measurements of the Shelby fleet show that flange heights have decreased slightly in the first 25 passes. This is not unexpected as the initial deformation on the flange tips is relatively large. The average flange height changed from 1.23 to 1.22 inches (statistically the same for each measurement).

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For comparison, Figure 2 also shows flange height versus FBF passes for other freight operations. The effect of the rate of miles operated to FBF diamond passes can be seen in this plot. The original tests performed at the TTCI, with cars going over a diamond every three miles, reduced flange heights over time. (2) The rate of flange deformation exceeded the amount of wheel tread wear. For operations more representative of revenue service, such as the OWLS flange bearing diamond at Chenoa, Illinois, the flange heights have increased with time.

Figure 3 shows a time series of profiles for one wheel being monitored. It is typical of the group. Note that the flange height decreased in this initial interval of flange bearing. From the shape change, it is clear that flowed metal on the tip flattened and accounts for much of the height loss. As was measured at TTCI and in revenue service tests, the flange tip flattens rapidly to become conformal to the diamond running surface. (2) The gauge side corner of the flange tip may also sharpen (i.e., decrease in radius). In future intervals, we expect the flange heights to grow, indicating that tread wear is exceeding flange height loss.

Frog running surface performance

The flange bearing running surfaces of the diamonds have been monitored for deformation and rolling contact fatigue. To date, the running surfaces have performed well. As with tread bearing austenitic manganese steel (AMS) casting diamonds, initial deformation was relatively large. The rate of running surface height loss has decreased with tonnage as the running surfaces work harden and become more conformal. Absolute measurements of flange bearing running surface height loss measurements were made using non-wearing portions of the ramp and frog castings as references.

Figure 4 shows average flange bearing running surface height loss versus main line tonnage. For comparison, running surface height loss measured under 315-kip, 40-mph traffic at TTCI is also shown. The two tests show similar trends, but the limited population of wheels at FAST resulted in a quicker reduction of wear rate. In both tests, the running surface hardness increased from under 400 BHN when installed to about 600 BHN (582 at Shelby and 610 at TTCI) after about 20 mgt of traffic.