Interface - The Journal of Wheel/Rail Interaction

RAIL GRINDING

Practical Rail Grinding (continued)

Union Pacific, for example, struggles to maintain grinding cycles in its Red-X 400-mgt territory. As a result, UP and the National Research Council Canada's Centre for Surface Transportation Technology (CSTT) developed new profiles to improve wheel/rail interaction and minimize the required grinding effort. Taking specific track features that included predominantly premium steel, mild curvatures (2.5 degrees or less), less than 1/4-inch wide gauge in curves, nominal 1/4-inch tight gauge in tangents, and minor cracking on the gauge corner of high rails and the gauge side of low rails into account, CSTT recommended new profiles for high rails in sharp curves, high rails in mild curves, low rails in all curves, and tangent track and curves less than 0.25 degrees. The profiles were designed to provide most of the benefits to be had from so-called "ideal profiles," in terms of reduced contact fatigue and wear, without excessive metal removal. (If these site-specific profiles were applied to other UP divisions, the benefits would be less—perhaps 70% - 80% of that achievable with the ideal profiles.)

The profile for the high rail in sharp curves, for example, provides some gauge-corner relief to protect from the initiation of rolling contact fatigue and allows for the longer grinding intervals that are needed on this high-density line. The profile also provides for conformal contact on the gauge corner to improve steering. The low rail profile produces a 10-inch radius contact band biased to the field side of center to take the load off the spalled center band. With UP’s excellent control of gauge, little field-side relief was required on the low rails to protect the rail against false flanges on wheels. In tangent track, all contact is shifted to the field side to address hunting and tight gauge. This approach, combined with the central or gauge-biased contacts that exist outside the Red-X territory, is meant to spread wheel wear to reduce hollowing. Figure 2 shows a metal-removal plot for the recommended low rail profile.

Preventive Grinding
Work done by MRS Logistica in Brazil represents another example of a profile design strategy that makes a modest compromise on wheel/rail performance to improve the practicality of implementation. MRS is a broad gauge (63-inch) railroad serving Minas Gerais, Rio de Janeiro and São Paulo. The main products hauled are iron ore (68%), steel products, cement, bauxite, coal, agricultural products and containers. In 1998, rail on the Steel Line, one of the four MRS lines, exhibited evidence of corrugation, head checks, spalling, severe plastic flow, dipped welds, engine burns and detail fractures. In 1998, 132 service failures occurred in 217 miles (350 km) of track.

Loram Maintenance of Way, Inc. and CSTT designed new rail profiles and developed a preventive grinding strategy tailored to MRS’s needs. As a result of the program, rail service failures have declined dramatically and the rail wear rate has been reduced nearly by half since 2002. (Fuel consumption also was reduced by 2% - 3%.) Consequently, MRS saved about $25 million in rail purchases over the past three years. A number of issues have arisen since the rail profiles were first designed and the grinding program began, however. These issues have had an impact on how effectively the profiles can be implemented in track and on the grinding interval required for staying ahead of rolling contact fatigue.

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