Interface - The Journal of Wheel/Rail Interaction

RAIL GRINDING

Successful Grinding: Starting with the Basics
(continued)

The North American track structure is experiencing an accelerated deterioration rate from the increasing percentage of 286K loading. Short lines that are becoming 286K-capable must focus on more than just the bridges. Even on lines with an infrastructure that is currently handling heavy-haul traffic, the increasing use of AC locomotives, which generate higher longitudinal loads, continues to up the ante.

Subsurface support is critical as axle loads increase. On some of the iron ore railways in Western Australia, for example, which handle heavier 35- to 40-tonne axle loads, very small deviations in track support have almost immediate effects on rail surface.

Contaminated ballast and poor drainage provide poor track support, causing ties and rail to wear, requiring maintenance or replacement sooner than expected. Oddly enough, these areas typically get the least overall inspection. Inspectors tend to fly by some of the worst parts of the track structure (tunnels, muddy areas, etc) instead of getting out and into the mud, and planning for repairs.

Arbitrarily running a grinder through areas without reference to the track structure can do more harm than good (see Figure 8). Incorrect rail profiles cause hard steering and accelerated wear on rail and wheels. Grinding also dries out the surface of the rail. This raises the coefficient of friction on the rail from the optimum 0.3 to 0.6 or greater. If the track structure is weak, this can result in rail rollover derailments. And as previously noted, grinding tipped rail is a waste of material, as the rail must be re-ground to avoid causing severe steering forces when the rail is reset to the proper cant.

Maintenance departments can save money and reduce the rail lifecycle cost by increasing inspection and planning resources in the following ways:

• Only grind where the track structure is strong enough and in good enough condition to benefit from the effort and expenditure.

• Determine the optimum point to correct wide gauge by understanding the underlying cause at each location. Optical measurement systems can identify when wide gauge is due to tipping, lateral movement or rail wear, for example.

• Correct the gauge sooner. FRA safety standards are not the optimum maintenance point.

• Devote more effort to marking and changing defective ties. A “junior” inspector typically performs the tie inspection work that is responsible for millions in expenditures. Marked ties and inspection results should be reviewed in advance of all replacement programs to ensure that bad tie clusters are eliminated and that there are good ties under joints and welds.

• Consider that a timely expenditure of thousands of dollars in regular Maintenance spending might defer millions of dollars in Capital spending, several years later.

References
1) AREMA “Manual for Railway Engineering,” Chapter 4, Section 4.8, Rail Grinding Best Practice.

2) Sroba, P. and Roney, M., “Rail Grinding Best Practice,” AREMA Presentation 2001

Norman Hooper, P. Eng., is Principal, Hooper Engineering.

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