Interface - The Journal of Wheel/Rail Interaction

RAIL GRINDING

Practical Rail Grinding
by Fred Prahl, Eric Magel & Peter Sroba • April 4, 2005

Rail grinding, first developed as a technique for treating corrugations, has become an essential component of track maintenance for freight railroads and transit properties. During the 1960s, railroads began seeing rail corrugations developing to depths of about 0.080 to 0.120 inches (2 to 3 mm) on the low rails of standard carbon steels after 50 mgt; corrugation occasionally developed on the high rails, as well. In the early days of rail grinding, railroads ground a 2-inch-wide running band in the center of the rail head to remove corrugations. While this worked reasonably well, the grinding motors in early grinders were fixed in orientation. This type of grinding left the rail head flat. Rail life was extended, but plastic flow was not removed and cracks remained where the valleys of the corrugations had not been removed. Contact with the sharp reverse convex curvature of hollow-worn wheels remained, and the cause of corrugation formation was not effectively addressed.

The modern rail grinder is a high-capacity, computer-controlled machine with the ability to grind at angles up to 70 degrees (in most cases) to the gauge side of the rail (see Figure 1). They are able to provide as much as 30 hp to each grinding motor and to apply various patterns to the rail by positioning the grinding motors at different angles. Rail grinding operators can precisely position the grinding motors and control individual power consumption with greater accuracy than ever before. The challenge facing railroads today is how to make the best use of the current grinding technology.

When it comes to rail grinding, the needs of one railroad can differ vastly from another. But for railroads in a preventive grinding mode, a relatively generic format can be followed. It includes:
• Forward single pass grinding as much as possible.
• Occasional (but infrequent) two or three passes to pick up curves that are particularly problematic.
• Optimization of rail profiles to minimize damage between intervals. These profiles may be specific to the territory.
• Optimization of patterns to make the most effective use of each grinding pass.

But even railroads with decades of grinding experience find that a formulaic approach only partially satisfies their needs. With increasing traffic density on many lines, railroads are struggling with the logistics of getting a rail grinder to demanding locations on cycle. Pressure to extend the grinding interval requires appropriate changes to the grinding process.

Designing a Practical Grinding Plan
Railroads grind primarily to control surface fatigue defects and to maintain rail profiles that significantly increase rail life, control corrugations, and improve train stability and curving. However, each property has unique characteristics, which vary from location to location. These variations drive rail profile design as well as the grinding strategy. It is more important to design a rail profile and grinding plan that is practically achievable than it is to design and apply a profile that might otherwise be "perfect" from a wheel/rail perspective.

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