Interface - The Journal of Wheel/Rail Interaction

RAIL GRINDING

Specification and Documentation of Rail Grinding Work in Europe
By Dr. Wolfgang Schoech • July, 2007

Rail grinding practices and requirements have evolved over the years. In the past, rail grinding programs were controlled by railway personnel who were responsible for selecting the sites, choosing the number of grinding passes and determining when a program was finished. Today, grinding programs and procedures are very different. With privatisation and restructuring, railway staffs have been reduced considerably. Many of the on-site tasks that were once performed by railway personnel now have been transferred to the grinding contractor. With this change has come the development of specifications and procedures, which include detailed documentation, that contractors must adhere to before the work is accepted.

European railways established the Euro-Norm EN 13231 “Railway applications — Track — Acceptance of works” in 2006. Part 3 of this standard, which was developed by the European Committee for Standardization (CEN), deals with the “Acceptance of rail grinding, milling and planing work in track.” The specifications, which represent an envelope of all of the individual railways' standards, deal with longitudinal and transverse profiles, and the condition of the rail surface. While tolerances vary, depending on line characteristics, on-site recordings are typically required to document the grinding work. Documentation (and payment only against certified performance) assures consistently good results. It also provides insight into the development of rail surface irregularities and profile changes, which enables railways and contractors to develop better grinding procedures and strategies.

The European Context
European railways, which are primarily state owned, developed independently. This, and "pride," which leads each railway to believe that its specifications are the best, explains the wide range in national designs and standards. Track gauge, for example, ranges from meter gauge to 1668 mm broad gauge. More than 20 standard rail profiles are in use. Even though grinding machines are designed to fit within the smallest overall clearance envelope, the wide array of in-track safety systems in use pose obstacles that make it difficult to operate the same grinding machine on multiple properties. Beyond design differences, there are also distinct operating characteristics.

On high-speed passenger lines that operate at speeds of up to 300 km/hr, stable running, in which equivalent conicity plays a determining role, is the highest priority. Noise and fatigue are other important issues. On urban transit systems where noise is the predominant issue, corrugation must be kept to a minimum. Mixed traffic lines are susceptible to wear, fatigue and noise. On the few dedicated freight traffic lines that exist, wear and fatigue are the greatest concern. Lines that handle high-speed passenger trains during the day and freight traffic at night represent the most challenging conditions under which to properly maintain rail and track.

Wheel/Rail Contact
Vertical, lateral and longitudinal forces are transmitted to vehicles and track through a small elliptical wheel/rail contact area (see Figure 2). Creep, rolling and sliding forces are also generated at the contact patch. As a result of this rolling contact, wheels develop small irregularities such as corrugation, surface cracks and indentations.

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