Increased availability and accuracy of rail profile measurement systems, as well as advancements in computing capability, offer the ability to evaluate rail profile condition in real time (as well as offline). This has improved the ability to monitor grinding quality and led to the development of quality control indices for evaluating grinding performance.

ZETA-TECH Associates, Inc., recently developed a “Grinding Quality Index” (GQI) to evaluate the ability of the grinding operation to accurately reshape the rail to the desired rail profile or template. Specifically, this index measures and quantifies the difference between the ground profile and the desired, or target, rail profile. The magnitude of the index reflects the magnitude of the difference between the actual and the desired profiles. This index can be determined separately for each rail, i.e. left and right rail, and also in front of and behind the grinding train, representing “before” and “after” grinding in a one-pass grind environment. By measuring before and after indices (from a front and rear profile measurement system), over a grinding segment, the effectiveness of the grinding pass (or passes) can be evaluated directly. In addition, the magnitude of the “after” profile GQI, provides a basis for planning future grinding, since it represents how close the rail is to the desired template.

Calculation of GQI
Most modern production rail grinders use train-borne profile measurement systems that capture the transverse rail profile as a train car moves over the rail. Once the actual rail head profile is measured, it can be compared to the desired (target) rail shape or template. The choice of the desired template shape depends on the degree of curvature and rail side (high or low) as well as the type of grinding to be performed. Thus, the track geometry as well as the profile grinding approach must be known for a given location in order to select the desired rail template. This is critical from the wheel/rail interface point of view, where relatively small differences in rail profiles can make significant differences in the final wheel/rail contact relationship and the corresponding effectiveness of the profile grinding activity.

The measured rail profiles and the required template (target profile) are then overlaid to examine grinding requirements (see Figure 1). The rail profile may be a pre-ground or a post-ground profile, depending on which rail profile measurement system (leading or trailing) generated the profile.