Best practices for turnout, crossing diamond grinding

Railway Track and Structures, July, 2000 by David Davis, Don Guillen, Satya Singh, V. Terrill, D. Mesnick

The questionnaire was sent to AAR chief engineers with a request to appoint a project representative knowledgeable in the areas of special trackwork and grinding. Amtrak, BNSF, CN-IC, CP, CSXT, NS, QCM and UP were all represented. Responses to the survey were solicited and follow-up questions were asked.

Results

A variety of switch and frog grinding practices were employed by the railroads surveyed. Some of the variation is due to the variety of operations, special track work designs, maintenance, and budgeting philosophies.

Several railroads use a semi-automated production-grinding program for special trackwork. These railroads are striving to reach the status of doing only preventive works (i.e., keeping the system in optimum condition).

The other group relies on an as-needed restore and repair program. The special-trackwork grinding programs on these roads are determined by budget, with prioritization based on line importance.

Interestingly, the railroads that are the largest users of advanced-design special trackwork are the ones in the latter group. This may reflect some of the benefits they are getting out of the advanced designs. It may also reflect capital vs. operating expense decisions.

Despite the philosophical differences, all railroads agree that grinding is effective in extending the life of special trackwork. One suggested that a proper grinding program could extend the life of special trackwork components by up to 100 percent on heavy-haul lines.

Due to the daunting challenges and numerous uncontrolled variables involved with running a large-scale field trial, little documentation of the effectiveness of grinding exists.

The surveyed railroads agree the main reasons for grinding are to restore the proper running surface profile and to repair the effects of hollow-tread wheels.

Respondents were also asked to rank the causes and mechanisms they felt were most critical to induce grinding, as Table 1 shows.

Certain worn-wheel profiles first cause detrimental surface conditions at the critical wheel transfer areas of frogs and switches. These include frog points, frog wings, switch point tips, and stock rails in the wheel transfer areas.

Grinding practices

Pre-grinding track restoration is used to increase grinding effectiveness. Removing any gauge, surface and alignment defects will improve the ability to grind the desired profiles.

Frog cracks, spalls and excessive flow are repaired prior to grinding. Production grinding programs are more successful when preceded by track repair.

The ability to accurately measure the running surface profile prior to and during grinding operations is used to optimize the grinding process. The best practice is to use a portable optical profile-measuring device for measuring.

As in rail profile grinding, the objective of special trackwork profile grinding is to center the wheel contact zone on a broad running surface.

Grinding railroads overwhelmingly prefer an eight-inch crown-radius profile. This radius provides a reasonably wide-worn running band while protecting the gauge corner from excessive contact.