Interface - The Journal of Wheel/Rail Interaction

DERAILMENT PREVENTION

Inspection and Analysis of Switch Derailments
(Part 2 of 2) continued

Frog points become chipped and broken (see Figure 5) when the guard rail is not properly adjusted with respect to the alignment of the frog. Section 213.143 of the FRA Track Safety Standards directly addresses the issue of guard rail placement vis a vis the location of the frog point. There are two important measurements that must be taken regarding the alignment of the guard rail and frog: Guard Check and Guard Face.

The Guard Check is a “not less than” measurement, and the Guard Face is a “may not be more than” measurement. Compliance with CFR213.143 is essential and there is little room for tolerance or slop in these measurements. Figure 6 shows a diagram of these two measurements. Figure 7 shows the measurements overlaid on a turnout. Figure 8 shows the allowable measurements as contained in 213.143.

If the guard rail is worn, allowing a wheel to drift toward the frog point, the wheel will “crowd” the frog point, and possibly chip or break the point. Figure 9 shows a frog point exhibiting early signs of wear, where wheels are “crowding” the point. This is a telltale sign that adjustment of the frog or guard rail is required.

The Track safety standards also specify that a minimum clearance of 1-1/2 inches must be maintained in the guard rail flangeway opening. If the guard rail is too close to the stock rail, the wheel can become pinched, and cause a climbing action of the wheelset.

Railway Mechanical departments do a good job of ensuring that all wheels are mounted on their axles with a back-to-back spacing of between 53 and 53-3/16 inches. These tight tolerances are closely checked and monitored. It is incumbent upon the track department to ensure that the wheelsets have the proper clearances when negotiating the frog area. Compliance with the track safety standards will ensure that the wheelsets stay on the “straight and narrow”.

There are other FRA rules and dimensions that should be checked following a derailment in a turnout. Railroaders are advised to become familiar with all the provisions of 213.133 thru 213.143. Many turnout derailments involve interaction of the car, wheels, turnout components, track geometry, speed and in-train forces. A systematic investigation of all phases of the operation is necessary anytime a turnout derailment occurs.

Gary P. Wolf is President of Rail Sciences Inc.

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