Interface - The Journal of Wheel/Rail Interaction

EFFECTS OF WIDE GAUGE

Effects of Wide Gauge on Derailment Potential
(part 2 of 2) (continued)

Sometimes it's not possible to get an accurate gauge measurement after a derailment because one or both rails have been rolled outward or the general pileup has compromised the integrity of the track structure. It may be possible in these instances, however, to measuring from the shoulder of one tie plate across to the shoulder of the other tie plate (if the ties are still present) to obtain the "base gauge." Table 1 illustrates what the base gauge should be, based on the rail weight. For instance, the nominal base gauge when the gauge is correctly set at 56-1/2 inches is 53-23/32 inches for a 136-pound rail section. By knowing what the actual base gauge is, and what it should be, the approximate track gauge can be determined. This method is fairly accurate, but additional gauge allowances must be factored into the assessment if the rail gauge face is severely worn, or if negative rail cant is present. (Table 1 indicates the base gauge dimension for different rail weights.)

Symptoms of a Wide-Gauge Derailment

When you inspect the derailment scene, and one or both wheels of the first derailed car are down between the gauge of the track, you may have a "suspect" wide-gauge derailment. You may even be able to see a mark where the wheels dropped off the gauge corner of the rail. In other situations, you may find one rail rolled outward and wheel markings down the web of the rolled rail. Either of these scenarios is consistent with a loss of gauge restraint, and what is commonly called a "wide-gauge derailment." (Figure 3 shows what a typical wide-gauge derailment looks like.

If the loaded gauge of the subject track leading up to the point of derailment has been correctly measured, and it exceeds the FRA standards, the use of the FRA T110 or T111 codes is appropriate. However, you may not have an exact violation of the FRA standards based on your gauge measurements. In this case, other issues should be assessed. The condition of the track, ties and fasteners leading up to the POD should be inspected for the following conditions:
• Spike killed ties.
• Missing or raised spikes.
• Evidence of dynamic gauge widening.
• Evidence of negative rail cant (or differential plate cutting).
• Evidence of heavy gauge-face wear on the rail.
• Severe plate cutting of the tie surface.
• Split or broken ties.

The presence of one, several, or most of these conditions at or near the POD, indicates a weakened track section that may fail under wheelset loading. In this case, even if the static gauge measurements don’t exceed the FRA standard, it is still appropriate to use the T110 or T111 cause code.

What if the track is in good shape, but wheels are between the rails?

On occasion, it is evident that wheels have dropped within the gauge of the track, but the tie condition is good, the spiking pattern and condition are good, there is minimal plate cutting, and the quantitative measurement of gauge leading up to the point of derailment is within FRA standards. In this case, two possible derailment causes are:
• Stiff or Warped truck Condition.
• Human error during switching.

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