By the time Norfolk Southern’s alarm system alerted the 23rd car of the 149-car train that there was trouble, even the sophisticated braking system was too late to avert disaster. It’s the equivalent of running out of gas at a car’s fuel gauge a block away.
The current system for monitoring the health of bearings relies on temperature. Every few miles, a “defect detector” takes the temperature of hundreds of bearings as the train rolls. The preliminary report describes the data of the accident: the 23rd car was initially 38 degrees above the ambient temperature. Ten miles later, it was 103 degrees above. The next detector — which came 20 miles later — “recorded the temperature of the suspect bearing at 253°F above ambient,” the NTSB report said. That’s when the alarm went off.
The best way to prevent this type of failure is to detect bearing problems early. Rail safety experts say one way is to require more detectors because of the lack of 20-mile spacing. One of the best is to install devices that monitor not only the temperature but also the vibration of the bearings.
“The bearing started to fail in September,” said Constantine Darawne, director of the University Transportation Center for Railway Safety in Texas. [vibration] Sensors are the answer. They tell you when the bearing is starting to fail.
Such monitors can be installed in individual railcars (a more expensive option) or at various locations along the track. They flag when a bearing begins to weaken, giving the crew plenty of time to inspect and replace defective parts. This upgrade across the rail system should be a major focus of Congress, President Biden and regulators.
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