The freight train derailment in eastern Ohio involved a failing wheel bearing that overheated without initially triggering the alert threshold set for the railroad’s defect detectors, according to a preliminary report by federal safety investigators.
The Norfolk Southern Railway train passed by three wayside detectors prior to the derailment that led to a toxic chemical spill from multiple train cars. Two of the three detectors recorded the rising temperatures of the overheating wheel bearing, but only the third detector in East Palestine, Ohio, recorded a temperature high enough to trigger a warning to the train crew.
“Norfolk Southern should re-examine their bearing criteria to include the rate of increasing temperatures between readings,” says Russell Quimby, a retired investigator for the US National Transportation Safety Board.
Within the privatised US freight rail system, freight railroad companies set their own temperature thresholds for the wayside detectors, which are also known as hot box detectors. The US Federal Railroad Administration, which creates and enforces US rail safety regulations, does not currently set standards for such detectors.
“Surprisingly, they are not required, nor are they regulated in any capacity,” says Jared Cassity, director of the transportation division at the International Association of Sheet Metal, Air, Rail, and Transportation Workers.
Cassity also expressed concern about the fact that the temperature increased by 65°F (36°C) between the first and second wayside detectors but no warning or information was sent to the train crew.
Only the third detector located near the East Palestine derailment site sent a warning to the train crew after recording a temperature that was more than 253°F (122°C) above ambient temperature.
Norfolk Southern typically requires train crews to stop and inspect warm wheel bearings if their temperatures are between 170 and 200°F (76-93°C). Railcars with wheel bearing temperatures beyond that threshold are supposed to be separated from the train and put aside in rail sidings that branch off from the main track.
“This one appears to have gone about 30 miles before failure, which was plenty of time to set the car out at a siding,” says Quimby. “Bearings that increase in temperature as progressively as this one don’t usually get cooler.”
After getting the detector’s warning, the train engineer increased application of the dynamic braking system that uses the train’s motors as generators to slow the train and dissipate mechanical energy as heat. An automatic braking system also activated the train’s main air brakes – something that can be triggered when a derailment disconnects the air brake hose between railcars.
The freight train was travelling at about 47 miles per hour (76 kilometres per hour) at the time of derailment.
Norfolk Southern said in a statement that its wayside detectors trigger at a temperature that is “among the lowest in the rail industry.” It also said that its all wayside detectors in the area of the incident and found they were operating as designed.
“As an industry, railroads will use this initial report in shaping a thoughtful, fact-driven approach to prevent another similar accident before it can occur elsewhere,” said the Association for American Railroads, an industry organisation, in a prepared statement.
But train worker unions have voiced safety concerns over the major US freight railroad companies having implemented precision-scheduled railroading strategies that pressure crews to perform train inspections faster. Cassity describes railcar inspection times as having decreased from 3 to 4 minutes per car to about 30 to 60 seconds per car.
The wheel bearing that failed was on a railcar with a load of plastic pellets, said Jennifer Homendy, chair of the National Transportation Safety Board, during a 23 February press briefing. The hot axle connected to the wheel bearing combined with the plastic pellets to start the initial fire that accompanied the derailment.
Such wheel bearings can fail for a variety of reasons, including fatigue cracking, water or mechanical damage, a loose bearing or a wheel defect. Federal investigators are still looking into the possible causes.
“Roller bearings fail,” said Homendy. “But it’s absolutely critical for problems to be identified and addressed early so that these aren’t run until failure.”
The investigation has not discovered any operational issues with the wayside detectors. But Homendy said that federal investigators would be looking at how Norfolk Southern uses and spaces wayside detectors, along with how train crews receive alerts from the detectors.
She also highlighted the many different detector standards among railroad companies and the lack of federal regulation for detectors. “The warning threshold is set by railroads, and it varies by railroad,” said Homendy. “We’re going to look at whether that should change.”
Before issuing a final report, the National Transportation Safety Board plans to hold a “rare” investigative field hearing in East Palestine this spring. That process would involve talking with the public, collecting facts from witnesses,and discussing and getting agreement on possible solutions.
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