A failing, flaming wheel bearing doomed the rail car that derailed and created a catastrophe in East Palestine earlier this month, but researchers have offered a solution to the faulty detectors that experts say could have averted the disaster unfolding in the small Ohio town.
These wayside hot box detectors, stationed on rail tracks every 20 miles or so, use infrared sensors to record the temperatures of railroad bearings as trains pass by. If they sense an overheated bearing, the detectors trigger an alarm, which notifies the train crew they should stop and inspect the rail car for a potential failure.
So why did these detectors miss a bearing failure before the catastrophe?
An investigation into hot box detectors published in 2019 and funded by the Department of Transportation found that one “major shortcoming” of these detectors is that they can’t distinguish between healthy and defective bearings, and temperature alone is not a good indicator of bearing health.
“Temperature is reactive in nature, meaning by the time you’re sensing a high temperature in a bearing, it’s too late, the bearing is already in its final stages of failure,” Constantine Tarawneh, director of the University Transportation Center for Railways Safety (UTCRS) and lead investigator of the study, told CNN.
As part of the investigation, the UTCRS researchers developed a new system to better detect a bearing issue long before a catastrophic failure. The key: measuring the bearing’s vibration in addition to its temperature and load.
The vibration of a failing bearing, Tarawneh says, often begins intensifying thousands of miles before a catastrophic failure. So his team created sensors that can be placed on board each rail car, near the bearing, to continuously monitor its vibration throughout its travels.
“If you put an accelerometer on a bearing and you’re monitoring the vibration levels, the minute a defect happens in the bearing, the accelerometer will sense an increase in vibration, and that could be, in many cases, up to 100,000 miles before the bearing actually fails,” he said.
Tarawneh, who argues the technology should be federally mandated, says had it been on board Norfolk Southern’s line it would have prevented the derailment in East Palestine.
“It would have detected the problem months before this happened,” he said. “There wouldn’t have been a derailment.”
A preliminary report from the East Palestine derailment, released Thursday by the National Transportation Safety Board, found hot box sensors detected that a wheel bearing was heating up miles before it eventually failed and caused the train to derail. But the detectors didn’t alert the crew until it was too late.
The bearing, according to the report, was 38 degrees above ambient temperature when it passed through a hot box 30 miles outside East Palestine. No alert went out, the NTSB said.
Ten miles later, the next hot box detected that the bearing had reached 103 degrees above ambient. Video of the train recorded in that area shows sparks and flames around the rail car. Still, no alert went to the crew.
It wasn’t until a further 20 miles down the tracks, as the train reached East Palestine, that a hot box detector recorded the bearing’s temperature at 253 degrees above ambient and sent an alarm message instructing the crew to slow and stop the train to inspect a hot axle, the report said.
The crew slowed the train, the report added, leading to an automatic emergency brake application. After the train stopped, the crew observed the derailment.
The reason those first two hot box readings didn’t trigger an alert, the report said, is because Norfolk Southern’s policy is to only stop and inspect a bearing after it has reached 170 degrees above ambient temperature. The NTSB is planning to review Norfolk Southern’s use of wayside hot box detectors, including spacing and the temperature threshold that determines when crews are alerted.
“Had there been a detector earlier, that derailment may not have occurred,” said NTSB Chair Jennifer Homendy at a Thursday press conference.
In a statement responding to the NTSB report, Norfolk Southern stressed that its hot box detectors were operating as designed, and that those detectors trigger an alarm at a temperature threshold that is “among the lowest in the rail industry.” CNN has reached out to Norfolk Southern for comment on vibration sensor technology.
Hot box detectors are unregulated, so companies like Norfolk Southern can turn them on and off at their own discretion and choose the temperature threshold at which crews receive an alert.
There are several causes for overheated roller bearings, including fatigue cracking, water damage, mechanical damaging, a loose bearing or a wheel defect, according to the NTSB, and the agency says they’re investigating what caused the failure in East Palestine.
“Roller bearings fail, but it is absolutely critical for problems to be identified and addressed early so these aren’t run until failure,” Homendy said. “You cannot wait until they’ve failed. Problems need to be identified early, so something catastrophic like this does not occur again.”
Hum Industrial Technology, a rail car telematics company, has licensed the vibration sensor technology created by Tarawneh and his team. And it has launched pilot programs with several rail companies. But at this point, those sensors are on very few trains operating in the United States, which Tarawneh largely blames on the cost of retrofitting and monitoring cars and what he sees as companies prioritizing profit.
It’s not clear exactly what it would cost to retrofit every train car in operation with sensors today, but Hum Industrial Technology stressed that it would cost less to put a sensor on a bearing than to replace a bearing.
“They see it as, well, why should we do it if it’s not mandated?” Tarawneh said. “It’s like a lot of people are saying, ‘well, I’m willing to take the risk. It’s not that many derailments per year.’”
But Steve Ditmeyer, a former Federal Railroad Administration official, says equipping every rail car with on board sensors may not be financially feasible.
“What they’re proposing will work, but it’s very, very expensive,” Ditmeyer told CNN. “And one does have to take cost into consideration.”
It would take more than 12 million on board sensors, according to Tarawneh, to fully equip the roughly 1.6 million rail cars in service across North America.
Ditmeyer says railroads should invest more heavily in wayside acoustic bearing detectors, which sit along the tracks – much like hot box detectors – and monitor the sound of passing trains. They listen for noise that indicates a bearing failure well before a potential catastrophe.
As of 2019, only 39 acoustic bearing detectors were in use across North America compared to more than 6,000 hot box detectors, according to a 2019 DOT report.
“They are the only way that I can think of that would have prevented the accident by having caught a failing bearing earlier,” Ditmeyer said.