Wheel bearing expert: In order to prevent derailments, railways should equip freight cars with sensors

A hotbox and towed gear detector on the Union Pacific near East Bernard, Texas. A wheel bearing expert says on-vehicle sensors, rather than roadside detectors, are the best way to find failures. Tom Klin

Installing sensors on boxcars is the only way to prevent another catastrophic derailment like the Norfolk Southern dangerous material wreck on February 3 in East Palestine, Ohio, a wheel bearing expert says.

Constantine Tarawneh, a mechanical engineering professor who directs the University Transportation Center for Railway Safety at the University of Texas Rio Grande Valley, says adding more trackside hotbox detectors will not be enough to eliminate derailments caused by wheel bearing failures.

“Temperature just isn’t the way to measure the state of a rotating object. Period. It’s a good secondary measure, but not a primary measure. And so I don’t care how close you place them…it won’t help,” Tarawneh said in an interview last week.

The Rail Safety Act of 2023, tabled in the Senate last week, would require railroads to place hotbox detectors every 10 miles. Today, detectors are an average of 25 miles apart, according to the Federal Railroad Administration.

There’s no question that hotbox detectors work. According to the FRA, train accident rates caused by axle and bearing-related factors have fallen by 81% since 1980 and by 59% since 1990, which can be attributed to the use of hot bearing detectors.

But bearings can overheat quickly, the FRA says, and can burn out in as little as 1 to 3 minutes. Hotbox detectors failed to diagnose 124 severely failed bearings in the United States and Canada from 2010 to 2018, 117 of which resulted in derailments.

“The one in East Palestine drew everyone’s attention because of the hazardous materials,” says Tarawneh. “These are accidents waiting to happen. They may not happen that often, but they will continue to happen because we’re just trying and hoping these trackside detectors are effective.”

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The disadvantage of both hotbox detectors and trackside acoustic detectors is that they are reactive and can only detect late-stage faults that pose an immediate safety threat, Tarawneh says.

A proactive solution, he says, would be to equip rolling stock with accelerometers that can detect telltale vibrations in wheel bearings up to 50,000 miles before they become a safety hazard.

The research team at the University Transportation Center for Railway Safety has developed a battery-powered sensor module that can measure operating load, temperature and vibration levels within a bearing. It sends the data wirelessly to a central processing unit for analysis. The system can warn railcar owners thousands of kilometers in advance of a potential failure and provide an estimate of how long the warehouse can safely remain operational.

The system was tested in the center’s lab as well as on the test track at the MxV Rail Transportation Technology Center in Colorado.

Some bearings can fail without getting hot enough to trigger a hotbox detector until a few minutes before a derailment, as was the case in East Palestine. On-board sensors would have indicated the problematic bearing several months in advance, says Tarawneh.

Amsted Rail, which supports research at the University Transportation Center for Railway Safety, is among the companies offering on-board sensor equipment.

RailPulse, the freight car telematics joint venture led by Norfolk Southern, is testing onboard sensors that track a car’s location, whether it is empty or loaded, whether it has experienced a significant impact, whether the hatches or doors are open or closed are, and whether the handbrakes are on or off.

The initial pilot program — in which NS and RailPulse members Union Pacific, short-line holding companies Genesee & Wyoming, Watco and Railroad Development Corp. as well as the auto manufacturers and leasing companies GATX, Greenbrier and Trinity are involved – does not test wheel bearing monitors.

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However, RailPulse general manager David Shannon says the goal is to ultimately monitor wheel bearing health. “We’re very interested in it,” he says.

According to Taranweh, it could cost $1,000 to retrofit a boxcar with a wheel bearing sensor system.

Byron Porter, the founder and CEO of telematics company Hum Rail, which licensed the rights to the system from the University of Texas, estimates that wheel bearing monitoring would cost between $400 and $500 a year over the 15-year life of his equipment. “This includes hardware, stock health, wheel dump (just like a wheel impact load detection system), truck chase monitoring, impact detection, GPS, software and firmware updates, and data access, either through APIs or through our own website,” he says.

Around two thirds of the 1.6 million freight cars in North America are owned by shippers or leasing companies.

“What I’ve been telling people is that there are three ways to look at the additional cost of outfitting their own fleet,” says Porter. “A fraction of the total cost of a new build (0.5-2%). An insurance premium that keeps your name out of the headlines. NS will cost less than the derailment of East Palestine.”

It costs about $200,000 to install a hotbox detector on a single track mainline and $350,000 on a double track. More than 6,000 hotbox detectors are currently in use. Doubling that number to reduce the distance between detectors would cost between $1.2 billion and $2.1 billion.

Equipping the entire freight car fleet with wheel bearing monitors could cost $1.6 billion or more. But the telematics system would also provide shippers with real-time vehicle locations and other vehicle status data, significantly reducing the number of trains having to stop and drop off cars along the way.

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According to Taranweh, the industry should start equipping tankers and other cars that transport hazardous materials with wheel bearing sensors. It would take years to equip the entire fleet. “It may take a decade or even two decades. But we have to start somewhere,” he says.

The Biden administration has backed the Rail Safety Act, but the FRA has yet to formally comment on all provisions of the bill, an agency spokesman says.

“Both wayside detectors and onboard sensors are expected to be discussed in detail at an upcoming Railroad Safety Advisory Committee meeting to be announced shortly,” says FRA spokesman Warren Flatau. “Otherwise, pending a more comprehensive investigation into potential future regulatory activity, it is somewhat premature to assess a researcher’s views on the merits of one technology over another.”

National Transportation Safety Board Chair Jennifer Homedy says the board’s investigation into the East Palestine derailment will include an analysis of route detection systems, how railroads use their data and whether temperature thresholds should be set lower.

The board will also look at alternatives to the traditional hotbox detector, including acoustic detectors and on-board sensor systems.

“We like redundancy at the NTSB, so there’s more than one way to ensure security,” Homendy said in a webcast with the Washington Post today. “We will look at all available technologies and make a recommendation.”

Some in the railway industry are skeptical that on-board sensors can be robust enough and reliable enough to be as effective as trackside detectors.