The derailment of a Norfolk Southern Corp. train in a small Ohio town last month is putting renewed attention on the role of sensors that railroads use in a bid to prevent such accidents.
The railroad, in response, announced new safety initiatives, including adding 200 temperature detectors to parts of its tracks where existing sensors are at least 15 miles apart, starting near the derailment site in East Palestine. Major freight railroads plan to add roughly 1,000 of these detectors across their key routes, according to the Association of American Railroads, an industry trade group.
The National Transportation Safety Board has launched a special review of Norfolk Southern and its safety culture. Norfolk Southern Chief Executive Alan Shaw has pledged further changes to the railroad’s operating practices and is slated to testify before a Senate panel on Thursday about the East Palestine derailment.
Railroads use a range of detectors along train tracks to identify problems with locomotives and railcars. Temperature detectors, also known as hot-box or hot-bearing detectors, are the most commonly used rail defect-monitoring system, according to the U.S. Department of Transportation.
About 6,000 temperature detectors were stationed throughout the North American freight rail network as of 2015, according to the most recent data available from the Transportation Department.
Temperature detectors use infrared thermal sensors to measure the temperature emitted from bearings, wheels, axles and brakes. Norfolk Southern said it has about 1,000 temperature detectors that are on average 13.9 miles apart on its network.
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Typically, railcar wheelsets pass temperature detectors without incident. Norfolk Southern’s train crews are supposed to receive an alert to stop and inspect equipment if sensors provide readings that are between 170°F and 200°F above the ambient temperature or if the difference between bearings on the same axle is at or above 115°F, according to Norfolk Southern. If a reading is 200°F above the ambient temperature, then the railcar should be set aside for maintenance, if needed.
There is no federal standard that determines how close together railroads should place temperature sensors along their tracks. Railroads also establish the temperature thresholds for when to inspect equipment and alert train crews to potential problems.
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The Feb. 3 derailment in East Palestine occurred after a wheel bearing on a hopper car overheated and failed, according to federal officials. The train passed temperature sensors that showed components of the hopper car getting warmer as it traveled. The detector that showed the bearing had reached a critical temperature was about 20 miles away from the prior one. Crews worked to stop the train after receiving an alarm about the temperature reading.
A bipartisan group of senators has introduced a bill that would implement new railroad safety rules, including a requirement for sensors along tracks to be no more than 10 miles apart. Jennifer Homendy, chair of the NTSB, has said the agency was also looking at lowering the temperature threshold that sets off overheating warnings.
Major freight railroads have agreed to stop trains and inspect bearings whenever the reading from a temperature detector is 170°F above the ambient temperature, according to the Association of American Railroads. Railroads are aiming for new temperature detectors to be installed with an average spacing of 15 miles between them, the group said. Temperature sensors that aren’t operating correctly will be prioritized for maintenance, it added.
Norfolk Southern also said it plans to add more acoustic sensors, which analyze vibrations for potential problems on bearings like spalling, brinelling and seams. Currently the railroad has five in service and will add 13 new acoustic detectors on high-traffic routes in its network.
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The acoustic detectors are designed to identify potential defects when trains pass sensors while traveling between 20 and 60 mph, according to the Federal Railroad Administration. By analyzing the sounds generated by the bearing components, the system can pinpoint which component has the fault present. Defects can include loose, cracked or broken components, peeling or smearing, and lubrication failure. When a defect is detected, the information can be relayed to the train’s operator.
The rail industry has received criticism from lawmakers and union members over the pace at which new safety technologies are introduced. The Association of American Railroads said that its members are identifying and deploying other technologies to further safety gains. It said the equipment-caused accident rate has declined 32% since 2000.
