A preliminary report from the National Transportation Safety Board doesn’t provide any more initial observations about the cause of the Feb. 3 derailment of a Norfolk Southern train in Ohio. But it does provide additional context on the wayside detectors used on NS’ network and the controlled venting of the rail cars carrying vinyl chloride on Feb. 6.
Additional information on overheated bearing
Despite the gradual heating of one of the bearings on a rail car, two hot bearing detectors recorded temperatures before the derailment site that did not warrant the alarm thresholds established by NS (NYSE: NSC), NTSB said. The wayside hot bearing detectors assess the temperature conditions of wheel bearings while en route, according to NTSB.
Early in the investigation, the agency had said an overheated bearing could have been the cause of the derailment in East Palestine, Ohio.
At milepost 49.81, the hot bearing detector recorded 253 degrees Fahrenheit above ambient temperature on the suspected bearing, which exceeds NS’ thresholds, sets off an alarm and compels the train crew to respond. The crew responded by applying the brakes so the train could stop and enable them to inspect the issue. As the train slowed, the automatic emergency brake initiated.
Twenty miles before the derailment site, the hot bearing detector noted a bearing temperature of 103 F above ambient on the suspected bearing of the 23rd car, while the hot bearing detector 30 miles before noted a bearing temperature 38 F above ambient. While both detectors indicated a temperature increase, they did not meet NS’ criteria for setting off an alarm.
NTSB provided the following criteria:
- Between 170 F and 200 F, warm bearing (noncritical); stop and inspect.
- Difference between bearings on the same axle greater than or equal to 115 F (noncritical); stop and inspect.
- Greater than 200 F (critical); set out rail car.
Why controlled venting of vinyl chloride rail cars occurred
The incident involved the derailment of 38 rail cars on mainline track 1 of the NS Fort Wayne Line of the Keystone Division in East Palestine, according to NTSB.
Of the derailed cars, 11 were tank cars carrying hazardous materials that subsequently ignited and fueled fires on 12 nonderailed cars.
Five derailed DOT-105 specification tank cars were carrying 115,580 gallons of vinyl chloride, stoking concern that one of them could pose an explosion hazard because the inside temperature was still rising, according to NTSB. That temperature increase could suggest the vinyl chloride was undergoing a chemical reaction that might trigger an explosion.
As a result, a controlled venting of the five rail cars carrying vinyl chloride was planned. To prepare for that event, which occurred Feb. 6 and lasted several hours, responders expanded the evacuation zone and dug ditches around the cars that would hold the vinyl chloride liquid as it vaporized and burned.
Other findings and NTSB’s next steps
NTSB also noted the train was traveling just below the speed limit of 50 mph, while positive train control — a safety technology aimed at preventing collisions — was also enabled and operating during the time of derailment.
The agency also said there were no reported fatalities or injuries resulting from the derailment. The train consisted of two head-end power locomotives, 149 rail cars and one distributed power locomotive located between cars 109 and 110. The train had 20 placarded hazardous material tank cars transporting combustible and flammable liquids, and flammable gas, including vinyl chloride, NTSB said.
NTSB’s investigation, which will continue over the next several months both on-site and at laboratories, will focus on the wheelset and bearings; tank car design and derailment damage; a review of the accident response, including the venting and burning of the vinyl chloride; rail car design and maintenance procedures and practices; NS’ use of wayside defect detectors; and its rail car inspection practices.
As mentioned previously, parties in the investigation in addition to NS and NTSB include the Pipeline and Hazardous Materials Safety Administration, the Federal Railroad Administration, Ohio State Highway Patrol, the Village of East Palestine, rail car lessors Trinity Industries Leasing (NYSE: TRN) and GATX (NYSE: GATX), and four unions — Brotherhood of Railway Carmen, International Association of Sheet Metal, Air, Rail and Transportation Workers, Brotherhood of Locomotive Engineers and Trainmen, and International Association of Fire Fighters.
The Environmental Protection Agency will be involved in air- and water-quality monitoring as Buttigieg: Expect more federal regulation on rail safetywell as remediation efforts.
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