The National Transportation Safety Board (NTSB) recently announced that a defective wheel bearing caused the derailment and subsequent hazardous material release in East Palestine, Ohio, last year. A total of 38 rail cars derailed, including 11 rail tank cars carrying hazardous materials.
NTSB investigators said in a press release that the derailment occurred when a bearing on a hopper car failed and overheated, leading to the fiery February 3, 2023, derailment.
Overheated wheel bearings are a common cause of rail accidents. Hot bearing detectors warn crews to stop the train before the hot bearing can cause a derailment.
However, the difficulty of accurately measuring temperature inside the bearing, combined with Norfolk Southern’s standard operating procedures and the spacing between detectors, meant the crew did not receive adequate warning to stop the train before the derailment, said NTSB investigators.
In addition to the failed wheel bearing, the investigators also addressed the vent-and-burn procedure that resulted in a mushroom cloud over the town and surrounding area.
Investigators said the local incident commander's decision to conduct a vent and burn of tank cars carrying vinyl chloride monomer was based on incomplete and misleading information provided by Norfolk Southern officials and contractors. The vent and burn was not necessary to prevent a tank car failure, NTSB investigators found.
According to the Federal Railroad Administration, a vent-and-burn procedure should be used as a last resort when a tank car is about to fail. Investigators found that Norfolk Southern rejected three other removal methods and began planning for a vent and burn shortly after the derailment.
The continued use of DOT-111 tank cars to transport flammable liquids and other hazardous materials also contributed to the severity of the release.
During the derailment, three DOT-111 cars were mechanically breached, releasing flammable and combustible liquids that ignited. The fire spread and exposed other tank cars to heat, leading to the decision to conduct vent-and-burn action on five tank cars carrying vinyl chloride.
According to the NTSB, the DOT-111 tank car is being phased out of flammable liquids service because of its long record of inadequate mechanical and thermal crashworthiness and propensity to release lading in a derailment. The agency is now calling for an accelerated phaseout of DOT-111 tank cars in hazmat service.
As a result of the investigation, the NTSB issued new safety recommendations to several agencies and associations, including the American Chemistry Council. The ACC has been closely following the derailment as it potentially impacts future chemical transportation safety measures. The NTSB recommendations address safety issues including:
- Failure of wayside monitoring systems to diagnose a hot wheel bearing in time for mitigation to prevent a derailment.
- Hazardous materials placards that burned away, preventing emergency responders from immediately identifying hazards.
- A lack of accurate, timely and comprehensive information passed to local incident commanders and state officials.
- The continued use of DOT-111 tank cars in hazmat service.
An abstract of the final report includes the findings, probable cause and all safety recommendations. The full final report will be published in the next few weeks.
