Broken axle caused events resulting in fiery Casselton accident

Written by Mischa Wanek-Libman, editor
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A Dec. 13, 2013, photo shows part of the tank car pileup and residual fire resulting from the train collision near Casselton, N.D. The DOT-111 tank car in the center of the photo sustained a thermal tear, and is still burning
NTSB

A broken axle has been cited as the probable cause of a series of events that resulted in two derailed trains and close to 476,000 gallons of crude oil being spilling near Casselton, N.D.

The NTSB found that the chain of events for the accident began when a train carrying grain derailed because of a broken axle on one of its cars. NTSB investigators found a void in the middle of the axle, which was used previously on another train car. In response to the NTSB’s urgent safety recommendation on the matter, the American Association of Railroads has moved to require testing of secondhand use axles.

A second train on an adjacent track, carrying crude oil, was unable to stop in time before colliding with the derailed cars of the grain train.

The accident did not result in fatalities or serious injuries, but nearly 1,500 people were evacuated from nearby homes.

The National Transportation Safety Board (NTSB) met Tuesday, Feb. 7, to review evidence of its investigation and determine the accident’s probable cause. NTSB reiterated its recommendations for quickly phasing out DOT-111 tank cars and its variants.

The oil spilled from 18 of the 20 derailed DOT-111 tank cars, which pooled and caught fire. NTSB says the fire’s heat weakened other derailed tank cars, causing internal pressure to build until oil vapor erupted in fireballs.

Since the accident, Congress and the U.S. Department of Transportation have established requirements for a new, stronger DOT-117 tank car to replace the DOT-111 with a deadline of 2029 in some cases. NTSB says that while relatively few DOT-111s currently remain in crude-oil service, a vast fleet of these tank cars continues in service for ethanol and other flammable liquids.

“The fact remains that trains carrying flammable liquids in DOT-111 tank cars continue to roll through America’s towns and cities,” said NTSB Chairman Christopher A. Hart. “Progress toward removing or retrofitting DOT-111s has been too slow.”

As part of the accident investigation, the NTSB studied advanced brake systems. While their use would not have prevented the Casselton accident, it may have mitigated the damage. In other scenarios, advanced brake systems have the potential to prevent train accidents altogether.

Among its recommendations, the NTSB suggested studying the use of additional “buffer” cars between locomotives and cars carrying hazardous materials to protect crews. The Casselton oil train had a single buffer car between the locomotives and its hazardous cargo.

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