Hazardous Consequences

Retrofitting rail cars can help avert disaster

On July 6th, the town of Lac-Mégantic in Quebec was forever reshaped by a train derailment and subsequent explosion. The incident leveled 30 buildings, left at least 38 dead and 12 more missing.  The devastation had several possible causes, including operator error. However, there was one factor that has become a theme in rail disasters. A factor engineers can address.

In Lac-Mégantic, the train was carrying was crude oil. In 2009, a train derailed outside of Rockford, Illinois that was carrying ethanol. Both had deadly consequences. Both used DOT 111 tanker cars.

About 69% of tanker cars are the DOT 111 type. This type of rail car has a history of safety problems going back to the 1990s. Starting in October of 2011, new cars had to be manufactured with increased head and shell thicknesses, use normalized steel and have adequate fitting protection.

The improvements mandated by the Association of American Railroads (AAR) do not affect the rail cars already in service. The effectiveness of the new cars is impeded when operated in conjunction with old cars. All cars have to have upgraded safety mechanisms to ensure the highest reliability.

This safety issue has not gone unnoticed. As reported in the Wall Street Journal, two Illinois Mayors, Karen Darch and Tom Weisner, are concerned about the tankers as rail traffic of hazardous materials is growing.  They state that in the wake of the 2009 Rockford tragedy, “we asked federal regulators to require that the DOT-111 fleet be retrofitted to make them more ‘crashworthy’ in derailments.”

The National Transportation Safety Board (NTSB) says retrofitting can be an effective alternative to replacement. The cost to retrofit the old cars is considered untenable by the rail industry. At $15,000 per car, it would top $1 billion to convert the entire fleet. Darch and Weisner counter that, asserting that the 31 year life expectancy of the fleet will make the investment well worth it.

So how extensive is the redesign? Not very. The updated tankers use steel 1/16” thicker than before. The steel is to be normalized. The air cooling used in normalization increases strength. Major reconsiderations occur in the protection and design of valves and covers. Because these are places where material is purposely transferred, they can become weak spots during a derailment.

The most recent derailment in Lawtell, Louisiana on August 4th emphasizes the urgency. Although no injuries have been reported in that accident, it has resulted in the release of hazardous substances including sodium hydroxide and lube oil. Another car carrying vinyl chloride was damaged but not leaking.

Because the safety improvements do not include a radically different design, old cars can be upgraded relatively simply. Thicker, stronger steel and adequate protection at vulnerable areas are sufficient improvements to reduce the likelihood of a catastrophe. Responsible design of hazardous transport should consider worst-case scenarios as real possibilities. This is essential should the “worst-case” become the current reality.

 A pictorial description of the factors contributing to the Lac-Mégantic derailment is shown below. Click on the image for the high-resolution version from the National Post.

Top image courtesy of: The Canadian Press/Paul Chiasson