Developing strategies for maintaining tank car integrity during train accidents

Accidents that lead to rupture of tank cars carrying hazardous materials can cause serious public safety hazards and substantial economic losses. The desirability of improved tank car designs that are better equipped to keep the commodity contained during impacts is clear. This paper describes a framework for developing strategies to maintain the structural integrity of tank cars during accidents. The target of this effort is to design a tank car capable of surviving impacts without loss of lading at twice the impact speed of current equipment (or, equivalently, is capable of absorbing four times the impact energy). The methodology developed breaks down the process into three steps: 1. Define the impact scenarios of concern 2. Choose strategies to mitigate failure modes present in each scenario 3. Design and select technology and tactics to implement the mitigation strategies The railroad accidents involving tank cars that occurred in Minot, ND, in 2002, and Graniteville, SC, in 2005, are examined to define the impact scenarios. Analysis of these accidents shows that two car-to-car impact scenarios are of greatest concern: head impact, where railroad equipment impacts the end of a tank car and possibly overrides it, and shell impact, where the tank car is impacted on its side, possibly off center. A conceptual design that can protect its lading at twice the impact speed of current equipment in the car-to-car impact scenarios is being developed. The conceptual design includes four functions to meet the impact requirements: blunts the impact loads, absorbs collision energy, strengthens the tank, and controls the load path to assure that loads are blunted and that energy is absorbed before the tank is loaded. Preliminary studies of available weight and space, strategies for increasing energy absorption, and strategies for strengthening the head and shell are ongoing; this paper describes the current results of these studies. Additional studies are also ongoing. The steps required to complete this effort are also described.