Risk Assessment for Damaged Pressure Tank Cars

Following an accident or derailment involving a freight train, emergency response, salvage, and repair personnel need to clear the right-of-way, repair the tracks, and remove the damaged rail cars. If the train contains pressure tank cars the potential hazard and safe handling procedures need to be determined prior to salvage and repair activities. The severity of the damage determines the appropriate course of action such as rerailing or unloading the damaged cars. The operations must avoid the risk to response personnel of a delayed rupture. A research program was performed to establish the validity of the existing industry guidelines for assessment of damaged pressure tank cars. The research program first focused on evaluating the technical foundation for the existing guidelines and the degree to which they have been validated. We then designed a program of experiments and analyses to validate the guidelines and estimate their margins of safety. The experimental effort used laboratory specimens to provide material property data as well as validation data for the analyses. The analyses used three different approaches: nonlinear elasto-plastic finite element simulations for modeling denting behavior, elasto-plastic fracture mechanics for analysis of cracks, and nonlinear finite element simulations combined with local fracture theories to quantify the severity of scores, gouges, and rail bums (longitudinal damage features caused by sliding a tank along a rail). This paper emphasizes the latter aspect of the work.