A full-scale rollover crash test was performed on a CPC-1232 specification, crude oil tank car to document the base-case safety performance of the car top-fittings in a roll-over scenario. The specimen tank car was placed into a test fixture designed to roll the entire loaded and un-trucked carbody about a fixed pivot. A concrete surface target was used as the impacting surface of the top-fittings manway bonnet. At an impact speed of 7.8 mph, the manway bonnet deformed inward and sheared off completely. In addition, the vacuum relief valve sheared off and caused leakage of water through the connection. Reasonable correlation was observed between the pre-test simulations and the test results, which were further improved post-test.
The effort has highlighted an alternate failure mode, bolt shear, which seems to be initiated when the top fittings bonnet structures are strengthened by the use of thicker or higher strength materials, i.e., strengthening the bonnet structure moves the weakest link to the bolted connections, resulting in failure and lading release. The railroad industry can use the test generated structural performance and behavior data to improve top-fittings protection.