Over the past two decades there has been significant research on improving the safety of hazardous material (HAZMAT) transport in railroad tank cars. This research was a collaborative effort of both the government and industry and motivated by significant rail accident/derailment events with HAZMAT releases. The research included both testing to measure the impact and puncture resistance of tank cars and the development of analysis methodologies capable of predicting the impact behaviors for a wide range of conditions. Consequently, a significantly improved understanding of the factors that improve HAZMAT tank car safety has been achieved and important analysis methodologies developed for evaluation of tank car puncture resistance.

The knowledge gained from these research programs supported the development of improved regulations for HAZMAT tank cars. These include the March 2009 regulations on poison inhalation hazard (PIH) tank cars (Federal Register, 74 FR 1769) and July 2015 regulations on high-hazard flammable tank cars (Federal Register, 80 FR 26643).

More recently, the Federal Railroad Administration (FRA) sponsored research to perform full-scale impact testing and analysis of cryogenic tank car designs, primarily supporting the transport of Liquid Natural Gas (LNG) by rail. This led to the Pipeline and Hazardous Materials Safety Administration (PHMSA) July 2020 ruling that allows transport of LNG in DOT-113C120W9 tank cars (Federal Register, 85 FR 44994). Subsequent to the rulemaking on the DOT-113 tank car for LNG service, there was still significant public interest in performing additional evaluations of the safety of LNG transport by rail. In September 2023, PHMSA suspended the authorization for LNG transportation in rail tank cars to allow for further investigation (Federal Register, 88 FR 60356).

The objective of this study was to evaluate the puncture risk of the DOT-113 LNG tank car. The approach was to first apply the existing tank car impact and material test data from the FRA research program to develop and validate a detailed impact and puncture analysis methodology. This analysis methodology was then applied to assess the puncture resistance of the DOT-113 LNG tank car under a range of impact scenarios. These scenarios included various impactors and impact conditions (normal and oblique impacts to the shell) as well as impacts on the tank head. The results of these puncture analyses are then used to assess the relative puncture resistance of the DOT-113 LNG tank car to a range of other HAZMAT tank car designs that were previously evaluated using the same methodology.

The results of this investigation show that the DOT-113 LNG tank car has a high level of puncture resistance relative to other HAZMAT tank cars over a wide range of impact conditions.

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