Fuel Tank Integrity Research: Fuel Tank Analyses and Test Plans

Abstract

The Federal Railroad Administration's Office of Research and Development is conducting research into fuel tank crashworthiness. Fuel tank research is being performed to determine strategies for increasing the fuel tank impact resistance to mitigate the threat of a post-collision or postderailment fire. In accidents, fuel tanks are subjected to dynamic loading, often including a blunt or raking impact from various components of the rolling stock or trackbed. Current design practice requires that fuel tanks have minimum properties adequate to sustain a prescribed set of static load conditions. Current research is intended to increase understanding of the impact response of fuel tanks under dynamic loading. Utilizing an approach that has been effective in increasing the structural crashworthiness of railcars, improved strategies can be developed that will address the types of loading conditions which have been observed to occur in a collision or derailment event.U.S. rail accident surveys reveal the types of threats fuel tanks are exposed to during collisions, derailments and other events. These include blunt impacts and raking impacts to any exposed side of the tank. This research focuses on evaluating dynamic impact conditions for fuel tanks and investigating how fuel tank design features affect the collision performance of the tank. Research activities will include analytical modeling of fuel tanks under dynamic loading conditions, dynamic impact testing of fuel tank articles, and recommendations for improved fuel tank protection strategies. This paper describes detailed finite element analyses that have been developed to estimate the behavior of three different fuel tanks under a blunt impact. These analyses are being used to understand the deformation behavior of different tanks and prepare for planned testing of two of these tanks. Observations are made on the influence of stiffeners, baffles, and other design details relative to the distance from impact. This paper subsequently describes the preliminary test plans for the first set of tests on conventional passenger locomotive fuel tanks. The first set of tests is designed to measure the deformation behavior of the fuel tanks with a blunt impact of the bottom face of the tanks. The test articles are fuel tanks from two retired EMD F-40 locomotives. A blunt impact will be conducted by securing the test articles to a crash wall and impacting them with an indenter extending from a test cart. This set of tests is targeted for late summer 2013 at the Transportation Technology Center (TTC) in Pueblo, Colorado.Both blunt and raking impact conditions will be evaluated in future research. Tests are also being planned for DMU fuel tanks under dynamic loads.

Test Requirements of Locomotive Fuel Tank Blunt Impact Tests

“…In addition to the obvious external differences between the two tanks, the internal arrangement of the baffles also differs. Previously, various baffle configurations were examined analytically to assess the relative influence of striking a tank on a baffle versus adjacent to a baffle [3]. Since that publication, TTCI has provided additional information on the internal configurations of the tanks, and the models have been updated to more accurately reflect the actual conditions within the tanks.…”

“…element deformation continues beyond this amount of strain, the element will fail and be removed from the analysis. Further discussion of the material properties used in this model can be found in reference [3].…”

Results of a Diesel Multiple Unit Fuel Tank Blunt Impact Test

“…The first two tests were performed at low speeds, 4.5 and 6.2 mph, chosen to impart permanent deformation to the tank and measure the force-deflection characteristics [2,3,4]. These preliminary tests provided valuable initial information on the variance of tank performance based on design details.…”

Reducing the Harm in Rail Crashes: Analysis of Injury Mechanisms and Mitigation Strategies

“…Research on fuel tank integrity is principally motivated by increasing application of diesel-powered selfpropelled passenger rail equipment, such as DCTA, CMTA, TexRail, and SMART. Tests are ongoing of fuel tank puncture resistance [24], and tests are planned for locomotives equipped with CEM features [25]. For table compartmentalization, current research on occupant protection is aimed at developing improved instrumentation for measuring abdominal load [26].…”