Technical Reports

Force Environment Evaluation of Stub Sills on Tank Cars Using Autonomous Over-the-Road Testing of the Instrumented Tank Car

  • 22
  • Dec
  • 2016
AUTHOR: Federal Railroad Administration
SUBJECT: Hazardous Materials, Crashworthiness - Tank Car
KEYWORDS: Tank cars, stub sills, ENSCO, track geometry, measurement, load environment, operating conditions, instrumented tank cars, data collection, vertical coupler force, longitudinal coupler force
ABSTRACT: Fractures have been observed on stub sill tank cars for many years. Undetected and unattended, these fractures can develop into a variety of tank car failures. While tank car ruptures are rare, the potential for a catastrophic hazmat release has made this a critical issue within the industry. The FRA contracted with ENSCO, Inc., to instrument and run an instrumented tank car over the road in autonomous measurement mode. The instrumentation and data collection focused on assessing the load environment seen by tank cars in regular service under full load conditions. Testing was conducted to collect data from the instrumented tank car over approximately 3,700 miles in the United States. The following key conclusions and recommendations are inferred from testing and analysis: 1) The high magnitude events that seem to cause damage to the stub sill are observed in yards and are attributed to train handling. Track geometry, specifically short chord vertical profile, is a contributing factor causing high vertical coupler force events, but typically is not a contributing factor for high longitudinal coupler force events. 2) If the coupling speeds are limited, the forces imparted to the stub sills would be kept lower than the yield limit for steel, reducing the occurrence of fractures in stub sills on tank cars. 3) A low-cost system can be developed for measuring vertical and longitudinal coupler forces in service.