The DOT-117A100W is the most recent example of the underframeless tank car that UTLX introduced in the 1950’s. The proven design relies on the tank shell to contain the product and to distribute and transfer the tensile and compressive loads the car experiences in service. The stub sill supports each end of the tank over the trucks and provides a housing for the car-to-car connections. Union Tank Car’s design incorporates pipe bolsters to cradle and stiffen the tank and provide the mount for side bearings to control rocking of the tank in transit.
Continuous reinforcments – or “repads” – are welded along the bottom of the tank to help spread loads the car will experience in service. The longitudinal repads moderate buff and draft train loads through the tank shell. They connect to the bottom outlet saddle and sump at the center of the tank and continue to each end of the shell and up the head knuckle to provide backing for the head shoe. Transverse “saddle” repads defuse stresses into the tank shell at the pipe bolsters.
After all components are welded to the tank and additional repads are applied where other componets will be attached, the entire assembly is post-weld heat treated to relieve residual stresses that may have formed during welding.