Tank cars are one of the most specialized freight cars on the rails today, with numerous design features and sizes available to handle a wide variety of products. Gases, liquids, slurries, and molten materials are all routinely transported in tank cars, with most being in dedicated commodity service to prevent contamination, or to take advantage of specific car designs.
The Funnel Flow concept – where the middle of the car is lower than the ends – was invented in 1967 by Union Tank Car Company. This distinctive “bent” design is used for products that are unloaded by gravity, and the shape works to funnel the material to the outlet at the lowest point of the car, which results in a faster and more complete unloading process than a standard straight-bottomed tank. This is especially helpful in unloading slurries (kaolin clay, carbonates, etc.) and thick materials such as asphalt or molten sulfur. Other common loads include foodstuffs such as oils, syrups, and molasses, and various chemical products and solvents.