Tank container chassis, also referred to as tank chassis, drop frame chassis or tank trailers, are a form of intermodal transportation for portable bulk liquid containers or ISO tank containers. They are characteristically longer and have lower deck height ideal for transporting constantly shifting payloads. The invention of the tank container revolutionized the way bulk liquids were transported, stored, and handled worldwide. It has improved safety, reduced costs and brought with it the benefits of convenience and efficiency associated with a multi-modal transport system. Invariably the invention of the drop frame chassis followed soon after to accommodate this new type of intermodal container.
Though in the USA tank containers are typically the same dimensions (20×8×8.5 ft or 6.10×2.44×2.59 m). as a standard ISO ocean container, tank chassis are much longer than the typical 20 ft (6.10 m) container chassis. Tank chassis typically measure 40–43 ft (12.19–13.11 m) in length by 8 ft × 4 ft (2.44 m × 1.22 m) wide x tall. This chassis has a standard drop-frame design providing a lower center of gravity than conventional trailers and an overall length suitable to legally scale most tanks. Twistlocks provide a secure mounting mechanism for the tanks and eliminate the need for straps or chains. The lower center of gravity is crucial for reducing the chances of a roll over with the constant shifting weight of the liquid cargo. These chassis can also be fitted with additional accessories including: lift kits to facilitate product discharge, hose tubes, and hi/lo kits to carry two empty tanks.
Tank chassis types
The tank chassis has evolved over the past years to accommodate greater payload weights. The tank chassis comes in tandem axle, spread axle, tri-axle, and hi/lo combo configurations. Tandem Axle Chassis were the industry standard initially. The closed tandem drop deck chassis typically have a GVWR of 65,000 lb (29,484 kg). The quest to increase payload capacities spawned the tri-axle chassis with the ability to scale 42,000 lb (19,051 kg). on the trailer axles. The addition of the third axle however added a significant increase to the tare weight of the chassis, thus limiting the permissible weight limits to comply with bridge laws. This led to the invention of the Spread Axle Chassis with a spread of 109 in (2,769 mm) allowing for the same weight to be dispersed on the rear axles of the trailer (42,000 lb or 19,051 kg) as the tri-axle. This is the new industry standard with a GVWR (Gross Vehicle Weight Rating) of 80,000 lb (36,287 kg).
- Tank chassis with a heating/cooling unit (reefer) attached. Used for hauling bulk liquid foods that need to be heated or cooled such as liquid sugar, water, wine, milk, soup, or juices.
History of the tank chassis
In response to the need for greater improved movement of bulk liquids, tank containers were invented in the mid 1960 by Bob Fossey who worked for Wiliams Fairclough in London. This first tank was a beam type designed in 1967 built onto a swap body design from Fossey in 1966. The eighties and early nineties saw two different trends. One was a quest to make the tank container both lighter and have a greater capacity. Through the following decades tanks have evolved to become a lighter and more space efficient means of transporting bulk liquids.