What is a tank wagon?

A tank wagon or tanker is a type of railway wagon used specifically for transporting liquids or gasses.

Tank wagons have been around since the mid-1800s although original designs were made from banded wood much like an old beer barrel, in the late 1860s wrought iron was used to construct the wagons and after WWII welding replaced riveting to create the basic tank wagon that we see today.

There are many different types of tank wagon transporting over a hundred different commodities with some types displaying obvious characteristics that indicate a bespoke intended use such as the Torpedo design that can pivot to facilitate the unloading of molten materials while other types have more discreet features such as an internal lining to protect the tank from its contents and vice versa.

In the UK there are many tank wagons of various sizes in operation including 4-wheeled fixed-axle variants as well as much longer bogie tank wagons which come in many shapes from straight forward cylinders to ones that sink between the axles to facilitate larger loads (known as a Whale Belly Tank).

One surprising fact about tank wagons is how heavy they are when loaded, although not used anymore, a fully laden milk tank wagon would weigh as much as a fully laden railway carriage meaning that it was not unusual to see larger mainline locomotives hauling them when in service, however, it was equally as common for tanks to be operated empty as the specialised nature of the rolling stock meant that return loads were usually not possible to avoid cross contamination of the tank's hold.