What type of vessel is classified as a tank ship without propulsion?

A tank barge is classified as a tank ship without propulsion because it is specifically designed to carry liquids, typically petroleum or chemical products, in bulk. Unlike self-propelled tankers, tank barges are not equipped with their own propulsion systems; instead, they rely on tugboats or other vessels for movement. This makes them distinct within the maritime industry, as they serve the crucial role of transporting liquid cargo while being towed or pushed.

Tank barges are often used in inland waters and coastal regions, where tugboats can efficiently maneuver the vessel. This configuration allows for flexibility in operations, as tank barges can be designed for various types of cargo and can be used in conjunction with port facilities that specialize in handling liquid bulk cargoes. This design and operational characteristic clearly delineates tank barges from other vessel types mentioned in the choices.