In essence, these are also tankers, but, as the name implies, due to the characteristics of the cargo, they have special specifics and stand out in a separate class of ships, which, in turn, is divided into different types.
Pressure – when gases are transported at atmospheric temperature, and therefore there is no need for a cargo cooling system and thermal insulation of the tanks themselves. Cargo tanks are cylindrical or spherical cylinders, which are usually designed for a pressure of 18.5 bar (which corresponds to the saturated vapor pressure of propane at a temperature of +55°C).
Semi-refrigerated – the design features of cargo tanks and the cooling system of such gas carriers make it possible to transport liquefied gases at a pressure of 4 to 8 bar and cargo temperature from 0°С to -89°С (-104°С for ethylene carriers).
Refrigerated – designed for the transportation of fully refrigerated liquefied gases at low temperature and pressure above atmospheric by a maximum of 0.3 bar. Gas carriers of this type are well suited for transporting large volumes of cargo, such as liquefied natural gas, ammonia or vinyl chloride over long distances. Such cargo is transported in insulated tanks with rigid thermal foam insulation. It is important to note that international regulations require the installation of a secondary barrier on refrigerated gas carriers to reduce the risk of cargo leaks in the event of an accident.