Liquefied natural gas ship (LNG ship or LNG transport ship) refers to a "vessel" specialized in transporting liquefied natural gas. It is a "sea super refrigerated vehicle" that carries LNG at minus 163 degrees Celsius. It is one of the most difficult ship types to build in the world and one of the three "pearls in the crown" of the shipbuilding industry. The earliest LNG ship was the 5100 square meter "Methane Light Duo" converted from an ordinary old oil tanker in the United States in 1958. According to the structural form of the cargo tank, it can be divided into independent tank type and membrane type. Newly built liquefied natural gas ships, especially large ones, often adopt membrane structures. The equipment of liquefied natural gas ships is complex.