Liquefied petroleum gas carriers are mainly used to transport petroleum hydrocarbons with propane and butane as the main components, including propylene, butene and other chemical products. In recent years, ethylene and ammonia have also been included in its transportation scope. Because of its special use, LPG carriers have many special requirements and are difficult to build. It is a high-tech, high-value-added ship representing the level of shipbuilding technology in the world today.