The LNG industry in the United States and other countries was developed to link huge gas reserves in geographically remote parts of the world with regions in need of more natural gas. For example, Japan and Korea import LNG to meet almost all their natural gas needs, and half of Spain's natural gas demand is met through the importing of LNG.


Most liquefied gases are hydrocarbons and the key property that makes hydrocarbons the world’s primary energy source – combustibility – also makes them inherently hazardous. Because these gases are handled in large quantities, it is imperative that all practical steps are taken while carrying through sea transports. 

The carriage of liquefied gases in bulk began in the late 1920s and the earliest ships carried butane and propane in pressure vessels at ambient temperature. The subsequent development refrigeration techniques and, more particularly, materials suitable for containment at low temperature permitted the carriage of cargoes at temperatures below ambient. 

In the late 1950s these gases began to be carried commercially in a partially refrigerated state in ships equipped with pressure vessels made with material tolerant of low temperatures. By the mid-1960s fully refrigerated LPG ships were in service carrying cargo at atmospheric pressure; ethylene and LNG ships had also entered service. In the meantime ammonia had become a common cargo, and “chemical” gases such as butadiene also became commercially important.


Source: http://www.liquefiedgascarrier.com/sea-transport.html