Liquid Natural Gas (LNG) is carried at atmospheric pressure and has been safely carried by sea for the past 50 years. Today the carriage of LNG employs a fleet of almost 400 purpose-built highly specialized vessels dedicated to meeting this growing sector of world energy demand.
Approximately 75,000 voyages have now been successfully completed.
In addition to being a traded commodity, LNG is also becoming a preferred fuel for the world’s merchant fleet as the International Maritime Organization seeks to regulate progressive reductions in vessel emissions. After being initially adopted for
coastal trading in Europe, BC Ferries, Seaspan and Washington State Ferries have all placed orders for gas fuelled new-buildings in addition to vessel conversions. We are also seeing the first orders placed for gas propulsion in the world international fleet in response to investments by a number of leading global ports in LNG bunkering infrastructure.
In North America, natural gas provides a substantial portion of energy needs in the domestic and commercial sectors, the energy for most new power generating stations and is also used as an essential raw material for many common products such as paints, fertilizers, plastics, antifreeze, dyes, photographic film and medicines.
The Transportation Cycle
Natural gas is liquefied for ocean transportation by cooling in the case of purpose built Liquid Natural Gas (LNG) carriers.
Gas is liquefied by cooling prior to loading and carried at atmospheric pressure at close to -162 degrees centigrade.
At this temperature 600 cubic meters of gas occupies only 1 cubic meter in its liquefied form which in turn translates to the efficient marine transportation of large volumes of LNG to the major consumers around world.
On a typical voyage, LNG cargo compartments are loaded to approximately 98.5% of their capacity in order to allow for expansion. The boil off is nearly always used as a fuel in the ship’s boilers and/or engines. Automated monitoring of cargo temperature and pressure is constant throughout the voyage.
Following discharge at the receiving port, the liquefied gas is returned to its gaseous state for delivery to the distribution system and ultimately the consumer. Natural gas is colourless, non-toxic, noncorrosive and odourless, but for safety reasons, and prior to distribution, a trace of chemical is added to give it a distinctive smell of rotten eggs.