LNG (Liquefied Natural Gas)

LNG (Liquefied Natural Gas) carriers are purpose built vessels for transporting gas in a liquid form.Gas reduces its volume by 1/600 when it is liquefied at -162 degree C. Therefore by liquefying the gas, a higher volume can be carried making transport by sea much more efficient.

The majority of gas carrying vessels are carrying around 140,000m3.In recent years, the size and capacity of LNG carriers has increased greatly. Qatargas has pioneered the development of two new classes of LNG carriers, referred to as Q-Flex and Q-Max. Each ship has a cargo capacity of between 210,000 and 266,000 cubic meters and is equipped with a re-liquefaction plant.

There are two main types of LNG carrying system:

Moss tanks

Designed by the Norwegian company Moss Maritime, the LNG is stored in spherical tanks. Most Moss type vessels have 4 or 5 tanks. The tanks normally have a working pressure of up to 22Kpa in normal use.

Membrane Tanks

The tanks are of a more box type construction and have a membrane which is designed to absorb the thermal contraction when the tank is cooled down. The primary barrier is the one in direct contact with the cargo liquid (or vapor in empty tank conditions). This is followed by a primary insulation which in turn is covered by a secondary barrier. This is again covered by a secondary insulation which in turn is supported by the ship’s hull structure from the outside.

Dasic products used on LNG Vessels

• Gas Freeing Fans: Jetfan 70 (water driven) / Jetfan 65 (air driven)