LNG carrier
The first oceangoing liquified natural gas tanker in the world was Methane Pioneer, which entered service in 1959 with a carrying capacity of 5,500 cubic metres (190,000 cu ft).
[6] The first LNG carrier Methane Pioneer (5,034 DWT) carrying 5,500 cubic metres (190,000 cu ft), classed by Bureau Veritas, left the Calcasieu River on the Louisiana Gulf coast on 25 January 1959.
The ships were fitted with Conch independent aluminum cargo tanks and entered the Algerian LNG trade in 1964.
In the late 1960s, opportunity arose to export LNG from Alaska to Japan, and in 1969 that trade with TEPCO and Tokyo Gas was initiated.
Two ships, Polar Alaska and Arctic Tokyo, each with a capacity of 71,500 cubic metres (2,520,000 cu ft), were built in Sweden.
The late 1970s and early 1980s brought the prospect of Arctic LNG ships with a number of projects being studied.
With the increase in cargo capacity to approximately 143,000 cubic metres (5,000,000 cu ft) costing $250 million,[7] new tank designs were developed, from Moss Rosenberg to Technigaz Mark III and Gaztransport No.96.
The size and capacity of LNG carriers has increased significantly,[8] to 170,000 cubic metres (6,000,000 cu ft).
Each ship has a cargo capacity of between 210,000 and 266,000 cubic metres (7,400,000 and 9,400,000 cu ft) and is equipped with a re-liquefaction plant.
[14] In November 2018, South Korean ship builders locked in 3 years worth of large-scale LNG carrier contracts - more than 50 orders - with a value of $9 billion.
[17] In 2018, South Korea's Hyundai Mipo Dockyard (HMD) delivered the world's first LNG-fueled bulk carrier.
[19] In 2017, Daewoo Shipbuilding & Marine Engineering delivered the Christophe de Margerie, an icebreaking LNG tanker of 80,200 deadweight tons.
[20] She completed her first revenue voyage from Norway via the Northern Sea Route in the Arctic Ocean to South Korea.
Once the hydrocarbon content reaches 5% (lower flammability range of methane) the inert gas is redirected to shore via a pipeline and manifold connection by the HD (high duty) compressors.
The shore terminal then burns this vapour to avoid the dangers of having large amounts of hydrocarbons present which may explode.
Boil-off gas can be burned in boilers to provide propulsion, or it can be re-liquefied and returned to the cargo tanks, depending on the design of the vessel.
However, self-supporting tanks are more robust and have greater resistance to sloshing forces, and will possibly be considered in the future for offshore storage where bad weather will be a significant factor.
If both main pumps fail then to remove the cargo, the tank's safety valves are adjusted to lift at 100 kPa (1 bar).
[26] Designed by Ishikawajima-Harima Heavy Industries, the self-supporting prismatic type B (SPB) tank is currently employed in only two vessels.
The primary barrier, made of corrugated stainless steel of about 1.2 mm (0.047 in) thickness is the one in direct contact with the cargo liquid (or vapour in empty tank condition).
This is followed by a primary insulation which in turn is covered by a secondary barrier made of a material called "triplex" which is basically a metal foil sandwiched between glass wool sheets and compressed together.
The tanks on board an LNG carrier effectively function as giant thermoses to keep the liquid gas cold during storage.
This maximises the amount of LNG delivered but does allow tank temps to rise due to lack of evaporation.
100% gas: Tank pressures are kept at a similar level to maximum boil off but as this may not be enough to supply all the boilers needs, additional LNG must be "forced" to vaporize.
advances in technology reliquefication plants to be fitted to vessels, allowing the boil off to be reliquefied and returned to the tanks.
Because of this, the vessels' operators and builders have been able to contemplate the use of more efficient slow-speed diesel engines (previously most LNG carriers have been steam turbine-powered).
This is a result of the IMO 2020 anti-pollution regulation that bans the use of marine fuel oil with a sulfur content greater than 0.5% on ships not fitted with flue-gas scrubbing plant.
[36] This drops to 1.7 kn for a fully loaded 300,000 dwt oil tanker collision into an LNG carrier.
Taking into account precautions, training, regulations and technology changes over time HAZID calculates that the likelihood of an LNG spill as approximately 1 in 100,000 trips.
[35] In the event that the tank integrity of a LNG transport is compromised, there is a risk that the natural gas contained within could ignite, causing either an explosion or fire.
