MHI develops new generation LNG carrier

01 Oct 2011
Conceptual drawing of ‘Extrem’, the new-generation LNG carrier developed by MHI

Conceptual drawing of ‘Extrem’, the new-generation LNG carrier developed by MHI

Japan’s Mitsubishi Heavy Industries (MHI) has completed development of a new-generation liquefied natural gas (LNG) carrier marking an evolutionary advance from Moss type 1 LNG carriers.

The new vessel-type, dubbed ‘Extrem’, is a type of newly developed ‘Sayaendo’ series, which features a peapod-shaped continuous cover for the Moss spherical tanks that is integrated with the ship’s hull, rather than a conventional hemispherical cover. The new configuration enables greater structural efficiency and size and weight reductions resulting not only in improvements in fuel consumption and operating economy but also in enhancements in terms of compatibility with LNG terminals and maintainability. MHI looks for the ‘Extrem’ to become a strategic product that will lead the LNG carrier market. The company is now targeting early order receipts.

In conventional Moss-type LNG carriers, the upper half of the spherical storage tanks above the ship’s deck is covered by a semispherical dome and the lower half under the deck is supported by a cylindrical skirt structure. By contrast, the ‘Extrem’ employs a continuous cover integrated with the ship’s hull to completely house all storage tanks, enabling the cover to be used as hull reinforced material for overall strength. In the conventional method, pipes, wires and catwalks atop the tanks are supported by complex structures. By covering the tanks with the integrated cover and making those supporting structures unnecessary, the new design improves maintainability.

The continuous cover over the tanks improves aerodynamics by substantially reducing wind pressure, which serves as a drag on ship propulsion, and contributes to reduced fuel consumption during voyages. At the same time the continuous cover minimizes exposure of support structures and equipments while it also facilitates reinforcement of overall strength to be effective in resisting ice impact load, thus making the system also suitable for LNG transportation in icy-water regions.

The new-generation LNG carrier, for which MHI has completed the basic design, measures 288.00m in length overall, 49.00m in width, 26.00m in depth and 11.50m in draught. The ship has a total cargo tank capacity of 155,000m³ using four Moss-type tanks. The ship is projected to respond to anticipated growth in demand for ships in the New-Panamax category (when completed in 2014, the enlarged Panama Canal will be able to take ships up to 366m in length oa, 49m in width and 15.2m in tropical freshwater draught).

Compared with conventional Moss-type LNG carriers of the same size, the ‘Extrem’ has the capacity to transport 8,000m³ more LNG by employing stretched Moss tanks and its steel hull structure is about 5% lighter in weight. The depth of the ship has also been reduced by 1m, enabling better compatibility with major terminals in Japan and other countries in view of cargo manifold and gangway landing arrangement.

For its main power plant, the EXTREM adopts MHI’s ‘ultra steam turbine plant’ (UST), a new turbine plant which achieves higher thermal efficiency through effective use of thermal energy by reheating steam. Together with downsizing, weight reduction and hull lines improvement, the new ship achieves a substantial 20% reduction in fuel consumption compared to conventional ships according to MHI.

Moss-type LNG carriers are widely used for their advantages in terms of high-reliability tank structure and strength against possible liquid sloshing inside the tank. These features enable the vessel to achieve a quick departure from the loading/discharging terminal pier in case of emergency and permitting safe voyages through rough waters. The ‘Extrem’ combines these advantages of Moss-type carriers with energy-saving, environmentally friendly features and higher LNG cargo transport capacity. MHI thus looks to its new-generation LNG carrier as a sure leader in tomorrow's shipping industry, and the company aims to conduct an aggressive marketing programme.

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