MHI to deliver first Sayaringo gas carrier

'Diamond Gas Orchid' heralds new thinking in LNG carrier construction and powering 'Diamond Gas Orchid' heralds new thinking in LNG carrier construction and powering

The imminent delivery of the 165,000m3 ‘Diamond Gas Orchid’ heralds a new phase in the development of cargo tank structure and propulsion systems for LNG carriers, writes David Tinsley.

Destined to service the Cameron LNG Project in Louisiana, the vessel is the first example of the Sayaringo STaGE next-generation type formulated by Mitsubishi Heavy Industries (MHI) and constructed at the Nagasaki complex of group company Mitsubishi Shipbuilding.

Cargo containment is a derivation of the Moss spherical tank solution, whereby the upper hemisphere of each tank is larger than the lower hemisphere, resulting in a shape that resembles an apple (“ringo” in Japanese), enclosed by a continuous steel cover (“saya” in Japanese, denoting a pod-like form).

In the case of Diamond Gas Orchid, this has achieved a 10,000m3 gain in carrying capacity within a similar hull envelope, at less than 300m in length overall and 49m in breadth, of the preceding Sayaendo LNG carrier series also developed and built by MHI. The width is governed by the new Panama Canal locks, while the main dimensions as a whole are compatible with Japanese import terminals and US outlets.

The continuous cover for the four independent tanks employed in the Sayaendo and Sayaringo STaGE ships is integrated with the hull, resulting in a lighter vessel while retaining overall structural strength, and reducing wind resistance relative to standard Moss-type tankers.

The incorporation of a hybrid propulsion arrangement is claimed to have significantly boosted fuel efficiency of the Sayaringo STaGE breed compared to the Sayaendo generation. STaGE, signifying “Steam Turbine and Gas Engines”, is a hybrid system that consists of MHI’s proprietary, ultra-steam turbine (UST) and reduction gear, on the one hand, and a combination of dual-fuel diesel gensets and electric propulsion motor on the other.

Both the dual-fuel reciprocating machinery and the UST can operate on cargo boil-off gas, while waste heat from the engines is recovered to heat the feedwater flows to the boiler in the steam turbine plant. The rationale for STaGE is to maximise efficiency at all speeds and enable gas usage in all operating modes.

Diamond Gas Orchid is co-owned by NYK Line and Mitsubishi Corporation through a joint venture which has entered into a long-term contract with Mitsubishi’s Singapore-based subsidiary Diamond Gas International. Ship management will be the responsibility of the NYK Group. Following scheduled handover towards the end of this month (June), the vessel will enter service transporting cargoes for the Cameron LNG Project, in which both NYK and Mitsubishi Corporation have a stake in partnership with Sempra, Mitsui & Co, and Engie.

Initial production this year for the first of three liquefaction trains at the site in Hackberry, Cameron County, southwest Louisiana, is expected to be followed by full commercial operation during 2019. Tapping US shale gas reserves, the new facilities will provide capacity for the export of 12m-15m tonnes of LNG per annum over the long-term, and will augment the existing import terminal.

A sister to Diamond Gas Orchid is under construction at Nagasaki. Orders have also been secured from Japanese interests for two 177,000m3 and two 180,000m3 versions of the Sayaringo STaGE design. Capacity variations are possible, within the New Panamax beam criterion, by adjusting the semi-circular cross-section of the tanks.


Length overall






Gross tonnage




Cargo capacity


Propulsion system

Steam turbine/dual-fuel engines





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