New incarnation of Japanese LNG system
Used in only a few vessels hitherto, a home-grown tank system has been revived for a series of LNG carriers now starting to enter service following long delays. David Tinsley reports.
After a gap of 25 years, Japanese-developed IHI-SPB cargo containment technology has made a comeback in the LNG carrier sector by way of the recently-completed, 166,500m3-capacity Energy Liberty.
As the first in a series of four sister vessels ordered from Japan Marine United(JMU) to lift cargoes on behalf of utility Tokyo Gas, Energy Liberty was constructed at the builder’s Tsu shipyard on Ise Bay in central Japan and completed during October. She will be mainly engaged transporting LNG to Japan from the Cove Point project in the USA.
The IHI-SPB system made its debut in 1988 in the 1,500m3 prototype LNG/ethylene carrier Kayo Maru, and was nominated for a pair of 89,900m3 LNGCs delivered in 1993 as the Arctic Sun and Polar Eagle for the Alaska/Japan traffic. Built at the IHI shipyard in Aichi yard to serve a long-term contract delivering Alaskan LNG to Tokyo Gas, Arctic Sun and Polar Eagle gave consistent performance over nearly 20 years’ non-stop service on the North Pacific.
Subsequent references were confined to two LPG offshore ‘floaters’ and a floating LNG storage and regasification barge, until the orders for the new series of LNGCs were confirmed in 2014.
Operational experience with the Arctic Sun and Polar Eagle had a signal bearing on the choice of containment solution for the current newbuild programme. Severe conditions characteristic of the North Pacific during the winter storm season confirmed the robustness of the IHI-SPB system. Moreover, numerous voyages undertaken by the ships with less than full cargoes during the latter years of the trade attested to the anti-sloshing properties of the SPB concept. Following sale to the Teekay Group in 2007, the ships were renamed Arctic Spirit and Polar Spirit, respectively, and are now deployed worldwide.
Energy Liberty has been built to dimensions suited to the new, larger locks of the Panama Canal, and embodies a new-generation IHI-SPB solution. Among the differentiating features relative to the initial deepsea vessel installations, the cargo tanks in the latest ship have an octagonal, transverse section profile in contrast to the rectangular shape in the Arctic Sun type. The changed tank configuration provides a trunk deck.
The containment solution provides an alternative, albeit at a price premium, to the market-leading, GTT membrane systems and Moss spherical technology and derivatives. The latest installation is claimed to offer a cargo boil-off rate(BOR) of only 0.08% of the cargo volume per day, which would rank among the lowest ever achieved on an LNG carrier.
The self-supporting, prismatic-shape IMO Type B(SPB) design for LPG and LNG containment was devised by IHI Marine more than 30 years ago. Large SPB tanks are subdivided into four spaces by a centreline, liquid-tight bulkhead and a transverse swash bulkhead. The compartmentalisation, in conjunction with the stiffened plate structure of both the shell and internal supporting elements, obviates the risk of cargo sloshing damage at any filling level. The immunity to sloshing, allowing partial loading even in harsh weather, is especially salient to the changing nature of the LNG trading and transportation market.
As with all IMO Type B tanks, the IHI-SPB units necessitate only a partial secondary barrier and can be constructed of either aluminium, as chosen for all LNG applications to date, stainless steel or 9% nickel steel. Cargo tank insulation consists of rigid polyurethane foam(PUF) panels. Cushion joints between panels absorb the relative movements of tank and insulation, and eliminate thermal stresses in the insulation. The fact that the insulation is not load bearing affords the manufacturer greater scope for materials that can better achieve very low BOR.
The prismatic form of the IHI-SPB tanks is reckoned to render the system the most space-efficient containment solution available, enabling ‘diamond-cut’ optimisation to the given hull envelope and dimensional parameters.
The series was ordered in three phases over the course of 2014, on the back of Tokyo Gas purchases of cargoes from the Cove Point export facility in Maryland, although the new class is also expected to be used for shipments from the Ichthys project in Western Australia.
Each of the four newbuilds has four IHI-SPB tanks of unprecedented size, creating manufacturing challenges. Deliveries of the first three vessels were originally scheduled for 2017, to be followed by the fourth in 2018. However, the programme has been beset by construction and installation delays, pushing back completions to an autumn 2018-mid 2019 timeframe.
While the ownership and management arrangements vary for all four vessels, the constant factor throughout is a 20-year charter commitment by Tokyo LNG Tanker, a wholly-owned subsidiary of Tokyo Gas. In the case of Energy Liberty, the charterer retains a 10% stake in the ship alongside majority owner Mitsui OSK Lines(MOL), which is responsible for all shipmanagement functions. The second newbuild, Energy Glory, is be owned on a 70%/30% basis by Tokyo LNG Tanker and NYK Line, respectively, with the latter also designated as ship manager. Energy Glory was named at the Tsu yard in October, and her entry into service is imminent.
As with the lead vessel, ownership of the third-of-class will be split 90%/10% between MOL and Tokyo LNG Tanker, respectively, while the final newbuild will be wholly-owned by MOL.
The Japanese series provides a new showcase for LNG-capable, tri-fuel diesel-electric propulsion, affording operational flexibility and ensuring compliance with the strictest emission controls in US waters. The installation in each ship is based on six generators of an aggregate 44,800kVA, and two ABB 12,400kW electrical propulsion motors.
Japan Marine United is also promoting the weight and space-saving advantages of the SPB system compared to IMO Type C tanks when used as bunker tanks in ships engineered to run on LNG fuel. A major endorsement of the Japanese technology for such applications was signified by United Arab Shipping Company’s(UASC) nomination of the IHI-SPB concept for the bunker tanks that will eventually be installed on its A14 and A18 series of 14,000TEU and 18,000TEU containerships built by Hyundai Heavy Industries.
UASC will adapt the main machinery and retrofit the tanks once its criteria as regards global availability, in terms of the LNG bunkering infrastructure, have been met. Tanks will be fitted in the cargo hold immediately forward of the engine room.
Operated by Dominion Energy, the Cove Point natural gas liquefaction and export facilities came on-stream this year, with the Shell Group’s 136,600m3 Gemmata sailing on March 1 with the inaugural shipment. Located on Maryland’s Chesapeake Bay, Cove Point started life 40 years ago as an LNG import terminal.
Against the backcloth of US exploitation of shale gas reserves, Dominion has invested US$4bn to create a bi-directional complex, featuring a single liquefaction train with a nameplate LNG production capacity of 5.25m tonnes per annum and associated export terminal conduits. Cove Point was the second new US LNG export project to go on-stream, following the start-up of the Sabine Pass facilities in Louisiana during February 2016.
The bulk of Cove Point’s production has been booked by the GAIL Group of India and ST Cove Point, the joint venture of Sumitomo Corporation and Tokyo Gas, under 20-year, take-or-pay contracts. As the world’s biggest buyer of LNG on the world market, Japan received its first consignment from Cove Point in May this year, signalling the start of the major ramp-up in US imports. The shipment to the Negishi terminal of Tokyo Gas was effected by the 177,000m3 LNG Sakura.
Of the 2.3m tonnes per annum purchased by Japan through ST Cove Point, 1.4m tpa is destined for Tokyo Gas and 0.8m tpa will be shipped for Kansai Electric, with the balance going to the spot market.
PRINCIPAL PARTICULARS: Energy Liberty
2 x 12,400kW
Diesel generator power
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