EVOLUTION AND INNOVATION IN LNG TANK DESIGN

GTT has attained a 0.07% cargo boil-off rate (BOR) with its latest Mark III Flex+ membrane system (image courtesy of GTT).
GTT has attained a 0.07% cargo boil-off rate (BOR) with its latest Mark III Flex+ membrane system (image courtesy of GTT).
Energy Liberty signalled the re-emergence of the IHI-SPB membrane tank design (photo copyright: Tokyo LNG Tanker Co).
Energy Liberty signalled the re-emergence of the IHI-SPB membrane tank design (photo copyright: Tokyo LNG Tanker Co).
Refined Moss-type LNG tanker: Bushu Maru, the latest in the Sayaringo STaGE series from Mitsubishi (photo: MHI).
Refined Moss-type LNG tanker: Bushu Maru, the latest in the Sayaringo STaGE series from Mitsubishi (photo: MHI).

As the market leader in LNG cargo containment and tank technology, Gaz Transport & Technigaz (GTT), continues to refine and extend its offering, the choice of systems available to shipowners and shipbuilders is also being expanded by other industry players, writes David Tinsley.

At the close of 2018, GTT’s orderbook comprised system designs for 97 units occupying delivery slots from the start of 2019 through to the end of 2021, entailing 83 LNG carrier newbuilds and 11 ‘floaters’, plus three onshore storage applications. Its most recently developed membrane solutions represented the lion’s share of the work, whereby the Mark III Flex system accounted for 45% of the contracts, the latest Mark III Flex+ design scored a further 5%, the No96 GW system amounted to 34%, while another 4% was attributable to the No96 L03+ version.

Having logged orders for containment technology in 14 more LNG carriers during the first quarter of 2019, GTT reported that its main business activity stood at an all-time high on March 31, with contracts outstanding for 101 systems. In addition, membrane LNG fuel tanks had been specified for 12 vessels.

As well as promoting efficiency to reduce vessel operating costs, research efforts are focused on continually driving down the cargo boil-off rate(BOR), an area of study that accounts for about half of GTT’s entire R&D commitment, and which involves a particular concentration on materials.

So as to ensure that it responds as effectively as possible to the expectations of its shipyard customers, which face enormous competitive pressures, the company also devotes R&D resources to investigations into the use of less costly materials and the simplification of assembly methods. Furthermore, the current R&D programme embraces the development and adaptation of existing technologies to cater to demand from new segments, notably LNG bunkering and LNG distribution by small-scale and mid-size carriers.

“The thermal performance of LNG cargo containment systems is one of the chief concerns in the LNG sector, as it has a direct impact on transport costs and CO2 emissions,” observed GTT’s technical director Karim Chapot. “Technological advances have made it possible to continuously improve this performance over recent years, halving LNGC emissions in the space of a decade. Furthermore, there is a strong correlation between thermal performance, vessel power usage, emissions and the efficiency of the containment system.”

The main parameters that dictate the behaviour of the LNG are the composition of the cargo, its gas pressure and liquid gas ratio, cargo temperature and accelerations. The latter two factors are themselves dependent on the insulation arrangements and effectiveness, and on vessel motions.

GTT has set a new benchmark for the industry by guaranteeing a BOR of 0.07% of cargo volume per day for its Mark III Flex+ solution. A similarly effective insulation rating is promised by the new No96 Flex design version, for which classification approval-in-principle was obtained last year.

Such is the intensity of the company’s R&D endeavours and resulting innovation, that GTT was ranked fourth among medium-sized French companies, across the industrial spectrum, as regards the volume of patents filed in 2018. The French National Institute of Industrial Property(INPI) recorded that GTT had made 19 patent applications over the course of the year.

A further strand in the company’s technical development strategy is now being woven through the planned creation of a Digital Hub of Excellence. To be located in Singapore and run by group subsidiaries Ascenz Solutions and GTT South East Asia, the rationale for the hub is to help accelerate GTT’s digital transformation, complementing the engineering R&D work undertaken at the company’s Saint-Remy-les-Chevreuse laboratories in France.

“In addition to LNG as fuel, a market in which GTT intends to grow, the digital services will enable us to explore new paths and deliver differentiating value to new segments within the shipping industry,” stated chairman and CEO Philippe Berterottière.

The Moss spherical tank system provides the foundation for the sustained production of LNG carriers by Mitsubishi Heavy Industries, through consecutive series deliveries of Sayaendo and Sayaringo STaGE designs of post-Panamax LNGCs, up to 180,000m3 capacity as embodied in the May 2019-christened Bushu Maru.

Whereas the Sayaendo type has a continuous cover over four pea-shaped Moss tanks, the cargo tanks in the Sayaringo STaGE iteration are apple-shaped. The upper half of each sphere has more of a bulge than the lower half, affording extra revenue-earning volume than in the Sayaendo without increasing ship width. The more efficient STaGE propulsion system combines a Mitsubishi ultra steam turbine, LNG dual-fuel engine and electric motor.

Well-proven, home-grown Japanese containment technology has made a market comeback through the entry into service of 166,500m3 LNG carrier newbuilds specified with the IHI-SPB self-supporting, prismatic-shape IMO Type B system. Ordered from Japan Marine United(JMU) for long-term charter to Tokyo LNG Tanker Co, series-leader Energy Liberty made her debut towards the end of last year, since followed by Energy Glory and Energy Innovator, and with the fourth and final unit expected in August.

The prismatic form of the IHI-SPB tanks makes for a space-efficient solution, enabling ‘diamond-cut’ optimisation to given hull dimensions. Anti-sloshing properties have been amply demonstrated by the operating record of two 1993-built, 89,900m3-capacity recipients of the system deployed in North Pacific service between Alaska and Japan. The latest generation hosts the largest-ever SPB tanks, and is claimed to offer a BOR of only 0.08% per day, ranking among the lowest attained to date. The tanks in the Energy Liberty class have an octagonal, transverse section profile rather than the rectangular shape of the previous IHI SPB installations.

The range of technologies in service with the LNG carrier fleet has recently been augmented through the commissioning of a ship in the not so numerous ‘mid-size’ category, the 45,000m3-capacity Saga Dawn. Delivered by China Merchants Heavy Industry(CMHI) in May, Saga LNG Shipping’s debut vessel heralds LNT Marine’s LNT A-Box design. The containment uses an IMO independent A tank as the primary barrier, and a conventional cargo tank support system and liquid-tight thermal insulation as a full secondary barrier. The self-supporting prismatic tanks allow for a comparatively simple construction and flexible design, while maximising utilisation of the hull envelope.

With a relatively shallow full-load draught of 9m, the vessel type is targeted at opening up demand for new trade flows and business models, especially in Asia. Saga LNG Shipping has drawn up proposals for a similarly draught-limited larger design, of 80,000m3, for the import traffic to regional terminals in China, plus 12,000m3 Yichang-max and 28,500m3 Wuhan-max types suited to navigation on the Yangtse River.

As the pre-eminent world force in LNG carrier and ‘floater’ construction, South Korea has been endeavouring for some time to develop its own solutions in cargo containment and thereby reduce its current, almost total dependency on foreign technology, which entails a very substantial expenditure in the form of licence fees.

A collaborative industry effort, led by natural gas importer, distributor and public utility KOGAS in conjunction with the country’s three leading shipbuilders, has borne fruit in the first applications of the KC-1 membrane system. Two KOGAS-chartered newbuilds of 174,000m3 incorporating KC-1 were handed over in early 2018 for engagement in the shale gas import traffic from the USA. Although it is understood that these vessels have subsequently faced certain technical issues, the technology has also been specified for two 7,500m3 newbuilds at Samsung’s Geoje yard, intended to provide an LNG shuttle service on the Korean coast.

In the meantime, Daewoo Shipbuilding and Marine Engineering (DSME) has recently received general approval from Lloyd’s Register for its enhanced Solidus cargo containment system. Solidus employs two metal barriers surrounding an insulation material developed in cooperation with Germany’s BASF Group. Claims for the systemsuggest that it will achieve a further reduction for the industry in BOR. Successful introduction will in any event provide another option for the market and increase bargaining power. A potential newbuild scheme involving Solidus is reportedly under discussion.

DSME has also this year taken a further initiative focused on developing core LNG carrier technology bysigning an agreement with a South Korean university to establish an institute that will conduct research up until the end of 2023 into containment and process systems.

The inextricably interrelated growth in the use of LNG as marine fuel and expansion of the LNG supply infrastructure has created new business opportunities for the containment specialists. A milestone in the uptake of the fuel was marked by CMA CGM’s decision to specific dual-fuel propulsion machinery for a series of 22,000TEU containerships, leading to a project by Mitsui OSK Lines (MOL) and Total to build the world’s largest LNG bunker vessel, of 18,600m3 capacity.

Ordered from CSSC Hudong Zhonghua, the latter will be installed with two GTT Mark III Flex membrane tanks, each of 9,300m3. The bunker vessel’s carrying volume will thereby align with that of the single Mark III LNG fuel tank of 18,600m3 in each of the French boxships, and she will not be subject to cargo tank filling restrictions. Total said that the vessel will achieve complete reliquefaction of the boil-off gas.

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