RECOMENDACIONES A PARTIR DE LA EXPERIENCIA INTERNACIONAL

the early years||LNG Shipping at 50LNG Shipping at 50

Never short of ideas, Cornelis Verolme settled on multiple vertical cylinders

One of many LNG design ideas that didn’t float – Dytam’s concept of a vessel with a concrete hull

A SIGTTO/GIIGNL commemorative issue

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32 ILNG shipping at 50

membrane tank system for LNG carriers. The system was based on the semi-membrane design as installed on the 72,344m3 _{LPG carrierBridgestone} Maru No 5, which had been delivered

by Kawasaki Heavy Industries in September that year.

Compared to the LPGC arrangement, with tanks in pairs, the LNG design proposed cargo tanks extending across the full beam of the ship. Depending on the design of the ship, the ‘metal’ membrane primary barrier was to have a thickness in the 3-10mm range. The flat walls were supported by load-bearing insulation on the hull structure, with cylindrical edges and large ball corners to allow for thermal expansion and contraction. The secondary barrier was coated plywood panels.

To be assembled separately before being lifted into the ship’s hold spaces, the tanks would be held in position at the tank dome by a large hanger system. The lifting of a completed tank would necessitate a temporary internal frame support for the unstiffened membrane.

Dytam Tanker GmbH began research into the use of reinforced concrete for cryogenic applications in August 1972. Based in Kiel, Germany, Dytam was a joint venture between Dyckerhoff and Widmann, a concrete firm, and Tampimex, an oil trader.

Dytam developed a design for a concrete 128,000m3 _{LNG carrier. The}

290m long vessel had a single hull made from concrete and 10 cargo tanks arranged in pairs. Internal insulation was either sprayed on or enclosed in stud-mounted fibreglass panels. The transverse bulkheads were dished in shape to allow for expansion and contraction. The thickness of the concrete was 60cm at the bottom hull, 45cm at the side hull and 20cm at centre. The concrete was reinforced longitudinally and transversely by stressed and unstressed steel rods. As a solution for developing the remote Arctic gas fields Boeing of Seattle proposed a unique air and sea LNG solution in 1974. A fleet of up to 14 Boeing 747 freighters were to fly planeloads of LNG south to a marine terminal on the US Pacific coast for the onwards sea leg of this LNG distribution chain. Each aircraft would be capable of carrying up to 350m3 _{of LNG over a}

distance of 1,100km.

In 1976 Owens-Corning Fibergl as of Toledo, Ohio introduced an internal

insulation LNG containment system called Perm-Bar II. The system was made up of prefabricated panels secured to the ship’s inner hull by studs. The insulation was made up of two panels. The main flat panels were rectangular in shape and provided a primary and secondary barrier of glassfibre-reinforced plastic (GRP) with polyurethane foam (PUF) between. A third barrier labyrinth of FRP was fitted at the inner hull. Panels could be curved or tapered to suit the shape of the cargo tank.

Dutch entrepreneur and innovator Cornelis Verolme formed his Naval Project Development team in Rotterdam in 1976. This group produced designs for LNGCs, fitted with a multitude of vertically mounted, cylindrical, aluminium alloy cargo tanks of the same size, with capacities up to 500,000m3_{. A typical}

3,500m3 _{tank for a 330,000m}3 _LNGC

would have a height of 35.5m and a diameter of 11.8m.

A grid framework on the ship’s inner bottom supported each tank and held it in place against ship movements. The cylinders were considered as IMO Type B tanks and had a maximum design pressure of 0.35 barg (135 kPa). Tanks could be positioned in three or five rows across the ship and in four or five holds, depending on the overall capacity. A 125,000m3 _{Verolme LNGC would have}

38 tanks, a 165,000m3 _{vessel 50 and a}

330,000m3 _{ship 93.}

In 1978 Spain’s Astilleros y Talleres del Noroeste (Astano) proposed a range of LNGC designs based on an internal insulation system called Metastano 20. Cargo capacities ranged from 130,000 to 300,000m3 _{while the 366m length of the}

largest design was similar to that of the

363,000 dwt very large crude carriers (VLCCs) built by the yard.

The individual cells of the Metastano internal insulation were made up of three components. The first consisted of two glassfibre-reinforced plastic (GRP) boxes with boundaries either curved or flat. These boxes were filled with rigid PUF, the second component. Adhesive was the third all-important component, as no studs were used to secure the cells. The system offered four GRP barriers and four PUF sealing barriers, with each designed to be impervious to cryogenic liquid leakage.

In 1981 General Dynamics in the US examined the feasibility of a 140,000m3 _{submarine LNG carrier}

for Arctic service. Nuclear and steam turbine propulsion systems were considered. The nuclear version would require a cargo reliquefaction plant while the conventional steam propulsion system would burn the cargo boil-off in the boilers.

The submarine design called for six cylindrical IMO Type B cargo tanks of equal size to be fitted along each side of the vessel. The tanks would be constructed of 9 per cent nickel steel and insulated externally with polyisocyanurate foam panels to provide a cargo boil-off rate of 0.2 per cent per day. Shipping routes from Prudhoe Bay in Alaska to the Canadian east coast and Europe were seen as viable.

The above paragraphs describe only a few of the LNGC containment system ideas that were considered over the past 50 years and that never came to fruition. Today’s bright naval architects, when contemplating a new revolutionary LNGC design, should first check out these pioneering efforts to spot potential drawbacks early on.SH

LNG Shipping at 50

LNG Shipping at 50||the early years

The Verolme LNG design was scaleable to the required cargo-carrying capacity by specifying a greater or smaller number of same-size aluminium tanks