GS48A

LNG Shipping at 50|the early years
membrane tank system for LNG
carriers. The system was based on the
semi-membrane design as installed on
the 72,344m 3 LPG carrier Bridgestone
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 128,000m 3 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 350m 3 of LNG over a
distance of 1,100km.
In 1976 Owens-Corning Fiberglas
of Toledo, Ohio introduced an internal
The Verolme LNG design was
scaleable to the required cargo-carrying capacity by
specifying a greater or smaller number of same-size aluminium tanks
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 500,000m 3 . A typical
3,500m 3 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
125,000m 3 Verolme LNGC would have
38 tanks, a 165,000m 3 vessel 50 and a
330,000m 3 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
300,000m 3 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
140,000m 3 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
32 I LNG shipping at 50
A SIGTTO/GIIGNL commemorative issue