39
The cargo containment system
Feasibility studies were performed for three cargo containment
systems considered proven in Polar conditions (spherical
tanks from Moss, the membrane type from Gaztransport &
Technigaz (GTT), and the Self Supporting Tank Type B (SPB)
from IHI Corp.). However, the ultimate choice was determined
by the cargo containment system’s behaviour when subjected
to the vibrations induced by the conditions in the ice-breaking
LNG carrier’s ahead and astern modes of operation, to induced
fatigue, and to ice collision. One of the systems seemed to
require anti-rolling keels, which are not appropriate for ice. In the
end, the GTT NO96 GW (with GlassWool replacing the perlite
inside the plywood insulating boxes of the cargo containment
system) was chosen after additional studies and laboratory
testing, with a guaranteed boil-off rate of 0.13% vol./d.
Further to this, a series of ice and open water model tests
were performed in Finland, Canada and Germany to optimise the
design of the hull and the propulsion plant configuration, plus the
performance required by the technical specification (e.g. speed in
1.5 m thick level ice: 2 knots in ahead mode, 5 knots in astern
mode, and 19.5 knots in open water).
Greenlight for the ice-breaking
LNG carrier and condensate tanker
This investigative work resulted in the basic outline specification
for the Arc7 ice-breaking LNG carrier. Some of the technical
solutions were also applied to the condensate tanker. In
parallel, a prequalification, followed by a selection process, was
performed for potential shipyards and shipowners for the total
fleet of 15 Arc7 LNG carriers.
The final choice was awarded to Daewoo Shipbuilding &
Marine Engineering (DSME) for the construction of the full fleet
of 15 vessels plus the option for an additional vessel, and to four
experienced shipowners (Sovcomflot: one unit; Teekay: six units;
Dynagas: five units; and Mitsui O.S.K. Lines (MOL): three units), in
venture with Chinese partners.
The first ice-breaking LNG carrier was launched in
mid-January 2016 in Okpo, South Korea. A joint task force was
created between the ship operators and the charterer,
Yamal Trade, in order to maximise and share the experience of ice
navigation, and set a common approach for the future operations
along the NSR in the various disciplines of plan approval and
construction follow-up; health, safety, quality and environment
(HSQE); crewing and training; operations and depot spares; and, of
course, the application of the new Polar Code, which will enter
force in 2017.
The delivery of the first ship is scheduled for 4Q16 before the
start-up of the first liquefaction train at the plant. This will allow
crews to train and carry out ice trials in the Kara Sea’s actual ice
conditions.
In parallel, two Arc7 ice-breaking condensate tankers with the
double-acting system were ordered at the end of 2015 by two
other shipyards (Archtech in Finland, owned by Russian OSK, and
GSI in China) with the same owner, Dynagas, for delivery at the
beginning of 2018.
This is, with the ongoing chartering of other conventional
LNG carriers, the unique solution to export LNG and gas
Meets the design standard of the
oil & gas, petrochemical, hydrocarbon
and LPG/LNG industries:
– Fully ANSI/ASME design
– Includes NACE requirements
Reliable level indication without external
power with three functions in one device:
– Liquid level indication
– Liquid level switch
– Liquid level transmitter
Equipment with optional bi-stable change over
or on/off switches and linear or non linear
transmitters (also as 2-wire systems
with 4…20 mA output, optional with HART
®
)
CE-conform and Ex-approval
For operating pressures from vacuum up to 400 bar and higher,
operating temperature from –196 °C up to +400 °C
Densities > 0.3 g/cm
3
Closed floats for condensing liquids up to 350 bar operating pressure
Construction in stainless steel grade 316/316L as standard.
Also possible in higher grades of stainless steel like 904L or Hastelloy
®
and Inconel
®
/Incoloy
®
alloys
Casing of indication rail in stainless steel
WEKA AG · Switzerland · Schürlistrasse 8 · CH-8344 Bäretswil
Phone +41 43 833 43 43 · Fax +41 43 833 43 49
·
ARCA Flow Group worldwide: Competence in valves, pumps & cryogenics
Level Measurement
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