Artist's conception of the future LNG ship designed by Moss Rosenberg of Norway.
130,000 cubic meters, a length be-
tween perpendiculars of 240 me-
ters, a molded breadth of 48 me-
ters, a molded depth of 27 meters,
a draft of 11 meters, four cargo
tanks with the first having a di-
ameter of 36.8 meters and the
other three of 40.7 meters and
speed of about 18 knots. The pro-
pulsion machinery would consist
of a large-bore slow-speed diesel
engine with a maximum continu-
ous rating of 26,000 kw. The aux-
iliary machinery would consist of
three diesel generators.
Resides being attractive as far
as construction costs are con-
cerned, this project also is at-
tractive as concerns the operat-
ing costs. Based on prices from
August 1981, it may be possible
to obtain savings for the pro-
jected ship of about $300,000 on
a standard 21-days round trip
when traveling at the economical
speed of 18 knots.
The Moss Rosenberg spherical
LNG tank design has been in
operation since 1973. A total of
101 spherical cargo tanks are in-
stalled on board 20 carriers trans-
porting LNG worldwide.
Moss Rosenberg
Energy-Saving
One of the many features that
characterizes an LNG carrier is
the presence of cargo boil-off, the
result of heat leakage to the car-
go from the surroundings. Until
now, the boil-off has been uti-
lized as fuel in producing steam
for the steam-turbine propulsion
plant. However, LNG has lately
become comparatively expensive,
and associated with relatively low
thermal efficiency of the steam-
propulsion-plant system, the use
of boil-off as fuel is now consid-
ered uneconomic.
Moss Rosenberg Verft a.s. of
Moss, Norway, decided to develop
a 130,000-cubic-meter LNG car-
rier, paying particular attention
to low operational costs and low
cargo losses. The primary objec-
tive of the project study was to
minimize boil-off and, therefore,
consider alternative propulsion
plants.
The firm developed a project
ship which is the result of com-
prehensive programs and analy-
ses, where the following areas
were closely studied: reduction
of boil-off, improvement of pro-
pulsion efficiency, reduction of
hull resistance and optimization
of the economical speed of the
vessel.
Research and development work
over the last few years have led
to improvements with respect to
reduced heat leakage to the cargo
tanks. By inserting a ring of aus-
tenitic steel, a thermal brake, in
the skirt supporting the spheri-
cal tank, heat leakage through
the skirt can be reduced by more
than 50 percent. Further, insula-
tion thickness can easily be in-
creased without any effect on the
ship's main dimensions. This com-
bination of improved insulation
thickness and a skirt with ther-
mal brake may reduce the boil-
off rate from 0.25 percent to 0.11
percent.
Different alternatives of pro-
pulsion machinery were studied.
The recent developments of large-
bore slow-speed diesel engines
with low fuel-oil consumption has
made such plants most attractive
Verft Develops
LNG Carrier
for LNG ship application. Such
installations, however, cannot
utilize cargo boil-off in the con-
ventional way and the installa-
tion of a reliquefaction plant for
the cargo is required. This also
will result in increased deliv-
ered quantities of LNG. Com-
pared to a steam-propulsion plant
without reheat, the savings in
fuel expenses on a diesel plant
with boil-off reliquefaction is in
the region of 36 percent (energy
prices mid 1981).
Due to the increasing fuel
costs, Moss Rosenberg also be-
lieves that the economical speed
of the future ship will be lower
than what is normally used today.
Based on the firm's studies so
far, the future LNG ship of their
design might have the following
particulars: cargo capacity of
Electric Boat Awarded
$7-Million Navy Contract
For SSBN Sub Overhaul
The General Dynamics Electric
Boat Division, Groton, Conn., has
been awarded a $7-million cost-
plus-fixed-fee contract for plan-
ning yard services for mainte-
nance support of SSBN subma-
rines design documentation and
services for overhaul support of
SSBN submarines. The work will
be performed at Groton. The
Naval Sea Systems Command,
Washington, D.C., is the contract-
ing activity. (N00024-82-C-2003)
$2.1-Million Title XI
Guarantee For Tanker
IGS And COW Retrofit
The Maritime Administration
has approved in principle an ap-
plication for a Title XI guaran-
tee to aid in financing the recon-
struction of the 264,000-dwt tank-
ers Massachusetts, New York,
and Maryland to comply with the
Port and Tanker Safety Act of
1978. Each of the vessels was
built with the aid of construction-
differential subsidy (CDS). They
were delivered in October 1975,
May 1976, and August 1976, re-
spectively.
The ships are time chartered
to subsidiaries of Seatrain Lines,
Inc. — Bay State Tankers, Inc.,
New York Tankers, Inc., and
Maryland Tankers, Inc. Seatrain
currently is operating under
Chapter 11 of the Bankruptcy Act.
Todd Shipyards, Galveston,
Texas, performed the work on the
Massachusetts and New York.
Triple A Shipyard, San Francisco,
Calif., reconstructed the Mary-
land. The work primarily in-
volved installation of crude oil
washing and inert gas systems.
The ships were redelivered in
April, October, and August 1981,
respectively.
The Title XI guarantee for this
reconstruction project totals $2,-
134,000 or 75 percent of the es-
timated depreciated actual cost
of $2,845,828. No CDS was in-
volved in this project.
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