Page 33: of Maritime Reporter Magazine (December 15, 1981)

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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December 15, 1981 Write 20fl on Reader Service Card 21