Page 18: of Maritime Reporter Magazine (May 15, 1981)

In attendance at recent SNAME Chesapeake Section were (L to R): William Rogalski

Jr., Gibbs & Cox, Inc., publicity chairman; Capt. James V. Jolliff, USN, Naval Sea

Systems Command, speaker; Robert J. Scott, Gibbs & Cox, Inc., chairman, Ches- apeake Section; and Alexander Landsburg, Maritime Administration, secretary- treasurer.

Electric Propulsion Systems

Discussed At SNAME Chesapeake Section i.e., superconducting machinery, were not discussed as the associ- ated risks are considered to be too high to meet the proposed goal of beginning detail design and construction of an electrical system for preliminary approval for service use (PASU) in Fiscal

Year 1986.

The electric propulsion option presented by Captain Jolliff is an integrated system, consisting of three General Electric LM 2500 gas turbines, each driving an 18- mw electric propulsion generator.

The generators feed a propulsion bus that powers two synchronous ac propulsion motors, one on each shaft. The generators and motors have water-cooled stators and air- cooled rotors, and the motors are rated at a maximum of 38,000 shp each.

Although the plant appears rather straightforward when viewed from a total system view- point, a number of new concepts have been included. One of the gas turbines is designated as an integrated cruise unit, and in ad- dition to its propulsion generator it powers a 4-mw ship's service generator through a single reduc- tion gear unit. This ship's service generator is complemented by two 4-mw diesel generator sets when required. Constant frequency is maintained on this unit by uti- lizing state-of-the-art power con- ditioners between the cruise gen- erator and the propulsion motors allowing steady speed operation of the gas turbine.

The ship can operate up to 23 knots on the cruise unit, and if additional speed is required one or two boost gas turbine genera- tor sets can be brought on line to supplement the cruise gas tur- bine generator. With both boost units on line, a sustained speed of 30 knots is achieved. The sys- tem is extremely flexible from an arrangements standpoint and can be reconfigured as necessary to obtain maximum performance in the context of speed, endurance and maneuverability. More im- portantly, the effects of battle damage on the propulsion system can be mitigated by reconfiguring the system around damaged por- tions by switchboard arrange- ments resulting in a type of se- lective degradation.

A recent meeting of the Ches- apeake Section, The Society of

Naval Architects and Marine En- gineers, was held at the Walter

Reed Army Medical Center in

Washington, D.C., and featured a presentation on electric propul- sion systems for naval combat- ants by Capt. James V. Jolliff of the Naval Sea Systems Command.

Electric propulsion has proven quite successful in the past in such ships as the Maryland class of battleships, the liner Norman- die, T-2 tankers, conventional submarines, and more recently, the Coast Guard's Polar class ice- breakers. Based on arrangement, flexibility, operational flexibility, speed control, and ability to use fixed-pitch propellers with non- reversing prime movers, electric drive is being investigated as a new propulsion option for Navy ships.

In his talk, Captain Jolliff con- centrated on "near term" or rel- atively conventional electric com- ponents for use in Navy surface combatants. Advanced concepts,

New Lifting Techn

In Construction

A new technique, which utilizes a multipurpose hydraulic system for constructing the main deck structures of offshore drilling rigs, has been announced by Hy- dranautics, Inc. The technique has been applied successfully by

Chicago Bridge & Iron Company (CBI) at Pascagoula, Miss., and

Ingleside, Texas, in fabricating a

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Of Drilling Rigs semisubmersible rig for World

Drilling Company of Tulsa.

The technique allows complete deck fabrication and installation of truss connectors at near- ground level, thereby saving on crane work and other costs asso- ciated with high construction.

Using part of a multipurpose hy- draulic tool designed and built by

Hydranautics for translating the finished drilling rig by skidding,

CBI was able to lift the 1,050-ton ground-level-fabricated deck sec- tion approximately 100 feet in the air in less than eight hours, and lock the structure on oil at that height for approximately 10 weeks.

With the suspended structure locked on oil, CBI was able to monitor in real time the weight of the total load as well as the actual load of each support point, and easily made the adjustments in height to compensate for sup- port settlement and to accomplish part fittings.

The lift was started on a week- end at 7:35 am and by 3:20 pm the total deck structure had been lifted to the elevation required for assembly of trusses under the platform by the regular work crew on Monday morning. The time required to accomplish the ground-level work staging prior to the actual lift was included in the eight-hour period.

The components used to lift the triangular deck (200 foot/ side) were later used as part of the Hydranautics transfer system to skid the entire 5,000-ton drill- ing rig. According to Hydranau- tics, the lift tool may be acquired 20 Maritime Reporter/Engineering News