EBDG Completes Contract Design for ATB

Elliot Bay Design Group (EBDG) recently completed a contract design, including an extensive model basin testing program, for an articulated tug and barge (ATB) for Sause Bros., Ocean Towing of Coos Bay, Ore. ATB has been designed specifically for oceangoing service in the North pacific petroleum product trade. The unit also incorporates many features requested by Sause Bros.

Elliot Bay's design calls for 135.5 ft.(41.3 m) tug combined with a 543.7 ft. (165.7 m) barge, connected by an Intercon coupler. The coupler provides a secure attachment between the tug and the barge, while allowing free motion about the pitch axis.

Both the tug and the barge are designed to meet SOLAS requirements, and will be classed by the American Bureau of Shipping. The barge will receive ABS Safehull certification, and will be classed as a Maltese Cross Oil Carrier. The design underwent extensive self-propelled resistance and seakeeping tests, conducted in Denmark and Sweden by the Danish Maritime Institute, to verify horsepower, speed and fuel consumption estimates.

Testing covered four major areas: (1) resistance in calm water and seas of 18-25 ft. (5.6-7.6 m); (2) measurement of acceleration at the raised pilot house level due to heavy seas; (3) measurement of forces at the Intercon connection in heavy seas; and (4) behavior of the barge in tow. Wave patterns and shapes used in tests were designed to match NOAA-measured wave patterns for the U.S. West Coast, including the "100-year storm," which produces wave heights up to 55 ft. (16.8 m).

The tug will feature six decks, with the pilothouse high atop an aluminum tower for maximum visibility. A standby pilothouse will also be provided on the third deck, to be used in the event that conditions make it uncomfortable for crew to work at the uppermost level. Power will be provided by a pair of EMD 16-710G7B diesels, with 8,000 hp driving twin fixed-pitch propellers through Lufkin reduction/reversing gears. Auxiliary power will come form a pair of 150-kW John Deere gensets on centerline in the engine room between the mains.

Accommodations will be provided for as many as nine crew, including private staterooms for the captains, chief engineers, first mate, and cook.

The barge will accommodate a variety of refined products in its seven pairs of tanks, with total capacity of 161,940 barrels. Ballast tanks will hold up to 65,700 barrels. Two pump engine and generator houses aboard the barge will contain a pair of 150-kW gensets and four engines providing for four Byron Jackson deepwell pumps, each rated at 3,500 gpm (13,230 lpm). On deck, the cargo manifold is arranged for either Chicksan headers or hoses on each side. A pair of 40-ft. radius (12.2m) hose handling cranes will be located adjacent to the manifold.

Additional features of the Elliot Bay design include a helicopter landing pad, a 700-hp bow thruster to aid in docking maneuvers, a 60-kW genset for normal electrical requirements, a vapor recovery system, hydraulic mooring equipment, and crew spaces that will include a control room, day-room, workshop, and spill response equipment room.