The first of a series of 12,000 hp ATB tugs being built for U.S. Shipping Partners, L.P. was recently launched. But the occasion was devoid of the usually expected thrill and large splash. The building site lacked suitable launching ways so a different, somewhat less dramatic, method was devised. Using multiple tired high capacity transporters the tug was rolled onto a barge, then towed to a graving dock. The graving dock was drained to allow the tug to be freed from the then ballasted barge. The dock was then filled with about as much excitement as turning a tap to fill a tub allowing the tug to float free in its element.
Guarino & Cox, L.L.C. of Covington, LA, prepared the design and provided all engineering support for the construction of the tug series and the accompanying 19,999 tonne DWT double skin tank barges forming the ATB units.
The design, equipment and standard of outfit of the tug and barge represent a considerable advance in the state of the art of ATB’s. Greg Cox, a principal of Guarino & Cox stated that the owner’s requirements placed a high priority on efficiency, safety, habitability and low life cycle cost in the design, construction and outfit of the tugs and barges. Many exterior fittings such as handrails, hatches, water tight doors and even the mast are fabricated of stainless steel to reduce maintenance. The accommodations for the crew, officers and tanker men are spacious and outfitted to a high standard uncommon for tugs.
The tug and barge are connected with an Intercon 64 ft. coupler system. The 45.7 meter tug is powered by two Wartsila 9L32 heavy fuel engines rated at 4590 kW (6150 hp) each, more than sufficient for a speed of 14 knots for the tug and barge combined unit. The remainder of the propulsion train is also by Wartsila including reduction gears, shafting, 4 meter diameter Wartsila/Lips CP propellers and HR high speed nozzles. Steering of the 192 meter long combined ATB unit is accomplished by two Rolls Royce Marine high lift rudders with Tenfjord rotary vane actuators. The tug’s aft body differs from many in that the shafts are not supported by struts. In lieu of struts it has twin skeg bossings to organize the flow into the propellers. Extra care has also been exercised in fairing the nozzles and rudder trunks into the hull to improve efficiency.
Electrical power is amply provided by two 500 kW shaft generators and one 260 kW Volvo Penta diesel generator. A 150 kW Volvo Penta diesel generator set is also fitted for emergency power. Southcoast Electric Systems electrical boards and switchgear are installed. Deck machinery, capstans and anchor winch, are electric and manufactured by Coastal Marine Equipment, Gulfport, MS. The SOLAS rescue boat and davit are both by Schat-Harding. The heavy fuel oil tanks, with a capacity of 224,200 U. S. gallons, have heating coils installed and an S-Man thermal oil heating system. The fuel oil is purified, conditioned and boosted by Alfa-Laval units. Capacity of the tug is 224,200 U.S. gallons of heavy fuel oil and there is an additional 28,000 U.S. gallons of diesel oil. There are also two tanks for fresh water totaling 18,600 U.S. gallons.
The barges of the series production are all identical in size and form and feature relatively fine ship shape fore bodies and the Guarino & Cox developed ‘Blended Skeg’ after body. The first of the159 meter tank barges is arranged with cofferdams and compartments for up to ten cargo segregations and equipped to carry up to 140,000 barrels of chemicals or petroleum products. The other barges are primarily intended to carry up to 155,000 barrels of oil or petroleum products with up to five segregations of cargo. FRAMO hydraulic pumps are fitted to both types of barge for cargo and ballast service. Cargos are heated by an S-Man thermal oil system and inerted by an Air Products nitrogen inert gas system