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First-ever lightering support vessels prove to be nimble

Aug 22, 2012 01:48 PM
AET Excellence, the world’s first purpose-built lightering support vessel, sails on Galveston Bay near its Galveston, Texas, homeport.

AET Excellence, the world’s first purpose-built lightering support vessel, sails on Galveston Bay near its Galveston, Texas, homeport.

In mid May, Capt. E.J. “Junior” Breaux was at the controls of AET Excellence, the second in a four-boat series of purpose-built lightering support vessels (LSVs) constructed at Leevac Shipyards in Jennings, La., for AET Offshore Services of Galveston, Texas. Excellence was preceded by AET Innovator (American Ship Review 2012), and followed by AET Partnership and AET Responsibility.

Above: from left, deck hands Antonio Silmaro, Kolton Jackson and Chance Kraft cinch up fuel transfer hoses used for lightering tankers.

Below: AET Excellence transports Yokohama fenders, deployed between vessels while lightering, in Galveston Bay.

The new class of LSVs represents the world’s first vessels specifically designed for lightering tankers. Lightering support services are typically accomplished by employing older offshore supply vessel (OSV) stock to transport mooring personnel and to deploy the fendering and hoses used to lighter crude oil from supertankers to smaller service tankers for delivery to refineries.

Safety, efficiency and crew comfort were the motivating factors for AET’s decision to build LSVs. Bill Merritt, the company’s general manager, received Professional Mariner’s Plimsoll Award for Outstanding Service by an Individual in 2012 for conceiving the idea of a purpose-built lightering vessel, an idea driven by a concern for safety, efficiency, maneuverability and crew comfort.

Propulsion is provided by two Caterpillar 3512 C Tier III diesels, Twin Disc gears and 80-inch diameter Sound propellers. The boats have Becker high-lift rudders and a 479-hp Schottel STT 170 bow thruster for maneuvering.

The LSVs maneuver and deploy equipment in close proximity to large tankers, sometimes underway, sometimes anchored and sometimes adrift, but usually in designated lightering zones in the Gulf of Mexico.

The hull design differs dramatically from OSVs, which are designed for maximum cargo capacities. The LSV is instead designed to sit low in the water at the stern, in order to more efficiently and safely deploy the huge Yokohama fenders over the stern roller. To achieve the low profile, the LSVs have much less hull under water and the stern is kept down by transferring ballast water aft as needed.

Running on economy mode at 10 knots, Breaux aboard AET Excellence noted that the boat was burning 27 gallons of fuel per hour. “The older OSVs in the fleet will burn double that,” he said.

Breaux credits the Becker high-lift rudders and the bow thruster for the boat’s nimble maneuverability. “When we’re maneuvering, we have the Becker rudders and the bow thruster. So we have a stern that will turn and a bow that will turn you around (within the length of the boat). Those are big safety features.”

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