OSG Horizon

The second of three large articulated tug-barges (ATBs) built for Overseas Shipholding Group (OSG) America went to work on the Delaware River this past spring, with a third identical combination expected to join its predecessors next spring.

New on the Delaware as of April is OSG Horizon, another in a class of vessel that is said to be the largest ATB operating in North America.

OSG Horizon, second in a series of three 12,100-hp ATBs built for Overseas Shipholding Group (OSG), is among the largest ATB tugs operating in the world. Measuring 153 feet in length, the tug is involved with lightering crude oil tankers on Delaware Bay. (Photo courtesy VT Halter Marine)

The tug itself is a 12,100-hp heavy-fuel-burning powerhouse with 77 feet height of eye at its massive wheelhouse. Horizon is matched to a 655-foot barge with capacity of 342,000 barrels of oil. The two are linked together with a coupler system using 64-inch pins provided by Intercontinental Engineering. It is described as the largest coupler system produced by that company.

Delivered a year earlier from the VT Halter Marine shipyard in Pascagoula, Miss., was OSG Vision, along with her own matching barge, constructed at the same shipyard. Parts of these vessels were started at Bender Shipbuilding & Repair before that company filed for bankruptcy.

OSG Horizon is actually the second of a series of so-called Costwise tug and barge designs from Ocean Tug & Barge Engineering of Massachusetts. The cost of each combined unit was reported as being about $75 million.

Each of these tugs is powered by a pair of medium-speed Wärtsilä 9L32 main engines, rated at 6,050 hp at 750 rpm and turning Lips controllable-pitch propellers mounted in Kort nozzles with independent triple-shutter rudders. The engines are set up to burn either marine diesel oil or heavy fuel, depending on operating circumstances.

Electrical power is produced by three 250-kW Cummins auxiliary power generators with backup provided by a 250-kW emergency generator.

These Costwise tugs have tankage for 214,000 gallons of heavy fuel oil and 60,500 gallons of diesel fuel. Power plants of this caliber are potentially consuming up to 35 tons of fuel per day when operating at full capacity, according to the designer.

Although these first two OSG super-ATBs are seemingly designed for far-reaching capabilities, for the present they are both earning their keep lightering crude oil from supertankers anchored near the mouth of the Delaware. From the anchorage, the tugs move the lightered oil upriver to any of a half-dozen refineries. More than a million barrels of crude oil are transported up the Delaware to these refineries each day, according to regional shipping reports.

OSG, which acquired Maritrans Operating Partners in 2006, continues to be the dominant lightering company on the Delaware. On a broader scale, the company operates a worldwide fleet of more than 100 full-size tankers including a dozen U.S.-flag tankers.

By Professional Mariner Staff