Its design causes it to float higher in the water, allowing it to travel up the Delaware's 40-foot-deep shipping channel to Sunoco's refineries with more crude on board than other tankers.
Sunoco has chartered the ship for three years from Concordia Maritime AB, of Sweden.
"We have been developing this ship side by side with Sun Oil for years" to come up with the best possible design for use in the Delaware, Lars Carlsson, president of Concordia, said.
It is loaded with features that make it the safest oil carrier in operation, Carlsson said. In addition to double hulls, which are required by law, the Stena Vision's safety features include two separate engine rooms, two rudders, and two propellers - instead of the usual one.
Carlsson said the ship, which was built by Korea's Hyundai Heavy Industries Co. Ltd., cost $75 million, about $10 million more than a standard vessel of this size because of the redundant systems and other safety features.
"It will take us 20 years to get that money back," he said.
Sunoco has brought 80 standard two-million-barrel ships up the river since 1996. But each had to be lightered once about 60 miles off shore and again at the Big Stone Anchorage near the mouth of the Delaware Bay.
Lightering moves some of the crude from the tanker to barges. With less weight on board, the ship rises and can travel through the shallower channel.
The Stena Vision has to be lightered only once, at Big Stone Anchorage - like the 15 one-million-barrel ships that deliver most of the crude to Sunoco's Philadelphia and Marcus Hook refineries each month.
"We wanted a ship that could carry two million barrels, and act like a million-barrel ship," James Fidler, Sunoco's vice president of distribution operations, said.
The Stena Vision is part of a trend toward larger vessels, including oil tankers, container ships, and dry-bulk carriers, Dennis Rochford, president of the Maritime Exchange for the Delaware River and Bay, said.
The Stena Vision's 25-member crew, under Capt. Nedjeljko Kapetanovic, made the 5,400-mile journey from the port of Qua Iboe in Nigeria to the mouth of the Delaware Bay in just under 14 days.
Eight to 10 nationalities are represented on the crew, which will head out today about noon for the trip back across the Atlantic. Its 17 cargo tanks will be empty.
Accommodations for the crew members, who work six months and then have three months off, include a small swimming pool and a basketball hoop.
The ship's panoramic bridge, 80 feet above the deck, looks like something out of Star Trek, with a pair of raised seats for the captain and the navigator. The seats have tracking balls and buttons on the armrests so officers can operate a panel of computers to monitor navigation, propulsion and cargo.
In a nod to tradition, the floor of the bridge is covered with West African teakwood.
The Stena Vision will make 10 to 11 round-trips a year, replacing two of 15 deliveries Sunoco receives with one-million-barrel ships, Fidler said. A second ship in the class, the Stena Victory, will arrive in Philadelphia for Sunoco in October.
Harold Brubaker's e-mail address is email@example.com.