Exxon’s new Alaska tankers described

More details are emerging about the pair of new double-hull tankers ExxonMobil’s shipping affiliate, SeaRiver Maritime Inc., has ordered to carry Alaska North Slope crude oil.

The tankers will be driven by a single diesel engine, says an article in the September newsletter from the Prince William Sound Regional Citizens’ Advisory Council, a Valdez-based industry watchdog organization.

“While the ships will not be constructed with double propellers, engines, or rudders, a SeaRiver representative indicated the design does include other navigational and propulsion redundancies,” The Observer newsletter article says. “Specifically, SeaRiver has tried to eliminate the possibility of single points of failure leading to loss of power or navigational failure. This will include items like the inclusion of redundant engine cooling water, installation of additional low fuel level alarms and increasing the reliability of things like fuel flow meters.”

The new tankers will be designed to operate in the North Pacific for a minimum of 25 years without suffering hull metal fatigue.

The newsletter article also says the ships will be among the first U.S. oil tankers built to meet specifications under “common structural rules” the major ship classification societies issued in 2006.

2014 delivery

On Sept. 29, ExxonMobil announced that SeaRiver had signed a $400 million deal with Aker Philadelphia Shipyard for the two new tankers.

Construction of the 820-foot, 115,000 deadweight ton tankers is expected to begin by mid-2012. The vessels are scheduled for delivery in 2014.

Each will have a carrying capacity of 730,000 barrels of crude.

That’s about 12 percent less than the capacity of the two SeaRiver tankers to be replaced, the Kodiak and the Sierra.

While the Kodiak and Sierra are double-hulled, they are old, built in the late 1970s.

—Wesley Loy