Wednesday, 15 January 2014

Semi-submersible vessel to give Concordia a lift

Semi-submersible vessel to give Concordia a lift

By Tom Stieghorst
*InsightOne of the more amazing sights when the space shuttle program was in its prime was the 83-ton shuttle atop a Boeing 747 being ferried from its landing field at Edwards Air Force Base in California. The shuttle needed an assist because, other than its launch and return from earth orbit, it could not fly on its own.

Something similar may be in store for the partly raised Costa Concordia cruise ship. The salvage team for the Concordia has secured an option to use the Dockwise Vanguard to transport Concordia, which would be a first for the world’s largest semi-submersible vessel.

Dockwise is a Dutch firm that specializes in semi-submersibles. The vessels fill their ballast tanks to sink below a cargo, and then expel water to float them on large, flat cargo decks.
*TomStieghorst

The Dockwise approach offers time and energy savings over towing large loads. Yacht captains have been using the Dockwise for years to transport their boats on long-distance journeys, saving wear, tear and crew costs.

But Dockwise Vanguard was not built for small payloads like mega-yachts. It was built to transport marine oil- and gas-drilling rigs, such as the Chevron Corp.'s 53,000-ton Jack/St. Malo oil platform, which it ferried from South Korea to the Gulf of Mexico last year.

The Concordia would be a bigger bite. According to the salvage team, Concordia will weigh about 75,000 tons, or about 1.5 million pounds, once it is refloated this June.

Dockwise Vanguard can handle it. The 900-foot-long ship, which was delivered last year, has a rated capacity of 110,000 tons. Of course, such a unique vessel doesn’t come cheap. The salvage team has paid $30 million just to secure an option to use the Vanguard for the job.

Without it, the Concordia would be towed in the conventional manner to port. But the seaworthiness of a ship that has been lying on its side in the ocean for two years is an open question.

What would it look like? You can see an online animation by Boskalis, the Dutch parent company of Dockwise, which shows how the Concordia would be loaded on Vanguard.

For the cruise industry, it can’t happen too soon.