Big claw makes marine salvage safer

Trelleborg, Sweden – Watching the VB 10000 in action is quite a sight. Four giant white C-shaped truss structures with prongs at the bottom, dubbed ‘the Claw’, hang below two massive yellow arched trusses, spanning a pair of barges measuring 22 by 88.5 metres (72×290 ft). Bearings are critical to the unit’s operation.

The Claw is designed to reach hundreds of feet below sea level to remove sunken oil rigs from the seabed, in one piece and in one day. It’s also designed to lift the heaviest of loads. Although most oil rigs weigh between 1,000 and 3,500 tons, the VB 10000 can lift 6,000 tons in its current arrangement, and when in double grapple configuration, it can lift as much as 10,000 tons.

“It’s a game changer,” says Paul Van Kirk, project engineer with salvage specialist Versabar, which built the Claw. “The industry has never seen anything like it. We can now retrieve platforms that have been knocked over by hurricanes without sending divers down to rig them up. That saves time and money.”

The materials used for bearings in several key locations are a significant part of the vessel’s innovation, says Van Kirk. Its predecessor, the smaller VB 4000, originally used bronze bushings in the critical hinged gantry and barge connection. The bushings required regular maintenance for lubrication, wore out quickly and made a lot of noise. “When we started the design process for the VB 10000 we knew we wanted to use Orkot,” the Versabar engineer explains, referring to a lightweight and durable composite material developed and manufactured by Trelleborg. “It’s maintenance-free, easy to install, flexible and quiet. It just has a good track record.”

The VB 10000 uses Orkot material for its bearings in the gantry and barge connections and the sheaves in the blocks used to open and close the Claw. “The material is perfect for the job,” says Jason LaBorde, sales engineer with Trelleborg, who worked closely with Versabar’s engineers to get the heavy lifter built. “Orkot is designed for heavy loads and slow movements in a seawater environment. It’s both resistant to UV rays and corrosion.”