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Multiple ways to salvage a sub. Only one way to beat the winter.

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The case

On August 12, 2000, a devastating explosion sank the Russian nuclear submarine Kursk in the Barents Sea. The Kursk hit the seabed 108 meters below, driving its bow 2 meters deep into the clay. Mammoet was awarded the salvaging contract in May, 2001, with the winter weather starting in early October. Within a 3-month period, over 3,000 tons of tailor-made equipment was designed, fabricated, installed and commissioned onto a barge which was mobilized to the Barents Sea in August.

Creative engineering at the bottom of the sea. 

The wreck of the Kursk had to be raised before the winter weather made salvaging impossible. The submarine’s bow was stuck so deep in the seabed, the biggest concern was that the heavily damaged bow might break off and destabilize the lifting process.

Apart from the delays a break-up would cause, it would also be extremely dangerous. The Kursk still contained a number of unexploded torpedoes and 24 cruise missiles – not to mention two nuclear propulsion reactors.

The tailor-made approach greatly improved safety and control.

Kursk

To safely raise the sub, Mammoet conceived a daring plan to first cut off the bow at the bottom of the sea. Using a tailor-made cutting wire that was hydraulically pulled back and forth between two suction anchors, the bow was sawed off in 10 days.

With the Kursk now free for lifting, 26 holes were cut in the hull to accommodate special lifting plugs. Each plug was connected to a set of strands that were gripped by a strand jack on deck of the barge above. The jacks were combined with heave compensators to offset the wave motion of the barge. This greatly improved the safety and control of the lifting process.

2000 The Kursk before the tragedy

Sept 2001 26 heave compensated strand jacks ready for action

Oct 2001 The Kurks pulled free, hanging under the barge

Oct 2001 The barge combination just before entering the dock

On October 8, 2001, the Kursk was pulled free from the seabed and raised to a level just below the surface - hanging under the barge. After the Kursk was towed to Murmansk, the lifting barge was raised out of the water by two additional tailor-made submersible barges, in order to set it down in the dry dock.

Fourteen months after that disastrous August morning, the Kursk and its crew were finally home again. 

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