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Metal Cutting - Traditional Machining

Kursk Bow Was Cut By New Sawing Technology

In September 2001 when the Mammoet-Smit salvage team succeeded in cutting off the bow from the nuclear submarine Kursk, they used a new cutting method developed by Smit's research and development department.

Close up of the sawing element cutting through the Kursk
Close up of the sawing element cutting through the Kursk

The submarine's 20-metre bow section was severely damaged by an explosion in the torpedo room.

Because of the section's structural instability caused by the explosion, it had to be removed before lifting could begin.

Two suction anchors were placed about 20m from each side of the submarine. These anchors consisted of two cylinders with a suction pump unit that gradually reduced the pressure inside the cylinder. This caused the suction anchors to work their way into the seabed. As the anchors moved deeper and deeper into the soil, pressure was exerted onto the sawing element, which was tensioned over the hull of the submarine. This sawing element was pulled from side to side through the submarine's thick, high tensile steel hull.

The sawing element consisted of a series of circular shaped bushes, linked by high-tension steelwire cables. The bushes were covered with a special abrasive material made from sintered grit grains, as hard as diamonds.

The cutting system is a patented invention based on Smit's in-house method of cutting shipwrecks. The traditional method involved the use of heavy steel chains and a large sheerleg crane. The sheer force of 300 to 500 tonnes exerted by the crane renders the chain a cutting element.

This method, though successful, caused damage not only to the ship being cut but also to the sheerlegs, as the crane would experience great shock loads during the cutting process.

Smit began researching a quicker and more cost effective cutting system a year before the Kursk disaster in association with Rotterdam-based tungsten carbide tool manufacturer Widia Nederland and research body T.N.O. Nederland. After securing the contract to lift the Kursk, Smit started working on a variant of the prototype cutting system as the original was surface based and designed to cut shallow water wrecks in depths to 30m.

After several modifications, an underwater drive system was developed and the cutting wire strengthened.

Following its Kursk deployment, a more compact and lightweight version of the cutting system has been developed, suitable for a wide range of salvage and wreck removal tasks.

It is expected to improve viability of a number of wreck removal operations.

Tel: 00 31 10 4549911

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Stevens Rowsell is a specialist precision sheet metal engineering company in East Sussex