Smit Salvage has developed a new, patented wreck removal cutting system that is designed to be fast and cost effective, and was used during the successful recovery of the Russian submarine Kursk last year.
The new system utilizes a special abrasive cutting wire — a series of grit-covered bushes mounted along a high-tension steel cable. This wire can then be positioned over a wreck and connected up to a drive system producing a sawing motion. Highly efficient, this cutting system can be used as an alternative option to the traditional chain-cutting method that uses heavy steel chains and floating sheerlegs.
According to Theo Hak, Smit Salvage Logistics and Technical Support Manager, "The new system can reduce project duration by up to 30 percent, and in addition, is easy to transport and suitable for a wide range of salvage and wreck removal tasks."
The cutting system was developed in association with Widia Nederland, a Rotterdam-based manufacturer of tungsten carbide tools, and T.N.O. Nederland. The original prototype was developed as a surface-based system for salvaging shallow-water wrecks at depths of up to 99 ft. (30 m). Subsequent to the Kursk contract, Smit modified the system for deep-water work and added an underwater drive system. Cutting wire was also strengthened to increase wear resistance. Prior to its deployment for the Kursk operation, the system's efficiency was demonstrated during trials in Rotterdam when it was used to cut an obsolete dredger into scrap.
Following an explosion in August 2000, the Kursk and its crew were lost in the Barents Sea. As a result, the submarine's bow sustained severe damage and had to be removed prior to the lift.
This practice was a challenging one, due to the water depth 354-ft. (108-m), adverse weather conditions and the thickness and hardness of the submarine's hull.
Cutting then commenced with the positioning of the wire over the Kursk's bow. The wire was then connected to two anchor points on the seabed — positioned 66 ft. (20 m) to each side of the hull. Each anchor point was comprised of a hydraulic cylinder and suction pump — the actions of the pumps caused the anchors to "bury" themselves into the seabed. As the seabed was penetrated by the pumps, pressure was exerted on the cutting wire, which moved in a sawing motion across the submarine's bow section. Despite the adverse conditions, the system was able to complete the cutting operation in 31 hours on September 13, 2001. The seabed's high stone content caused significant friction, thus causing several guide cables to part. This was corrected through the installation of closing plates around the sheave assembly — thus preventing direct contact with the seabed. Concurrently, the cutting wire demonstrated greater wear resistance than indicated in the initial tests and was replaced after 12 hours of intense cutting.