The capability of an explosive cutting tool has been dramatically demonstrated during the sinking of a Portuguese naval warship to create an artificial reef.
The corvette Afonso Cerqueira, which was retired from service in 2015, was sunk 450 metres off the coast of Madeira.
SABREX™, an explosive cutting charge, was used to cut 16 x 1 square metre holes out of the ship’s hull under the waterline. She sank in less than 100 seconds.
“We needed to rapidly and very precisely cut holes big enough to allow in the water, but without weakening or damaging any of the superstructure. The idea is for the ship to remain intact and upright to help improve biodiversity and develop underwater tourism,” said Chris Smith of Chemring Energetics UK (CEUK) who manufacture SABREX™.
The company worked closely with the regional government of Madeira, the Portuguese Navy and contractors Tecnovia Madeira on the project.
SABREX™ is supplied globally by CEUK from its site in Ardeer on Scotland’s west coast, where in 1871 Alfred Nobel – the inventor of dynamite and founder of the Nobel Prize – built the world’s largest explosives factory.
“Its use is pretty well limited to the user’s imagination. By delivering a fine, fast and accurate shape charge jet, SABREX™ is a cutting tool that can be used for anything that needs cutting quickly, accurately and precisely,” said Mr Smith.
It is easily formed to fit complex target shapes and designed to cut some of the toughest man-made and natural materials. “The project in Madeira demonstrates its potential in marine salvage operations. SABREX™ has excellent underwater capabilities with very minimal preparation,” said Mr Smith.
SABREX™ can be used in depths of 12m with no adverse effect on its performance and has been used to sever 25mm of steel plate at a depth of 25m. It is supplied in lengths of 4m in six different sizes, allowing the engineer to minimise the Net Explosive Quantity (NEQ) needed to sever the target. A single length of SABREX™, for example, can be used to sever an I-Beam.
The specialist explosive used on the Afonso Cerqueira, which will become a haven for marine wildlife as well as a destination for diving enthusiasts, was put in place by a team of Portuguese Navy Explosive Ordnance Disposal divers. They first used SABREX™ two years ago when another corvette – the General Pereira d’Eça – was sunk to form another artificial reef.
Just hours before the scheduled sinking, it was discovered that the vessel was lighter than anticipated and therefore floating higher in the water.
“The charge locations had to be changed at the last minute to ensure that they were correctly positioned below the waterline. With SABREX™ that was a very easy straight-forward job,” said Mr Smith.
The Afonso Cerqueira’s project manager Alberto Braz – a former senior Portuguese military officer – said the Explosive Ordnance Disposal divers appreciate both the quality of SABREX™ and how easy it to use. “They are completely satisfied with this method,” he said.
Paolo Oliveira, from Madeira’s Institute of Forestry and Marine Conservation, was in charge of the operation. “With this technique it’s very quick, it’s very precise. The boat goes exactly where we want. So I think it’s the best choice and also with little impact on the ecosystem around it,” he said.
With diving tourists already exploring the Afonso Cerqueira, Mr Oliveira is confident that the Regional Government of Madeira will soon see the financial return on the project and plans are already underway for two more warships to be sunk.
The Portuguese Navy’s Chief of Staff of the Navy, Admiral António Mendes Calado, said: “It’s a very beautiful way to end our ships. They continue, even after being disarmed, to serve as sources of life in our seas.”
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Demolition and Recycling International