Submarine ‘crawlers’ save diamond industry | Mining | ocean technology | submarine mining | oceanic resources | big five of ocean colonization | New-Atlantis™ | Wilfried-Ellmer-Group™ | oceanic business alliance™ | oceanic invest | marine networking | key player network |
19 June 2014 | Allan Seccombe
DE BEERS is using a 286-tonne machine to suck up diamonds from the seabed off the Namibian coastline. Over the past decade the company has advanced the technology that has saved its marine mining business, but which has come too late for its South African sea venture.
De Beers Marine Namibia uses two machines, called the Green Crawler and the Orange Crawler, each more than four times heavier than a main battle tank, to suck diamonds out of sediment up to 6m thick in a 6,000km2 concession area south of Lüderitz.
The crawlers, which are individually used at depths of about 150m, are rotated annually for maintenance in Cape Town.
These are the third generation of the machines, which dwarf anybody standing next to them, and they extract 500,000 carats of diamonds a year, half of Namibia’s diamond production.
But it is their efficiency and reliability that have been a key factor in saving the marine side of the De Beers business in Namibia — although they were unable to make mining off the South African west coast viable; it was suspended in 2010 after three years.
The licences for areas between the mouths of the Orange and Buffels rivers are held by De Beers Consolidated Mines (DBCM), the South African mining arm of the Anglo American subsidiary.
“DBCM has applied for a closure certificate for the South African Sea Areas,” Domingos Valbom, the GM of De Beers Marine, said on Wednesday.
That could have been the fate of the Namibian marine business if not for the step-changes made in the performance of the crawler during research and development by De Beers Marine, which provides technical, exploration, maintenance and sampling services to De Beers Marine Namibia.
“The crawler has driven up the economics and sustained the life of mine way beyond what you might otherwise be able to do,” says Kevin Richardson, manager of research and development at De Beers Marine.
“The marine mining business would probably have ended in the mid-2000s had it not been for technological improvements. It would have been a loss-making venture had it not been for the major technological changes that have come along,” he said, referring to the crawler.
A decade ago, an earlier generation crawler mined about 250m² an hour. There has been a fourfold improvement to 1,000m² an hour.
The sediment is pumped onto a ship, the Mafuta, where it is processed. The processing plant treats up to 140 tonnes an hour, meaning between 400 and 860 tonnes of waste are being pumped overboard.
There are five mining vessels in the Namibian fleet, including the Mafuta. The other four ships use large-diameter drills attached directly to the hulls to stir up the sediment and pump it to the surface, and these can generally produce between 180,000 and 200,000 carats a year.
One of the key areas the research department is studying is a way to sort the material before it is pumped onto the ship, Mr Richardson says.
The plant will be upgraded in two years to make adjustments, possibly in the nozzle sucking up the sediment, resulting in increased volumes, he says.
The crawler, operated by a pilot on board the Mafuta, has a utilisation rate of more than 70%, up from the mid-50% range when De Beers first started work with crawlers. The researchers are investigating ways to iron out any inefficiency in the way the crawler operates, sweeping an arm with the vacuum nozzle in a 22m arc.