More than two decades after innovating its first subsea crawler technology for diamond recovery, diamond major De Beers Group’s Upstream Technology business has developed its next generation of advanced subsea diamond recovery crawlers for use off the coast of Namibia.

Debmarine Namibia is a wholly owned subsidiary of Namdeb Holdings, which, in turn is owned in equal shares by De Beers Group and the government of Namibia.

The new crawler, following four years of development, was developed for Debmarine Namibia’s flagship vessel the Benguela Gem, marking a significant leap in marine diamond recovery capability, according to Cape Town-based Upstream Technology Next Generation Crawler (NGC) project manager Rudi Agostinho.

Agostinho says the next generation crawler represents a careful blend of automation, precision engineering and lessons from decades of operational experience to provide a robust platform for the future of marine diamond recovery.

“We have taken everything we have learned from earlier models and engineered a crawler that can operate with significantly enhanced efficiency, with greater reliability,” he says, adding that the upgrade allows the Benguela Gem to boost its effective rates by about 20% with minimal increase to operating cost. This extra capacity means the vessel can now fully benefit from the throughput capability of its onboard treatment plant.

A second identical unit is already being assembled so as to be ready to take over operations during scheduled servicing of the first, ensuring minimal downtime of subsea diamond recovery.

The new crawler is bigger than its predecessors, weighing 370 t and measuring 28 m long, and 8 m high and wide.

With a sweeping mining arm that covers a 21 m arc in just 25 seconds, it includes several powerful systems.

The crawler operates between 100 m and 135 m below the surface, drawing a combination of seawater, sand, gravel and diamond-bearing material through an 800-mm-diameter pipeline.

The goal was to extend engineering availability from 82% to 87%, supporting the drive for extra production, says Upstream Technology mining system specialist Sebastian van der Laer.

He points to the crawler’s new track tensioning system as a key innovation, where a hydraulic tensioning system automatically adjusts as conditions change, thereby reducing wear, extending the life of the track chain and improving gearbox torque.

Automation has been central to embedding consistent best-practice operation into the crawler, says technology development manager Imraan Parker.

“Automation enables more predictable performance and better control over the stresses on the machine which in turn extends its structural life,” he explains, adding that the high level of automation also extends to deployment of the crawler from the vessel.

Among the features is a forward-looking sonar system that provides clear images of the seabed allowing operators to recover right down to the footwall.

Innovation Hub

At Upstream Technology’s Cape Town facility, the building of the bigger crawler led to other innovations.

An example was evidenced by the lifting of the 47 t dredge motor into the crawler frame with two synchronised overhead cranes – a method now formalised for future builds, says senior workshop engineering officer Abdul-Gameed Davids.

Getting the completed crawler to the harbour took careful planning, according to senior project engineer Steven Smith, who adds that, once at the dock, a 750 t crane hoisted the crawler onto the quay.

Before going to sea, the crawler underwent full-scale land-based simulations to test all systems under realistic loads. The machine contains over 2.2 km of cabling and more than 10 000 connections, each of which was verified before departure.

Close collaboration with Debmarine Namibia’s operational team during assembly meant feedback from the vessel’s own operating crew could be incorporated.

“By combining advanced tools, adaptive systems, automation and predictive maintenance, we have delivered a crawler that will recover more material, more consistently, with less downtime, even in tougher conditions,” he says.