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Blue Nodules: harvesting at 5.5km depth

Aug 16, 2022 2:15:00 PM / by Peter Brussee

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The EU aims to reduce dependency on imports of raw materials. ROVs and ROV Cables play an important role in harvesting such materials in European waters.


For a cutting-edge EU Research Project, DeRegt was asked to join an EU-funded consortium of 14 companies. Industry, research institutes and service companies across seven different countries joined forces.

Harvesting Polymetallic Nodules

The most important question of the research project was how to harvest deep-sea polymetallic nodules, avoiding serious harm and minimizing the environmental risks.


Polymetallic Nodules contain relatively high concentrations of Nickel, Copper and Cobalt. Cobalt is especially valuable to harvest since it is used in batteries for electric cars. Nodules occur at any depth, but the highest abundance has been found between 4,000 and 6,000m. How do you harvest these nodules at such depths? 


DeRegt’s challenge, as a cable solutions company, was to develop and test a unique deep-water umbilical to link into pumps and the mining tool.


Power and communication over 5.5 km

blue_nodulesThe system can be best compared with a giant vacuum cleaner with a 5.5 km long hose. The vacuum cleaner, called the harvesting system, collects the nodules from the seafloor. Six powerful pumps, called booster stations, transfer the nodules through a 5.5 km long vertical transport system to the surface vessel. The umbilicals connect the booster stations and the harvesting system to the vessel’s power supply and allow data transmission. It interacts with the system at many different points. We had to provide connectivity and an automated clamping system along the entire 5.5 km vertical transport system.



Common design

One of our main challenges for the sake of economic viability and sustainability was ensuring that we had a one-fits-all solution. The same design for each of the sections of the vertical transport system was selected. So that if a part needs to be replaced or you need to cut back, you can simply replace a single part and shift the other components.


Learn more about the challenges and the needed collaboration in this video:

Automatic clamping system

For safety reasons, no human interference was allowed, so we needed to develop a clamping system that allows the cables to be fixed to the vertical transport system. Therefore we’ve developed a system that automatically clamps and de-clamps the umbilicals along the 5.5 km long hose during the launch and recovery of the system. An innovative method was used to minimize the mechanical loading onto the umbilicals and vertical transport system.


The umbilicals contain a double steel armor to transfer loads and to protect the electrical and optical components from crushing. Fragile components are placed towards the center of the cable. For corrosion prevention, we’ve jacketed every single steel wire. This means that if the cable is damaged and its water tightness is compromised, it will have a minimal impact on its durability.


The Ultimate ROV Cable Guide

Each ROV Cable Design is different, and every subsea project requires its specific specifications. In our Ultimate ROV Cable Guide, you can read everything there is to know about projects like these, ROV cable construction, and trends in the ROV market. 


For any questions about ROV Cables, schedule a meeting with me here or download the Guide below for free:

Download the Ultimate ROV Guide


Topics: Naval cables, Innovation, Raw materials, Subsea, Deep-sea cables, Deep sea mining

Peter Brussee

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