Delcon Marine & Industrial (DMI) in South Africa recently completed the electronic and electrical design & manufacture of a Control System for NAMCO’s new 190ton Sub-Sea Diamond Mining Tool. The mining tool is fitted with an 1800kW submersible dredge pump for pumping gravel to the surface processing plant via a riser system. The tool, fitted with a 500kW hydraulic power pack and a 500kW jetting motor, is a tracked vehicle with a movable boom and knuckle to control the position of the suction nozzle. An umbilical cable fed through a slip-ring assembly provides electrical power and control signals to the tool.

There are approximately 140 field instruments fitted to the tool for monitoring various pressures, temperatures, forces, positions and fluid levels. It also has a sonar system, a gyrocompass, lights and underwater cameras. A pilot controls the tool from the Surface Control Room where a 7-bay console is located. The console is fitted with various sonar and navigation displays as well as the main operating screens that include graphical animation as well as system mimics and maintenance information.
The Mining Tool’s electronic equipment is housed in an Electronics Bottle. Fibre optics is used as the primary communications medium between the vessel and the Mining Tool.

This provides immunity against interference generated by the variable frequency drive of the 1800kW dredge motor. Standard wire communications is also incorporated as a back up.

DMI has been involved with the project together with NAMCO’s design team, from the concept phase to final hand-over. DMI’s main areas of responsibility were for the development of the control software, the design and manufacture of the underwater and surface electrical hardware, including underwater cables, junction boxes and sensors. DMI was also responsible for integration and interfacing to equipmentThe Mining Tool was designed to operate to depths of 250m and was commissioned in December 2000. The complete system is now operational and mining.