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We move everything. With massive strength.

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Iaan Du Toit
Regional Engineering Manager
Hytec/Bosch Rexroth in South Africa

Welding torches are glowing, hammer strokes booming, and everywhere the buzzing of giant screwdrivers can be heard: The MV Coral Sea is getting a complete overhaul at a dockyard in Cape Town, South Africa. For three years, she was travelling non-stop off the Namibian coastline for Debmarine Namibia, to explore the ocean floor for gemstones.

“We are overhauling and modernizing the entire hydraulics equipment within a span of only five weeks”, Iaan Du Toit said. He works for Hytec, a company in which Bosch Rexroth holds a share since 2014. He knows the MV Coral Sea particularly well: In 1991, when the former oil drilling ship was transformed into a vertical diamond digger in Cape Town, he was working right along. Even then, De Beers counted on Bosch Rexroth hydraulics. The vessel has remained in class with American Bureau Shipping (ABS) throughout this period.

With a 1000 kW central hydraulic power unit, those hydraulics are the heart of this hardworking vessel. “It provides the power for material handling, compensates the wave motion, and keeps the vessel on course”, Du Toit explains. To search the ocean floor for gems, anchors are dropped onto the ocean floor like a net in the exploration area, covering a radius of up to four kilometers.

The anchor winches with hydraulic drives by Rexroth pull the MV Coral Sea across the exploration corridor slowly and with precise control. A 500mm diameter solid drill pipe descends from a tall steel tower to the ocean floor 90 to 140 meters below. Like a vacuum hose, it sucks up the detritus from the ocean floor to the surface via airlift. Here, the raw diamonds are separated.

The vessel has active wave compensation to keep the drill head on the sea bed at all times in choppy waters. “Even with swells up to four meters high, the drill head always is kept and remains with the correct weight because two hydraulic cylinders compensate for the wave motion”, said Du Toit.

“Our unique portfolio and application experience allow us to conquer even the most complex projects”, said Du Toit. The MV Coral Sea's modernization requires a large degree of joint planning with the client and streamlined project management for the reconstruction so that the vessel is ready for service on time after nine weeks of reconstruction.

During the modernization process, Hytec specialists remove all hydraulic cylinders and replace them with new ones or refurbish them so that they are just like new. “Corrosion protection is of utmost importance because the cylinders are constantly exposed to salt water”, the engineer explains. A Rexroth Enduroq 2200coating is capable of protecting them against corrosion for at least five years.

When the vessel is leaving the ship yard towards Namibia, a Rexroth specialist will be on board for the first ten days to accompany the start-up operations. In the meantime, Du Toit is already planning the next modernization of another one of the six De Beers mining vessels.