OSVs find new lives as dredgers
Delivered to Netherlands-based Jan De Nul Group, Giovanni Venturi is a newly converted water-injection dredger capable of a maximum operating depth of 27.5 m and water jet pump flow rate of 16,000 m3/hr.
“The conversion of the first offshore supply vessel to a water-injection dredger has been a complex and challenging project for both shipyard and owner,” said Jan De Nul Group technical division director Frederik Deroo. The conversion was performed by Singapore’s PaxOcean Shipyard.
Giovanni Venturi is the former Surf Perwira, originally built as Bourbon Liberty 117 at Dayang Shipbuilding in Yangzhou China in 2010. It was part of series of anchor handling tug supply (AHTS) vessels built for France’s Bourbon Offshore based on a GPA 254L design from Seattle-based Guido Perla Associates Inc. Each AHTS vessel had an overall length of 59.8 m, beam of 15 m, depth of 5.5 m and draught of 4.3 m. Built with dynamic positioning class 2 capability to ABS class, each AHTS had diesel-electric propulsion with two azimuthing stern thrusters, one fixed stern thruster and two bow thrusters for manoeuvrability and station keeping.
The design also moved the engineroom to the main deck, creating more space below deck for cargo capacity.
In its new role, Giovanni Venturi will perform water-injection dredging (WID), a hydrodynamic technique in which the dredging sediments are not removed from the channel or seabed. Instead, water is injected by the vessel from a horizontal bar onto the river bed, creating a layer of fluidised sediments that are carried away by the waterway’s natural currents and forces. WID eliminates the need to excavate and transport dredged material by hoppers or barges.
Two other OSVs, Henry Darcy (built as Bourbon Liberty 111 in 2008) and Henri Pitot (built as Bourbon Liberty 110 in 2008) are being converted by PaxOcean Shipyard for delivery to Jan De Nul in Q2 2019.
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