Ballasting Mission Ship Dawn
Customers interest
Humanitarian support vessel Dawn began life as a Damen Platform Supply Vessel 3300 CD. Her transformation is executed at Damen Shipyards’ facility in Amsterdam, where she’s expanded with a steel superstructure, completed with two heavy-duty cranes and helipad. How do you restore stability to a ship whose center of gravity has shifted too far towards the bow due to her conversion? In what way can solid ballast be installed in water ballast tanks, retaining her original functionality to trim the vessel with water ballast?
Conditions
Calculations done by Damen, resulted in the project scope for delivery and installation of a ballast mass of 40 tons each for tanks SB and PS. As the tanks retain their original functionality, supply and discharge of ballast water shall proceed unhindered and the tanks need to stay accessible for visual inspection. Accessibility of the tank limits the fill height at 0.95 meter. A wooden formwork at the water inlets guarantees proper functioning of the pump system.
The scope is completed with the installation of solid ballast in the skeg, with a total mass of 110 tons. With an available volume of 28.7 m3 and a obtained fill rate of 90%, the target density is 4,259 kg/m3. The skeg consists of 20 interconnected compartments and a total of 7 strategic located fill points.
Milestones
Water ballast tanks SB and PS
- Installation of 65 tonnes of heavy concrete in tanks PS and SB
- A concrete density of 3,060 kg/m3 (191.03 lb/ft3), with a of fill height 0,90 m
- Free access to the tanks and pump holes remains
- Simultaneous installation in both tanks, using 2 identical sets of pump equipment on both sides of the dock and live communication between the installation crew
Skeg
- Design theoretical mixture compositions, selection of the most suitable raw materials and laboratory tests
- Full scale test to determine the exact ballast composition and pump settings
- Installed mass of 103 tonnes solid ballast with a density of 4,260 kg/m3 (265.94 lb/ft3)
- Theoretical fill rate of 84% v/v
- Pipe length between the pump and the skeg approximately 80m
