Split hopper dredger conversion

Vlaanderen XXI

The split hopper dredger ’Vlaanderen XXI’ is frequently engaged in gravel dredging with delivery of the gravel to various North Sea ports between Le Havre, France and Flushing, The Netherlands. For unloading in the various ports, the Operational Manager used its own mobile hydraulic crane, traveling by road between these ports. This became highly unpractical. Therefore the Belgian owner DEME decided to equip the vessel with its own hydraulic crane.

Description of system

To install the Sennebogen hydraulic crane with grab, Vuyk Engineering Rotterdam was ordered to redesign the deck area for the conversion. Due to the split hopper discharge system, the crane support had to be placed on one side of the hopper and as close as possible to the centre line of the vessel. A construction was created in the centre of the hopper area to support the crane foundation on SB side. The existing overflow duct had to be relocated to the centre of the hopper. To avoid contact between the crane and overflow duct during splitting, the overflow was also placed on the SB side. The large hole in the construction, serving as crane foundation warranted a FEM calculation to ensure the necessary strength in all directions.

The loading piping was redesigned, because of the relocation of the overflow duct and the limitation of the original system for sand and silt only. Loading openings were positioned at the fore and aft side of the hopper area. Overboard discharges with grids were created to wash a substantial amount of sand overboard before the gravel enters the hopper. Finally an inclining test was conducted and a new stability booklet, approved by the Flagstate Authorities, could be handed over to the Operational Manager. Early September 2007, the vessel’s trails were successfully executed and the vessel is now fully operational again.


Principal dimensions

Length overall

76,02 m

Breadth moulded

14,50 m

Depth moulded

5,00 m


Hopper capacity

1 635 m³

Hopper load

2 289 t

Dredging depth, maximum

33,00 m

Vuyk scope of works

On behalf of DEME Building Materials, the following engineering was performed by
Vuyk Engineering Rotterdam for this conversion:

  • Inclination test and stability calculations
  • Finite Element Method calculations for foundations hydraulic crane
  • Re-arrangement of delivery pipes above deck
  • Check of vessels’s longitudinal strength
  • Re-integration of vessel’s hopper overflow system



Classed by Bureau Veritas as a I HULL MACH AUT-UMS DYNAPOS AM/AT R CLEANSHIP 7+ UnrestrictedNavigation


An air-conditioned accommodation space is arranged above main deck in the fore ship suitable to accommodate 70 persons. All cabins have an integrated wet space.

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