Innovation in Dredger Technology

Dredging is a highly specialised business - and often an essential one for many harbours and rivers around the world. One particular country, The Netherlands, has a permanent need for ongoing reclamation projects. Among Dutch new smaller types of dredgers are twin sisters, Waterway and Coastway, completed last year and earlier this year respectively by Merwede Shipyard at Hardinxveld-Giessendam. These two trailing suction hopper models have very unusual dimensions, aimed at allowing them to work in very confined areas and particularly very close to beaches.

They have a very wide beam and shallow draught - the length/breadth ratio is exceptionally low at 3.656, while the breadth/draught ratio is conversely high. A requirement to operate in exceptionally shallow water and particularly to conserve as much energy as possible (avoiding losses during conversion from mechanical to electric drive) has called for some novel dredge pump drive. The single IHC dredge pump is driven from a long shaft off the free end of the starboard main engine. A similar shaft is fitted to the port engine to power the jet pumps (needed to fluidise and help remove any stuck spoil in the hopper). Any disadvantage from the use of a directly driven dredge pump is mitigated by a new type of planetarygearbox from IHC; this enables variable output speed to be chosen over two ranges but at constant input speed from the main engine.