International Dredging Review

International Dredging Review

De Groot Nijkerk Dredging Equipment has delivered a plain suction dredge to the Dutch construction company Infracon. The model EDPZ300 dredge can dig to 35 meters (115 feet) is driven by shore power and is completely automated and remote controlled. Two DOP pumps are installed one submerged and one on deck as a booster. Infracon specializes in infrastructure such as roads and dikes. Prior to purchasing this dredge the company contracted all its aggregate but will now mine sand and gravel in several concessions along the Dutch/German border. The new dredge is working in a sand pit in Germany. .


All De Groot Nijkerk dredges are designed to suit the needs of the customer. Infracon specifically needed an electrically-driven stationary dredge in order to meet the strict environmental requirements imposed by the German government. The dredge is provided with a 250 kW drive on both the submerged pump and on the booster pump. The dredge pump and winch motors are frequency-controlled. Shore power is provided via an electrical cable running over the floating pipeline.


The DOP 3025 submersible dredge pump is used to win sand of an average grain size between 350 and 500 mu at a depth of 35 meters. The electrically-driven DOP pump is lowered to the right depth by a steel cable and winch. The DOP pump brings the material approx. 400 m3 of solids per hour to a booster pump. The material is pumped through a 300 mm discharge pipe to a sand classification installation on shore. The dredge pumps are identical in order to facilitate maintenance and stock control.


The dredge is fully automated i.e. radio-operated from land by the operator of the sand classification plant. The software automatically controls the dredging mixture concentration taking density readings to keep the dredging process stable and continuous. After the maximum dredging depth is entered into the system the dredge continues working until the depth is reached and alarms the operator when the dredge is to be relocated. The operator can monitor the dredging process (concentration flow vacuum pressure dredging depth) as well as all components as electric motors and frequency converters as their status can be read on the various |!|pages|!| on the screen.


The dredge has a void portside side-pontoon and the discharge pipe and booster pump are mounted on deck. The jet water pump is installed in the starboard pontoon. All electrical cabinets are placed in the main pontoon. The control cabin is mounted on the main pontoon in a raised position for a good overview of the situation. The DOP submersible dredge pump is hung in an A-frame. The main dimensions are: length 14 meters width seven meters draft 1.25 meters; diameter of suction and discharge piping 300 mm (approximately 12 inches.)

The entire dredge including automation and instrumentation was designed by De Groot Nijkerk Control the automation and instrumentation department of De Groot Nijkerk Dredging Equipment.

The company was founded 55 years ago in Nijkerk in the middle of the Netherlands. The company was founded in an area where new land was won from the sea (the large Flevopolder.) Beginning as a dredging contractor the company began building its own dredging equipment for themselves and others and eventually abandoned its contracting work in favor of becoming a dredge designer and builder.

The yard employs 60 people and the engineering sales purchasing and administration are located in the same location. The company’s product line includes cutterhead and plain suction dredges from 150 to 750 mm discharge trailing suction pipes from 350 mm to 900 mm diameter; diesel and electric booster stations all types of equipment with instrumentation and controls including density and flow meters suction tube position indicators and vacuum/pressure gauges.

Company directors are David Tenwolde and Jan Brouwer. De Goot Nijkerk is a member of the Damen Shipyards Group.