The conditions for extracting sand and gravel depend on the location, extraction depth, soil character, water volume and the situation regarding existing buildings or ecological and environmental conditions.
For each situation Holland Dredge Design has developed a program of suction dredgers, air-lift dredgers, booster stations and soil pressure systems, designed for modular construction. This modular design for the large components, such as pontoons and power supply, not only generates flexibility, but also minimizes the costs for the user.
Within this modular system different configurations can be realized. Just like the big stationary systems, the small mobile suction dredgers can be mounted or dismounted within no more than 10 working hours.
All HDD dredgers are equipped with computer control in keeping with the latest technological developments for positioning, handling and extraction control. An optional satellite-supported dGPS navigation system can additionally be installed for the purpose of exact and reproducible positioning.
As the situation demands, there is a choice between three different pump drives:
- Direct diesel drive of the dredging pump
- Diesel/electric drive, all pumps powered by one diesel generator on board
- Fully electric drive with energy supply from the shore
The fully electric driven system complies with the strictest environmental standards with regard to sound insulation, emissions and water pollution. The energy for stationary suction dredgers can be supplied with the aid of the energy net ashore. The energy supply for mobile dredgers can be effected by a generator located in a container ashore which is sound insulated.
All electric dredgers are equipped with frequency control. Thus it is possible to power the pumps at constant speed using a generator or the energy net, whereby the speed of single pumps can vary.