Overflow systems

Overflow systems are designed to optimise the efficiency of the dredging process by ensuring the maximum retention of solids in the hopper in parallel with fast discharge of water overboard. The overflow system must thus optimally encourage separation of solids and water. This it does by reducing mixture turbulence and giving the solids maximum time to settle. It must naturally also be able to handle the volumes dredged.

An overflow system generally consists of a fixed outer part and a sliding inner part, both tubular. At the top of the moving part is a cone or rectangular shaped weir the purpose of which is to obtain a non-turbulent, uniform flow to encourage settling. The moving part is raised or lowered by means of a hydraulic cylinder attached to the fixed part. The travel of the moving part is matched to the desired minimum and maximum overflow levels. The stroke can be enlarged by the use of a telescopic three part overflow.

Anti-turbidity

An anti-turbidity valve in the overflow duct controls the water level in and above the overflow. It slows water movement, and prevents the carry-over of air by reducing turbulence in the overflow pipe. It thus avoids the creation of a wide turbid wake.

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