Abstract: A cutting-head suction-dredger comprises a floating body, a ladder and a cutting-head carried by the lower end of the ladder. The ladder supports against the floating body through a rail guide which is adapted to tilt with respect to the floating body and which extends in the direction of length of the ladder. This prevents that the engagement of the cutting-head upon the ground is disturbed during heaving movements of the floating body.

Abstract: A dredging pipe assembly includes at least two rigid sections physically connected together by a cardan joint and connected for fluid continuity by a pair of flexible sections disposed in spaced apart relation with the cardan joint between them. A flexible duct serving additional equipment bridges the cardan joint without interfering with the flexible sections.

Abstract: In a suction dredger, the connection between the water tube flange and the water duct flange is more reliable in operation, if the slush tube is adapted to turn by means of a rotary gland with respect to the slush tube flange to be rigidly coupled with the floating body, with the slush tube flange being connected through an arm with a water tube piece, while the water tube piece is connected through a flexible tubing with the water tube.

Abstract: In a method for drawing at least one fraction of solid substance by suction from a heterogeneous stock of several solid substances, which are segregated according to granular size and/or specific weight by supplying a segregation fluid, for example water, into a segregation zone at a distance from a suction nozzle of a suction pipe held in the stock, a selected fraction of segregated solid substances together with the fluid being conducted away in the form of a suspension through the suction nozzle water is vigorously injected into a ground layer for washing out the soil so that a fraction of fine grains is picked up in a whirl and can thus be directly sucked off through the suction pipe. With this method it cannot be avoided that both fine and coarse grains are sucked up together by one and the same suction nozzle.

Abstract: A suction dredger, comprising a vessel and a suspension conveying conduit provided with a pump and having a nozzle suspended by means of at least one cable of a lifting device on the vessel is improved for preventing breaking of the cable or damage of other dredger parts. To this aim the lifting device comprises a cable length variator delivering cable and each time hauling essentially all delivered cable in work condition with a high cable tension being lower than the inadmissible cable tension, but being higher than a predetermined low cable tension, in order to prevent an inadmissible cable tension during a downward ground reaction upon the nozzle.