The present invention concerns a device for removal or extraction of non-consolidated materials at seabed in a lenient and controlled manner as indicated by the preamble of claim 1, causing a minimum of disturbance to the subsea environment.

Background

Conventional dredging systems have a suction head that is trailed by a vessel. By design their purpose is to remove as much sediment as efficient as possible over a predefined grid. This activity not only causes significant disturbance of the seabed itself but also suspends small sediment particles into the water column.

NO 20180830 A describes a system for the removal and treatment of sediment specifically from fish farms. The process also refers to the use of a suction piece but does not provide any details on the functionality of this. The use of a hovering ROV together with a standard suction piece is likely to result in inaccurate removal and suspension of smaller sediment particles in the water column.

JP 2000220164 A describes a system for the removal of sediment by means of rotational agitators and using a screw conveyor system for transport of the sediment mixture to surface.

KR 20140043425 A describes a system for the removal of sediment by means of a suction cone with ejector type function. The ejector creates a venturi effect resulting in a negative suction pressure inside the cone.

EP 0047803 Al describes a method and a suction dredging device for sucking up dredging spoil. The device includes a suction head which comprises a flexible wall allowing adjustment in dependence of a pressure difference between the pressure of a suspension stream and the pressure in the ambient water.

Among other publications In this technical area, JPS 534330 A and US 5 970635 A could be mentioned.

Objectives

It is an objective of the present invention to provide a device for removal of non-consolidated mass at seabed, such as contaminations in an area under a fish pen or the like or from an area of contaminated seabed or substances of value worth to be extracted from the seabed due to their inherent value. It is a further objective to provide a device as indicated above, which is able to perform the said task with a minimum of disturbance of the environment, hereunder to leave the consolidated, cohesive sediment of the seabed intact and with a minimum of particles being suspended in the surrounding water column.

The present invention

The above indicated objective is achieved by the device according to claim 1, which constitutes the subject matter of the present invention.

Preferred embodiments are disclosed by the dependent claims

With "lenient" as used herein is understood in a manner in which the non-consolidated layer to be removed is removed in a controlled manner, e.g. to a controlled depth and without excessive turbulence in the water mass, thereby largely avoiding particles to be spread throughout the nearby water mass.

Sediment precipitated on the seabed over time tends to become consolidated, i.e. compacted and sticking together in a cohesive manner, requiring a certain hydraulic or mechanic force to disintegrate the sediment to particles. Such sediment will not be removed by the present device, which only intends to remove non-consolidated mass like mud, fish excrements and nonconsumed fish fodder resting on top of the consolidated, cohesive sediment constituting the more permanent seabed. The term "non-consolidated" as used I herein shall be understood to cover the rather loose mass on top of cohesive sediment irrespective of their origin.

Terms like "upper" and "lower", "top" and "bottom", "below" and "above" etc shall be interpreted in the context of an operational position of the device.

By "front end" is understood the end towards which the device is moving under normal operation.

Unlike conventional dredging, the removal of non-consolidated mass according to the present invention is conducted in a very controlled and lenient manner, with a minimum of disturbance at the seabed. An important aspect is this connection is the fact that dispersal of small particles can cause oxygen depletion in the water column and spread pollution over a larger area. The use of the present device could also be denoted extraction of mass rather than dredging of mass, due to its inherent leniency.

While non-consolidated mass may refer to mass of any origin, the present invention is particularly aimed at removal of organic matter, such as waste from fish farms, as well as extraction of industrial polluted sediments in harbour and coastal areas or valuable substances worth extracting due to their inherent value.

Typically, the device according to the present invention is interfaced with a Remotely Operated Vehicle (ROV), typically an ROV arranged to crawl on the seabed and to accurately position the device according to the present invention on the seabed as desired.

The suction device connectable to the device according to the present invention is not part of the invention, and can be carried by the ROV or arranged at sea level or in any other suitable manner. Attachment of the device to an ROV and to the suction device may be separate or integrated as one unit comprising both functionalities, i.e. mechanical connection as well as fluid connection.

Means for adjustment of the suction force may be arranged locally on the device or on the suction device or both. Typically, the device according to the present invention is provided with adjustable valves to regulate the suction force, the main inlet area, to the void or both.

Monitoring systems may be provided to monitor one or more of suction force, flow rate, depth of non-consolidated mass and to provide visual monitoring by cameras and possibly sonar. It may also be provided with equipment to accurately keep track of its horizontal and vertical movement.

In comparison with the prior art publication NO 20180830 A, the present invention is unique a. o. in that the flexible collar allows for a tight seal against the seabed and accurate height adjustments. The height can be adjusted very accurately by adjusting the volume inside the flexible collar. Increased volume will raise the suction system and a decrease will achieve the opposite. Liquid will be used as a medium to adjust the volume.

Nozzles distributed around the circumference of the passage between the void in the main housing and the external environment will, when the device according to the present invention is connected to a suction device as indicated, be able to remove particles that come into suspension during the removal process and ensure a minimum of contamination of the environment around the work site.

Below, the present invention is described in further detail with reference to the accompanying drawings, where:

Figure 1 is an exploded view of the main components of an embodiment of the device according to the present invention

Figure 2 is a side sectional view of the embodiment illustrated in Figure 1 By schematic is understood that the drawings present the principle of the invention but that the mutual dimensions of different components not necessarily are in scale with real life embodiments.

By simplified is understood that elements that typically will be present in real-life embodiments may be omitted from the drawing for the sake of simplification and better illustration of the components shown.

Figure 1 shows the main components of an embodiment of the device according to the present invention, specifically a suction manifold 11 and below that a filter 12, a main housing 13, a flexible collar 14, and a tube-shaped member 15 provided with nozzles, the latter visible in Fig. 2. In front of the main housing 13 an adjustable gatel6 is shown as well as a grizzly bar 17 and an object diverter 18. An interface 19 for attachment to an ROV is shown from the suction manifold 11. Visible in Figure 1 are also a front cover 132 of the main housing, covering only upper part of the front, an internal void 131 in the main housing and a bottom edge 133 of the main housing at three side wall surfaces thereof.

While the flexible collar illustrated in Figure 1 appears to have a circular cross-section, other cross- sectional shapes are within the scope of the present invention, such as oval cross-sections and cross-sections of asymmetrical shape, e.g. pointed cross-sections with the pointed side facing downwards.

Attention is now drawn to Figure 2, showing a side sectional view of device in operation, moving from right to left as indicated by arrow M. The ROV causing the movement is omitted from the drawing for the sake of simplicity, but would be connected to the interface 19. One side of a U- shaped tube member 15 having approximately the same shape and extension as the flexible collar 14, runs around the backside and the lateral (left and right hand) sides of the bottom edge 133 of the main housing 13, externally of the connection between the main housing 13 and the flexible collar 14. As indicated by Figure 2, the flexible collar 12 is immersed in non-consolidated mass 23 while supported by the more permanent, cohesive sediment 22.

As indicated by the dotted line 21, the non-consolidated mass passes through the grizzly bar 17 and is sucked up into and through the internal void 131 and passed further on out through the suction manifold 11. Minor particles that escape the opening into the outer void are largely sucked into nozzles 151 in the tube-shaped member 15 which is connected to a suction source, preferable the same suction force that generates suction in the manifold 11 and the internal void 131.