WO2012158028A1

WO2012158028A1 - Dredger provided with a remotely operable dredging vehicle, and method for dredging using such a dredger system

Info

Publication number: WO2012158028A1
Application number: PCT/NL2012/050333
Authority: WO
Inventors: Emile Arthur Henri Marie RUPERT; Pieter Abraham LUCIEER; Harmen Derk STOFFERS; Laurens Jan De Jonge
Original assignee: Ihc Holland Ie B.V.
Priority date: 2011-05-13
Filing date: 2012-05-14
Publication date: 2012-11-22
Also published as: ZA201308530B; EP2707548B1; AU2012256499A1; EP2707548A1; AU2012256499B2; CN103649420A; CN103649420B; NZ617636A; NL2006782C2

Abstract

A dredger system (100) for collecting material (112) from a sea floor (110), comprising a dredging vessel (102) with a hopper (116) for storing the material (112), and a suction tube (118) which at a first tube end (122) is arranged for discharging the material (112) into the hopper (116), the suction tube (118) having a second tube end (124) for receiving the material (112). The dredger system (100) comprises a remotely operable dredging vehicle (130) with a suction head (132) and a riser (134) that is at a first riser end (136) connected to the suction head (132). During use, the remotely operable dredging vehicle (130) is situated on the sea floor (110), and a second riser end (138) of the riser (134) is releasably connected to the second tube end (124), for guiding the material (112) from the bottom surface (110) to the hopper (116).

Description

Dredger provided with a remotely operable dredging vehicle, and method for dredging using such a dredger system

TECHNICAL FIELD

The invention relates to a dredger system for collecting material from a bottom surface of a water column, comprising a dredging vessel with a hopper for storing the material, and a suction tube which at a first tube end is arranged for discharging the material into the hopper, the suction tube having a second end for receiving the material.

Furthermore, the invention relates to a method of collecting material from a bottom surface of a water column, comprising providing a dredging vessel with a hopper for storing the material, the dredging vessel comprising a suction tube which at a first tube end is arranged for discharging the material into the hopper, and which at a second tube end is arranged for receiving the material.

BACKGROUND

Such a dredger vessel is known from patent document EP1857598. Here, the dredger vessel comprises a suction tube which at one tube end has a suction dredging head for removing material from a bottom surface of a water column (e.g. a sea floor). The other tube end is connected to the dredger hull through a hull pivot with a pivot axis that is transverse with respect to the hull. The term "tube" refers herein to a fluid conveyance with an implied rigidity such that the shape of the suction tube sufficiently stable for controlled positioning of the suction dredging head at the sea floor during suction dredging operations. The term "tube" is contrasted to the term "hose", which is considered a relatively flexible fluid conduit. Common suction dredging vessels are provided with a hull wherein a hopper for storing the material is arranged. The pivot joint (with rotation axis substantially horizontal to the water surface and transversely oriented with respect to the dredger hull) provides a mechanical connection between the suction tube and the hull, as well as a fluid aperture that facilitates in discharging the material conveyed through the suction tube into the hopper. As is customary for common suction dredger vessels, the "hopper" is construed herein as part of the vessel hull that is shaped as a receptacle to provide a reservoir for material collected from the sea floor. In the augmented dredger vessel disclosed by EP 1857598, the suction tube has considerable length and consists of several frame reinforced tube sections in order to increase the depth at which the dredging operations can be executed. Problems arise if the dredging operations are to be carried out in waters having considerably greater depths. Such greater depths may occur in several operations, such as mining operations, dredging operations, sand extraction, etc. But in general, an increase in the length of a frame reinforced suction tube inevitably leads to increased mechanical stress in the tube and the surrounding frame under deep mining or dredging operational conditions.

Consequently, the maximum length for such a suction tube construction is still limited.

SUMMARY

It is an object to provide a dredger system with a dredger vessel, which allows dredging operations at considerably larger depths, but without the need for substantial structural changes to the dredger vessel.

Therefore, according to an aspect, there is provided a dredger system according to the preamble of claim 1, characterized in that the dredger system comprises a remotely operable dredging vehicle with a suction head and a riser that is at a first riser end in fluid communication with the suction head for receiving the material from the suction head, wherein during use, the remotely operable dredging vehicle is situated on the bottom surface, and a second riser end of the riser is releasably connected to the second tube end, for guiding the material from the bottom surface to the hopper.

The proposed dredger system allows reaching a greater dredging depth of 150 - 400 meters or more, while using a common suction dredging vessel. Such suction dredging vessels are ordinarily provided with a suction head on the second end of the suction tube. In the proposed system, the suction head is replaced by a remotely operable dredging vehicle with a riser connected with the second tube end of the dredging vessel's suction tube. By the use of mainly standard equipment, the common dredging vessel's functionality can be retained, while providing the possibility of retrofitting the dredging system with the remotely operated dredging vehicle for dredging at greater depths at any moment and within a minimal amount of time.

In an embodiment, the suction dredging vessel comprises a bow coupling with a gland for connection to a flexible fluid conduit, wherein the bow coupling is in fluid communication with the hopper, wherein the remotely operable dredging vehicle is with the second riser end releasably connectable to the gland, and wherein the suction dredging vessel comprises a further pump for straining the material removed by the dredging vehicle from the bottom surface via the riser and the bow coupling into the hopper.

Common suction dredging vessels are often also provided with such a bow coupling for connection to a fluid conduit, which allows discharging of collected material from the hopper. In the proposed system, the remotely operable dredging vehicle is, in addition to connectivity between the second riser end and the second suction tube end, also connectable with its second riser end to the gland of the bow coupling. The further pump required for transporting the collected material into the hopper may be formed by the pump that is already provided on the vessel for discharging the dredged material from the hopper via the bow coupling, but this pump should then also be operable in reverse. Alternatively, the further pump may be formed by an additional pump provided on the dredger vessel. The connection between the second riser end of the remotely operable vehicle and the gland of the vessel's bow coupling provides an additional possibility for employing the already present dredging vessel's functionality for dredging at greater depths at any moment and within a minimal amount of time.

In an embodiment, the dredger system comprises a coupling element that is with one end arranged to be coupled to the second tube end and with another end arranged to be coupled to the second riser end.

The second end of the suction tube of the dredging vessel is commonly suitable for connecting to a suction head, yielding a default dredging vessel combination. By providing a matching coupling element at the end of the riser of the remotely operable dredging vehicle, the default dredging vessel combination is easily converted to the augmented dredging system of the dredging vessel with the remotely operable dredging vehicle, without requiring further adjustments or additions to the dredging vessel. The suction tube may have a different diameter than the riser. The coupling element may thus have a funnel shaped flow path to bridge the difference in diameter.

In an embodiment, the dredger system comprises a further vessel, wherein the remotely operable dredging vehicle is provided with a communication cable connecting the remotely operable dredging vehicle to the further vessel for transmission of control or data signals.

The further vessel allows control of and/or data communication to and from the remotely operable dredging vehicle, without the need for installing communication facilities for operating the remotely operable dredging vehicle aboard the dredging vessel. The communication cable provides a low maintenance, cost-efficient means of transmitting control and/or data signals between the further vessel and the remotely operable dredging vehicle, with transmission quality that is relatively independent of the dredging depth.

In a further embodiment of the dredger system, the communication cable is provided with an extended upper cable portion terminating in a communication coupling, wherein the extended upper cable portion extends to above a water surface of the water column during use.

The extended upper cable portion extending to above the water surface allows for the communication coupling to be kept at a location above the water surface during use of the dredger system. In this way, no expensive water resistive measures have to be taken for protecting the communication coupling against water induced wear.

In an embodiment of the dredger system, the riser is at the second riser end provided with at least one floating body for retaining the second riser end substantially near the water surface, in an uncoupled state of the remotely operable dredging vehicle and the dredging vessel.

The floating body provides a means for retaining the riser end near the water surface while the remotely operable dredging vehicle is in an uncoupled state with respect to the dredging vessel. In this way, the riser end is easily locatable, manageable, and connectable to the suction riser by operating personnel on board the dredging vessel. The extended upper cable portion may be connected to the further vessel.

Alternatively, the presence of a communication coupling on the extended upper cable portion allows the communication cable to be connectable to or storable on or inside the floating body, while not coupled to the further vessel. According to an embodiment of the dredger system, the remotely operable dredging vehicle is provided with a propulsion device.

Furthermore, according to another aspect, there is provided a method of collecting material from a bottom surface of a water column, according to the preamble of claim 8, characterized by:

- providing a remotely operated dredging vehicle positioned on the bottom surface and comprising a suction head and a riser with a first riser end in fluid communication with the suction head for receiving the material;

- establishing a releasable connection between a second riser end of the riser and a second tube end of the suction tube;

- removing the material from the bottom surface by means of the suction head, and

- guiding the material through the riser and the suction tube into the hopper.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

FIG. 1 schematically shows a side view of an embodiment of the dredging system;

FIG. 2 presents a side view of a remotely operable dredging vehicle;

FIG.3 schematically shows a side view of another embodiment of the dredging system.

The figures are only meant for illustrative purposes, and do not serve as restriction of the scope or the protection as laid down by the claims.

DETAILED DESCRIPTION

FIG. 1 schematically shows a side view of an embodiment of the dredging system 100 for collecting material 112 from a bottom surface 110 of a water column 106. In FIGs. l and 2, the material 112 is depicted as individual rock objects embedded in the bottom surface 110. In this description, the term "material" is to be construed broadly as a collection of objects and/or a granulate volume situated in or on the bottom surface 110 or forming the bottom surface 110 itself, i.e. sludge, sand, clay, deposits, rocks, scraps of ore, etc. In the embodiment shown, the dredging vessel 102 has a dredger hull 114 provided with a hopper 116 for storing the material 112. The suction tube 118 is at a first tube end 122 connected to the dredger hull 114 by means of a pivot connection 120 which is substantially horizontal to the water surface 108 and transversely oriented with respect to the dredger hull 114. The pivot connection 120 has an aperture for guiding the material 112 flowing through the suction tube 118 into the hopper 116, so that the first tube end 122 is effectively arranged for discharging the material 112 into the hopper 116. The suction tube 118 has a second end 124 for receiving the material 112. Furthermore, the dredger combination 100 comprises a remotely operable dredging vehicle 130 with a suction head 132 and a riser 134 that is at a first riser end 136 in fluid communication with the suction head 132 for transporting the material 112 from the suction head 132 to a second riser end 138. At least a portion of the riser 134 may be constructed from a flexible material e.g. rubber or the like. During use, the remotely operable dredging vehicle 130 is positioned on the bottom surface 110, and the second riser end 138 is connected to the second tube end 124.

In this configuration, the material 112 that is removed from the bottom surface 110 into the suction head 132 may be guided through the riser 134 and the suction tube 118 into the hopper 116.

The suction head 132 may for example be a suction drag head, or an excavation tool (not shown) provided with cutting means e.g. a drum cutter or dredging wheel.

As shown in FIG.1, the dredging vessel 102 may comprise a gantry 126 by means of which the suction tube 118 can be displaced between a substantially horizontal rest position and an inclined dredging position.

FIG. 2 presents a side view of a remotely operable dredging vehicle 130, according to an embodiment. In general, the remotely operable dredging vehicle may be a crawler, drone, or the like.

Here, the dredger system 100 comprises a coupling element 212 that is with one end arranged to be coupled to the second tube end 124 and with another end arranged to be coupled to the second riser end 138. The coupling element 212 may for instance comprise a known ball joint. The second riser end 138 shown in FIG.2 is at least partially flexible.

The remotely operable dredging vehicle 130 shown in FIG.2 comprises the suction head 132, which is in fluid communication with the riser 134 at its first riser end 136. The remotely operable dredging vehicle shown is provided with a pump 222 for generating a pressure difference required for transporting the material 112 from the bottom surface 110, into the suction head 132, through the riser 134, to the second riser end 138, and further toward the dredging vessel 102. If desired, the pump 222 may also be operable in reverse, for depositing material 112 back onto the bottom surface 110.

The dredger system 100 shown in FIG.2 comprises a further vessel 204. The further vessel 204 may be provided with means (not shown) for deploying and/or hauling up the remotely operable dredging vehicle 130 into and out of the water column 106. Furthermore, the remotely operable dredging vehicle 130 is provided with a communication cable 214 connecting the remotely operable dredging vehicle 130 to the further vessel 204, for the purpose of transmitting control or data signals between the further vessel 204 and the remotely operable dredging vehicle 130. Here, the further vessel 204 is arranged to control the remotely operable dredging vehicle 130 and/or to maintain a data communication link between the further vessel 204 and the remotely operable dredging vehicle 130.

The connection of the communication cable 214 to the further vessel 204 may be permanent. Alternatively, the communication cable 214 may be provided with an extended upper cable portion 216 terminating in a communication coupling (not shown), for releasable connection between the remotely operable dredging vehicle 130 and the further vessel 204. For a communication cable 214 with a releasable

communication coupling, the extended upper cable portion 216 may extend to above a water surface 108 of the water column 106 during use, for protecting the

communication coupling from water influences.

In another embodiment of the dredger system 100, no further vessel 204 is present but control and/or data communication may instead be established between the dredging vessel 102 and the remotely operable dredging vehicle 130.

In FIG.2, the riser 134 has several floating bodies 220 at the second riser end 138, for keeping the second riser end 138 near the water surface 108, while the remotely operable dredging vehicle 130 and the dredging vessel 102 are in an uncoupled state. The floating bodies 220 may consist of individual buoyancy units connectable to the second riser end 138. Alternatively or in addition, one or more buoyancy structures may be integrated with the second riser end 138. Furthermore, the floating bodies 220 may have coupling elements for supply of power and/or jet water for the remotely operable dredging vehicle 130. The extended upper cable portion 216 and

communication coupling in a decoupled state may be connectable to or storable on or inside the floating body 220.

The remotely operable dredging vehicle 130 shown in FIG.2 is provided with a propulsion device 224. Here, the propulsion device 224 comprises caterpillar tracks 226 for driving the remotely operable dredging vehicle 130 along a direction of motion A during use. Alternatively or in addition, the propulsion device 224 may comprise other means of propulsion e.g. Archimedes screws, thrusters, wheels, etc. The caterpillar track based propulsion device 224 provides a robust low-maintenance means of propulsion. Consequently, the remotely operable dredging vehicle 130 may remain under water for a relatively long time, both during use in combination with the dredging vessel 102, and in an uncoupled state in which it may rest idle on the bottom 110 of the water column 106.

As illustrated in Fig.3, an embodiment of the suction dredger vessel 102 may have a bow coupling 228 to which a high-pressure conduit (e.g. a flexible hose or floating pipeline) is connectable, and wherein the bow coupling 228 is in fluid communication with the hopper 116 via suitable fluid channels in such a way that dredged material can be discharged via the bow coupling 228 from the hopper 116 by means of a centrifugal pump 232 provided on the vessel 102. The bow coupling 228 may be used for attaching the high-pressure conduit to the dredger vessel 102 without needing assistance of a further vessel. The powerful pump 232 on board the dredger vessel 102 can pump the material via the high-pressure conduit over a distance of several kilometers. Such a bow coupling 228 may furthermore be provided with an inclined jet for spraying discharge of dredged material from the hopper 116 to a shore ("rainbowing"). The bow coupling 228 comprises a frame 234, which is mounted on the bow 229 of the dredger vessel 102. The bow coupling 228 further comprises a turning gland or swiveling body 230 (for example a swiveling body described in patent document EP2148120) for fluid tight connection of the high pressure-conduit to the bow coupling 228, and a hoisting winch 236 for lifting or lowering the conduit.

According to this embodiment, the remotely operable dredging vehicle 130 is provided at the second riser end 138 with coupling means for releasable connection to the gland 230. The suction dredging vessel 102 may have a further pump, which is needed for straining the dredged material removed by the dredging vehicle 130 via the riser 134 and via the bow coupling 228 into the hopper 116. This further pump may be formed by the centrifugal pump 232 that is provided for discharging the dredged material from the hopper 116 via the bow coupling 228. If this is the case, then the further pump 232 needs to be suitable for both forward and reversed pumping action (even though the reversed pumping i.e. suction power of this centrifugal pump 232 may still be significantly less than the forward pumping power). Alternatively, an additional pump 232 may be provided on the dredger vessel 102 to be able to pump the material into the hopper 116. In accordance with the proposed dredger system 100, the method for collecting material 112 from a bottom surface 110 of a water column 106 comprises the actions of providing a dredging vessel 102 with a hopper 116 for storing the material 112, and a suction tube 118 which at a first tube end 122 is arranged for discharging the material 112 into the hopper 116. Furthermore, the method involves providing a remotely operated dredging vehicle 130 positioned on the bottom surface 110 and comprising a suction head 132 and a riser 134 with a first riser end 136 in fluid communication with the suction head 132. In the method, a second riser end 138 of the riser 134 is connected to a second tube end 124 of the suction tube 118. By using the dredger system 100, the material 112 is removed from the bottom surface 110 through the suction head 132, the material 112 subsequently being guided through the riser 134 and the suction tube 118 into the hopper 116.

In a further embodiment of the method, the suction dredging vessel 102 comprises a bow coupling 228 with a gland 230 for connection to a flexible fluid conduit, wherein the bow coupling 228 is in fluid communication with the hopper 116, as was described herein with reference to Fig.3. This method comprises the actions of selectively establishing a releasable connection between the second riser end 138 of the remotely operated dredging vehicle 130, and the second tube end 124 or the gland 230 of the suction dredging vessel 102. Once connection is established, the material 112 is removed from the sea floor 110 by means of the suction head 132. This material is conveyed 112 through the riser 134. Depending on the selected connection type, the dredged material is conveyed through the suction tube 118 or the bow coupling 228 into the hopper 116. The suction dredging vessel 102 may have a further pump 232, which is needed for straining the dredged material removed by the dredging vehicle 130 via the riser 134 via the bow coupling 228 into the hopper 116.

Prior to use, the remotely operable dredging vehicle 130 can be deployed on the bottom 110 of the water 106 by a further vessel 204, e.g. a crane barge or the like. The further vessel 204 may be part of the dredger system 100. The further vessel 204 may be provided with means (not shown) for deploying and/or hauling up the remotely operable dredging vehicle 130 into and out of the water column 106. The further vessel 204 may be arranged for controlling the remotely operable dredging vehicle 130 and/or maintaining a data communication link during use. For this purpose, the remotely operable dredging vehicle 130 may be provided with a communication cable 214 that is connected to the further vessel 204 during use. Preferably, the remotely operable dredging vehicle 130 is sufficiently durable for staying under water on the bottom 110 for a considerable period. The dredging vessel 102 is allowed to connect to the remotely operable dredging vehicle 130 at will, by establishing a releasable connection between the second riser end 138 of the suction tube 118 of the remotely operable dredging vehicle 130, and the second tube end 124 of the suction tube 118 of the dredging vessel 102. If by the use of the dredger system 100 a sufficient amount of material 112 has been collected in the hopper 116 of the dredging vessel 102, then the dredging vessel 102 may be disconnected from the remotely operable dredging vehicle 130. While the disconnected dredging vessel 102 returns to a discharge location, the remotely operable dredging vehicle 130 may remain on the bottom surface 110. After the return of the emptied dredging vessel 102 or the arrival of another dredging vessel, the releasable connection between the remotely operable dredging vehicle 130 and the dredging vessel 102 may again be established. Here, the floating bodies 220 attached to the riser 134 of the remotely operable dredging vehicle 130 facilitate the localization and (re)connection to the remotely operable dredging vehicle 130. Repeated disconnection and reconnection of the emptied dredging vessel 102 or another dredging vessel to the remotely operable dredging vehicle 130 allows for continuous use of the remotely operable dredging vehicle 130 without redeployment.

LIST OF FIGURE ELEMENTS

100 dredger system

102 dredging vessel

106 water column

108 water surface

110 bottom surface

1 12 material

1 14 dredger hull

116 hopper

1 18 suction tube

120 pivot connection

122 first tube end

124 second tube end

126 gantry

130 remotely operable dredging vehicle

132 suction head

134 riser

136 first riser end

138 second riser end

204 further vessel

212 coupling element

214 communication cable

220 floating body

222 pump

224 propulsion device

226 caterpillar tracks

228 bow coupling

229 bow

230 gland

232 vessel pump

234 frame

236 winch

Claims

1. Dredger system (100) for collecting material (112) from a bottom surface (110) of a water column (106), comprising a suction dredging vessel (102) with a dredger hull (114) provided with a hopper (116) for storing the material (112), and a suction tube (118) which at a first tube end (122) is connectable to the dredger hull (114) by means of a pivot connection (120) which is substantially horizontal to the water surface (108) and transversely oriented with respect to the dredger hull (114), and wherein the suction tube (118) is at the first tube end (122) arranged for discharging the material (112) into the hopper (116), the suction tube (118) having a second tube end (124) for receiving the material (112),

characterized in that

the dredger system (100) comprises a remotely operable dredging vehicle (130) with a suction head (132) and a riser (134) that is at a first riser end (136) in fluid communication with the suction head (132) for receiving the material (112) from the suction head (132), wherein during use, the remotely operable dredging vehicle (130) is situated on the bottom surface (110), and a second riser end (138) of the riser (134) is releasably connected or connectable to the second tube end (124), for guiding the material (112) from the bottom surface (110) to the hopper (116).

2. Dredger system (100) according to claim 1, wherein the suction dredging vessel (102) comprises a bow coupling (228) with a gland (230) for connection to a flexible fluid conduit, wherein the bow coupling (228) is in fluid communication with the hopper (116), wherein during use, the remotely operable dredging vehicle (130) is with the second riser end (138) releasably connectable to the gland (230), and wherein the suction dredging vessel (102) comprises a further pump (232) for straining the material (112) removed by the dredging vehicle (130) from the bottom surface (110) via the riser (134) and the bow coupling (228) into the hopper (116).

3. Dredger system (100) according to claim 1 or 2, wherein the dredger system (100) comprises a coupling element (212) that is with one end arranged to be coupled to the second tube end (124) and with another end arranged to be coupled to the second riser end (138).

4. Dredger system (100) according to any one of the claims 1 - 3, comprising a further vessel (204), wherein the remotely operable dredging vehicle (130) is provided with a communication cable (214) connecting the remotely operable dredging vehicle (130) to the further vessel (204) for transmission of control or data signals.

5. Dredger system (100) according to claim 4, wherein the communication cable (214) is provided with an extended upper cable portion (216) terminating in a communication coupling, wherein the extended upper cable portion (216) extends to above a water surface (108) of the water column (106) during use.

6. Dredger system (100) according to any one of the preceding claims, wherein the riser (134) is at or near the second riser end (138) provided with at least one floating body (220) for retaining the second riser end (138) substantially near the water surface (108) in an uncoupled state of the remotely operable dredging vehicle (130) and the dredging vessel (102).

7. Dredger system (100) according to any one of the preceding claims, wherein the remotely operable dredging vehicle (130) is provided with a propulsion device (224).

8. Method of collecting material (112) from a bottom surface (110) of a water column (106), comprising:

- providing a suction dredging vessel (102) with a dredger hull (114) provided with a hopper (116) for storing the material (112), the dredging vessel (102) comprising a suction tube (118) which at a first tube end (122) is connectable to the dredger hull (114) by means of a pivot connection (120) which is substantially horizontal to the water surface (108) and transversely oriented with respect to the dredger hull (114), and wherein the suction tube (118) is at a first tube end (122) arranged for discharging the material (112) into the hopper (116), and which at a second tube end (124) is arranged for receiving the material (112),

characterized by

- providing a remotely operated dredging vehicle (130) positioned on the bottom surface (110) and comprising a suction head (132) and a riser (134) with a first riser end (136) in fluid communication with the suction head (132) for receiving the material

(112);

- establishing a releasable connection between a second riser end (138) of the riser (134) and a second tube end (124) of the suction tube (118);

- removing the material (112) from the bottom surface (110) by means of the suction head (132), and

- guiding the material (112) through the riser (134) and the suction tube (118) into the hopper (116).

9. Method according to claim 8, wherein the suction dredging vessel (102) comprises a bow coupling (228) with a gland (230) for connection to a flexible fluid conduit, wherein the bow coupling (228) is in fluid communication with the hopper (116), wherein the method comprises:

- selectively establishing a releasable connection between the second riser end (138) of the remotely operated dredging vehicle (130), and the second tube end (124) or the gland (230) of the suction dredging vessel (102);

- guiding the material (112) through the riser (134) and the suction tube (118) or the bow coupling (228) into the hopper (116).