U.S. patent application number 14/654354 was filed with the patent office on 2016-07-07 for dredging arrangement for dredging material from an underwater bottom.
The applicant listed for this patent is IHC SYSTEMS B.V.. Invention is credited to Cornelis De Keizer.
Application Number | 20160194851 14/654354 |
Document ID | / |
Family ID | 47790457 |
Filed Date | 2016-07-07 |
United States Patent
Application |
20160194851 |
Kind Code |
A1 |
De Keizer; Cornelis |
July 7, 2016 |
DREDGING ARRANGEMENT FOR DREDGING MATERIAL FROM AN UNDERWATER
BOTTOM
Abstract
The invention relates to a dredging arrangement for dredging
material from an underwater bottom (6). The dredging arrangement
comprises a drag head (10) and a suction pipe (2). The drag head
(10) comprises a drag head body (11) which is attachable to the
suction pipe (2). The drag head (10) comprises at least one
moveable part (12, 14), such as a visor and a valve, which can be
controlled to change the dredging characteristics of the drag head
(10). The dredging arrangement comprises wire connector (15) and
transferring device (16). The wire connector (15) being connectable
to a wire (4) via which a pulling force can be applied, wherein the
transferring device (16) are arranged to transfer the pulling force
to the at least one moveable part (12, 14) to control the
characteristics that part.
Inventors: |
De Keizer; Cornelis;
(Dordrecht, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IHC SYSTEMS B.V. |
Sliedrecht |
|
NL |
|
|
Family ID: |
47790457 |
Appl. No.: |
14/654354 |
Filed: |
December 20, 2013 |
PCT Filed: |
December 20, 2013 |
PCT NO: |
PCT/NL2013/050935 |
371 Date: |
June 19, 2015 |
Current U.S.
Class: |
37/333 ;
37/195 |
Current CPC
Class: |
E02F 3/905 20130101;
E02F 3/9218 20130101; E02F 3/9293 20130101; E02F 3/9212 20130101;
E02F 3/8841 20130101 |
International
Class: |
E02F 3/90 20060101
E02F003/90; E02F 3/88 20060101 E02F003/88; E02F 3/92 20060101
E02F003/92 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2012 |
NL |
2010030 |
Claims
1. A dredging arrangement for dredging material from an underwater
bottom, the dredging arrangement comprising a drag head and a
suction pipe, the drag head comprising a drag head body which is
attachable to the suction pipe, the drag head comprising at least
one moveable part which can be controlled to change dredging
characteristics of the drag head, wherein the dredging arrangement
comprises a wire connector, a wire controller and a transferring
device, the wire connector being connectable to a wire via which a
pulling force can be applied, wherein the transferring device is
arranged to transfer the pulling force to the at least one moveable
part, and the wire controller is arranged to exert a controllable
pulling force on the wire and also functions as hoisting device for
lowering and lifting the dredging arrangement towards and from the
underwater bottom.
2. The dredging arrangement according to claim 1, wherein a biasing
device is provided exerting a biasing force on the at least one
moveable part and wherein the wire connector and the transferring
device are arranged such that the transferred pulling force opposes
the biasing force.
3. The dredging arrangement according claim 1, wherein the at least
one moveable part is a visor, the visor being rotatable with
respect to the drag head body about a rotational axis which, in
use, is substantially horizontal and perpendicular to a dredging
direction.
4. The dredging arrangement according to claim 3, wherein the drag
head comprises a biasing device exerting a biasing force on the
visor such that the visor is biased in a downward direction.
5. The dredging arrangement according to claim 4, wherein the
biasing device comprises at least one of a mechanical spring, a
hydraulic spring, and a gas spring.
6. The dredging arrangement according to claim 4, wherein the wire
connector and the transferring device are positioned such that the
transferred pulling force opposes the biasing force.
7. The dredging arrangement according to claim 1, wherein the
moveable part is a valve provided to open and close an opening in
the drag head or a lower part of the suction pipe to allow water to
enter.
8. The dredging arrangement according to claim 7, wherein the drag
head or suction pipe comprises a biasing device exerting a biasing
force on the valve such that the valve is biased towards a closed
position.
9. The dredging arrangement according to claim 8, wherein the wire
connector and the transferring device are positioned such that the
transferred pulling force opposes the biasing force.
10. The dredging arrangement according to claim 1, wherein the
transferring device comprises one or more pulleys and a
transferring cable being guided by the one or more pulleys, wherein
the wire connector is connected to one of the pulleys being a
moveable pulley, the transferring cable being arranged to transfer
the pulling force from the wire connector to the moveable part.
11. The dredging arrangement according to claim 1, wherein the
transferring device comprises a hydraulic force transmitter.
12. The dredging arrangement according claim 1, wherein the
transferring device comprises a lever which is connected to the
wire connector and to the at least one moveable part.
13. A dredging vessel comprising a dredging arrangement for
dredging material from an underwater bottom, the dredging
arrangement comprising a drag head and a suction pipe, the drag
head comprising a drag head body which is connected to the dredging
vessel by means of the suction pipe, the drag head comprising at
least one moveable part which can be controlled to change dredging
characteristics of the drag head, wherein the dredging vessel
comprises a wire connectable to the dredging arrangement for
lifting and lowering the dredging arrangement from and to the
underwater bottom, wherein the dredging arrangement comprises a
wire connector, a wire controller and a transferring device, the
wire connector being connectable to the wire via which a pulling
force can be applied, wherein the transferring device is arranged
to transfer the pulling force to the at least one moveable part,
and wherein the wire controller is arranged to exert a controllable
pulling force on the wire and also functions as hoisting device for
lowering and lifting the dredging arrangement towards and from the
underwater bottom.
14. The dredging vessel according to claim 13, wherein the dredging
vessel comprises a gantry via which the wire can be guided from the
wire controller to the dredging arrangement.
15. A method for dredging material from an underwater bottom using
a dredging arrangement, the dredging arrangement comprising a drag
head and a suction pipe, the drag head comprising a drag head body
which is attached to the suction pipe, the drag head further
comprising at least one moveable part which can be controlled with
respect to the drag head body to change dredging characteristics of
the drag head, the dredging arrangement being connected by a wire
to wire controller to lift and lower the dredging arrangement from
and to the underwater bottom, wherein the method comprises a)
lowering the dredging arrangement to an underwater position with
the drag head positioned on the underwater bottom, and b) dredging
by dragging the drag head over the underwater bottom in a dredging
direction by means of a dredging vessel, the dredging arrangement
comprising a wire connector and a transferring device, the wire
connector being connectable to the wire via which a controllable
pulling force can be applied by the wire controller, wherein the
transferring device is arranged to transfer the pulling force to
the at least one moveable part, wherein the method further
comprises: b1) controlling the wire controller to dynamically
control a pulling force exerted on the wire during dredging.
16. The method according to claim 15, wherein the pulling force is
controlled dynamically during dredging in a range which lies below
a lifting force required for lifting the dredging arrangement from
the underwater bottom and more than a minimum force to prevent
slackening of the wire.
17. The method according to claim 15, wherein the wire controller
comprises a first wire controller and a second wire controller, and
wherein action a) is performed by the first wire controller and
action b1) is performed by the second wire controller.
18. The method according to claim 17, wherein action b1) comprises
temporarily operating the first and second wire controllers in
opposite directions.
19. A method for dredging material from an underwater bottom using
a dredging arrangement according to claim 1.
Description
TECHNICAL FIELD
[0001] The invention relates to a dredging arrangement for dredging
material from an underwater bottom, the dredging arrangement
comprising a drag head and a suction pipe, the drag head comprising
a drag head body which is attachable to the suction pipe, the drag
head comprising at least one moveable part, such as a visor and a
valve, which can be controlled to change the dredging
characteristics of the drag head.
[0002] The invention further relates to a dredging vessel
comprising such a dredging arrangement and a method for dredging
material from an underwater bottom using such a dredging
arrangement.
BACKGROUND
[0003] Dredging is often done by dragging a drag head over an
underwater bottom by a dredging vessel, such as a trailing suction
hopper dredger vessel. The drag head is connected to the vessel by
means of a suction pipe. The drag head is lowered to the underwater
bottom by one or more hoisting wires, possibly in combination with
cranes or gantries. One or more pumps are provided to suck bottom
material from the underwater bottom via the drag head, the suction
pipe into a hopper of the dredging vessel.
[0004] The hoisting wires may be controlled by winches which may be
equipped with heave compensation means to counteract wave induced
vessel motion and variations in bottom height.
[0005] During dredging, the dredging conditions will vary, for
instance as a result of [0006] changing draught of the dredging
vessel as a result of loading process, [0007] changing underwater
bottom conditions (underwater dunes etc.), [0008] changing water
level as a result of wave and tidal movement, and [0009] changing
soil type.
[0010] From the prior art dredging arrangements are known in which
the dredging arrangement can be controlled to adapt to changing
conditions, including to prevent choking when too much material and
too little water gets into the suction pipe. U.S. Pat. No. 366,468
discloses a dredging apparatus which uses a simple valve which can
open automatically or may be operated by a cable or rod if chocking
occurs. Similarly, U.S. Pat. No. 528,022 discloses a valve which
may be operated by an operator pulling on a rope to allow water to
flow in and cut up the choking material. The dredging arrangement
may be adapted on board of a vessel before being lowered to the
underwater bottom. Alternative solutions require active components
mounted on the dredging arrangement, which can require expensive
and fragile components and power to be supplied to active
components. Also, the use of hydraulic fluid forms an environmental
risk.
SUMMARY
[0011] It is an object to provide a drag head which can be adapted
to changing dredging condition in an easy and reliable way.
[0012] Therefore, according to an aspect, there is provided a
dredging arrangement for dredging material from an underwater
bottom, the dredging arrangement comprising a drag head and a
suction pipe, the drag head comprising a drag head body which is
attachable to the suction pipe, the drag head comprising at least
one moveable part, such as a visor or a valve, which can be
controlled to change the dredging characteristics of the drag head,
wherein the dredging arrangement comprises a wire connector and a
transferring device, the wire connector being connectable to a wire
via which a pulling force can be applied, wherein the transferring
device is arranged to transfer the pulling force to at least one
moveable part.
[0013] The pulling force may be applied by a wire controller
positioned on board of a dredging vessel. The wire controller may
be arranged to give out or take in wire and to control a pulling
force exerted on the wire. The wire controller may be formed by or
may comprise a winch. If the winch is the only wire controller then
this winch has to be operated in constant tension mode, that means
that the winch is giving out and taking in wire constantly to
compensate the constantly changing difference between drag head and
vessel or gantry.
[0014] The wire and the wire controller may also be provided by a
heave compensator, for instance known from the prior art, now
controlled differently, i.e. now also used for controlling the
dredging characteristics of the drag head besides it main function
to tension the wire (preventing slackening of the wire).
[0015] As further explained with reference to the drawings, the
wire controller may also comprise a combination of a winch and a
separate heave compensator. In other words, the wire controller may
comprise a first wire control device and a second wire control
device, wherein the first wire control device, e.g. formed by a
winch, is arranged to lift and lower the dredging arrangement
including the suction pipe and to prevent that the second control
device gets out of its working range, and wherein the second wire
control device, e.g. formed by a heave compensator, is arranged to
dynamically take in or give out wire and/or to dynamically adapt
the pulling force to control the moveable parts to adapt to
changing dredging conditions.
[0016] In that case the constantly changing dredging conditions are
compensated by the second wire control device (heave compensator)
and the first wire control device is operated when the second wire
controller reaches its maximum or minimum position.
[0017] The wire controller (first and/or second) is used to control
the length of the wire and the pulling force acting on the wire.
The wire is primary used to hoist the dredging arrangement, e.g. to
lower it to the seabed and to hoist it to its top position where it
will be able to put it to its resting position on board.
[0018] When the drag head is making contact to the seabed, the
pulling force in the wire is reduced to keep the drag head in
contact with the bottom. The remaining force (between lifting force
of the dredging arrangement and the minimum force to prevent
slackening of the wire) will be dynamically controlled to adjust
the dredging characteristics of the drag head.
[0019] In use, for the purposes of this invention, the pulling
force may be controlled dynamically in a range wherein it is less
than the force required for lifting the dredging arrangement from
the underwater bottom and more than a minimum force to prevent
slackening of the wire. The second wire control device may
therefore be made less strong than the first wire control device,
as the second wire control device is not used to lift the dredging
arrangement from the underwater bottom.
[0020] In use, the winch control device may be used to constantly
adjust the pulling force to control the moveable parts of the drag
head.
[0021] The drag head may comprise a drag head body, which is open
at a side directed towards the material to be dredged to allow
dredging material to be sucked into the drag head and a connection
to a suction pipe to transport the dredging material away from the
drag head, for instance towards a hopper on board of a dredging
vessel.
[0022] The wire connector may be attached to the lower end of the
suction pipe or to the drag head body.
[0023] The transferring device may be connected to the lower end of
the suction pipe or to the drag head body and to the moveable part
in order to transfer pulling force exerted by the wire towards the
moveable part.
[0024] The wire connector may be formed by a ring or the like to
which a wire can be connected. The wire connector may be connected
to the transferring device.
[0025] By pulling the wire the moveable parts can be influenced,
for instance be moved or the moving behavior of the moveable parts,
as will be explained in more detail below. The moveable parts are
moved with respect to the drag head body.
[0026] This allows easy and direct control of moveable parts of the
drag head.
[0027] According to an embodiment a biasing device is provided
exerting a biasing force on the at least one moveable part and
wherein the wire connector and the transferring device are arranged
such that the transferred pulling force opposes the biasing
force.
[0028] The wire can be pulled by the wire controller. Pulling is
done in a direction away from the wire connector. Because the
biasing force and the transferred pulling force of the wire are
oppositely directed, the position of the moveable part can be
adjusted. Also, as long as the transferred pulling force is less
than the biasing force, the position of the moveable part is not
changed, but the behavior of the moveable part can be adjusted,
i.e. the spring characteristics of the moveable part can be
adjusted. The transfer device may be arranged to reduce the pulling
force, i.e,. the transferred pulling force is less than the pulling
force in the wire.
[0029] According to an embodiment the at least one moveable part is
a visor, the visor being rotatable with respect to the drag head
body about a rotational axis which, in use, is substantially
horizontal and perpendicular to a dredging direction.
[0030] The visor can be used to control the dredging
characteristics of the drag head, such as the excavation depth
(layer thickness) and the ratio between water and sand being
dredged. By controlling the pulling force, the position and/or
behavior of the visor can be controlled.
[0031] The visor may be provided at the trailing end of the drag
head body.
[0032] Instead of rotational visors, visors may be used which are
moveable in another manner, such being slideable, translational or
are arranged to perform a combination of a rotational and
translational movement.
[0033] According to an embodiment the drag head comprises a biasing
device exerting a biasing force on the visor such that the visor is
biased in a downward direction.
[0034] The downward direction may be a rotational downward
direction.
[0035] Such a biasing device may be applied to force the visor to
follow the contour of the underwater bottom and to deal with
obstacles present on the underwater bottom. Also, the biasing
device can be used to set the excavation depth.
[0036] The biasing device may for instance be an additional weight
positioned on the moveable part to bias it in a downward
direction.
[0037] The biasing device may be adjustable to set the biasing
force. Also, a force transferring construction may be used to
transfer the biasing force to the moveable part. The force
transferring construction may be adjustable to set a moment of
force exerted to the moveable part.
[0038] The biasing device is connected to the visor and to the drag
head body and/or suction pipe.
[0039] According to an embodiment the biasing device comprises at
least one of a mechanical spring, an hydraulic spring, a gas
spring.
[0040] This is an advantageous way to provide a biasing force. In
this way, the visor is provided with spring characteristics, which
will contribute to the capability of the visor to follow the
contour of the under bottom. Also, no energy supply is needed to
the dredging arrangement. The moving characteristic of the visor
(flexible or stiff) will depend on the spring constant, the pulling
force, the gravitational force and the ground force.
[0041] The mechanical spring may for instance be a torsion spring,
a rubber element or a coil or helical spring.
[0042] The hydraulic spring and gas spring may comprise a
compressible chamber in which a fluid or gas is comprised.
[0043] According to an embodiment the wire connector and the
transferring device are positioned such that the transferred
pulling force opposes the biasing force.
[0044] One end of the wire can be connected to the wire connector.
The other end may be connected to the wire controller, which is
arranged to pull the wire with a controllable pulling force,
thereby at least partially cancelling the biasing force. This
allows to change the relative position of the visor with respect to
the drag head body and/or to adjust the moving behavior of the
visor, i.e. the spring constant describing the behavior of the
visor (its deflection in response to forces exerted on the visor,
such as by the underwater bottom).
[0045] According to an embodiment the moveable part is a valve
provided to open and close an opening in the drag head or lower
part of the suction pipe to allow water to enter.
[0046] The valve (also known as water flap or water valve) may be
used to control the amount of water entering the drag head. The
admission of water to the drag head makes it possible to control
the dredging process. According to the prior art, the valve usually
opens towards the outside by active control of hydraulic or
pneumatic means (cylinders). According to these embodiments, the
valve opens towards the inside while the differential pressure at
which the valve opens can be adjusted by the pulling wire
force.
[0047] The valve may also open in any other suitable manner. The
valve may for instance open to the outside, may open in a sliding
manner or may open by rotation, where part of the valve rotates to
the outside and part of the valve rotates to the inside.
[0048] The opening may be provided in the drag head and the valve
may be attached to the drag head to open and close the opening. The
opening may also be provided in the lower end of the suction pipe
and the valve may be attached to the suction pipe to open and close
the opening in the suction pipe.
[0049] According to an embodiment the drag head or suction pipe
comprises a biasing device exerting a biasing force on the valve
such that the valve is biased towards a closed position.
[0050] According to an embodiment the wire connector and the
transferring device are positioned such that the transferred
pulling force opposes the biasing force.
[0051] By pulling the wire, the biasing force is counteracted and
thus reduced enabling the valve to open.
[0052] One end of the wire can be connected to the wire connector.
The other end may be connected to the wire controller, which is
arranged to pull the wire with a controllable pulling force,
thereby at least partially cancelling the biasing force. This
allows to open and close the valve and/or to change the relative
position of the valve with respect to the drag head body or suction
pipe and/or to adjust the moving behavior of the valve, i.e. the
spring constant describing the behavior of the valve.
[0053] According to an embodiment the transferring device comprises
one or more pulleys and a transferring cable being guided by the
one or more pulleys, wherein the wire connector is connected to one
of the pulleys being a moveable pulley, the transferring cable
being arranged to transfer the pulling force from the wire
connector to the moveable part.
[0054] According to an embodiment the transferring device comprises
a hydraulic force transmitter. Possibly, the hydraulic force
transmitter comprises an actuator.
[0055] According to an embodiment the transferring device comprises
a lever which is connected to the wire connector and to the at
least one moveable part.
[0056] The lever may be rotatably mounted to the drag head body or
to the lower end of the suction pipe. Levers are suitable for
transferring the pulling force to the moveable part.
[0057] According to an aspect there is provided a dredging vessel
comprising a dredging arrangement for dredging material from an
underwater bottom, the dredging arrangement comprising a drag head
and a suction pipe, the drag head comprising a drag head body which
is connected to the dredging vessel by means of the suction pipe,
the drag head comprising at least one moveable part, such as a
visor or a valve, which can be controlled to change the dredging
characteristics of the drag head, wherein the dredging vessel
comprises a wire connectable to the dredging arrangement for
lifting and lowering the dredging arrangement from and to the
underwater bottom, wherein the dredging arrangement comprises a
wire connector and a transferring device, the wire connector being
connectable to the wire via which a pulling force can be applied,
wherein the transferring device is arranged to transfer the pulling
force to the at least one moveable part.
[0058] The dredging vessel may be a trailing suction hopper dredger
(TSHD).
[0059] According to an embodiment the dredging vessel comprises a
wire controller, the wire controller being arranged to exert a
controllable pulling force on the wire.
[0060] The wire controller may be formed as already described
above. It may comprise a first wire control device and a second
wire control device which work in cooperation with each other. The
second wire control device is dynamically controlled during
dredging, while the first wire control device is operated in case
the second wire control device reaches an end position, i.e. a
minimum and maximum position. In that case, the first wire control
device and the second wire control device are operated oppositely,
to bring the second wire control device back to the centre of its
working area. The first wire control device may be formed by a
winch, while the second wire control device may be formed by a
heave compensator. Both may be positioned on (the deck of) the
dredging vessel.
[0061] The wire controller is arranged to control a pulling force
in a range wherein it is less than the force required for lifting
the drag head from the underwater bottom and more than a minimum
force to prevent slackening of the wire. The wire controller
comprises means for dynamically controlling a pulling force during
dredging.
[0062] The wire controller may also be arranged to exert a pulling
force sufficient to lift the drag head from the underwater
bottom.
[0063] According to an embodiment the dredging vessel comprises a
gantry via which the wire can be guided from the wire controller to
the dredging arrangement.
[0064] According to an embodiment the wire controller also
functions as hoisting device for lowering and lifting the dredging
arrangement towards and from the underwater bottom.
[0065] As described above, the wire controller may comprise first
wire controller suitable for lifting and lowering the dredging
arrangement and second wire controller for controlling the moveable
parts and to compensate for heave motion.
[0066] Once the dredging arrangement is in position on the
underwater bottom, the wire controller may control the pulling
force in a range less than needed for lifting the dredging
arrangement from the underwater bottom, but sufficient for
controlling the position of the moveable part and/or moving
behavior of the moveable part, while the wire is kept under
tension.
[0067] According to an aspect there is provided a method for
dredging material from an underwater bottom using a dredging
arrangement, the dredging arrangement comprising a drag head and a
suction pipe, the drag head comprising a drag head body which is
attached to the suction pipe, the drag head further comprising at
least one moveable part, such as a visor and a valve, which can be
controlled with respect to the drag head body to change the
dredging characteristics of the drag head, the dredging arrangement
being connected by a wire to the wire controller to lift and lower
the dredging arrangement from and to the underwater bottom, wherein
the method comprises
[0068] a) lowering the dredging arrangement to an underwater
position with the drag head positioned on the underwater
bottom,
[0069] b) dredging by dragging the drag head over the underwater
bottom in a dredging direction by means of a dredging vessel,
[0070] the dredging arrangement comprising a wire connector and a
transferring device, the wire connector being connectable to the
wire via which a pulling force can be applied by the wire
controller, wherein the transferring device is arranged to transfer
the pulling force to the at least one moveable part, wherein the
method further comprises:
[0071] b1) controlling the wire controller to dynamically control a
pulling force exerted on the wire during dredging.
[0072] As a result, the position and/or moving behavior of the
moveable part can be controlled during dredging.
[0073] During lifting and lowering, the pulling force is at least
equal to a lifting force required for lifting the dredging
arrangement. As a result, during lifting and lowering the moveable
parts will be pulled to an end position. For instance, in case the
moveable part is the visor, the visor will be in its most upward
position during lifting and lowering. During dredging the pulling
force will be less than the required lifting force but more than a
minimum force to prevent slackening of the wire and the visor can
thus be controlled between its upper end position and its lower end
position by controlling the wire.
[0074] According to an embodiment the pulling force is controlled
dynamically during dredging in a range which lies below the lifting
force required for lifting the dredging arrangement from the
underwater bottom and more than a minimum force to prevent
slackening of the wire.
[0075] According to an embodiment, the wire controller comprise
first wire controller and second wire controller, and action a) is
performed by the first wire controller and action b1) is performed
by the second wire controller.
[0076] According to an embodiment, action b1) comprises temporarily
operating the first and second wire controller in opposite
directions.
[0077] This is done when the second wire controller reach an end of
its working range. By operating temporarily the first and second
wire controller in opposite directions, the second wire controller
are brought back to the centre of its working range. The term
temporarily is used that this is done a relatively short period
during action b1) to reset the second wire controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0078] 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:
[0079] FIG. 1 schematically shows an embodiment of a dredging
vessel according to an embodiment,
[0080] FIGS. 2a-2d show different embodiments of the dredging
arrangement and
[0081] FIGS. 3a, 3b and 4 schematically show further embodiments of
the dredging arrangement.
[0082] 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
[0083] FIG. 1 schematically depicts a dredging vessel 1 according
to an embodiment. The dredging vessel 1 comprises a drag head 10
which is attached to the dredging vessel 1 via a suction pipe 2.
The suction pipe 2 comprises a hinge point.
[0084] The drag head 10 and the suction pipe 2 are shown in a
lowered position with the drag head 10 resting on an underwater
bottom 6. In use, the dredging vessel 1 sails in a dredging
direction DD and drags the drag head 10 over the underwater bottom
6.
[0085] The drag head 10 and the suction pipe 2 are connected to a
wire 4, the wire 4 being controlled by a wire controller 5. Half
way the suction pipe 2, the suction pipe 2 may be connected to a
further wire 4' controlled by a further wire controller 5'. The
further wire and wire controller is mainly used for lifting and
lowering the suction pipe 2.
[0086] The wire controller 5 comprises a first wire control device,
in this case formed by a controllable winch 51. The wire controller
5 may further comprise a control unit 55 or the like to control the
winch 51. The winch 51 is used to lower and lift the dredging
arrangement from the vessel 1 to the underwater bottom 6 and vice
versa by giving out or taking in the wire 4.
[0087] The wire controller 5 comprises a second wire control
device, in this case formed by a number of pulleys 52 on board the
vessel 1 to guide the wire 4. The second wire control device
comprises means for dynamically controlling a pulling force exerted
on the wire 4 during dredging. Second wire control device for
dynamically controlling a pulling force may for instance be formed
by providing at least one of the pulleys 52 in a moveable manner,
moveable in a direction perpendicular to the rotational axis of the
pulley 52 by an actuator 53. In FIG. 1, the actuator 53 is an
hydraulic actuator comprising a cylinder and a piston which can
move up and down the cylinder. The moveable pulley 52 is connected
to the cylinder. The actuator 53 is also under control of the
control unit 55. The actuator 53 and the moveable pulley 52 may be
provided by hardware similar to a heave compensator. However,
according to the embodiments provided here, the actuator 53 and the
moveable pulley 52 are controlled differently to control moveable
parts of the dredging arrangement, as will be explained in more
detail below.
[0088] The control unit 55 may be a standalone control unit or may
be arranged to cooperate with other remote control units. The
control unit 55 may be a computer. The control unit 55 may also be
arranged to receive instructions from an operator via a user
interface.
[0089] The drag head 10 comprises two main parts: the drag head
body 11 and the visor 12. The drag head body 11 is on one side
connected to the suction pipe 2 via an appropriate connection 13.
The drag head body 11 and the (lower end of the) suction pipe 2 may
also be formed as one piece.
[0090] The drag head body 11 may have any suitable shape and its
main purpose is to form a chamber in which an underpressure can be
created to vacuum up dredging material from the underwater bottom
6. A pump 21 may be provided to create the required underpressure.
The pump 21 may be positioned on board of the dredging vessel 1 (as
shown in FIG. 1) and/or at or nearby the drag head 10. The drag
head 10 may comprise jet nozzles 22 to create a water jet to loosen
the underwater bottom 6. A jet pump 23 and a jet pipe lane 24 may
be present.
[0091] The visor 12 is a moveable part of the drag head 10. The
visor 12 is moveable with respect to the drag head body 11 to
change the dredging characteristics of the drag head 10. The visor
12 is moveable with respect to the drag head body 11, in this
embodiment rotatable about a rotational axis RA, which runs
perpendicular to the plane of the drawing of FIG. 1. The visor 12
is provided on a trailing end of the drag head body 11. In use, the
rotational axis RA runs substantially horizontal in a direction
perpendicular to the dredging direction DD. The drag head 10 may
comprise a further moveable part formed by a valve 14. As shown in
FIG. 1, the valve 14 is attached to drag head body 11 and is
arranged to open and close an opening 18 in the drag head body 11.
Alternatively, the valve 14 may be attached to the (lower end of
the) suction pipe 2 and be arranged to open and close opening 18 in
the suction pipe 2.
[0092] The moveable parts 12, 14 can both move with respect to the
drag head body 11 respectively to the suction pipe 2 and are both
provided to change the dredging characteristics of the drag head
10. For instance, moving the visor 12 to a lower position (rotating
counter clockwise in FIG. 1), results in deeper dredging and a
higher sand-water ratio. Opening the valve 14 results in a lower
sand-water ratio.
[0093] During dredging, the dredging circumstances will change, for
instance as a result of increased draught of the dredging vessel 1,
uneven underwater bottom 6, changing dredging depth (distance
between underwater bottom 6 and water surface) as a result of wave
and tidal movement, changing soil type.
[0094] According to the embodiments provided here and explained in
further detail below, the dredging arrangement comprises a wire
connector 15 which is connectable to the wire 4 to control the
moveable parts 12, 14 by means of the wire 4. The wire connector 15
is preferably dimensioned in such a way that lifting and lowering
of the dredging arrangement is possible i.e. is strong enough to
allow lifting and lowering.
[0095] According to the embodiments, the dredging arrangement
further comprises a transferring device 16 for transferring a
pulling force exerted on the wire 4 to one or both of the moveable
parts, such as visor 12 or valve 14. The wire controller 5 and in
particular the means for dynamically controlling a pulling force
(second wire control device) are used to dynamically control a
pulling force exerted on the wire 4 during dredging to control the
moveable parts 12, 14. By transferring the pulling force in the
wire 4 to a moveable part, the moveable parts 12, 14 can be
controlled by the wire controller 5, and in particular by the
second wire control device for dynamically controlling the pulling
force.
[0096] FIG. 1 shows an example wherein the transferring device 16
comprises one or more pulleys 161 and a transferring cable 162
being guided by the one or more pulleys 161. The transferring
device is similar to the transferring device shown in FIG. 2a, and
will be explained below with reference to FIG. 2a. The transferring
device 16 may be arranged to ensure that the transferred pulling
force is reduces with respect to the pulling force in the wire 4 to
prevent the visor from being pulled to its upper most position as a
result of the minimum pulling force needed to prevent the wire from
slacking.
[0097] Alternatively, the wire 4 may be directly connected to the
visor 12, preferably in situations wherein the minimum pulling
force needed in the wire 4 to prevent slackening is below the force
needed to lift the visor 12.
[0098] However, in the embodiment shown in FIG. 2a, one of the
pulleys 161 is a moveable pulley, moveable in a direction
perpendicular to a rotational axis of the moveable pulley 161.
Although not shown, it will be understood that guiders may be
present to guide the moveable pulley in the direction perpendicular
to the rotational axis. The wire connector 15 is connected to the
moveable pulley 161 thereby transferring the pulling force from the
wire 4, via the wire connector 15 and the transferring device 16 to
the visor 12.
[0099] In the embodiments shown, the wire controller 5, in
particular the second wire control device for dynamically
controlling the pulling force in the wire 4 can be used during
dredging to adjust the pulling force in the wire 4 and thus the
force exerted on the visor 12 via the transferring device 16. If
the wire controller 5 increases the pulling force exerted to the
wire 4, the moveable pulley 161 will move upward, thereby causing
the transferring cable 162 to pull the visor 12 upward against the
gravity, suction force and possibly a biasing force. If the
transferred pulling force is large enough to lift the visor 12, the
position of the visor 12 can be adjusted. However, even if the
transferred pulling force is not large enough to move the visor 12
to a new position, the gravity, suction force and possibly biasing
force may at least partially be cancelled, resulting in a different
behavior of the visor 12. By controlling the pulling force
dynamically during dredging, the dredging characteristics of the
drag head 10 can be adjusted during dredging.
[0100] In the embodiments described below depicted in FIGS. 2a-2d,
the visor 12 is biased. Biasing device 17 is provided for this
purpose on the dredging arrangement. The biasing device 17 is
provided on the visor 12 and on the drag head body 11 or lower end
of the suction pipe 2 such that the visor 12 is biased in a
direction towards the underwater bottom 6. The biasing device 17
exerts a biasing force on the visor 12 pushing the visor in a
downward direction, in this case such that it tends to rotate in a
downward direction towards the underwater bottom 6.
[0101] The transferring device 16 is provided to transfer the
pulling force on the wire 4 to the visor 12 such that the
transferred pulling force opposes the biasing force, i.e. cancels
or at least partially cancels the biasing force, suction force and
gravity acting on the visor 12.
[0102] Different embodiments are shown wherein the moveable part is
the visor 12 in FIGS. 2a-2d and which will be explained in more
detail below.
[0103] FIG. 2a shows an embodiment comprising a transferring device
16, comprising one or more pulleys 161, at least one of the pulleys
161 being a moveable pulley 161 and a transferring cable 162 being
guided via the one or more pulleys 161. Different to FIG. 1 is that
the dredging arrangement comprises a biasing device 17, biasing the
visor 12 in a downward direction by a spring 179, e.g. a mechanical
spring, connected to the visor 12 and the drag head body 11 and/or
lower end of the suction pipe 2. The (mechanical) spring is
normally mounted on top of the drag head 10 and may also be formed
by a plurality of parallel springs, e.g. one on the left and one at
the right side with respect to the dredging direction DD.
[0104] FIG. 2b shows an embodiment wherein the transferring device
16 comprises an hydraulic force transmitter, comprising two coupled
hydraulic cylinders. The hydraulic force transmitter comprises a
first hydraulic cylinder 164 and a first moveable piston 165 inside
the first hydraulic cylinder 164. The first hydraulic cylinder 164
is with one end connected to the moveable part, in this embodiment
the visor 12, and with its other end connected to the drag head
body 11.
[0105] Again, a biasing device 17 is provided, biasing the visor 12
in a downward direction by a (mechanical) spring 179 connected to
the visor 12 and the drag head body 11 and/or lower end of the
suction pipe 2.
[0106] The hydraulic force transmitter comprises a second hydraulic
cylinder 166 and a second moveable piston 167 inside the second
hydraulic cylinder 166. The second hydraulic piston 167 is
connected to the wire 4 by the wire connector 15.
[0107] The hydraulic force transmitter further comprises a fluid
reservoir 168 to compensate for differences in volumes of the first
and second hydraulic cylinders 164, 166 when the pistons are
moving.
[0108] The first and second hydraulic cylinders 164, 166 are in
fluid communication with each other, such that movement of the
first moveable piston 165 and second moveable piston 167 are
coupled: movement of the second moveable piston 167 will result in
movement of the first moveable piston 165. Fluid conduits 169 are
provided. A first fluid conduit 169 connects the underchamber 173
in the first hydraulic cylinder 164 (formed under the first piston
165) to the second underchamber 171 in the second hydraulic
cylinder 166 (formed under the second piston 167). A second fluid
conduit 169 connects the upperchamber 172 in the first hydraulic
cylinder 164 (formed above the first piston 165) to the second
upperchamber 170 in the second hydraulic cylinder 166 (formed above
the second piston 167).
[0109] Pulling the wire 4 will result in a pulling force being
exerted on the second piston 167. The second piston 167 will move
upward, pushing the hydraulic fluid out of the second upperchamber
170 of the second hydraulic cylinder 166 into the first
upperchamber 172 of the first hydraulic cylinder 164, causing the
second piston to move thereby transferring the pulling force to the
moveable part, in this embodiment the visor 12, counteracting the
biasing force.
[0110] Of course, the first and second hydraulic cylinders 164, 166
may be provided by a plurality of parallel cylinders.
[0111] Normally the first hydraulic cylinder 164 is mounted on top
of the drag head 10.
[0112] FIGS. 2c and 2d show embodiments wherein the transferring
device 16 comprises a lever 163, 163' which is connected to or
comprises the wire connector 15 and is connected to the at least
one moveable part 12, 14. The lever is rotatably connected to the
drag head body 11 or to the lower end of the suction pipe 2.
[0113] Again, biasing device 17 is provided, biasing the visor 12
in a downward direction by a mechanical spring 179 connected to the
visor 12 and the drag head body 11 and/or lower end of the suction
pipe 2.
[0114] FIG. 2c shows an embodiment wherein the lever 163 is formed
as an angled rod or bar, which rotatably connected to the lower end
of the suction pipe 2 at its angle. A first end of the lever 163 is
connected to the moveable part, for instance by means of a rod or
by means of a cable or wire 176 as shown in FIG. 2c. A second end
of the lever 163, opposite the first end, is connected to the wire
4 via the wire connector 15.
Of course, a plurality of parallel levers 163 may be provided,
which are each connected to the wire 4.
[0115] FIG. 2d shows an embodiment wherein the lever 163' is with
one end rotatably connected to the lower end of the suction pipe 2
and with a second end, opposite the first end, rotatably connected
to the moveable part, for instance by means of a cable or wire or
by means of a rod 176 as shown in FIG. 2d. Wire connector 15 is
provided halfway the lever 163'. Of course, the wire connector 15
may be provided at any other suitable position along the lever
163', to achieve an optimal balance of forces and moments of
force.
[0116] In general, the transferring device 16 may be dimensioned
such that a desired and suitable transfer rate of pulling force
into transferred pulling force is achieved. In the embodiments
shown in FIGS. 2c and 2d this may be achieved by selecting the
dimensions of the lever 163, 163'. In the embodiment shown in FIG.
2b, this may be done by selecting the dimensions of the hydraulic
cylinders 164, 166. In the embodiment shown in FIG. 2a this may be
achieved by positioning of the pulleys 162.
[0117] FIGS. 3a and 3b show alternative embodiments wherein the
moveable part is the valve 14. The valve 14 is shown as a rotatable
member, rotatable about an axis of rotation R1. The valve 14 may
rotate between a closed and an opened position. The valve 14 as
shown in FIGS. 3a and 3b is shown in an opened position. It is
noted that the part of the valve rotating towards the inside of the
dredging arrangement is larger than the part of the valve rotating
towards the outside of the dredging arrangement.
[0118] The transferring device 16 is similar to the transferring
device as shown in FIG. 2c. A lever 141 is connected to the valve
14 which is rotatable connected to lever 163 by a rod 176. Also
connected to rod 176 is biasing device 17, in this embodiment
formed by a mechanical spring 179, which is with its other end
connected to the drag head body 11. As will be explained below, in
the embodiment of FIG. 3b both the visor 12 and the valve 14 will
be controlled.
[0119] Optionally the embodiment shown in FIG. 3a may comprise a
further spring provided between the visor 12 and the drag head body
11.
[0120] The biasing device 17 biases the valve to its closed
position. By controlling the pulling force, which opposes the
biasing force, the under pressure needed to open the valve 14 can
be controlled. Also, the valve 14 can be opened by exerting a
pulling force which is large enough to overcome the biasing force.
It will be understood that other transferring devices 16, such as
shown in FIGS. 1-2d may be used as well.
[0121] FIG. 3b allows to control both the visor 12 and the valve
14, as the biasing device is provided by a mechanical spring 179a
provided between the drag head body 11 and the valve 14 and by a
second mechanical spring 179b provided between the visor 12 and the
drag head body 11. The visor 12 is connected to the force
transferring device 16 via an additional rod 176'.
[0122] The use of the embodiments shown will now be described in
more detail.
[0123] The biasing force acting on the visor 12 exerted by the
biasing device 17 pushes the visor 12 downwards, for instance with
a force of 8 ton and an arm of 0.5 meter, resulting in a downward
moment of 4 tonm, not taking into account the force of gravity and
the suction force.
[0124] The pulling force exerted on the wire 4 is transferred by
the transferring device 16 opposing the biasing force, resulting in
an upward moment of force. The pulling force can be controlled
dynamically during dredging.
[0125] In case no substantial pulling force is exerted, the
resulting upward moment resulting from the transferred pulling
force will be negligible. The visor 12 rests on the underwater
bottom 6 with a moment of force of 4 tonm.
[0126] If the transferred pulling force is increased but the
resulting upward moment resulting from the transferred pulling
force is in the range of 0-4 tonm, the visor 12 will not rotate
upward by the transferred pulling force only, but the visor 12 can
move upwards when the ground force moment exceeds the moments of
biasing device minus transferred pulling force moment, which will
result in a smaller excavation depth. This will also result in a
different behavior of the visor 12 when meeting obstacles.
[0127] If the pulling force is increased such that the resulting
upward moment resulting from the transferred pulling force exceeds
the 4 tonm, the visor 12 will be lifted and rotate upward. This
results in maximum upwards position of the visor 12 with respect to
the drag head.
[0128] When the visor 12 is in its lowest position and the
transferred pulling force is smaller than the downward force on the
visor (gravity+suction force+biasing force-ground force), the visor
will not move upward, but remains in its lowest position. Varying
the pulling force will result in a varying moving behavior of the
visor. Increasing the pulling force will result in a more flexible
visor behavior, which can be lifted more easily by the ground
forces.
[0129] When the visor 12 is in its highest position and the
transferred pulling force is greater than the downward force on the
visor (gravity+suction force+biasing force-ground force), the visor
will not move downward, but remains in its highest position.
Varying the pulling force will result in a varying moving behavior
of the visor. Decreasing the pulling force will result in more
flexible visor behavior.
[0130] By varying the pulling force of the wire 4, the visor can be
positioned in an intermediate position. The position of the visor
depends on the sum of all forces, including the transferred pulling
force, counter force of the underwater bottom 6 (ground force),
suction force and the gravity all acting on the visor. The sum of
these forces determines the position of the visor 12 during
dredging. In this intermediate position the production of the drag
head 10 can be controlled by changing the pulling force. If the
production is too high (i.e. visor 12 is in a too low position),
the pulling force has to be increased and vice versa.
[0131] There are two modes in which the dredging arrangement can be
operated.
[0132] In a force control mode, the biasing force is relatively
small with respect to the ground force. The force control mode
results in a dredging arrangement which can follow contours of the
underwater bottom 6 relatively well as it responds to changing
dredging conditions, for instance visor 12 will respond to a
changing ground force, without active control during dredging.
During dredging the exact position of the moveable parts 12, 14 may
be unknown, but this is not very relevant. The pulling force can be
controlled by monitoring the production.
[0133] In a position control mode, the biasing force is relatively
large with respect to the ground force. In such a mode, controlling
the pulling force and balancing the transferred pulling force with
the biasing force allows to control the position of the moveable
part 12, 14 and thereby the production of the drag head. The ground
force has little influence on the position of the moveable parts
12, 14. This allows to control the production accurately, although
for instance the visor 12 will not be able to follow contours of
the underwater bottom 6 very smoothly. For instance, if the
production is too high (visor angle is too large), the pulling
force may be increased to lift the visor 12 and vice versa.
[0134] A further embodiment is shown in FIG. 4. The embodiment
shown in FIG. 4 comprises a similar transferring device 16 as shown
in FIG. 2c. The biasing device 17 is with one end connected to the
lever 163 and with its other end to the drag head body 11 or lower
end of the suction pipe 2. The biasing force exerts a biasing force
opposing the pulling force.
[0135] First end of the lever 163 is connected to the visor 12, for
instance by means of a rod 176. Rod 176 is however not directly
connected to the visor 12, but via a lever 181 which can move
between a lower stop 182 and an upper stop 183. This provides lever
181 with a free moving range, in which the visor can be controlled
in a force control mode. Once the lever 181 abuts to one of the
stops 182, 183, the visor 12 is in a position control mode.
[0136] The descriptions above are intended to be illustrative, not
limiting. It will be apparent to the person skilled in the art that
alternative and equivalent embodiments of the invention can be
conceived and reduced to practice, without departing from the scope
of the claims set out below.
* * * * *