Field of the invention

The present invention relates to a dredge gate valve, generally used in offshore dredging operations whereby slurry is moved through a network of pipes and/or hoses from a first location to a second location. The invention further relates to a method of constructing a dredge gate valve.

Background art

From US 1 ,681 ,328 a gate valve is known for use with dredging machines, wherein a disc shaped valve of a proper diameter is placed within a Y-coupling which has an inlet end and two outlet branches. The disc shaped valve is supported within the Y-coupling to be moveable substantially horizontally between two openings of the outlet branches. Each of the outlet branches is provided with a ring that is fixed to the inner surface, e.g. by welding or brazing, so that the valve can be pushed against the ring when dredging material is supplied from the inlet end.

A gate valve that is suited for use with abrasive and corrosive slurries is known from European patent application EP 0 895 01 1 A2 which describes a gate valve assembly comprising two body housing members having coaxial through passages and being secured together in end to end relation, each of said passages being defined by a housing plate, with means to define a relatively narrow transverse gate chamber, in which a gate member is slidable between a valve open position in which the gate does not block fluid flow through the passages, and a closed position in which the gate is interposed between the passages.

In the art of dredging, gathering and/or depositing of dredging material, such as sand, is preferably carried out as a continuous process in which each of a multitude of pipes for transporting dredging material runs from one of multiple corresponding locations where dredging material is stored, to a site where the material is to be deposited. The locations from which the dredging material is transported typically comprise different compartments of a dredging vessel, e.g. ship equipped for gathering dredging material and/or for depositing the material at a desired site, each compartment holding some of the dredging material. At each of the locations a dredge gate valve is provided, which when in a closed position, prevents dredging material from passing from the corresponding location beyond the valve and through the pipe connected to the downstream end of the valve. When the valve is in an open position, the dredging material can be transported from the location upstream of the valve, through the valve to downstream of the gate valve and subsequently through the pipe to the site where it is to be deposited.

The pipes running from the downstream ends of two such valves may be joined at a Y- piece which has two branch pipes, each connected to a corresponding one of the pipes and which merge into a main pipe of the Y-piece. By closing off and/or opening corresponding dredge valves the location(s) from which dredging material is supplied to the site can be selected, e.g. based on amount and/or properties of dredging material at the two locations.

A drawback of this known arrangement is that when the relative position of one dredge valve to the other dredge valve is unknown, during connection of the branch pipes of the Y-piece to their respective dredge valves, the Y-piece typically will have to be modified to fit the gate valves. Moreover, the use of the gate valves themselves is costly, not only in material costs, but also since any space and weight occupied by the gates on a vessel cannot be used for storing dredging materials on the vessel.

It is an object of the present invention to provide a dredge gate valve that can be connected more easily to a Y-piece.

It is a further object of the present invention to provide a compact and light weight dredge gate valve. Summary of the invention

To this end, the present invention provides a dredge gate valve comprising: a housing; a first gate through said housing, for passage of dredging material; a second gate through said housing, for passage of dredging material; and a closing element, movable within said housing in a plane which intersects said first and second gate, between a first position in which it closes off said first gate, and a second position in which it closes off said second gate; wherein a maximum distance between edges of said first gate and said second gate within said plane is greater than the length of the closing element. The length of the closing element is the distance from a first edge portion of the closing element to an opposing second edge portion of the closing element, wherein upon movement of the closing element from the second position to the first position the second edge portion passes through the second gate, and wherein upon movement from the closing element from the first position to the second position the first edge portion passes through the first gate. The length of the closing element is preferably less than half the maximum distance between the edges of the first and the second gate. The edges of the first and second gate referred to lie in the inner circumferential surface of the respective gate and generally extend perpendicular to the closing element.

The relative position between the gates of this gave valve is substantially fixed as the two gates are provided in a single housing and fixed thereto. As a result, any Y-piece that is to be attached with its branch pipes to the two gates can be manufactured in advance, with the ends of the branch pipes being in the same relative position to each other as the two gates. The Y-piece may thus be attached to the gate valve in a quick and efficient manner, substantially without modifying the Y-piece. Moreover, the use of a common closing element for both gates instead of two separate closing elements results in a significant savings of space, weight and material cost. By using such a common element it can further be ensured that when one of the gates is completely open, the other gate is closed off by the closing element. Accidental opening or closing off of both gates is thus prevented.

The closing element is preferably adapted for linear movement between the first and second positions, substantially without rotating relative to the housing.

In an embodiment, the dredge valve further comprises a guide rail attached to the housing and adapted for supporting the closing element such that the closing element is suspended therefrom, wherein the closing element is movable between said first and second position in a direction parallel to the guide rail. Preferably, during use, the guide rail substantially completely supports the weight of the closing element, e.g. when the closing element is completely unsupported at its lower side, in particular at its lower distal edge. This manner of mounting the closing element within the housing allows the closing element to be moved between its first and second position with relatively little friction. In particular, any dredging material that may have gathered at a lower side of the closing element, opposite to the side of the closing element proximate to the guide rail, will be prevented from causing substantial friction during movement of the closing element.

In use the guide rail will generally be oriented substantially horizontally, so that moving the closing element between the first and second position requires a mainly horizontally directed force and no or only a relatively small vertically directed force. Thus, if an actuator such as a hydraulic cylinder is used for moving the closing element, then this actuator does not need to be able to support the weight of the closing element. In the event of failure of such an actuator, the closing element will simply remain in place supported by the guide rail, rather than fall down.

In an embodiment the guide rail extends in a linear direction, wherein said first and second gate are spaced apart along said linear direction. This configuration allows the closing element to slide easily between its first and second position in the linear direction, while supported by the guide rail. Preferably, the guide rail is arranged

In an embodiment the lower distal edge of the closing element hangs free and is spaced apart from the seals of both gates. Dredging material that has inadvertently entered the interior of the housing can thus flow along with gravity past the lower distal edge of the closing element. As a result, wear of the distal lower edge due to friction with dredging material when the closing element is moved between the first and second position is substantially avoided.

In an embodiment the housing comprises a main shell through which said first and second gate extend, and a detachable cover box substantially closing off said housing on a side of the guide rail opposite from where the closing element is suspended, said housing encapsulating the closing element. When the detachable cover box is detached from the housing, the interior of the housing can easily be inspected and accessed.

Preferably, an actuator is arranged partially or completely within the detachable cover box, for driving movement of the closing element between the first and second position. Besides substantially blocking ingress of material into the interior of the main shell, the cover box then also forms a protective shell around the actuator or part thereof

In an embodiment the dredge valve further comprises an actuator adapted for driving substantially linear movement of the closing element between said first and second positions, wherein the closing element is connected to a part of the actuator via a rotatable connection. The rotatable connection between the closing element and the actuator is preferably provided by a connecting element that is rotatably attached at least one of the closing element and the actuator, and is also attached, either fixedly or rotatably, to the other of the closing element and the actuator. Thus, even if the guide rail is not perfectly planar the closing element may be moved across the guide rail without risk of jamming. During frequent use of the valve it there is typically some wear between contacting surfaces between the guide rail and the closing element. The increased tolerance to wear and impression in machining of the contacting surfaces provided by the rotatable connection improves the operability of the valve and reduces maintenance costs. The rotatable connection may be adapted to allow the closing element to rotate relative to the guide rail in the plane which intersects the first and second gate during movement between the first and second position.

In an embodiment the rotatable connection comprises a slotted connection which allows both rotation and translation between the closing element and the part of the actuator. Such a slotted connection provides additional freedom of movement between the part of the actuator and the closing element to compensate for wear and/or dredging material or other material on the guide rail. Moreover, as substantially no load transfer occurs between the closing element and the actuator other than in the direction of actuation, the actuator is substantially prevented from being damaged due to transverse loads or bending loads thereon.

In an embodiment another part of said actuator is rotatably connected to the housing. The another part for instance comprises a part or end of the actuator which is spaced apart from where the actuator is connected to the closing element. Mounting the actuator in this manner to be rotatable with respect to the housing, provides additional freedom of movement for the actuator during movement of the closing element between the first and second position, to compensate for wear of the guide rail and/or dredging material or other material thereon.

In an alternative embodiment a part of the actuator is fixedly attached with respect to said housing. For instance, if the actuator is a hydraulic actuator, then its cylinder barrel may be fixedly attached with respect to the housing, while its piston can move to drive movement of the closing element. At least that part of the actuator which is fixed with respect to the housing may be arranged on the exterior of the housing as it does not require protection from external influences, thus facilitating inspection and maintenance of that part of the actuator.

In an embodiment said actuator comprises a hydraulic cylinder, wherein preferably water is used as hydraulic fluid. The use of water as hydraulic fluid is of great advantage offshore as it does not pose a risk to the environment.

In an embodiment said guide rail, when viewed in projection onto said plane, is arranged on a first side of said first and second gate, said dredge valve further comprising one or more flushing ports for passage of flushing liquid from the exterior of said housing to the interior of the housing and/or vice versa, wherein said flushing ports are preferably arranged on a second side of said first and second gate opposite said first side. Thus, any dredging material or other material which may collect in the interior of the housing and could eventually block the sliding movement of the closing element, can be removed and disposed of by flushing the interior with flushing liquid. Flushing may be carried out during movement of the closing element between the first and second position, or when the closing element is stationary with respect to the housing. In this embodiment, the housing is preferably substantially closed off at least on its a lower side, in such a manner that water in the interior of the housing can only exit the housing through the flushing ports and/or the first or second gate. In an embodiment, when viewed in projection onto said plane, the housing is provided with one or more openings are arranged for allowing dredging material to move out of the housing in a direction substantially parallel to said plane (P). Preferably, the guide rail is arranged in said housing on one side of the first and second gate, and the openings are provided in an opposite side of said housing and run from a portion of the first and/or second gate to debouching in said opposite side. The openings may be provided instead of the flushing ports described above and allow most or all material to move out of the interior of the housing, e.g. fall out at a bottom side of the housing, without requiring flushing liquid to be supplied. This kind of valve is therefore particularly suitable for use in locations where flushing liquid is not easily available.

In an embodiment the inner circumference of said second gate is of equal or smaller size than the inner circumference of said first gate. This allows two pipes having different inner diameters to be connected to the dredge valve.

In an embodiment the first and second gate have an inner diameter equal to or larger than 350 mm. Preferably the inner diameters are equal to or smaller than 1600 mm, more preferably equal to or smaller than 1200 mm.

In an embodiment a distance between the centers of said first and second gate is less than 1 ,5 times the diameter of said first gate and/or the diameter of said second gate. The dredge gate valve may thus be of a very compact construction.

In another embodiment each gate is provided with a seal adapted for substantially sealing the circumferential inner surface of the gate when the closing element is in a position in which it leaves the gate open, and adapted for abutting the closing element when the closing element is in a position in which it closes off the gate. Each seal preferably comprises multiple sealing elements, and is preferably made of, or comprises a plastic or rubber material. The addition of seals ensures the majority of dredging material flows through the pipes, instead of collecting in the interior of the housing. Preferably, each seal substantially fixed to the housing, so that the closing element can slide against the seal when it is moved between a position in which it leaves the gate that the seal is associated with open, to a position in which the closing element closes off said gate.

In an embodiment the closing element comprises or is made of stainless steel.

In an embodiment the closing element is provided a substantially rectangular plate having a thickness of between 1 and 3 cm.

According to a second aspect, the present invention provides a method of manufacturing dredge gate valves, preferably dredge gate valves according to the present invention as described herein, comprising, for each dredge gate valve to be manufactured, the steps of:

- constructing a housing comprising a frame, sidewalls and one or two front plates and one or two corresponding back plates, wherein said front and back plates are provided with openings for forming a first and a second gate through the housing;

- providing a guide rail in said housing on one side of said first and second gates;

- providing a closing element within said housing, in such a manner that the closing element is suspended from the guiderail and moveable within said housing between a first position in which it closes off said first gate, and a second position in which it closes off said second gate, wherein a maximum distance between edges of said first and second gate within said plane is greater than the length of the closing element.

Preferably, an actuator for driving said movement of the closing element is provided for each dredge gate valve as well.

When the housing has only one front plate and one back plate, both the front and back plate are each provided with an opening for the first gate and an opening for the second gate. When the housing has two front plates and two back plates, each of the front plates and back plates are provided with only a single opening for forming either the first or the second gate.

In an embodiment during manufacture of different dredge gate valves front and back plates with openings of different sizes are used for the production of different dredge gate valves, said different dredge gate valves having a same size housing, frame and sidewalls. A same type and dimension frame and sidewall can thus be used for constructing each housing, whereas the dimension of the inner circumferences of the gates of each valve is determined by the kind of front and back plates that are used. Dredge gate valves according to the invention may thus be efficiently manufactures in series.

Short description of drawings The present invention will be discussed in more detail below, with reference to the attached drawings, in which:

Fig. 1 shows an isometric view of a first embodiment of a twin gate dredge valve according to the present invention,

Fig. 2A shows an interior view of the twin gate dredge valve of Fig.1 ,

Fig. 2B and 2C respectively show a cross-sectional side view of the dredge valve of Fig. along line ll-B and along line ll-C of Fig. 2A,

Fig. 2D shows a cross-sectional side view of to a second embodiment of the invention,

Fig. 3 shows an isometric view of a third embodiment of the invention,

Fig. 4 shows a cross-sectional side view along plane IV of Fig.3,

Figs. 5A-5F schematically shows a number of front and back plates as may be part of a twin gate dredge valve according to the present invention, and

Fig. 6 schematically shows a dredging arrangement with Y-piece connected to a twin gate dredge valve according to the invention. Description of embodiments

Fig. 1 shows a dredge gate valve 100 according to the present invention with a housing comprising a housing main shell 1 and a cover box 2. The housing main shell 1 comprises a frame 10 to which a metal front plate 20 and a metal back plate 30 are attached. The dredge gate valve further comprises a first gate 3 and a second gate 4 which both extend completely through the housing main shell 1 and thus through the front and back plates 20,30. At a top side of the housing, i.e. at a side of the housing which during use of the dredge gate valve lies above the gates 3, 4, the cover box 2 is provided within which an actuator (see Fig. 2A) is arranged. Besides substantially closing off the housing main shell 1 , the cover box 2 protects the actuator against outside influences.

Within the first and second gate a respective seal 36,46 is provided which will be described in greater detail with reference to Figs. 2A and 2B. The dredge gate valve 100 further comprises a single closing element 5 that is completely arranged within the housing, and shown in Fig.1 in a position in which it closes off the second gate 4 while leaving open the first gate 3. Additionally, flushing ports 7 are provided at a lower side of the housing, i.e. on a side opposite from where the cover box 2 is arranged, through which flushing liquid may be introduced into the interior of the housing and discharged therefrom, to flush away any dredging material that may collect in the interior of the housing. The cover box 2 comprises an access port 29, here shown closed off by an access port cover 1 1 , for inspection and maintenance of the actuator.

The front and back plates 20,30 are welded to the frame 10, preferably in a water tight fashion, and such that the closing element 5 is substantially surrounded by the frame 10, front plate 20, and back plate 30 of the housing main shell 1. The closing element 5 is moveable within the housing main shell 1 between a position in which it leaves open the first gate 3 while closing off the second gate 4, as shown, or vice versa.

The seals 36,46, which may be provided on either or both front and back plates 20,30, enclose the circumference of the first and second gate 3,4, allowing the closing element 5 to pass past said seals when moving between the first gate and the second gate. The seals are provided to prevent, when a gate is open, dredging material from falling into the interior of the housing main shell 1 instead of being transported through the gate 3,4 in the axial direction of the gate. Any material that still falls through the seals 36,46 can be removed from the housing by flushing the inside of said housing with water, through flushing ports 7. In order to provide easy access to the interior of the housing, e.g. for maintenance purposes and/or replacing the seals, the cover box 2 is detachably attached to the housing main shell 1 . Fig.2A schematically shows an interior view of the dredge gate valve 100 of Fig.1 wherein the front plate 20 has been removed from the main housing shell 1 . The gates 3,4 have equal diameters and respective inner circumferential surfaces 3a, 4a, with inner circumferential surface 4a shown in dotted lines as the closing element 5 is shown lying in front thereof. The respective centres C1 , C2 of the first and second gate 3,4 are arranged such that a virtual line connecting these centres C1 ,C2 is substantially parallel to the guide rail 50. The single closing element 5 has a length L in its direction of movement between the two gates 3, 4. As this length L is less than half the maximum distance d between the inner circumferential surfaces 3a, 4a of gates 3,4, the closing element may be relatively light weight and can be constructed using relatively small amount of material. The closing element 5 is connected to hydraulic cylinder 60 by means of a connecting element 6 that is supported on a linear guide rail 50. The closing element 5 is thus suspended from the guide rail 50, with the weight of the closing element 5 substantially completely supported by the guide rail 50 via the connecting element 6. At one end 61 the hydraulic cylinder 60 is rotatably connected to the connecting element 6, and at an opposite end 62 the hydraulic cylinder 60 is rotatably connected with respect to the housing, in particular with respect to cover box 2 thereof.

Both the guide rail 50 and connecting element 6 may be subjected to wear each time the closing element is moved over the guide rail, and even without such wear a surface of contacting surfaces guide rai 50 and/or connecting element 6 may not be completely planar. By rotatably connecting the hydraulic cylinder at both of its ends, some of this wear and/or unevenness can be compensated for by rotational movement of the hydraulic cylinder relative to the guide rail.

The hydraulic fluid used for actuating the cylinder 60 is preferably water, though other hydraulic fluid, e.g. oil, may be used instead. The actuator is adapted for moving the closing element between a first position in which it closes off said first gate 3 while leaving open the second gate 4, and a second position in which it closes of the second gate 4 while leaving open the first gate 3, thus ensuring that at no time both gates are completely closed or completely open.

Seals 36, 46 lie against the back plate 30 of the housing. Two flanged ports 7 which are located on opposing short sides of the housing frame provide passage for flushing liquid to and from the interior of the housing for flushing any dredging material out of the interior and/or away from the seals. Thus, water may be injected through the first port 7 adjacent to the first gate 3, using the port as an inlet, and may exit the housing through the second port 7 adjacent to the second gate 4 together with any dredging material that may have collected inside the housing. The in which the flushing liquid flows within the housing can be switched by switching the inlet and outlet ports.

Fig.2B and 2C show respectively a cross-sectional side view of the dredge valve through the first gate 3 when open, taken along line MB of Fig. 2A, and through the second gate 4 when closed, taken along line IIC of Fig. 2A. Both figures show the housing main shell 1 , the housing cover box 2 and the guide rail 50 arranged in the cover box 2. The cover box 2 is detachably attached to the housing main shell 1 , e.g. by means of a bolt and nut connection, and contains the guide rail 50. The housing main shell 1 comprises the front and back plates 20,30 which are welded to the housing frame 10 and provided with openings for the first gate 3 and second gate 4. The opening of flushing port 7 on the interior of the housing main shell 1 can be seen below the first gate.

Fig. 2B shows two seal parts 36a and 36b of seal 36, which abut each other along the inner circumference of the first gate 3. As a result, inner circumference of the first gate 3 is substantially contiguous, and dredging material flowing there through is substantially prevented from entering the interior of the housing when the gate is not closed off by the closing element.

Fig. 2C shows two seal parts 46a, 46b of seal 46, which each abut an opposite side of the closing element 5 along the inner circumference of the second gate 4. The seals substantially prevent dredging material from entering the interior of the housing when the gate 4 is closed off by the closing element 5. As can be seen, the closing element 5 is completely arranged within the housing formed by main housing shell 1 and cover box 2, with main housing shell 1 enclosing more than 80% of the closing element, and with cover box 2 enclosing guide rail 50 as well as connecting element 6 which is fixedly connected to the closing element 5 such that the closing element is suspended, via connecting means 6, on the guide rail 50 and can be moved along the guide rail. Though the seals 46a, 46 contact opposite sides of the closing element 5, the weight of the closing element 5 is substantially supported by the guide rail 50. The lower edge of the closing element which extends between the opposing sides thus hangs substantially or completely free, avoiding friction along the lower edge and facilitating removal of any dredging along said edge. Any dredging material that has passed beyond the seals into the interior of the housing can be flushed out via the flushing channel 7. The cover box 2 can be detached from the housing main shell 1 to provide access to replace the seals 36,46 and/or carry out maintenance of the valve.

Fig. 2D shows a cross-sectional side view of the dredge valve through the second gate 4 when closed off for a second embodiment. This second embodiment is similar to the first embodiment shown in Fig. 2A, but the housing main shell 1 , instead of being substantially water tight at a bottom side thereof below the gate, is provided at its bottom side with an elongated opening 8 which extends from a lower side of both gates 3,4 and debouches in said bottom side. The opening 8 is arranged such that, when dredging material passes from within the inner circumferential surface of gate 3 or 4 to the interior of the housing main shell 1 , the dredging material can fall out of the housing main shell 1 at the bottom side due to gravity. Thus, less or no flushing of the seals 36a, 36b, 46a, 46b is required, and the risk of dredging material filling up the interior of the housing main shell is reduced. The seals 36,46 within the housing main shell 1 can easily be inspected and/or accessed through the opening 8. Moreover, even during use, i.e. while dredging material is transported through one of the gates of the valve, functioning of the seals can be monitored by checking the amount of dredging material that passes through the opening in the bottom side of the housing main shell.

When viewed in projection on the plane P, both gates 3,4 are arranged between the side of the housing in which the opening or openings debouch and the guide rail 50. Though preferably the bottom side of the housing main shell 1 is provided with a single such opening 8 having a length substantially equal to the maximum distance between the edges of the first gate and second gate within the plane P, alternatively, multiple openings can be used, for example two openings, each located below its corresponding gate and having a length equal to or greater than the length L of the closing element 5.

Fig. 3 shows an isometric view of a third embodiment 200 of the present invention, with a housing main shell 1 ', a housing cover box 2' and an actuator 60'. The housing main shell 1 ' comprises a housing frame 10, two separate front plates 21 ,22 and two separate back plates 31 ,32, as well as seals 36,46. The housing main shell 1 ' encapsulates a single closing element 5. Here a first gate 3 is provided through the first front and back plates 21 ,31 and a second gate 4 is provided through the second front and back plates 22,32. The flushing ports 7 which are provided in the housing main shell 1 ' on opposite side of the gates are here shown covered by plates 9 which close off access to the interior of the housing through the ports when the valve 200 is not in use. The housing cover box 2' is fitted with an access port 29'here also shown covered by a removable cover 1 1 ', for inspection and maintenance.

The housing is constructed in a similar manner as the embodiment of Fig.1 , with both gates 3,4 having a substantially same diameter. Fig.3 however shows the front and back of the housing main shell 1 ' comprise respectively two front 21 ,22 plates and two back plates 31 ,32. By using two front plates and two corresponding back plates instead of a single front plate and a single back plate, construction of a single valve with two different types of gates, e.g. have different gate diameters, is facilitated. Though the outer dimensions of the front and back plates for the two gates are preferably the same, pairs of front- and back plates 21 ,31 and 22,32 may thus be selected such that the diameters of the gate-openings of one pair of front- and back plate for one gate of the valve differ from the diameters of another pair of front- and back plate that is used for the other gate of the valve.

The actuator 60', here an hydraulic cylinder, is fixedly attached to the housing cover box 2' by means of a bolt connection 65 such that the position of the cylinder barrel 66 of the actuator is fixed with respect to the housing, while the actuator piston 64 (see Fig. 4) can move relative to the cylinder barrel 66.

Fig. 4 shows the interior of the twin gate dredge valve shown in Fig.3. The closing element 5 is connected to the actuator 60' by means of a slotted connection 63 formed by an end of actuator piston 64 which is rotatably and translatably received in a slot 67 in connecting element 6. The slotted connection is adapted for compensating for wear and/or manufacturing impression of the guide rail 50 in a similar manner as described for the first embodiment shown in Fig. 2A. Fig. 5 A-F schematically show various configurations of twin gate dredge valve front and back plates as may be used in the present invention. Figs. 5 A-C each schematically show a single front- or back plate 20,30 with two through openings to form part of respective first and second gates 3,4. Figs. 5 D-F each show two separate smaller plates 21 ,31 , 22,32 which together from a front of back of the housing main shell, each of the plates having only one through-opening to form part of either the first gate 3 or second gate 4. During construction of the twin gate valve the through openings for the first and second gate 3,4 may thus conveniently be selected to be of a same diameter d1 ,d2, as shown in Figs. 5A and 5D, or of different diameter as shown in Figs. 5B, 5C, 5E and 5F. Generally, when the plates form part of the housing main shell of the invention, the through openings for the first gate 3 and second gate 4 will lie on a line parallel to the upper and/or lower edge of the plates, as shown in Figs. 5A, 5B, 5D and 5E, and thus parallel to the guide rail. However, this is not required. For instance, when the through openings for the first gate 3 and the second gate 4 are of different diameters, as illustrated in Figs. 5C and 5F, in order to facilitate removal of dredging material from the interior of the housing and/or from the covering element, it may be advantageous to arrange these openings such that their lower edges lie on a line parallel to the lower edge of the plates and thus parallel to the guide rail. The front and back plates can be manufactured either as single front- and back plates each provided with two through openings and having width W and height H, or as two separate front- and back plates each provided with only a single through opening and having a joint width smaller or equal to W and a joint height equal to H. Welding such plates of standardized outer dimensions onto matching housing frames of standardized dimensions results in only requiring a relatively small amount of components to create a series of twin gate valves catering for dredging pipes of a range of dimensions. Housing frames, cover boxes, actuators and/or closing elements of same construction and dimensions could thus be combined with selected front and back plates to create twin gate valves with gate diameters anywhere in a range between 350 mm and 1600 mm, preferably within a range of between 800 and 1200 mm.

Fig. 6 shows a schematic overview of a dredging arrangement including a twin gate dredge valve 140 according to the present invention, e.g. a dredge valve 100 as shown in Fig. 1 or a dredge valve 200 as shown in Fig. 3. The dredging arrangement comprises a Y-piece 1 10 connected to a downstream end of the twin gate valve 140 for transport of dredging material that is supplied from one of pipes 120, 130 connected at a upstream end of the twin gate valve 140. In the configuration shown, closing element 145 of the twin gate valve, which is shown in dotted lines, closes off the first gate 143 while leaving open the second gate 144 so that dredging material may flow through the gate along direction of flow F. The closing element may be moved to another position in which it closes off the second gate 144 while leaving open the first gate 143.

Branch pipes 1 12, 1 13 of the Y-piece 1 10 merge into a single main pipe 11 1 of the Y-piece, from which the dredging material can be transported to a location where it is to be deposited. As the relative positions of the gates 143, 144 of the twin gate valve 140 are fixed, both the pipes 120, 130 and the Y-piece 1 10 can be accurately positioned, e.g. on a dredging vessel, before the twin gate valve 140 module is placed therebetween, and substantially without requiring further modification and/or repositioning thereof once the twice gate valve has been placed between.

The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims.