LOADING SPACE AND METHOD OF LOADING SUCH A LOADING SPACE WITH SLURRY

The method of loading a loading space (1) of a vessel with dredging materials includes   a) loading a slurry including of dredging materials and water into the loading space (1), and   b) generating at least one pressure wave through the slurry inside the loading space (1) to enhance the formation of a settled bed (5) of the dredging materials.

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

DETAILED DESCRIPTION

As described above,FIG. 1shows a loading space1, for instance of a trailing suction hopper dredger (TSHD) or a cutter suction dredger (CSD).

FIG. 2shows a loading space1according to an embodiment. Also shown are loading means, here represented by a pump10with a discharge conduit11provided to pump slurry into the loading space1, indicated by the dashed arrow. The pump10may be provided on the deck of the vessel or on any other suitable location. The loading means10may of course comprise further equipment, such as dredging equipment, not shown in the figures.

During the dredging operation, the level of the mixture in the loading space1rises, while the dredging materials settle, i.e. sink to the bottom of the loading space1. The settled part is referred to as the sand bed or settled bed5(settled sand). The unsettled mixture above it is referred to as the mixture soup3. If the maximum loading space level is reached, the top layer of the mixture soup3is fed outwards via a so-called overflow7and loading can continue for a further period (this situation is not shown inFIG. 2).

The loading space1further comprises pressure wave generating means20for generating pressure waves through the slurry in the loading space1, especially through the mixture soup3. This is done because pressure waves accelerate the settling of the dredging materials and thus promotes growth of the settled bed5.

The pressure wave generating means20comprise a moveable member21which is moveable and positioned at least partially inside the loading space1. The pressure wave generating means20further comprise an actuator22arranged to move the moveable member21to generate the pressure waves. The actuator22may be a hydraulic cylinder or an hydraulic ram arranged to move the moveable member21in a substantially horizontal reciprocating manner. The reciprocating movement may be a movement comprising movement in a first direction with a velocity which is at least five time greater than the reciprocating movement in the opposite, second direction. This is explained in more detail below with reference toFIG. 4. As shown, the actuator22may comprise a cylinder with a piston moveable positioned inside the cylinder. The actuator22is driven or energized by a hydraulic system, which is not shown in the Figures. It will be understood that alternative actuators22can be used instead.

The actuator22may be connected to a part of the moveable member21which protrudes above the loading space1, such that the actuator22may be positioned outside the loading space1, for instance on the deck8of the vessel.

The moveable member21may be a plate21which is positioned parallel to a side wall of the loading space1and has substantially the same dimensions as that side wall of the loading space1. In that case, the actuator22may be with one end connected to an upper edge of the wall212protruding above the loading space1. A lower edge211of the plate21is hingeably connected to the side wall of the loading space1, for instance by way of a flexible connection member24, such as a rubber strip.

The moveable member21may be flexible, for instance a flexible plate, to prevent breakage of the moveable member21when part of the moveable member21is fixed by the rising settled bed5and can thus not move. The moveable member21may be made of a fibre enforced material to provide flexibility and strength.

FIG. 3shows an alternative embodiment in which the plate21is made of a frame of flexible spring steel strips215in which a number of partially overlapping plate parts216are mounted. When the plate21bends, the frame bends, while the plate parts216slide over each other.

A control unit40may be provided to control the pressure generating means20. The control unit40may be formed as a computer and may comprise a central processing unit41and a memory42which are capable of communicating with each other (both not shown), the memory42comprising programming lines or instructions which can be read and executed by the central processing unit41to provide the control unit40with the functionality as described. The functionality of the control unit40may also be embedded in suitable hardware circuitry.

The control unit40may be arranged to control the frequency, the length of the stroke and the velocities in the first and second directions of the actuator22.

Examples of a reciprocating motions are schematically shown inFIGS. 4a-b, showing diagrams in which movement of the actuator22is shown as a function of time.FIG. 4ashows a saw tooth function in which movement in the first direction is substantially, at least five times, faster/shorter than movement in the second, opposite direction.

The control unit40may control the loading means and the pressure wave generation means20to perform the following actions:

a) loading a slurry comprising dredging materials and water into the loading space1, and

b) generating at least one pressure wave through the slurry inside the loading space1to enhance the formation of a settled bed5of the dredging materials.

Action b) may be performed during action a), however, according to an embodiment, action b) is at least partially performed while action a) is stopped or interrupted. Action b) may comprise generating pressure waves as shown inFIG. 4a.

During action b), the control unit40may control the actuator22to alternately go through periods of pressure generation (I) and idle periods (II). An example of such an embodiment is shown inFIG. 4b.

During the periods of pressure generation (I) one or more reciprocating motions (only one is shown inFIG. 4b) may be performed. In other words, the pressure generating means20may be controlled to generate one or more pressure waves, followed by an idle period (II) in which no pressure wave(s) is/are generated, followed by a new period of pressure generation (I) in which one or more new pressure wave(s) is/are generated, etc.

The control unit40may also be arranged to control the loading means to stop or interrupt loading during action b) in order to reduce the kinematic disturbance of the mixture soup3to create optimal conditions for the settling process.

Also, the control unit40may control the loading means to load another loading space1or another sub-space of the loading space during action b).

FIG. 5shows an alternative embodiment in which the loading space1comprises a plurality of sub-spaces1′,1″, each having a (telescopic) overflow7. The control unit40may be arranged to control the loading means to load slurry into the first or second sub-space1′,1″ via a first and second discharge conduit11′,11″.

The control unit40may be arranged to control the loading means to load slurry into the second sub-space1″ while action b) is performed with respect to first sub-space1′. This way, loading can be done even more efficiently. It will be understood that more than two sub-spaces (as shown inFIG. 5) may be provided. The different sub-spaces1′,1″ may be loaded one after the other, such that no overflow is generated, while pressure waves are generated (i.e. action b) is applied) to the sub-spaces already loaded. After the last sub-space is loaded, the loading means10may be controlled by the control unit40to continue performing action a) (loading) with respect to the first sub-space1′, causing overflow which is now relatively clean as the settled bed5has been given time to form enhanced by the generated pressure waves. Continued loading may be continued for the first sub-space1′ until the density of the overflow reaches a predetermined level. Then, the next sub-spaces may be loaded one after the other. This process may be repeated several times.

As mentioned above, the overflow7may be a telescopic overflow of which the height can be adjusted. In order to create an even cleaner overflow, after performing action b) and before resuming performing action a) with respect to a specific a loading space1or sub-space1′.1″, the telescopic overflow7may be lowered in order to overflow the relatively clean top layer of the mixture soup3. The overflow7is then again raised before action a) is resumed for the specific loading space1/sub-space1′,1″. Again, this process may be repeated several times.

In case the loading space1is provided with doors in the bottom of the loading space1, the sub-spaces1′,1″ are preferably not smaller than the size of one such door. On the other hand, the loading space1or the sub-spaces1′,1″ may not be too large, as the pressure wave preferably reaches the other side of the loading space1or sub-space1′,1″.

The embodiments make it possible to create a relatively clean overflow, for instance an overflow with a density of ρ-1050 kg/m3 or even 1020 kg/m3 even in a situation wherein the settled bed is relatively high, i.e. close to the height of the overflow7. This is an improved with respect to an overflow having a density close to the density of the slurry being pumped into the loading space1, which may be in the range of 1200-1700 kg/m3.

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.