CN1606649A - Suction manifold for dredging - Google Patents

Abstract

A suction pipe for dredging, comprising two inlets or two sets of inlets (1, 2), the first inlet or lower inlet or lower group of inlets (1) being arranged at or near the lower end of the suction pipe and adapted to be drawn from the bottom To suck up the sediment together with a quantity of water, a second or upper inlet or group of inlets (2) is placed at a vertical distance above the first inlet or group of inlets (1) and is adapted to suck in water only. The suction line comprises an inner tube (3) suitable for transporting water and sediment, the upper end of which is adapted to be connected to a suction hose of approximately the same diameter, the lower part of said inner tube being surrounded by an outer sleeve (4) encloses thus substantially delimiting an annular space (5) between the inner tube (3) and the outer sleeve (4). At least one opening forming the upper inlet (2) is arranged at the upper end of the sleeve (4) into the space (5), while the inlet (1) is arranged in the lower part of the tube (3), close to the at least partially open inner The axial ends of the tube (3), and the outer sleeve (4) are also open in the direction of axial extension of the inner tube (3).

Description

Suction pipes for dredging

technical field

This invention relates to suction pipes for dredging in subsea reservoirs and the like. More particularly the present invention relates to a suction pipeline for dredging, said pipeline comprising two inlets or two groups of inlets, the first inlet or group of inlets being located at or near the lowermost part of the dredging apparatus and adapted to extract water from the seabed The sediment is pumped together with a quantity of water and a second inlet or group of inlets is arranged at a vertical distance from the first inlet or group of inlets and adapted to pump water only.

Background technique

In many instances it is desirable to remove sediment from areas of the ocean floor. These situations may be in harbours, shipping channels or areas of polluted sediment. It may be desirable to deposit the sediment elsewhere underwater or it may be more convenient to deposit the sediment ashore or to purify the sediment before being deposited.

Furthermore, mainly in rural water reserves, where rivers contain large amounts of sediment and where water resources are substantially filled with sediment to such an extent that the water capacity becomes small. Furthermore the deposits can affect stability, block sluice gates/channels etc. and cause unwanted wear of the turbines if aqueous deposits enter the power plant. Sediments may range from large boulders and the like to very fine grained silt and clay.

When dredging by means of a suction pipe, the pipe is placed in a defined first position on the seafloor in contact with the sediment and will suck up the sediment to form a sinkhole in the bottom. This depends somewhat on how loose or compact the sediment is at a particular location. Sediment around the sinkhole will eventually start to fall into the sinkhole as the sinkhole gets deeper and its walls steeper. Sometimes large amounts of sediment fall into the trap without any warning, which leads to possible filling and/or blockage of the suction line.

A special suction duct like a saxophone head has been proposed for dredging. The saxophone head is the first known example of a suction duct having two inlets or two sets of inlets, the first inlet or set of inlets being placed at or near the lowermost part of the duct and adapted to suck up deposits from the bottom and a certain amount of water, while a second inlet or group of inlets is arranged at a vertical distance above said first inlet or group of inlets and is adapted to absorb water only. This suction line has the advantage that it is largely self-regulating with respect to the concentration of the sediment to be sucked up, so that it can largely disregard the low risk of clogging or loss of its efficiency. On the other hand it has the disadvantage of being relatively large and at the same time the sediment has to be transported through curved pipes with the risk that large particles may clog the pipes. Furthermore, the device is not particularly well adapted to on-site dredging.

A particular problem is that the conditions of the seafloor vary so much that suction pipes that work well in loose sediments often do not work in denser sediments. Thus limiting the ability to adjust the suction characteristics with subsea conditions, and much better for saxophones than conventional pipes. The advantages of such pipes can be summarized as follows: At high concentrations of deposits in pipes and hoses/pipes, the velocity inside the pipe is reduced and thus its suction force is reduced. In the next time interval, therefore, a smaller amount of sediment and a larger amount of water are sucked up. As a result the concentration of sediment in the pipes and tubes decreases, the velocity increases and the suction power increases again. Suction force in this context means that there is a pressure lower than atmospheric pressure at the sediment inlet of the pipe.

If there is a hard crust at the surface, the saxophone head will not be well suited to penetrate this crust into looser sediments which are more easily sucked up.

Danish patent application No. 120070 describes a suction device for dredging underwater sediments which comprises a pipe with two inlets. A substantially closed sleeve surrounds the straight inner tube, which sleeve has at its upper end two openings through which water is ejected from the surface under pressure. Near the lower end of the sleeve, there is a hole for entering the inner tube, the length of which is telescopically adjustable. In working condition the pipe is forced into and fluidized by using super water supply pressure into the part of the sediment close to the pipe, after which the sediment is sucked/pumped up together with a certain amount of water. The disadvantage of this device is that it includes movable parts that can become clogged and that it requires maintenance, in addition to a system for supplying water under pressure.

Contents of the invention

It is therefore an object of the present invention to provide a suction pipe for dredging which is largely self-regulating with respect to the concentration of the sediment to be sucked up, which makes it possible to treat large particles of large diameter like stones without the risk of clogging the tubes.

Another object of the present invention is to provide a suction duct that is relatively compact and can be easily controlled by a remote controlled vehicle (ROV).

It is a further object of the present invention to provide a suction pipe as described above which is capable of penetrating into the upper part of the generally denser layers of the seabed so that dredging can be carried out from below the sediment and looser layers.

The above object is achieved by a suction line of the type described at the outset and characterized by the features defined in claim 1 .

Preferred embodiments of the invention are disclosed by the dependent claims.

The difference from known saxophone heads is that the suction line according to the invention can penetrate relatively dense sediment layers. At the same time it exhibits the nice property shared with the sax head, that it is largely self-regulating, so that after a period in which a larger amount of sediment has been sucked up, a period in which a smaller amount of sediment will be sucked up is followed The up cycle causes the concentration of the sediment in the pipe 3 to fluctuate around the normal level.

Due to its smaller design, the suction head according to the invention can be adjusted and controlled by the ROV, so it can be easily controlled and positioned with high precision. This is important for certain types of dredging situations, while in other situations precise control may not be required. A suction duct according to the invention is therefore generally no better than a saxophone, but it is better in the case of dredging work where accuracy and maneuverability are crucial factors. An example of such dredging is dredging performed to expose certain sediment-covered objects or areas, such as sluice gates, pipes or other equipment for association with dam installations or other subsea installations.

The detailed design of the suction duct according to the invention can vary, but it is preferred that the suction duct is substantially straight and when connected to a pipe comprises a predominantly straight axial extension of the suction pipe or hose .

Furthermore, it is expedient for the sleeve to surround the inner tube and to limit the space around the inner tube to have such a simple and regular shape, ie its outer shape is substantially cylindrical. The inner space element or support element which keeps the sleeve in a fixed position relative to the pipe can be designed in many different ways. The element may be the described means for attaching the sleeve to the pipe, for example may comprise screws, bolts, rivets, adhesive means, welding, brazing or other means. The invention is not limited to any particular method of arrangement of such fastening means or spacing means to the sleeve.

It is actually possible to replace parts of the sleeve with a special tube or the like which is arranged partly along the "inner" tube and thus does not surround or encase it in the entire area from the upper inlet to the lower inlet. Such a solution is equivalent to the solution described here when based on the same hydrodynamic principle as the preferred embodiment of the invention.

At its lower end the sleeve may differ slightly from a simple cylinder, for example tapered to a cross-section of a dimension close to the cross-section of the inner tube, possibly reinforced and/or provided with a wall or with teeth suitable To break through the dense sediment layer. In addition, the lower edge of the sleeve can be provided with an annular flange, which includes nozzles connected to means for supplying water under pressure, thus making it possible to high-pressure scour where it would be difficult to penetrate the sea bottom without it.

Description of drawings

Figure 1a is a longitudinal sectional view of an embodiment of the invention in working mode,

Fig. 1 b is an enlarged cross-sectional view of the pipeline in Fig. 1 taken along line II-II,

Figure 2a is a longitudinal sectional view of a different embodiment of a pipe according to the invention,

Figure 2b is an enlarged cross-sectional view of the pipeline of Figure 2a taken along line II-II,

Fig. 3 is a longitudinal sectional view of another embodiment of the present invention,

Fig. 4a is also a longitudinal sectional view of another embodiment of the present invention,

Fig. 4b is an end view of the embodiment according to Fig. 4 .

Detailed ways

FIG. 1 a shows a suction duct according to the invention comprising an inner tube 3 and an outer sleeve 4 defining the inner and outer boundaries of an annular space 5 . An opening 1 into the inner tube 3 is provided in the lower part of the suction line, said opening having the same or similar cross-section as the inner tube 3 . At the upper end of the outer sleeve 4 at least one opening 2 into the space 5 is provided. By inserting the vertical extension of the sleeve at the relevant use or application it can be ensured that opening 2 will generally only suck up water, whereas opening 1 will suck up a certain amount of water and sediment. In the upper part of the pipe, the inner pipe 3 is connected to a suction hose 6 through which the sediment is conveyed for further processing or for storage in some other place.

Fig. 1b is a cross-sectional view of the suction duct along line I-I of Fig. 1a. For the shown embodiment there are four inlets 2 into the space 5 . The illustrated embodiment comprises eight joining members 8 for joining the outer sleeve 4 with the inner tube 3 and delimiting the opening 2 . The joining member 8 may have a limited vertical extension which may have an extension which corresponds exactly or substantially to the extension of the outer sleeve, whereby the space 5 is divided into a corresponding number of separate cavities. Another option is not to set the support member at the uppermost end of the outer sleeve, but at the lower end. There is also an option to use more or less than 4 support members.

The cross-sectional areas of the space 5 and the upper opening 2 and the lower opening 1 are generally determined and designed to determine the relationship between the suction force and the amount of water entering the upper opening 2 .

Figures 2a and 2b show another embodiment of the suction duct according to the invention. The difference is not great, while in the upper region between the outer sleeve 4 and the inner tube 3 is partially closed by a "cap" 7 to limit the opening 2 into the space 5 . Yet another option is to use a cover with a valve (not shown), which allows the size of the opening 2 to be varied according to the area used or even under operating conditions when the valve is set remotely. The valve can optionally be designed as a "safety valve" which opens when the subatmospheric pressure becomes sufficiently high.

Figure 3 shows details of an additional option of the suction duct according to the invention. Here the lower edge of the outer sleeve 4 is provided with a special edge 9 suitable for penetrating particularly hard deposit layers. Instead of smooth edges, teeth can be used which, when worn, can be replaced individually or in groups.

Instead or in addition to such edges or such teeth, the same area of the suction pipe can also be provided with nozzles 11 for high-pressure flushing of deposits, as shown in FIGS. 4a and 4b, in order to loosen particularly hard or dense deposit layers. These nozzles can be arranged on an annular flange 10 surrounding the opening 1 and can be arranged in such a way that the water jets are operative in an axial direction relative to the inner tube 3, as indicated by the arrows in FIG. 4a.

Figure 4b shows an end view of the suction duct of Figure 4a with any number of nozzles 11 distributed around the opening 1 around the annular flange 10. The construction of Figures 4a and 4b is generally somewhat more complex than the other shown embodiments due to the inclusion of pressurized water supply at or near the suction line.

Among other things, the device according to the invention has the advantage that, in its simplest form, the device also includes any movable parts, while working only by means of simple hydrodynamic principles. The device does not require a supply of pressurized water, and it is convenient if for some purposes pressurized water or mechanical means are used to break up dense clumps of sediment.

claims

(Amended in accordance with Article 19 of the Treaty)

1. A suction pipeline for dredging, said pipeline comprising two inlets or two groups of inlets (1, 2), the first or lower inlet or group of inlets (1) being arranged at or close to the suction pipeline and is suitable for sucking up the sediment at the bottom together with a certain amount of water, the second inlet or upper inlet or inlet group (2) is arranged at a vertical distance above the first inlet or inlet group (1) and suitable only for the suction of water, the suction duct comprises an inner tube (3) adapted to transport water and sediments, the upper end of which inner tube (3) is adapted to be connected to a suction hose of approximately the same diameter, said The lower part of the inner tube is surrounded by an outer sleeve (4) such that a substantially cylindrical space (5) is defined between the lower part of said inner tube (3) and said surrounding sleeve (4), which It is characterized in that the space (5) is opened to the surrounding water through the upper inlet or group of upper inlets (2) and the lower inlet or group of lower inlets (1).

2. Suction duct according to claim 1, characterized in that the suction duct is substantially straight.

3. The suction line as claimed in claim 1, characterized in that the surrounding outer sleeve (4) is substantially cylindrical.

4. Suction duct according to claim 1, characterized in that said duct comprises means (10, 11) of high-pressure external flushing at the lower inlet (1) of the suction duct.

5. Suction duct according to claim 1, characterized in that said means comprise a rim (9) with teeth for penetrating dense deposits at its lower end.

6. Suction duct according to claim 1, characterized in that the upper opening (2) is provided with an adjustable valve.

7. Suction duct according to claim 1, characterized in that the upper opening is provided with a normally closed valve which is arranged to open when the subatmospheric pressure reaches a predetermined level.

Claims (7)

1. A suction pipe for dredging comprising two inlets or two sets of inlets (1, 2), the first or lower inlet or group of inlets (1) being arranged at or near the lower end of the suction pipe , and is adapted to suck up the sediment at the bottom together with a certain amount of water, the second opening or upper inlet or inlet group (2) is arranged at a vertical distance above the first inlet or inlet group (1), and only Suitable for suctioning water, the suction duct comprises an inner tube (3) adapted to transport water and sediments, the upper end of which is adapted to be connected to a suction hose of approximately the same diameter, the lower part of said inner tube Encased by an outer sleeve (4), thus defining a substantially annular space (5) between the lower part of said inner tube (3) and said enclosed outer sleeve (4), characterized in that At least one opening forming the upper inlet (2) is arranged at the upper end of the outer sleeve (4) into the space (5), while the inlet (1) is arranged in the lower part of the inner tube (3), close to the at least partially open inner tube The axial end of (3), while the outer sleeve (4) is open in an axially extending direction of the inner tube (3). 2. Suction duct according to claim 1, characterized in that the suction duct is substantially straight. 3. The suction line as claimed in claim 1, characterized in that the surrounding outer sleeve (4) is substantially cylindrical. 4. Suction duct according to claim 1, characterized in that said duct comprises means (10, 11) of high-pressure external flushing at the lower inlet (1) of the suction duct. 5. Suction duct according to claim 1, characterized in that said means comprise a rim (9) with teeth for penetrating dense deposits at its lower end. 6. Suction duct according to claim 1, characterized in that the upper opening (2) is provided with an adjustable valve. 7. Suction duct according to claim 1, characterized in that the upper opening is provided with a normally closed valve which is arranged to open when the subatmospheric pressure reaches a predetermined level.

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