PANFLUTE OVERFLOW SYSTEM

Abstract

An overflow system for a hopper dredger includes an overflow tube; and a plurality of canals adjacent and substantially parallel to the overflow tube. The plurality of canals have inlets at different heights for taking in head water from the hopper. The plurality of canals fluidly connect to the overflow tube at a point downstream from the inlets.

Claims

1. An overflow system for a hopper dredger, the overflow system comprising: an overflow tube; and a plurality of canals adjacent and substantially parallel to the overflow tube, the plurality of canals having inlets at different heights for taking in head water from the hopper; wherein the plurality of canals fluidly connect to the overflow tube at a point downstream from the inlets.

2. The overflow system of claim 1, wherein the plurality of canals at least partially surround the overflow tube, and are positioned around the overflow tube in order from the canal with the highest positioned inlet to the canal with the lowest positioned inlet.

3. The overflow system of claim 1, wherein each of the plurality of canals comprises an open top serving as an inlet for the canal.

4. (canceled)

5. The overflow system of claim 1, wherein at least one of the plurality of canals varies in diameter and/or inlet size.

6. (canceled)

7. (canceled)

8. The overflow system of claim 1, wherein the overflow tube comprises an opening able to take in head water from the hopper and release air from the overflow system.

9. The overflow system of claim 8, wherein the opening of the overflow tube is located at a higher position than the inlets of the plurality of canals.

10. The overflow system of claim 1, wherein the plurality of canals fluidly connect to the overflow tube at an overflow channel, wherein the overflow channel is larger in cross-section than the overflow tube.

11. (canceled)

12. The overflow system of claim 10, wherein the overflow channel is substantially equal in cross-section to the sum of the cross-sections of the plurality of canals and the overflow tube.

13. The overflow system of claim 1, wherein each of the plurality of canals have a smaller cross-sectional area than the cross-sectional area of the overflow tube.

14. The overflow system of claim 1, wherein at least one of the canals reduces in cross-section going downstream from the inlet.

15. The overflow system of claim 14, wherein the overflow tube expands in cross-section while the at least one canal reduces in cross-section.

16. The overflow system of claim 15, wherein the reduction in cross-section of the at least one canal corresponds to the expansion in cross-section to the overflow tube.

17. A vessel comprising the overflow system of claim 1, wherein the overflow system extends at least to a bottom of the vessel.

18. (canceled)

19. (canceled)

20. An overflow system add-on for an overflow system comprising an overflow tube with a pipe in a hopper, the add-on comprising: a plurality of canals, each canal with an inlet at a different height, connectable adjacent to or inside of the overflow tube such that the inlets of the plurality of canals will sit at a lower level than an inlet of the overflow tube and that the plurality of canals fluidly connect to the overflow tube downstream from the inlets.

21. The overflow system of claim 20, wherein each of the plurality of canals comprises an open top serving as an inlet for the canal.

22. The overflow system of claim 20, wherein at least one of the plurality of canals varies in diameter and/or inlet size.

23. (canceled)

24. The overflow system of claim 20, wherein each of the plurality of canals have a smaller cross-sectional area than the cross-sectional area of the overflow tube.

25. The overflow system of claim 20, wherein the plurality of canals are connectable inside the overflow tube and form a new central overflow tube with a smaller cross-sectional area within the plurality of canals.

26. A method of forming an overflow system, the method comprising: connecting a plurality of canals adjacent to an overflow tube in a hopper; and fluidly connecting the plurality of canals to the overflow tube downstream from inlets such that liquid entering inlets of the plurality of canals will be transported to the overflow tube downstream from the inlets, wherein the plurality of canals are sized and/or positioned such that the respective inlet to each canal is at a different height.

27. The method of claim 26, wherein the step of connecting a plurality of canals adjacent to an overflow tube in a hopper comprises connecting a plurality of canals at least partially around the overflow tube.

28. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 illustrates a trailing suction hopper dredger during a dredging operation. FIG. 2A illustrates side view of an overflow system with an overflow tube and a plurality of canals.

[0028] FIG. 2B illustrates a perspective view of parts of the overflow system of FIG. 2a.

[0029] FIG. 2C illustrates a side view of an alternative embodiment of the canals for an overflow system.

[0030] FIG. 3 illustrates a cross-sectional view of second embodiment of an overflow system.

DETAILED DESCRIPTION

[0031] FIG. 1 illustrates a trailing suction hopper dredger (TSHD) 10 during a dredging operation. Trailing suction hopper dredger 10 is suctioning a mixture of water and solid particles through suction tube 12. This mixture is then transported to a hopper in THSD 10 (not shown). Excess liquid in the hopper is overflowed, and plume 14 forms due to mixing of air with the overflow, the vertical orientation of the overflow, and the speed and the general flow causing the overflow water to mix with air.

[0032] Plume 14 can have an adverse impact on local marine biotope, as it reduces the entrance of light into the water body. Additionally, in some cases, the settling particles smother bottom life, and the suspensions can reduce the ability for microorganisms to develop. The bubbles in the flow also cause a resistance in the overflow, reducing the effective transport capacity of the overflow. Forming an overflow which is adjustable to control the flow of head water into and through the overflow can help to reduce turbidity and the mixing of air into the head water, thus reducing or eliminating the plume 14 exiting vessel 10.

[0033] FIG. 2A illustrates a side view of a dredger hopper 18 or a loading space within a TSHD, and overflow system 20 which can transport head water from the hopper 18 back into a liquid body. FIG. 2B illustrates a see through perspective view of overflow system 20, with some canals 26 not shown for ease of viewing. FIG. 2C illustrates a side view of an alternative embodiment of the canals 26a-26e for overflow system 20. Overflow system 20 includes overflow tube 22 with opening 24, canals 26a-26e with inlets 28a-28e, flow channel 30 and fluid outlet 32.

[0034] Overflow system 20 has five canals 26a-26e shown in this embodiment, but could include more or fewer canals (for example, 8 total extending all around overflow tube 22) in this or other embodiments. Canals 26a-26e can extend to different heights in hopper 18 and/or can have different cross-sectional areas and/or inlets 28a-28e. Each canal 26 is open at the top, which acts as an inlet 28 for each canal 26. In other embodiments, such as that shown in FIG. 2C, each canal 26a-26e may be closed at the top, and have one or more inlets 28a-28e on a side.

[0035] Overflow tube 22 can sit adjacent to canals 26a-26e, and canals 26a-26e can extend at least partially around overflow tube to allow flow substantially parallel to that of overflow tube. In the embodiment shown, canals 26a-26e are in order of tallest to shortest extending around overflow tube 22. This sets inlets 28a-28e in order of tallest height to shortest height extending around overflow tube 22. Downstream from inlets 28a-28e, canals 26a-26e fluidly connect to overflow tube 22, at flow channel 30. As can be seen in FIG. 2B, this is a downstream section into which overflow tube 22 and canals 26a-26e flow. In this embodiment, it is shown to be about equal in cross-section to that of canals 26a-26e and overflow tube 22 combined, though in other embodiments the cross-section could be less, for example, flow channel 30 could be just an extension of overflow tube 22 or more.

[0036] Opening 24 in overflow tube 22 is at a top of overflow tube 22, and typically sits at a position higher than any of inlets 28a-28e of canals 26a-26e. This position is also set to be typically higher than an expected liquid level in hopper 18. This allows opening 24 to be used as an inlet for emergency draining when liquid needs to removed rapidly. Opening 24 can also function as an outlet, allowing any trapped air bubbles in the overflow to escape through overflow tube 22. While opening 24 is shown as an opening at the top of overflow tube 22 in FIG. 2A, one or more openings functioning as an inlet and/or outlet could be used and could be sized and/or positioned differently than shown, for example, radially oriented around the side of overflow tube 22.

[0037] Outlet 32 of overflow system 10 could be at a bottom of vessel 10, at a point below vessel 10 or at another point. Outlet 32 must be below a minimum fluid level in the overflow system 20 so as to avoid additional introduction of air bubbles into the overflow mixture.

[0038] In operation, as discussed above, TSHD suctions a mixture of liquid and fractions, and deposits that mixture into dredger hopper 18. The head water in dredger hopper 18 continues to rise as particles and fractions settle. When the head water reaches the level of lowest canal inlet 26e, the head water enters overflow system 20 through inlet 26e. The head water flows through canal 26e into flow channel 30 and finally to outlet 32. As water in hopper 18 rises, it comes to a level where the water level allows for flow into inlets of more of canals 26a-26e. This allows for sufficient intake of head water for proper drainage in hopper 18 while controlling the amount of overflow and the flow into flow channel 30 and through overflow system 20.

[0039] Each canal 26a-26e can handle a certain amount of flow based on its inlet and cross-sectional area, and when flow rises, one or more additional canals 26a-26e are used, thereby giving overflow system 20 more capacity through reaching an additional inlet 28a-28e. Once flow reaches through one or more canals 26a-26e channel 30 downstream from inlets 28a-28e, mixture velocity is low and any air in the flow can rise and leave through overflow pipe 22 opening 24, allowing mostly or only liquid to flow through flow channel 30 to outlet 32.

[0040] Overflow system 20 works to control the intake, velocity and flow of head water into and through overflow system 20 to reduce or eliminate air in the mixture, and thereby reduce or eliminate any plume exiting the vessel as a result of this air. This is done with a simple self-regulating system which has few or no moving parts. The plurality of canals 26a-26e with inlets 28a-28e adjacent to an overflow tube 22 are each set with a certain inlet location and flow area to provide an overflow system which can respond progressively and regressively in capacity for overflow system 22. Because canals 26a-26e are set parts, they could be added to existing overflow systems, connecting downstream to an existing overflow tube, providing existing overflow tubes with the ability to vary capacity based on liquid levels in hopper 18.

[0041] This system with different inlet 28a-28e heights to allow flow into overflow system 20 handles variations in fluid levels in hopper 18 and thus the total flow in overflow system with a simple design with few or no moving parts. This can lead to a more reliable system and a longer lifespan of overflow system 20 which can handle large fluctuations in needed capacity for overflow liquid while minimizing and/or eliminating air in the overflow by allowing escape through overflow tube 22 opening 24. As canals 26a-26e are relatively small in cross-section, the larger wall friction from the plurality of small canals 26a-26e can also help to control the flow. This ensures a cleaner overflow liquid to reduce or avoid turbidity and/or a plume upon exit of flow from overflow system 20, and maximized capacity of overflow system 20.

[0042] FIG. 3 illustrates a cross-sectional view of second embodiment of an overflow system 20. Parts are labelled similarly as in FIGS. 2A-2B. Overflow system 20 includes overflow tube 22 with opening 24, canals 26a, 26i with inlets 28a, 28i, flow channel 30, fluid outlet 32 and cone 33.

[0043] This embodiment is set up, connected and functions very similar to overflow system 20 in FIGS. 2A-2C, only overflow system 20 includes a much larger amount of canals, 16 in total. Each canal 26 reduces in cross-section from its inlet 28 to the point at which it connects to flow channel 30. Additionally, canals are shaped to have a smoother transition of inlet 28 levels, thereby not allowing for additional build-up of liquid and/or pressure when inlets 28 of canals are spaced out further.

[0044] Cone 33 is an optional feature of overflow systems, and can help to control flow into overflow system 20.

[0045] In this embodiment, the reduction in cross-section of canals 26 is coupled with an increase in cross-section of overflow tube 22, such that the overall total cross-section of the overflow remains constant. By reducing the cross-sectional area of canals (as shown in the cross-sections of 26a, 26i) from inlets to the point at which they enter flow channel 30, acceleration and flow can be slowed even when releasing air in the mixture, ensuring a mostly or only liquid to flow through flow channel 30 to outlet 32. This further helps to reduce or eliminate any plume generated by overflow liquid.

[0046] Overflow system 20 shows a simple way which could be used to adapt existing overflow tubes to the use of canals 26 and a central overflow tube. Canals 26 and central overflow tube 22 can simply fit within the existing overflow perimeter to provide the benefits of overflow system 20, easily handling variations in fluid levels in hopper 18 and thus the total flow in overflow system with a simple design to slow down flow and reduce or eliminate any plume from overflow.

[0047] While canals 26a-26f are shown cylindrical and placed around overflow tube 22, canals can be a different shape and/or configuration to assist in forming a plurality of flow channels with inlets at different level and with a desired cross-sectional area and inlet. For example, canals can be shaped to form a cylinder together around the outer circumference or could be placed inside an overflow tube 22 (ensuring that overflow tube inlet 24 is raised to be above canal inlets) to form flow channels within overflow tube. This can bring about the same advantages, and may be easier when adapting existing systems to using canals. Further components can be combined with the overflow system, such as filters and/or other existing means, to further reduce plumes. These can be placed anywhere within the overflow system, including in the canals and/or the central overflow tube.

[0048] While the term head water is used for the mixture entering and flowing through overflow system, this could be liquid and/or a combination of liquid and particles which were dredged and remain suspended.

[0049] While the system is referenced as having no moving parts, this is in relation of movement between the canal inlets and the overflow inlets. An additional system could be in use for moving part or the whole overflow system, for example, allowing the overflow tube inlet 24 and canal inlets 28 move to generally follow the water level in the hopper.

[0050] While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.