Field of the invention

[0001]The invention relates to a system for gently and efficiently transport fluid and biomass, preferably fish.

Background of the invention

[0002] In aquaculture and onboard fishing vessels the need to transport fish from a destination, such as a fish pen, to another enclosure, such as a transportation vessel, often requires an arrangement of pumps and tubes to forcefully move the fish. These conveyances occur multiple times during the lifespan for farmed fish; from early stages when they are moved from land-based hatching facilities to sea based cages or pens, or at later stages when they are transported from fish pens to a well boat or from a well boat to a processing facility. Further handling and transportation may be required as methods for removing parasites or treatment against deceased may be performed on specialized treatments vessels.

[0003]These transportation stages put the live fish at risk of being harmed, and great care and resources are put into performing these tasks as gently and harm free as possible. In addition to causing harm to living organism, harming the fish may cause financial losses and regulatory problems for the aquaculture farmer.

[0004] When transporting fish from a lower position to a higher destination, a continuous flow of fluid is required from an intake of water and fish to the delivery of water and fish at a higher point, while achieving the necessary working lift height and adequate capacity without exposing the live fish to high pressure or to height velocities. This combination of the need for gentle treatment of the live fish and the need for high capacity and lifting range makes the need for purposed build systems necessary.

[0005]The type of handling the fish is exposed to has a great impact on the quality of the fish and economical gain of the farmer. Various systems and devices have therefor been developed to transport live fish as efficient and gently as possible. One type of pump is the vacuum pump which sucks vacuum into a tank which causes the vacuum to suck fish and water from an origin to the vacuumed tank. The downside with vacuum pump arrangement is the low theoretical lift height of around 10 meter, which more frequently is not enough as vessels and facilities becomes lager, and the harmful effect low pressure has on live fish when the pressure decreases towards 0 atm. Other common pumps and arrangements used for transporting live fish are jet type pumps or rotary ejector pumps where a fast-moving fluid is introduced through a nozzle into a larger volume stream causing the larger body of water to move which creates a suction inlet and a discharge port. Documents NO 337898 Bl discloses an ejector pump to transport water and live fish in water. Common ejector pumps do not provide a satisfactory lifting height. Other variants such as a rim driven impeller such as disclosed in NO343685B1 where the impeller is rim driven around what may be considered the transportation stream.

[0006]The above mentions systems and methods have the downside of suddenly introducing a fluid in a stream over a small area, causing a sudden change in pressure over a short distance. In the ejector type pump, there will be a sudden and large increase in both speed and pressure downstream of the introduction nozzle, while for the rim driven impeller pump there will be a sudden decrease in pressure upstream of the impeller and a sudden increase in pressure downstream of the impeller. Both these sudden increases of decreases in pressure occurs where fluid is removed or introduced into the pump stream. These abrupt changes in fluid velocity and pressure can often cause great harm to the soft tissue and organs of the live fish and case the live fish to be violently forced into tube walls, sharp edges or each other.

[0007] It is therefore an aim of the present invention to overcome the shortcomings of the disclosed prior art and to provide an alternative to the prior art. It is a further aim of the present invention to provide a system for transporting fluid and biomass in evenly and gentle manner without sudden increases in pressure. To achieve this objective a system according to the independent claims is provided.

Summary of the invention

[0008]The invention is set forth and characterized in the main claims, while the dependent claims describe other characteristics of the invention.

[0009] In a preferred embodiment of the invention the system comprises a main tubular structure comprising a suction inlet end adapted for suction flow of biomass and fluid, and a discard outlet end adapted for discard flow of biomass and fluid, an outer tubular structure concentrically aligned around the outside of the main tubular structure, for at least a length along a longitudinal axis, and having closed ends, thus arranging for an annular volume around the main tubular structure. Further, at least one pressure device is adapted to provide a pressurized motive fluid flow, and the outer tubular structure comprises an inlet for said motive fluid flow from the pressure device. The main tubular structure comprises multiple openings in the wall of the main tubular structure along at least part of the length of the outer tubular structure, wherein the openings have an angle with the mentioned longitudinal axis to create a flow. [0010] In another embodiment the of invention the length of the outer tubular structure (5) along the longitudinal axis is at least a length corresponding to the height of the pumping height of the system.

[0011] In yet another embodiment the of invention the multiple openings are substantially distributed along the peripheral of the main tubular structure for at least a length corresponding to the height of the pumping height of the system.

[0012] In yet another embodiment the of invention the openings have an angle with the mentioned longitudinal axis by having an inlet on an the outside of the wall of the main tubular structure and an outlet on an inside of the wall of the main tubular structure the outlet being positioned further in a direction towards the discard outlet end in relation to the inlet of the openings.

[0013] In yet another embodiment the of invention the outer tubular structure having an extent from the inlet at least in the direction towards the discharge outlet.

[0014] In yet another embodiment the of invention the outer tubular structure having an extent from the inlet at least in the direction towards the suction inlet end.

[0015] In yet another embodiment the of invention the system further comprises at least one spacing member radiating from the main tubular structure, the at least one spacing member comprises multiple radiating spoke structures, said spoke structures being supported between the main tubular structure and the outer tubular structure, the at least one spacing member being adapted for supporting the outer tubular structure a distance away from the main tubular structure in a radial direction.

[0016] In yet another embodiment the of invention the multiple openings have a round, oval, elliptical, slit shaped or crescent shaped cross section. A slit shaped opening should be understood as an opening having a longer length than with.

[0017] In yet another embodiment the of invention the pressure device having a fluid transportation member in one end disposed in a fluid source and in another end disposed to the pressure device for providing fluid from at least said fluid source to the pressure device, the pressure device further comprises a second fluid transportation member in one end disposed to the pressure device and in a second end disposed to the inlet of the outer tubular structure.

[0018] In yet another embodiment the of invention the fluid source is a first basin containing fluid and biomass to be transported, the system further comprises; a second basin, for the fluid and biomass to be transported to, the second basin may be located higher than the first basin, wherein the suction inlet end and the fluid transportation member is disposed in the first basin, and the discard outlet end is disposed into the second basin.

[0019] In yet another embodiment the of invention the system further comprises at least a second pressure device and at least a second outer tubular structure concentrically aligned around the outside of the main tubular structure, for at least a predetermined distance along a longitudinal axis, and having closed ends, thus arranging for a second annular volume around the main tubular structure downstream of the first tubular structure. The second outer tubular structure comprises an inlet for the motive pressured fluid from the second pressure device, wherein second pressure device having a fluid transportation member in one end disposed at an output from the first outer tubular member and in another end disposed to the pressure device for providing fluid from the first outer tubular structure to the second pressure device, the second pressure device further comprises a second fluid transportation member in one end disposed to the second pressure device and at a second end disposed into an inlet of the second outer tubular structures. The main tubular structure further comprises multiple openings in the wall of the tubular structure along at least part of the length of the second outer tubular structure, wherein the openings have an angle with the mentioned longitudinal axis to create a flow. The first and second outer tubular structures thereby being fluidly coupled in series to increase the capacity and length for transport of fluid and biomass. ,

Brief description of the figures

[0020] These and other characteristics of the invention will become clear from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached schematic drawings.

Figure 1 shows a cross-section view of the system.

Figure 2 shows an overview of the system.

Figure 3 shows a cut-out portion of the outer and main tubular structure.

Figure 4 shows two pressure devices and outer tubular structures fluidly connected in series.

Figure 5 shows a close-up view of a cross-section of the system.

Figure 6 shows a close-up view of a cross-section of the main tubular structure. Figure 7 shows a cut out of the outer tubular structure showing the spacing member.

Detailed description of the invention [0021] The following description will use terms such as "horizontal", "vertical", "lateral", "back and forth", "up and down", "upper", "lower", "inner", "outer", "forward", "rear", etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader's convenience only and shall not be limiting. Like numerals on different drawings describe the same feature. Numerals with apostrophe represents an additional feature represented by the same numeral, for instance the number 1 will represent one or the first of multiple, and the numeral 1' represents an additional of the same feature, like a second or multiple of the same feature.

[0022] Reference in the description to "one embodiment" or "one embodiment" means that a specific feature, construction, or characterization portion described in connection with one embodiment is included in at least one embodiment of the application object. Accordingly, the use of the term "in one embodiment" or "in one embodiment" at various locations in the specification will not necessarily refer to one and the same embodiment.

[0023] Figure 1 shows a perspective view of an embodiment where a pressure device 1, preferably a pump, has a suction inlet for fluid through a first fluid transportation member 14, preferably a pipe. The first fluid transportation member 14 fluidly connects the pressure devise 1 with a fluid source, in this illustrated example a first basin 12 containing biomass 8 and fluid. The inlet end of the fluid transportation member 14 may comprise a grid or obstacle to prevent biomass from entering into the fluid transportation member 14. The pressure device 1 must be able to move and deliver a flow of fluid and the pressure device 1 may be any type of fluid pump intended to move fluid in a continues manner, such as rotary or centrifugal pumps. A centrifugal water pump uses a rotating impeller to move water into the pump and pressurize the discharge flow. As the biomass is not traveling though the pressure device 1, the pressure device may therefor comprise propellers or impellers otherwise harmful to the biomass. The pressure device 1 may also be a positive displacement water pump that delivers a fixed amount of flow through a mechanical contraction and expansion of a flexible diaphragm. In figure 1, the biomass 8 is to be transported from the first basin 12 comprising both biomass 8 and a fluid, such as water, to a second basin 7. In the illustrated example the second basin 7 is located higher than the first basin 12. The first basin 12 may be a fish farm cage or fish pen in the ocean or on land, or it may be treatment facility such as a delousing tank, hatching facility or a well boat. The second basin 7 may also be a fish farm cage or fish pen in the ocean or on land, or it may be treatment facility such as a delousing tank, well boat or processing facility such as a slaughterhouse. When using terms like biomass it should be understood as living or dead organism that are present in the fluid that are to be transported by the system. Biomass may refer to live or dead, but are not limited to only fish, it may also include other relevant elements such as shrimp and smolt or other products, such as eggs from poultry or the like, to be transported. The term "fluid" is used to describe the transport medium, or pump medium, which may be both liquid, preferably water or sea water, and/or gas, preferably air. The term may also be understood as a mixture of liquid and gas, such as water with air bubbles. For instance, the system may be used to transport live fish from an basin where the fluid is liquid, or it may be used to transport eggs from a basin where the fluid is air.

[0024]The illustrated embodiment in figure 1 comprises a main tubular structure 10 running the entire length from the first basin 12 to the second basin 7. The main tubular structure 10 comprising a suction inlet end 11 adapted for suction flow of biomass 8 and fluid from the first basin 12, and a discard outlet end 6 adapted for discard flow of biomass 9 and fluid into the second basin 7. The main tubular structure 10 may be any type of tube. On the outside of the main tubular structure 10 there is an outer tubular structure 5 concentrically aligned around the outside of the main tubular structure 10, the has a length running for at least a predetermined distance along and longitudinal axis of the tubular structures.

[0025] In figure 2 the invention is illustrated with the main tubular structure 10, the outer tubular structure 5, the inlet 2 and the suction inlet end 11 and discard outlet end 6. The outer tubular structure 5 has closed ends, as seen on the aft, or downstream portion of the inlet 2. The closed ends and the outer tubular structure 5 walls being watertight and impenetrable so fluid introduced through the inlet 2 can only escape the annular volume into the main tubular structure 10 through multiple openings 3, thereby arranging an annular volume around the main tubular structure 10 that can be pressurized. The outer tubular structure 5 establishes the annular volume around the main tubular structure 10. The pressure device 1, being adapted to provide a pressurized fluid flow, known as a pressurized motive fluid flow or a motive flow 4, into an inlet 2 of the outer tubular structure 5. The pressure device 1 sucks fluid only from the first basin 12 and moves said fluid into the outer tubular structure 5 via the inlet 2. The pressure device 1 is in fluid communication with the inlet 2 of the outer tubular structure 5 via a second fluid transportation member 13, preferably a pipe. The second fluid transportation member 13 fluidly connects the pressure devise 1 with the outer tubular structure 5. The diameter of the main and outer tubular structure may vary according to the required use and should not be limited. The diameter of the outer tubular structure may be from 1 - 100% larger than the diameter of the main tubular structure 10 dependent on the requirements and use of the system. The wall thickness of the main tubular structure 10 should be adapted to withstand the pressure from the motive fluid 4 in the annular volume, and so the openings 3 defines a channel with a direction. The material of the main and outer tubular structure 5, 10 may be any flexible, rigid or semi rigid material such as but not limited to PVC, rubber, reinforced rubber, polyethylene, homo-polymer, copolymer and others.

[0026] In figure 3 a cut-out view of the inlet 2 is illustrated to show the flow of fluid from the pressure device 1 (seen in figure 1) as it enters through the outer tubular structure 5 in a single point and disburses into the annular volume around the main tubular structure 10. As the end portion of the outer tubular structure 5 is closed, the fluid 4 introduced is moved, or pushed, by the pressure from the pressure device 1, further along the annular volume, displacing fluid 4 further downstream of the inlet 2. In this embodiment the closed end of the outer tubular structure 5 is located in close proximity of the inlet 2, but the outer tubular structure 5 may elongate both in the downstream direction and upstream direction of the inlet 2. The inlet 2 may also be located in the end portion of the outer tubular structure 5. In figure 3 it is illustrated that the main tubular structure 10 comprises multiple openings 3 in the wall of said main tubular structure 10 along at least part of the length where the outer tubular structure 5 is surrounding the main tubular structure 10. The multiple openings 3 have an angle with the longitudinal axis through the wall of the main tubular structure. The fluid introduced by the pressure device 1 and pumped into the outer tubular structure 5 is thereby introduces through the multiple openings 3 into the main tubular structure. As the multiple openings 3 have an angle with the longitudinal axis, they create flow in the main tubular structure 10 in that the fluid is introduced with a velocity in the direction of the intended flow, due to the angle, which is towards the discard outlet end 6. The angle between the openings 3 and the longitudinal axis is between 0 and 90 degrees, preferably between 10 and 80 degrees, and even more preferably between 20 and 70 degrees. When using terms like upstream it should be understood as the area or direction at the inlet for fluid and biomass i.e. the suction inlet 11 itself or towards the suction inlet 11. When using terms like downstream it should be understood as the area at the pump outlet for fluid and biomass i.e. the discard outlet 6 itself or towards the discard outlet 6.

[0027] Figure 5 illustrated a cut-out view of an embodiment where the outer tubular structure 5 has an extent both in the upstream and downstream direction compared to the inlet 2. The motive flow 4 enters through the inlet 2 and flows around the main tubular structure 10 along the length of where the outer tubular structure 5 surrounds the main tubular structure 10. In figure 5 multiple openings 3 is illustrated as open passages in the wall of the main tubular structure 3. The multiple openings 3 being open passages through the wall of main tubular structure 10, the openings 3 positioned in a tilted direction, the passages being tiled in the direction towards the discard outlet end 6, such that the flow of motive fluid flow 4 being introduced through the multiple openings 3 in the direction towards the discard outlet end 6. When the motive flow 4 is introduced through the multiple openings 3, the movement of said flow 4 induces the movement of a main flow 8 in the direction towards the discard outlet end 6. The embodiment illustrated in figure 5 has multiple opening spaced evenly along the entire section illustrated. Depending on the required height the system is required to lift or pump the fluid and biomass, the length of both the distribution of the multiple openings 3 and/or the length of the outer tubular structure in relation to the main tubular structure, may vary. The multiple openings 3 should be substantially distributed along the peripheral of the main tubular structure 10 for at least a length corresponding to the height of the pumping height of the system. The pumping height, often described as pump head, should be understood has the difference in height from the suction inlet end 11 to the discard outlet end 6. The length of the outer tubular structure 5 along the longitudinal axis (i.e. along the length of the tubulars) is preferably at least a length corresponding to the height of the pumping height of the system. For instance, if a specific minimum pumping height is required, such as difference of X meters from the suction inlet end 11 to the discard outlet end 6, the length of the outer tubular structure 5 and/or the distributed length of the multiple openings 3 should correspond to said height and therefore be at least X meters. In this example X may be understood as any number of meters, for instance 0.2, 2, 5, 10, 30 etc., and should not be considered limiting. The maximum length of the outer tubular structure 5 and the longitudinal distributed length of the multiple openings is limited only by the length of the main tubular structure 10, and the outer tubular structure 5 the main tubular structure 10 may be of equal length. The invention may be utilized with a longer outer tubular structure 5 than the height of pump height. This ensures that the system as disclosed may vary in size and capacity depending on the required workload and lifting capacity. The outer tubular structure 5 may be located at any position along the length of the main tubular structure. The openings 3 may be distributed evenly apart at predetermined distances within the boundaries of the outer tubular structure 5. To ensure the flow 4 entering evenly into the main tubular structure, the openings 3 are also evenly distributed in around the circumference of the main tubular structure 10. The density of the distribution of openings 3 may be between 10 to 10 000 openings distributed on an area equal to one square meter of wall of the main tubular structure 10. The multiple openings 3 may have a round, oval, elliptical, square, elongated or crescent shaped cross section and the width of said openings 3 may preferably be between 1-50 mm, more preferably between 1-20 mm and even more preferably between 1-10 mm. The width of said openings 3 being measured at the extremities or the outer moats extremities of the opening on a curved surface with a curvature equal to the wall of the main tubular structure.

[0028] In figure 6 the openings 3 is further illustrated in a close up view, wherein the openings 3 have an angle with the mentioned longitudinal axis, in said figure illustrated by the flow 8, by having an inlet on an the outside of the wall of the main tubular structure 10 and an outlet on the inside of the wall of the main tubular structure 10, the outlet being positioned further downstream in a direction towards the discard outlet end 6 compared to the inlet of the openings 3, such that the opening defines a channel or tunnel with an defined direction tilting towards the discard outlet 6. Further in figure 6, the motive fluid flow 4 passing from the annular volume in is introduced into the main tubular structure 10 in the direction towards the discard outlet end 6 caused by to the angle of the openings 3. The flow 4 thereby introduces motion energy into the main tubular structure 10, said motion energy being transferred to the fluid in the main tubular structure 10, the motion energy thereby induces motion onto the body of water inside the main tubular structure 10, creating a main flow 8 which comprises a suction flow by the suction inlet end 11 and the discard flow by the discard outlet end 6 of the main tubular structure 10 by displacing the fluid in the direction of flow 8 towards the discard outlet end 6. The motive fluid 4 is introduced into an angled direction of travel compared to the main flow 8, and the motive flow 4 merges with the main flow 8 in a gradual transition 16, transforming displacement of fluid and velocity directed inwards, to velocity directed towards the discard outlet 6. The pressure on the motive fluid 4 from the pressure device 1 is to introduce the motive fluid 4 through the opening 3 and throughout the length of annular volume. As more motive fluid 4 is introduced through the opening 3 along the direction of travel for the main fluid stream 8, the velocity of the main fluid stream will increase, as the more fluid is displaced further along the direction of the main fluid flow 8. The amount of fluid in the main tubular structure 10 should increase as more fluid is introduced along the length, the expansion, end hence the increase in velocity, will therefore be towards the discard opening end 6. The angle of the opening 3 therefore ensures an initial introduction of the motive fluid 4 in the downstream direction. As the velocity of the main fluid stream 8 increases the pressure inside the main tubular structure 10 should decrease, but at the same time more motive fluid 4 is introduced through the openings 3, which in turn increases the pressure. The sum is that pressure is stable, and the velocity is evenly increasing over the entire segment length of the outer tubular section 5 where the openings 3 are present, causing a gentle and even transportation of any live fish passing through, without any sudden or abrupt changes. [0029] In figures 1 and 2, the outer tubular structure 5 has an extent from the inlet 2 at least in the direction towards the discharge outlet 6. In the figures the outer tubular structure 5 is situated almost the entire length of the main tubular structure 10, leaving the portions at each end of the main tubular structure 10 more free to wield and maneuver. In figure 5 the outer tubular structure 5 also has an extent from the inlet 2 in the direction towards the suction inlet end 11.

[0030] In figure 7 an embodiment of the invention is illustrated where the system comprises a spacing member 17 radiating from the main tubular structure 10, the spacing member 17 comprises multiple radiating spoke structures, said spoke structures being supported between a support ring around the main tubular structure 10 and an support ring on the inside of the outer tubular structure 5. In figure 7 one spacing member is illustrated, but it should be understood that multiple spacing members may be outfitted along a part of the length or along the entire length outer tubular structure 5 to support the outer tubular structure 5 a distance away from the main tubular structure 10 in a radial direction, creating the annular volume between the tubular structures 5, 10. In figure 7 the distribution of the multiple openings 3 is illustrated, where the openings are substantially equal in distance, both in the transverse direction and in the longitudinal direction. The openings may be distributed more closely in the transverse direction than in the longitudinal direction, or more closely in longitudinal the direction than in the transverse direction.

[0031] In figure 4 an embodiment of the invention is illustrated where the system comprises two outer tubular structures in a series connected pump system. In situations where extra lifting height or elongated travel distance is necessary, compared to what a single system may provide, the system may be expanded by one or multiple additional outer tubular structures 5' and an equal amount of additional pressure devices 1'. In the illustrated embodiment the system further comprises at least a second pressure device 1', and at least a second outer tubular structure 5' concentrically aligned around the outside of the main tubular structure 10, for at least a distance along a longitudinal axis, and having closed ends, thus creating a second annular volume around and additional section of the main tubular structure 10, downstream, i.e. in the direction towards the discard outlet end 6, of the first tubular structure 5. The second outer tubular structure 5' comprises an inlet 2' for the motive pressured fluid from the second pressure device 1', wherein second pressure device 1' has a fluid transportation member 1, preferably a tube, in one end disposed at an output from the first outer tubular member 5 and in another end disposed to the pressure device 1' for providing fluid from the first outer tubular structure 5 to the second pressure device 1'. The second pressure device 1' further comprises a second fluid transportation member 13', preferably a tube, in one end disposed to the second pressure device 1' and at a second end disposed into an inlet 2' of the second outer tubular structures 5'. The main tubular structure 10 further comprises multiple openings 3 in the wall of the tubular structure 10 along at least part of the length of the second outer tubular structure 5', wherein the openings 3 have an angle with the mentioned longitudinal axis to create a flow. This coupling for fluid communication between the first and second outer tubular structure 5, 5' fluidly couples the system in series to increase the lifting capacity i.e. increases the working height and working length for transport of fluid and biomass.

[0032]The invention may also be used to remove sea lice and parasites from a biomass, such as a fish, wherein the pressurized motive fluid flow 4 is freshwater, warm water, or a lice removal fluid such as hydrogen peroxide, adapted to remove the lice from the body of the fish, whereby the invention may be used both to transport and to de-lice the fish. In an embodiment of the invention the fluid transportation member 14 connected to the pump 1, is adapted to transport pressurized lice removal fluid from a fluid source 12 holding said fluid, to the pump 1, wherein the pressurized fluid is introduced into the inlet for outer tubular structure. In yet another embodiment of the invention a fluid transportation member 15 is in one end fluidly connected to an output from the outer tubular member 5 a distance downstream from the inlet 2, and in another end connected to the another pressure device 1' for providing suction of fluid from the outer tubular member 5 at the outlet, wherein the suction created is adapted to suck out a portion of the fluid from the outer tubular member 5 and therein from exit openings in the main tubular structure 10. In an embodiment of the invention the main tubular structure 10 comprises fluid openings arranged a at least distance along the main tubular structure, wherein the exit openings are arranged along a length at least upstream and/or downstream from where the fluid transportation member 15 is fluidly connected to the output from the outer tubular member 5. The fluid openings may have an angle with the longitudinal axis by having an inlet on an the inside of the wall of the main tubular structure 10 and an inlet on an inside of the wall of the main tubular structure 10, the outlet being positioned further in a direction towards the discard outlet end 6 in relation to the inlet of the openings. In use, wherein the invention is used to remove lice i.e. fresh water, warm water or a lice removal fluid is used, the lice that has been removed from the fish can be removed through the fluid exit openings. In another embodiment of the invention the main tubular structure 10 comprises a section with reduced diameter in relation to the remaining main tubular structure 10, wherein the reduced section comprises the fluid openings for water to exit the main tubular structure 10 and wherein the fluid is to be sucked out by the second pressure device 1'. The reduced diameter section, for at least a length, will bring the exit openings closer to fish to increase the suction effect close to the fish and thusly remove sea lice more efficient if the sea lice has not been fully released from the fish.

[0033] In an embodiment of the invention the system further comprises at least a second pressure device 1' and at least a second outer tubular structure 5' arranged concentrically aligned around the outside of the main tubular structure 10 for at least a distance along a longitudinal axis, and having closed ends, thereby creating a second annular volume around the main tubular structure 10 downstream of the first tubular structure 5. The second outer tubular structure 5' comprises an outlet adapted for the motive pressured fluid to be sucked out by the second pressure device 1', wherein second pressure device 1' having a fluid transportation member 15 fluidly connecting the second pressure device 1' and the outlet. The main tubular structure 10 further comprises exit openings arranged at least distance along the main tubular structure, wherein the exit openings are arranged along a length at least upstream and/or downstream from the outlet and within the upstream and downstream boundaries defined by the second outer tubular structure 5'. In this embodiment fluid will be introduced into the main tubular structure 10 along the first outer tubular structure 5 and fluid will be removed, by suction, from the main tubular structure along the second outer tubular structure 5'. The exit openings are passages for fluid through the wall of the main tubular structure 10 and may have a round, oval, elliptical, slit shaped or crescent shaped cross section.

[0034] Having described preferred embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the concept may be used. These and other examples of the invention illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the following claims.

Reference numerals.

1. Pressure device, pump

2. Inlet for outer tubular structure

3. Openings for fluid to enter the main tubular structure

4. Mixed fluid

5. Outer tubular structure

5' Second outer tubular structure

6. Discard outlet end of main tubular structure

7. Second basin of fish and fluid, Discard basin

8. Flow and direction of flow through main tubular structure

9. Biomass, preferably fish

10. Main tubular structure

11. Suction inlet end of main tubular structure

12. First basin of fish and fluid, fluid source

13. Fluid transportation member from pressure device

13' Second fluid transportation member from pressure device

14 Fluid transportation member to pressure device

15 Fluid transportation member from tubular member

16 Gradual transition between fluid flows

17 Spacing member