WO2022265515A1

WO2022265515A1 - Semi-closed or closed fish farm construction

Info

Publication number: WO2022265515A1
Application number: PCT/NO2022/050134
Authority: WO
Inventors: Jan Erik KYRKJEBØ
Original assignee: Fiizk Ecomerden AS
Current assignee: Fiizk Ecomerden AS
Priority date: 2021-06-16
Filing date: 2022-06-15
Publication date: 2022-12-22
Anticipated expiration: 2023-12-16
Also published as: NO20210776A1; NO346372B1

Abstract

A semi-closed or closed net cage construction (10) comprising an outer flexible canvas bag (12) suspended in a floating collar (16) and with an inner net (14), where fresh water is sucked in by a number of suction pipe lines (18) attached to the floating collar (16) projecting into the sea and causing the water to flow into the net cage construction (10) via a number of upper water inlets (20). The canvas bag (12) is divided into several zones (12a, 12b, 12c), an upper zone (12a) is comprising an approximately vertical wall, a central zone (12b) connected to the upper zone (12a), where the central zone (12b) is comprising a number of water outlets (24) of a canvas material distributed with a mutual distance around the circumference, where the water outlets (24) are comprising outlet pipes with inflatable balloon valves (30) and a lower zone (12c) connected to the central zone (12b) and which forms a conical shape with a drain (26) at the bottom for removal of waste particles.

Description

SEMI-CLOSED OR CLOSED FISH FARM CONSTRUCTION

Field of the invention

The present invention relates to a semi-closed or closed net cage construction comprising an external flexible canvas bag suspended in a floating collar and with an inner net, where fresh water is sucked in by means of a number of suction pipes which are attached to the floating collar and project into the sea, and which bring the water to flow into the net cage construction via a number of upper water inlets.

Background of the invention

In semi-closed and closed net cages where there is a dense wall between the volume where the fish reside and the surrounding environment.

From prior art it is known that the watertight wall is suspended in a floating collar consisting of pontoons which comprise a rigid floating collar. On the inside or outside, there is normally an inner net that secures against the escape of fish. Water is taken from a lower layer in the sea under the lice belt with a number of suction inlets with pumps and which set up a stream of rotating water flow which the fish swim against thus becoming more robust. It is normal to have a main water outlet in the bottom section of the membrane bag. In addition, the fish are supplied with oxygen from either oxygen generators or from oxygen tanks on land.

The current solution is vulnerable if there is a power failure and the pumps that take in water stop. As long as the water flows out of the outlet and the pumps stop, the bag will be able to collapse, and fish will escape.

In addition, it is a great problem to establish a flow of the water in the bags due to the effect of eddy current or so-called vortex effect. Then, instead of flowing out into the bottom section, the water will be thrown out into the periphery due to centripetal force and increase the pressure and weight of surface water in the canvas bag. This will reduce the supply of fresh water to the fish throughout the water volume and reduce fish welfare. In addition, it will create major challenges for the reserve buoyancy of the floating collar and thus the danger of fish escaping.

For larger dimensions of the net cage construction, it can be problematic to mount and transport the net cage construction with the canvas bag completely assembled. This is due to the uncertainty with towing and the risk of damaging the canvas bag during transport from the yard to the fish farm. It will therefore be an advantage to be able to install the canvas bag after the floating collar is anchored at the site. Prior art

Reference is made, among other things, to NO 332955 B1 , which deals with a closed net cage with hatches. The hatches are mechanical, rotatable hatches that are placed circumferentially around the net cage wall, and which can be opened and closed to control water flow in the net cage. The wall of the net cage is preferably provided with rows of panels fitted with hatch openings, and where the hatch is comprising a rear wall for sealing the opening when the hatch is in the closed position. The net cage is further comprising side walls, a front wall and a water- permeable bottom fitted with a first grid.

Furthermore, reference is made to NO 332341 B1 , NO 175341 B, NO 342403 B1 and NO 340026 B1 as examples of closed net cages.

Objects of the present invention

The new solution includes a watertight flexible membrane bag or canvas bag that has significant new features with consequent advantages and innovation.

In recent times, there have been demands to collect waste from the fish and the net cages. This creates a great challenge for this type of flow-through system as there are large amounts of water that must flow through the semi-closed or closed net cage. There will therefore be a need to be able to reduce the vertical speed and the rotational speed in the limited net cage volume where fish are present. In addition, it is important that the impact area in the net cage where the vertical velocity is low that this area is as large as possible and that the drain is pulled out to the sides so that as much waste as possible sinks uninterrupted into the lowest area of the canvas bag, and that the waste is sucked out in the lower part of the canvas bag.

In the prior art, there are known solutions which have a canvas bag in which the water outflow and the waste lie together at the bottom of the bag. This results in a very limited waste separation as most of the waste particles are entrained along with the main water stream. Then the waste separation is very limited.

With the new canvas bag according to the invention, one will in a simple way solve problems which are mentioned in a simple and cost-effective way.

Summary of the invention According to the invention, a semi-closed or closed net cage construction is provided comprising an external flexible canvas bag suspended in a floating collar and with an inner net, where fresh water is sucked in by a number of suction pipes which are attached to the floating collar projecting into the sea and causing the water to flow into the net cage construction via a number of upper water inlets. The canvas bag is divided into several zones, where an upper zone is comprising an approximately vertical wall, a central zone connected to the upper zone, where the central zone is comprising a number of water outlets of canvas material distributed with mutual distance around the circumference, said water outlets comprise outlet pipes with inflatable balloon valves, and a lower zone connected to the central zone and which forms a conical shape with a drain at the bottom for the removal of waste particles.

The central zone of the canvas bag can be comprising a reinforced canvas belt with said water outlet, where the water outlets are individually able to be opened and closed to regulate water flow in the net cage construction.

The central zone can have a smaller circumference than the upper zone.

Respective inflatable balloon valves can be comprising several canvas sides welded together in the outlet tube to form a watertight and inflatable balloon which fills the outlet tube.

Furthermore, the outlet pipes to the water outlets are usually made of a canvas material.

Respective inflatable balloon valves can be connected via a compressed air hose to a compressor on the net cage construction, for blowing air into and extracting air from, respectively, the balloon valves.

The compressor can further be connected to a control system for regulating respective inflatable balloon valves, whereby water flow in each water outlet can be controlled individually.

In one embodiment, the water outlets can be surrounded by an outer canvas bag arranged to direct outflowing water to one or more vertical main outlets. The main outlet can similarly be equipped with a balloon valve which is supplied with air via a compressed air line.

The net cage construction, further in the upper part, can comprise one or more inflatable and buoyancy-regulating floating tubes.

Respective inflatable floating tubes can be connected via a compressed air hose to a compressor on the net cage construction.

The canvas bag can also be comprising a number of inner and strengthening brackets which extend completely or partially circumferentially around the canvas bag.

Furthermore, the upper zone can be comprising a number of said upper water inlets.

Description of figures

Preferred embodiments of the invention will be discussed in more detail below with reference to the accompanying figures, in which:

Figure 1 shows a first embodiment of a net cage construction according to the invention.

Figure 2 shows the net cage construction in figure 1 seen from above.

Figure 3 shows a second embodiment of a net cage construction according to the invention.

Figures 4a, 4b show a valve for use in the net cage construction, where the valve is in the closed state.

Figures 5a, 5b show the valve shown in figures 4a, 4b in open condition. Figure 6 shows a drain for use in the net cage construction.

Description of preferred embodiments of the invention

The invention relates to a closed or semi-closed net cage construction 10, hereinafter called net cage, which floats in a known manner on a water surface 48. The net cage 10 is comprising a floating collar 16 with equipment for operating the net cage. The net cage further is comprising an outer canvas 12 of a canvas material, such as a membrane material, and an inner net 14 which houses the fish. The internal net is illustratively referred to by reference number 14. Water is supplied by means of preferably several water inputs in the form of suction pipes 18 attached to the floating collar 16. The water is taken from a lower layer in the sea under the lice belt and added inside the net cage 10 so that a flow of rotating water flow is set up which the fish swim against and become more robust. The water is added to the net cage 10 via a number of upper water inlets 20 located in or at the floating collar 16. The water inlets or water sprayers are directionally adjustable for spreading and agitating the water and are illustrated by the arrows in figure 2. Oxygen can be added from either oxygen generators or oxygen tanks on the land.

In order to regulate the buoyancy of the net cage, the net cage construction 10 in the upper part can be comprising one or more inflatable floating tubes 28, which are connected via a compressed air hose 36 to a compressor 34 on the net cage construction.

The canvas bag 12 is divided into several zones 12a, 12b, 12c, where an upper zone 12a is comprising an approximately vertical wall, preferably with a number of said upper water inlets 20 for supplying the water, a central zone 12b connected to the upper zone 12a, where the central zone 12b is comprising a number of water outlets 24 of a canvas material spaced apart around the circumference, and a lower zone 12c connected to the central zone 12b and forming a conical shape with a drain 26 at the bottom for removal of waste particles.

By "central zone" is meant a zone between the upper and lower zones 12a, 12c and need not be a centred zone in the net cage construction.

As shown in figure 2, the central zone 12b can be comprising six water outlets 24 spaced apart circumferentially about the canvas bag 12.

The central zone 12b can in its simplest form consist of a part of the canvas bag 12 and constitute a canvas belt 22 around the canvas bag 12. However, the canvas belt can also be a reinforced canvas belt 22, reinforced for example with one or more additional canvas layers. The canvas belt 22 is shown in the figures as a narrow canvas belt, but can, if desired, extend well up on the upper zone 12a of the canvas bag 12.

The central zone 12b can have the same circumference as the upper zone 12a, or as shown in the figures have a smaller circumference than the upper zone 12a. A smaller circumference can be made by means of the canvas belt 22 which keeps the central zone 12b tight. Alternatively, or in addition, a number of inner and strengthening brackets 46 can be used which extend wholly or partially circumferentially about the canvas bag 12. A strengthening bracket 46 can be used in the upper vertical wall of the canvas bag 12 and a strengthening bracket 46 of smaller diameter in an area above the central zone 12b, as shown in the figures, so that a transition area is formed with a tapered canvas bag 12 in the lower part of the upper zone 12a.

The drain 26 is usually in the form of a funnel which is mounted to the lower part of the canvas 12, such as the lower zone 12c. The drain 26 can be made of fiberglass and welded to the canvas 12. The drain is shown in figure 6. From the drain 26 a drain line 38 runs up to the upper part of the net cage construction 10.

The water outlets 24 in the central zone 12b of the canvas bag 12 comprise canvas outlet pipes with inflatable sealing balloons or balloon valves 30 which are individually able to be closed and opened to regulate water flow in the net cage 10.

By being able to regulate the pressure in the balloon valves 30, it is possible to throttle the outlet and thereby increase the internal pressure or the elevation inside the canvas bag 12 relative to the outside. This is an advantage when installing the net cage construction in flow-exposed fish farms. Then the pressure inside the canvas bag 12 will resist the flow forces on the canvas bag walls and thus prevent the canvas bag from collapsing. By reducing the throttling, the water pressure down in the central zone 12b will normally ensure that the area of the balloon valves can be reduced and thus open for an increased water flow if desired.

The canvas bag 12 or the water outlets 24 can internally in the canvas bag be equipped with a filter or grid which prevents unwanted particles from being dragged into the water outlets.

A number of such horizontal water outlets 24 placed in an annular shape in the central zone 12b will be able to reduce the sinking rate of the waste in this area of the net cage and prevent the waste from entering the water outlets by making the projected discharge area almost zero. Experiments performed on waste indicate that almost all waste such as feed waste and faeces from the fish sinks faster than 2.5 cm/sec. By having a water outlet in this central zone 12b located horizontally about the canvas wall downstream of the fish, and at a distance from the intake of water in the net cage, it is possible to achieve a large area in the outlet zone and a minimal vertical velocity of the water flow in the net cage, so that the waste will sink past the outlets 24 and be collected in the lower zone 12c, through the conical bottom with the drain 26 connected to the waste line 38 for removal of the waste.

In this way, a total separation of all major particles can be achieved, while at the same time controlling the velocity and dry matter content of the waste line 38, by throttling the balloon valves 30 to regulate the pressure in the waste line 38.

The result is a simple, reliable and cost-effective transport away from the net cage and a simple and cost-effective drying process of the waste, for example in a treatment process plant on land away from the net cage.

Figure 3 shows a further variant of the invention. The net cage 10 is designed in the same way as shown and described in connection with figures 1 and 2. In this embodiment, the canvas belt 22 and the outlets 24 are surrounded by a canvas bag 40 or tube which is tunnel-shaped, and which directs outflowing water to one or more main vertical outlets 42, where the arrows in figure 3 illustratively show water flowing out of the main outlet 42 and vertically down into the sea. The main outlet 42 is provided with a corresponding balloon valve 44 as the water outlets 24 and is supplied with air via a compressed air line 32a. This solution is relevant if the intake line of water into the net cage is to be taken from a deeper level, as it is not desirable that the intake and outlet of water are too close to each other. It has been pointed out by the Norwegian Food Safety Authority that drains from the semi-closed net cages must always be below and at a good distance from water intake.

The water outlets 24, and the main outlet 44 if used, in the central zone 12b of the canvas bag 12 comprise, as mentioned, outlet pipes with inflatable balloon valves 30, and are shown in more detail in figures 4a, 4b and 5a, 5b. The outlet pipes are made of canvas material similar to the canvas bag 12.

The inflatable balloon valves 30 are comprising several layers of canvas which are welded together on opposite sides inside the outlet tube to form a watertight and inflatable balloon. For example, two canvas sides 30a, 30b can be welded inside the outlet tube, which is also made of canvas, so that the canvas sides are directly opposite each other, and which are connected to the compressed air line 32, or the compressed air line 32a in the case of the balloon valve 44 in the main outlet 42. As shown in figure 5b, when filled with air, the canvas sides 30a, 30b expand so that they fill the outlet tube like a balloon, as shown in figure 4b with the internally shaded field.

Respective inflatable balloon valves 30, 44 are connected via the compressed air hose (s) 32, 32a to a compressor 34 on the net cage construction 10, for blowing air into, and extracting air from, respectively, the balloon valves. Furthermore, the compressor 34 can be connected to a control system for regulating respective inflatable balloon valves 30, 44, whereby water flow in each water outlet 24 or main outlet 42 can be controlled individually. To ensure that the balloon valves close in the event of a power failure in the net cage 10, the compressor 34 can be connected to a battery pack so that the balloon valves inflate and close.

Because the flexible canvas bag 12 made of membrane material is free of heavier metallic components, it can be mounted and dismounted in a very simple and cost- effective manner. Today, it is a major logistical challenge to install canvas bags in closed net cages as they are sensitive to wind and forces applied during loading because the canvas bags must be high in the air. On larger closed net cages, it has been common to mount the canvas bag on land with a safety and towing net that holds the canvas bag in place when towing and the closed net cage from the yard to the farming site.

It is a known solution that at the bottom of the canvas bags a particle separator of metal is arranged which is blinded off during assembly, and which is still on to create a watertight bag which is to be filled with water before the canvas bag is attached to the floating collar. This is an expensive and cumbersome way where you have to have an entire diving team for the job and there is a limited time a diver can stay at such shallow depths.

With the new canvas bag 12 in a full membrane without metallic components and with a drain at a right level in the sea, installation will be much easier. The balloon valves help to ensure that the canvas bag can be made completely closed, and thus be able to be filled with water and mounted without the need for a diving team being present. The canvas bag 12 can be laid winched into the net cage by the canvas bag being laid out on deck in a ball and then the whole canvas bag is pulled into the net cage by a winch on the opposite side of where the work boat docks. After the canvas bag has been pulled into the net cage, it must be filled with water, which is then carried out by existing pumps that have already been mounted and connected to the floating collar.

It is also an advantage to have a remote-controlled closure of the canvas bag, which among other things will be an advantage when inactivating the premises, so you do not have to continue running the pumps to avoid the canvas bag collapsing, which saves electricity and extra costs.

Claims

Patent claims

1. A semi-closed or closed net cage construction (10) comprising an external flexible canvas bag (12) suspended in a floating collar (16) and with an inner net (14), where fresh water is sucked in by a number of suction pipe lines (18) which are attached to the floating collar (16) and which project into the sea and cause the water to flow into the net cage construction (10) via a number of upper water inlets (20), characterised in that the canvas bag (12) is divided into several zones (12a, 12b, 12c), where an upper zone (12a) comprises an approximately vertical wall, a central zone (12b) connected to the upper zone (12a), where the central zone (12b) comprises a number of water outlets (24) of a canvas material spaced apart around the circumference, said water outlets (24) comprises outlet pipes with inflatable balloon valves (30), and a lower zone (12c) connected to the central zone (12b) and which forms a conical shape with a drain (26) at the bottom for removal of waste particles.

2. The net cage construction (10) according to claim 1 , characterised in that the central zone (12b) of the canvas bag (12) comprises a reinforced canvas belt (22) with said water outlet (24), and wherein the water outlets (24) are individually closable and openable to regulate water flow in the net cage construction (10).

3. The net cage construction (10) according to claim 1 , characterised in that the central zone (12b) has a smaller circumference than the upper zone (12a).

4. The net cage construction (10) according to claim 1 , characterised in that respective inflatable balloon valves (30) comprises several canvas sides (30a, 30b) which are welded together in the outlet pipe to form a watertight and inflatable balloon which fills the outlet pipe.

5. The net cage construction (10) according to claim 1 , characterised in that the outlet pipes of the water outlets (24) are made of a canvas material.

6. The net cage construction (10) according to claim 1 , characterised in that respective inflatable balloon valves (30) are connected via a compressed air hose (32) to a compressor (34) on the net cage construction (10), for blowing air into and extracting air from the balloon valves, respectively. (30).

7. The net cage construction (10) according to claim 6, characterised in that the compressor (34) is connected to a control system for regulating respective inflatable balloon valves (30), whereby water flow in each water outlet (24) can be controlled individually.

8. The net cage construction (10) according to claim 1 , characterised in that the water outlets (24) are surrounded by an outer canvas bag (40) arranged to direct outflowing water to one or more vertical main outlets (42).

9. The net cage construction (10) according to claim 8, characterised in that the main outlet (42) is equipped with a balloon valve (44) which is supplied with air via a compressed air line (32a).

10. The net cage construction (10) according to claim 1 , characterised in that the net cage construction (10) in the upper part comprises one or more inflatable and buoyancy-regulating floating tubes (28).

11. The net cage construction (10) according to claim 10, characterised in that respective inflatable floating tubes (28) are connected via a compressed air hose (36) to a compressor (34) on the net cage construction (10).

12. The net cage construction (10) according to claim 1 , characterised in that the canvas bag (12) comprises a number of inner and strengthening brackets (46) which extend completely or partially circumferentially around the canvas bag (12).

13. The net cage construction (10) according to claim 1 , characterised in that the upper zone (12a) comprises a number of said upper water inlets (20).