CA3061424A1 - Device for supplying water to a sea pen - Google Patents

Abstract

Device for supplying water to sea pen (100) comprises a pipe-shaped body (10) in the form of a water impermeable canvas (14) of plastic stretched fast around an elongate framework (15) in the form of numerous mutually distanced rings (17) of light metal or plastic.
The pipe-shaped body (10) exhibits an upper end (11) serving as water outlet, and a lower end (12) with a sieve serving as water inlet. A hose for pressurized air is guided from the surface along the pipe-shaped body (10) and down to the lower end (12) to discharge air bubbles into the pipe-shaped body (10).

Description

DEVICE FOR SUPPLYING WATER TO A SEA PEN
Background The fish farming industry has a strong focus on fish welfare and risk of escape, and the industry is, among other things, aiming at maintaining good water quality having sufficient oxygen concentration, including lowest possible concentration of salmon lice and other parasites affecting fish welfare and product quality.
Salmon lice constitute a substantial challenge to the fish farming industry, and in particular reduced fish welfare and increased mortality. Today, delousing is performed regularly, often by means of fish carriers, where the fish is pumped up into containers aboard the fish carrier, where it is flushed and treated with delousing agent, such as hydrogen peroxide (H202), before being pumped back to the sea pen. This operation is tough for the fish, and a mortality of 5% has been experienced. Moreover, fish can be subjected to injury, which affects fish welfare and product quality. It is therefore desirable to prolong intervals between each delousing operation.
With the object of maintaining a reduced concentration of salmon lice in the upper layer of the water mass, solutions have arised for supply of lice-free water, or water having low salinity, which results in deteriorated living conditions for the salmon lice.
Supply of water from larger depths in the sea below the so-called the lice belt in the upper water layer and water-impermeable skirts in the upper part of a sea pen is well-known, and has been used for many years with varying success in the fish farming industry to reduce the lice concentration and maintain good water quality and oxygen concentration.
In that connection, devices have been provided for supply of water to a sea pen, from depths below the lice belt, using an elongate pipe arranged vertically, with propeller pump and water distributor means at the top of the pipe. Pipes of this type are typically arranged at a distance a bit away from the center of the sea pen by means of a set of wires to avoid intake of faeces, feed remains and other foreign objects from the bottom of the sea pen.
However, pipe based structures are heavy and have mechanical and electrical components that needs inspection. Moreover, it is in general undesirable to arrange components with high weight inside a sea pen in case the component detaches in strong wind and high waves, whereupon the pipe structure may damage the sea pen net, with escape of fish as a result.

2 NO 342827 describes a method of establishing a vertical water column in a sea pen. A circular ring with nozzles is submerged to the bottom of the sea pen to a depth below the lice belt, whereupon pressurized air is supplied to the nozzles. Air bubbles flow out of the nozzles and rise up in the water mass thus forming a bubble carpet which entrains water, and sets the water in circulation in the upper part of the mass of water.
However, water circulation in the lice belt, particularly combined with skirt arranged to prevent water exchange with the surrounding sea, will contribute to maintenance of the lice concentration and bad water quality.
GB 2 200 822 B describes an arrangement for supply of optionally oxygenated water to a sea pen having a water impermeable bottom and wall. Water is fetched from a depth having desired water temperature, and is discharged into the sea pen at the surface. Air and/or oxygen is supplied to the water from nozzles during its trip to the surface.
NO 892 188 A describes a method and a plant for oxygenating a water storage.
Oxygenation gas under pressure is supplied to the lower part of a submerged riser, wherein the water flows out of the riser at the surface.
NO 20170630 Al describes a circulation- and oxygenating system for a sea pen.
A riser is arranged in the sea pen to fetch water from a desired depth in the sea pen to supply the same at the surface.
The water is supplied with pressurized air at the lower end of the riser. The diameter of the riser is stated to be in the range of 0.5-1.5 meter.
Other examples from the prior art can be found in WO 2015/147743 and NO 342 818 Bl.
Object An object of the present invention is to provide a device which improves the water quality in the upper part of the water mass inside a sea pen. Another object is to supply water by a device of this type, from a depth below the lice belt to the surface, without contacting water within the lice belt during its trip up through the lice belt. A further object of the invention is to provide a device of this type that also supplies air and hence oxygen to the water in the upper part of the water mass. Yet another object is to provide a device which does not constitute any risk of damaging the sea pen net and escape of fish as a result.

3 The invention These objects are obtained by a device for suppling water to a sea pen, comprising a pipe-shaped body with water impermeable walls, arranged to be fixated inside a sea pen, with its longitudinal axis extending substantially vertically, stretched inside the sea pen by a number of wires attached to the rim of the sea pen. The pipe-shaped body exhibits an upper end, serving as an outlet for sea water to the surface of the sea inside the sea pen, and a lower end with a sieve, serving as an inlet for sea water from a depth below the lice belt in the sea, where the sieve prevents foreign objects from entering the pipe-shaped body. The pipe-shaped body comprises a water impermeable canvas stretched in an elongate framework, and having a hose extending from a source of pressurized air at the surface and further down along the framework to one or more diffusors located at the lower end of the pipe-shaped body.
In a particularly advantageous embodiment, the framework consists of a material having low weight and small volume, particularly a frame of aluminum or plastic. In one embodiment, the framework comprises a set of (numerous) mutually distanced individual rings, distributed along the elongate extension of the elongate framework, wherein the canvas is stretched around the rings. In this embodiment, a collapsible device is formed.
In another embodiment, the individual rings in the set of rings are arranged at a mutual distance along the elongate extension of the pipe-shaped, but attached to two or more elongate assembly struts extending in the longitudinal extension of the elongate framework, where the canvas is stretched around the numerous rings.
In a third embodiment, the framework is formed by a grid having sufficient strength to hold the canvas in a stretched condition.
The canvas is made of a tear resistant, water impermeable and flexible material, such as a plastic canvas. A plastic canvas of polyvinyl chloride is one example of such a canvas. The canvas is in the illustrated embodiment snake-shaped with a circular cross-section. However, it is also conceivable to utilize a polygonal framework, e.g. square.
In use, the inside of the flexible canvas is subjected to a weak underpressure and will hence to a certain degree be drawn together. In order to reduce friction between flowing water and the inside of the canvas, and hence compression of the canvas, the framework is preferably formed with a large cross-section. A non-limiting example is a cross-section in the range of about 1-3 meters, . 4 . .
, particularly about 2.5 meters. These dimensions may naturally vary with the size of the sea pen in question.
In order to obtain a best possible dispersion of air and hence oxygen in the water, including obtaining best possible contact with the water and entrainment of water up through the flow path at the inside of the canvas, the diffusor is arranged to discharge air bubbles with a size of about 1-2 mm.
It should be noted that the size of the discharge openings in the diffusor may vary with the depth at which the discharge openings are located. Larger depths will require discharge openings with less cross-section, since the air bubbles will expand gradually at reduced depths during their trip up to the surface, for in the end to become sufficiently large to burst at the surface.
Drawings The invention is in the following described in further details by means of drawings, where Fig. 1 shows the device in accordance with the invention arranged inside a sea pen, and Fig. 2 shows a lateral sketch of the device in accordance with the invention.
Now with reference to Fig. 1, the device in accordance with the invention is described, having a vertically extending pipe-shaped body 10, in the following also denoted as hose 10, stretched in a fixed position inside a sea pen 100 by means of four wires or ropes 18 anchored to the rim of the sea pen. The hose 10 is positioned a bit away from the middle of the sea pen 100 to avoid suction of faeces and other foreign objects with the water guided up to the surface of the sea. The hose 10 exhibits an upper end 11 serving as an outlet for sea water guided up from a depth below the lice belt by means of air bubbles discharged from a diffusor (not shown) arranged at a lower end 12 of the hose 10. The hose 10 is stretched firmly around an elongate framework 15, which in use exhibits a length extending from the surface and down to a depth below the lice belt but above the bottom of the sea pen net. Water current at the lower end 12 and the upper end 11 is indicated by arrows.
Fig. 2 shows a more detailed lateral drawing of the device in accordance with the invention. This drawing illustrates a preferred embodiment, where the framework 15 is constituted by numerous mutually distanced separate rings 17, distributed along the elongate extension of the framework 15. A flexible canvas 14 is stretched around the rings 17, thus forming a snake-shaped bellow. The snake-shaped bellow can be stored and transported in a compact, totally collapsed, form and simply launched into the sea where it because of its specific gravity unfolds into its fully expanded length, and is anchored by a number of ropes 18. The upper end 11 exhibits an outlet manifold 19 with an =
upper ring 20 and a lower ring 21, mutually connected to vertically extending ribs or struts 22. When the device has been launched into the sea pen, the upper ring 20 rests in or a bit below the surface.
Hence, water flowing out of the upper end 11, will flow out through the top of the upper ring 20 and laterally out through space between the ribs 22. Alternatively, the upper ring 20 can be replaced by a lid, so that all of the water flows laterally out through the upper end 11 and distributed evenly in the sea pen. The section indicated by reference numeral 13 illustrates the internal of the hose 10 with air bubbles flowing up together with water.
The lower end 12 of the hose 10 exhibits an inlet manifold 23 with a sieve (not shown), which prevents foreign objects from being sucked into the hose 10. The inlet manifold 23 can in a similar manner as the outlet manifold 19 be provided with a lid at the lower end 12 and with the sieve openings arranged in the periphery of the inlet manifold 23. In this manner, sea water is sucked into the inlet manifold 23 from the side, thus reducing risk of intake of seabed sediments.
Technical effect The device in accordance with the invention provides supply of sea water from a depth below the lice belt and to an area at the surface, the skirt volume, without being intermixed with water in the lice belt during its trip to the outlet. However, water on its way out of the skirt volume will not be drawn back again, but will flow out into the water outside the sea pen. The device also provides supply of oxygen-enriched water. The large dimensions of the device allows for supply of large amounts of water with low pressure loss. Moreover, the device is in one embodiment collapsible and can be stored and transported with little space requirement. The low weight and collapsible embodiment facilitates handling, and provides low risk of damage to the sea pen net in case it detaches in extreme wind and high waves.

Claims (9)

Claims

1. A device for supplying water to a sea pen, said device comprising a pipe-shaped body with water impermeable walls, arranged to be fixated with its longitudinal axis extending substantially vertically inside the sea pen, said pipe-shaped body exhibiting an upper end serving as an outlet for sea water to the surface of the sea inside the sea pen, and a lower end having a sieve serving as an inlet for sea water from a depth below the lice belt in the sea, wherein a hose is extending from a source of pressurized air at the surface and down along the pipe-shaped body, wherein the pipe-shaped body exhibits a cross-section in the range of about 1 to about 3 meters and comprises a water impermeable flexible canvas stretched in an elongate framework, and the hose extends to one or more diffusors located at the lower end of the pipe-shaped body, wherein the elongate framework comprises numerous mutually distanced individual rings, distributed along the elongate extension of the elongate framework, and wherein the canvas is stretched around said numerous rings, thus forming a collapsible device.

2. The device of claim 1, wherein the elongate framework consists of a light metal.

3. The device of claim 2, wherein the light metal is aluminum.

4. The device of claim 1, wherein the elongate framework consists of a rigid plastic material.

5. The device of any one of claims 1 to 4, wherein said numerous rings are attached to two or more elongate assembly struts, extending along the longitudinal extension of the elongate framework.

6. The device of any one of claims 1 to 5, wherein the elongate framework is a grid.

7. The device of any one of claims 1 to 6, wherein the canvas is made of polyvinyl chloride.

8. The device of any one of claims 1 to 7, wherein said one or more diffusors is arranged to discharge air bubbles with a size of about 1 to about 2 mm.

9. The device of any one of claims 1 to 8, wherein the elongate framework exhibits a cross-section of about 2.5 meters.