WO2010087714A1

WO2010087714A1 - Device for an anchoring system for a fish farming net pen

Info

Publication number: WO2010087714A1
Application number: PCT/NO2010/000026
Authority: WO
Inventors: Alf Kristian Fjelldal
Original assignee: Akva Group Asa
Priority date: 2009-01-30
Filing date: 2010-01-22
Publication date: 2010-08-05
Also published as: NO20090486L

Abstract

A device for an anchoring system (16) for a fish-farming net pen (1) including a net bag (11) in which an upper portion is attached to buoyancy means (12) which are connected to the anchoring system (16), a lower portion of the net bag (11) being provided with shape-stabilizing means, there being arranged a secondary anchor line (166) between the shape-stabilizing means (13) and a portion of a primary anchor line (161) extending between the buoyancy means (12) and a net-pen anchorage element (165).

Description

DEVICE FOR AN ANCHORING SYSTEM FOR A FISH FARMING NET PEN

The invention relates to a device for an anchoring system for a fish-farming net pen including a net bag, in which an upper portion is attached to buoyancy means, which are connected to the anchoring system, and a lower portion of the net bag is provided with shape-stabilizing means, more precisely by there being arranged a secondary anchor line between the shape-stabilizing means and a portion of a primary anchor line extending between the buoyancy means and a net-pen anchorage element .

Fish-farming net pens are anchored by several anchor lines extending between an upper portion of the fish-farming net pen, typically in a floating ring surrounding the opening of a net bag, and bottom or land anchorage elements spaced around the fish-farming net pen. In a lower portion of the fish-farming net pen, there is placed a bottom ring which is suspended from the floating ring by means of chains or other elongated elements extending vertically downwards from the floating ring on the outside of the net bag, and, addition- ally, the bottom ring is connected to the lower portion of the net bag by means of chains or the like. The purpose of the bottom ring is, together with the floating ring, to keep the net bag spread, so as to provide a largest possible effective volume in the net bag.

Because of the fish-farming net pen depending freely from the floating ring without the lower portion of the fish-farming net pen being anchored to bottom or land anchorage elements, strong currents in the water masses, in which the fishfarming net pen is placed, may lead to the lower portions of the net bag, together with the bottom ring, being carried with the currents. This deformation of the fish-farming net pen entails several disadvantages, inter alia that the volume of the fish-farming net pen is reduced so that the fish are packed together and become stressed, the wall of the net pen may be forced against the suspension chains, and there may be a risk of the net material being damaged, with the consequence that the fish which are in the net pen will be able to escape through holes that have formed in the net-pen wall, the bottom ring and net bag may catch on the anchoring system with the consequence that the net pen may get damaged in addition to it being strenuous to free the bottom ring and net bag so that the net pen may again take its normal position.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art .

The object is achieved through features which are specified in the description below and in the claims that follow.

A device for an anchoring system for a fish-farming net pen is provided, wherein, from the shape-stabilizing means of the fish-farming net pen, typically a bottom ring, arranged at the bottom of the fish-farming net pen, several secondary anchor lines extend to a coupling element which is arranged on corresponding primary anchor lines connecting the buoyancy means, typically a floating ring, of the fish-farming net pen to the bottom anchorage elements of the anchoring system. The coupling element is arranged at a distance from the floating ring, advantageously in such a way that the depth below the surface of the water mass in which the fish-farming net pen is placed is equal to or larger than half the maximum distance between the floating ring and the bottom ring; that is to say, the depthwise extent of the fish-farming net pen.

The invention relates more specifically to a device for an anchoring system for a fish-farming net pen including a net bag, in which an upper portion is attached to buoyancy means connected to the anchoring system, and in which a lower portion of the net bag is provided with shape-stabilizing means, characterized by there being arranged a secondary anchor line between the shape-stabilizing means and a portion of a primary anchor line which extends between the buoyancy means and a net-pen anchorage element.

The secondary anchor line may be attached to a first coupling element arranged on the primary anchor line.

An anchor buoy may be attached to the first coupling element.

The anchor buoy may be attached to a second coupling element arranged at a distance from the first coupling element.

In an operative position, the first coupling element may be arranged at a vertical distance from the buoyancy means, and the distance equals at least half a maximum vertical distance between the buoyancy means and the shape-stabilizing means.

In an operative position, the first coupling element may be arranged at a vertical distance from the buoyancy means, and the distance equals at least three quarters of a maximum vertical distance between the buoyancy means and the shape-stabilizing means.

In what follows is described an example of a preferred embodiment which is visualized in the accompanying drawings, in which :

Figure 1 shows a side view of a fish-farming net pen with an anchoring system according to the invention shown on the left side of the net pen, there being shown, on the right side of the net pen, an alternative anchoring arrangement ;

Figures 2a and 2b show schematic side views of the fish-farming net pen with different placements of the connection between the primary and secondary anchor lines and also an indication of the maximum vertical movement of the bottom ring of the net pen.

In the drawings, the reference numeral 1 indicates a fishfarming net pen including a net bag 11 with buoyancy means 12, shown here as a floating ring, known per se, floating on a water surface 21 and being secured to an upper portion 11a of the net bag 11, and also shape-stabilizing means 13, shown here as a bottom ring, known per se, connected to a lower portion lib of the net bag 11. In a manner known per se, the net bag 11 delimits the fish-farming net pen 1 from the water masses 2 of the surroundings by one or more net walls 111 and a net bottom 112.

The floating ring 12 is provided with railing 121 defining a walkway 122. The floating ring 12 is further attached to an anchoring system 16 which includes a number of net-pen anchorage elements 165 arranged on a seabed 22.

The bottom ring 13 is typically provided with ballast (not shown) to contribute to keeping the net bag 11 spread in the water mass 2.

The bottom ring 13 is suspended from the floating ring 12 by means of several elongated suspension elements 14, typically in the form of chains or the like. From the bottom ring 13 several attachment chains 15 extend to the lower portion lib of the net bag 11.

The anchoring system 16 is provided by several primary anchor lines 161 (two shown here) being extended between the floating ring 12 and their respective net-pen anchorage elements 165. In a manner known per se, at a distance from the fish-farming net pen 1, there are arranged several anchor buoys 163 which are each connected to a primary anchor line 161 by means of a buoy line 164 attached to a first coupling element 162, alternatively a second coupling element 162'. The coupling elements 162, 162' are provided as securing elements which are fixed relative to the longitudinal direction of the lines 161, 164, but which allows the directions of the lines 161, 164 relative to each other to vary without subjecting the lines 161, 164 to a bending moment. In one embodiment the coupling elements 162, 162' are formed as a perforated plate.

The purpose of the anchor buoys 163 is partly to provide markers which can warn ship traffic, partly to provide a favourable angle between the anchor line 161 and the net-pen anchorage element 165 which is typically provided as a large- mass weight or as a suction anchor, and partly to provide an anchoring system having a certain compliant effect.

Between the bottom ring 13 and each primary anchor line 161, there is arranged a secondary anchor line 166 which is connected to the primary anchor line 161 by means of the first coupling element 162.

When the anchor buoy 163 is attached to the second coupling element 162 ' , the first coupling element 162 is arranged at a distance from the second coupling element 162 ' , as it is shown in the right half of figure 1.

The relationship between the vertical distance of the first coupling element 162 from the water surface 21 and the 5 maximum vertical distance a, see figures 2a and 2b, between the floating ring 12 and the bottom ring 13 affects the stabilizing properties of the anchoring system 16. When the lower portion of the net pen 1 moves vertically, the position of the first coupling element 162 will define the rotationalo centre R of the secondary anchor line 166 and thereby define the upper position of the bottom ring 13, as the bottom ring 13 can maximally be lifted to the intersection between a circular arc, with its centre on the attachment of the secondary anchor line 166 to the first coupling element 162,s and a vertical line extending through the bottom ring 13 when this is in a normal position; that is to say, at its maximum distance from the water surface 21. A geometric analysis will thereby establish how different placements of the first coupling element 162 relative to the vertical extent of the0 net pen 1 may affect the stabilizing effect of the anchoring system 16 on the bottom ring 13 and thereby on the net bag 11.

Figure 2a shows a situation in which the distance d of the first coupling element 162 from the water surface 21 equals5 half the maximum vertical distance a between the floating ring 12 and the bottom ring 13. When d < l/2a, the bottom ring 13 may be moved all the way up to the water surface. The circular arc indicates the theoretical travel path of the joint between the bottom ring 13 and the secondary anchoro line 166 when this rotates around its rotational centre R and the bottom ring 13 is not connected to other secondary anchor lines 166. Figure 2b shows a situation in which the distance d of the first coupling element 162 from the water surface 21 equals three quarters of the maximum vertical distance a between the floating ring 12 and the bottom ring 13. When l/2a > d >a, the bottom ring 13 may be moved vertically upwards, but not all the way up to the water surface. When d = 3/4a, the bottom ring 13 may, for example, be moved vertically upwards to a distance equalling l/2a from the water surface 21. The circular arc indicates the theoretical travel path of the joint between the bottom ring 13 and the secondary anchor line 166 when this rotates around its rotational centre R and the bottom ring 13 is not connected to other secondary anchor lines 166. Broken lines indicate the bottom ring 13 and the secondary anchor line 166 in their upper positions.

Claims

C l a i m s

1. A device for an anchoring system (16) for a fishfarming net pen (1) including a net bag (11) in which an upper portion is attached to buoyancy means (12)

5 which are connected to the anchoring system (16) , and a lower portion of the net bag (11) being provided with shape-stabilizing means (13), c h a r a c t e r i z e d i n that between the shape- stabilizing means (13) and a portion of a primary an-o chor line (161) extending between the buoyancy means (12) and a net-pen anchorage element (165), a secondary anchor line (166) is arranged.

2. The device in accordance with claim 1, c h a r a c t e r i z e d i n that the secondary anchor lines (166) is attached to a first coupling element (162) arranged on the primary anchor line (161) .

3. The device in accordance with claim 2, c h a r a c t e r i z e d i n that an anchor buoy (163) is attached to the first coupling element (162) . 0

4. The device in accordance with claim 3, c h a r a c t e r i z e d i n that the anchor buoy (163) is attached to a second coupling element (162 ') arranged at a distance from the first coupling element (162) .

5. The device in accordance with claim 2, c h a r a c -5 t e r i z e d i n that, in an operative position, the first coupling element (162) is arranged at a vertical distance (d) from the buoyancy means (12) , and the distance (d) equals at least half a maximum vertical distance (a) between the buoyancy means (12) ando the shape-stabilizing means (13) . The device in accordance with claim 2, c h a r a c t e r i z e d i n that, in an operative position, the first coupling element (162) is arranged at a vertical distance (d) from the buoyancy means (12), and the distance (d) equals at least three quarters of a maximum vertical distance (a) between the buoyancy means (12) and the shape-stabilizing means (13) .