PARAVANE FOR A BARRIER TOWED BY A VESSEL

A paravane for a barrier towed by a vessel includes a floating body and a main skirt suspended below the floating body. The main skirt is defined with a longitudinal direction between its front end and its rear end. An upper lamella has a first point secured to the front end of the main skirt, a second point secured to the rear end of the main skirt and a third point provided at a distance from the main skirt. A lower lamella has a first point secured to the front end of the main skirt below the upper lamella, a second point secured to the rear end of the main skirt below the upper lamella and a third point provided at a distance from the main skirt. A front towing interface is connected to the third point of the upper lamella and the third point of the lower lamella. The floating body, the main skirt, the upper lamella and the lower lamella are made of one or more flexible materials. The upper lamella has a skirt facing edge defined as the edge between the first point and the second point. The skirt facing edge is secured continuously or at intervals to the main skirt. The paravane includes at least one intermediate lamella having a first point secured to the front end of the main skirt between the upper lamella and the lower lamella, a second point secured to the rear end of the main skirt between the upper lamella and the lower lamella and a third point provided at a distance from the main skirt. The third point is connected to the front towing interface. The paravane includes a plurality of stiffening plates fastened to the main skirt. The stiffening plates have a height being lower than a height between the lamellae. The stiffening plates are fastened to the main skirt between the lamellae.

FIELD OF THE INVENTION

The present invention relates to a paravane for a barrier towed by a vessel. The present invention also relates to a barrier system towable by a vessel. The present invention also relates to a method for deploying a barrier from a boom reel. The present invention also relates to a method for retrieving a barrier from water.

BACKGROUND OF THE INVENTION

An oil boom system is a system for containing or collecting oil floating on top of a water body. The oil boom system comprises a typically U-shaped or V-shaped barrier towed behind one or several vessels, wherein the oil spill is collected at the apex of the barrier. The barrier comprises a floating body and possibly also a skirt suspended into the water body below the floating body.

WO 2000034589 describes an oil boom system for collecting oil spill on water whereby e.g. one end of an oil boom is towed from the shore of a watercourse with flowing water e.g. a river, at an angle to the water current, to a suitable position in the watercourse, using a waterborne current rudder. The current rudder is secured to one end of a line, the other end of the line is secured to an upstream point ashore, allowing the current rudder to move out into the stream and to maintain one end of the oil boom in a suitable position in the watercourse, while the other end of the oil boom is secured to a downstream point ashore, where an oil recovery device is positioned. The current rudder is fitted with a balance rudder operated by a line or a remote control from shore, allowing the current rudder and the oil boom end attached thereto, to be recovered to shore when so required.

WO 2010126426 describes a method for applying a dispersant or other substances to a water surface. Significant for the method that a nozzle hose system is used, said system comprising a hose or a set of hoses, that the hose or set of hoses is elevated at both ends, that one end of the hose or set of hoses is based at an operation unit, and that the other end of the hose or set of hoses is connected to a paravane that is towed by or connected to the operation unit.

A paravane is commercially available under the name Boom Vane® by the applicant of the above publications WO 2000034589 and WO 2010126426.

EP 3185679 describes a paravane for floating barrier. The paravane has at least one foil with a first side, a second side, a leading end, a trailing end, a top and a bottom, wherein at least one foil is straight and at least one second foil is curved, where one side of the straight foil and the other side of the curving foil are interconnected by a number of stays, where at least one foil is connected at the top to at least a first buoyant body and that at least the one plane at the bottom is connected to at least one ballast element, and that at the second side of the straight foil there are at least one towing line and a tow eye by which there is achieved a paravane that can keep an arrangement of lines, nets, floats in a water body in a position suitable for performing the task.

WO 2016/029915 describes a paravane for floating barrier including at least one foil with a first side, a second side, a leading end, a trailing end, a top and a bottom, wherein at least one foil is straight and at least one second foil is curved, where one side of the straight foil and the other side of the curving foil are interconnected by a number of stays, where at least one foil is connected at the top to at least a first buoyant body and that at least the one plane at the bottom is connected to at least one ballast element, and that at the second side of the straight foil there are at least one towline and a tow eye by which there is achieved a paravane that can keep an arrangement of lines, nets, floats in a water body in a position suitable for performing the task.

JP 2002315472 describes a net-extender for trolling, attached to the midway of a towing rope as well as a conventional Otter board by using a flexible net-extender. The net-extending body has a rigid member arranged at the upstream side and a flexible net-extender joined to the rigid member and arranged at the downstream side.

JP 2011067182 describes a fishnet expander capable of improving fishnet-expanding performance, and to provide a trawl fishing including the same. The fishnet expander is such that a warpage is formed at a blade part and the efflux port of a ridge part is formed on the end opposite to an influx port in the first direction of the ridge part, thus markedly improving lifting force acting on the blade part as compared with conventional cases and securing the shape stability of the blade part in towing.

JP S5518959 U describes another type of paravane.

The object of the present invention is to provide an improved paravane for a barrier.

The object of the present invention is also to provide a floating barrier system which may utilize the properties of the improved paravane.

A further object of the present invention is to provide a method for deploying a barrier and a paravane to a water body and to retrieve the barrier and the paravane from a water body.

In particular, the object is to provide an improved paravane for a barrier, a floating barrier system and a method for deploying or retrieving the barrier and the paravane which achieves increased efficiency, and which achieves reduced risk for personal injuries.

SUMMARY OF THE INVENTION

The present invention relates to a paravane for a barrier towed by a vessel, wherein the paravane comprises:a floating body;a main skirt suspended below the floating body, wherein the main skirt is defined with a longitudinal direction between its front end and its rear end;an upper lamella having a first point secured to the front end of the main skirt, a second point secured to the rear end of the main skirt and a third point provided at a distance from the main skirt;a lower lamella having a first point secured to the front end of the main skirt below the upper lamella, a second point secured to the rear end of the main skirt below the upper lamella and a third point provided at a distance from the main skirt;a front towing interface connected to the third point of the upper lamella and the third point of the lower lamella;
wherein the floating body, the main skirt, the upper lamella and the lower lamella are made of one or more flexible materials;
wherein the upper lamella has a skirt facing edge defined as the edge between the first point and the second point, wherein the skirt facing edge is secured continuously or at intervals to the main skirt;
wherein the paravane (10) comprises a plurality of stiffening plates (25) fastened to the main skirt (20).

In one aspect, the lower lamella has a skirt facing edge defined as the edge between the first point and the second point, wherein the skirt facing edge of the lower lamella is secured continuously or at intervals to the main skirt.

In one aspect, the one or more flexible materials comprises fabrics.

In one aspect, the floating body is an inflatable floating body. The material of the floating body may be fabrics consisting of a reinforcement weave covered on one or both sides with thermoplastics like polyurethane, polyvinyl chloride, etc. or rubber, nitrile, etc.

In one aspect, the floating body has two layers of material, one airtight inner bladder and a mechanically strong outer fabric.

In one aspect, the main skirt is made of a non-permeable material.

In one aspect, the main skirt is made of reinforcement weave covered on one or both sides with thermoplastics like polyurethane, polyvinyl chloride, etc., or rubber, nitrile etc.

In one aspect, the main skirt is made of two fabrics which are joined together. The term “joined together” here refers to joining processes such as welding, gluing, vulcanizing, or sewing etc.

In one aspect, the upper lamellae and/or the lower lamellae are at least partially made of a permeable material.

In one aspect, the upper lamellae and/or the lower lamellae are at least partially made of a perforated fabric, a net fabric or a net structure etc.

In one aspect, the stiffening plates are built into the main skirt between two layers of fabric, wherein the fabric of the main skirt around the stiffening plates are formed by joining the fabrics together.

In one aspect, the stiffening plates are fastened directly to the main skirt only on one side. In another aspect, some stiffening plates are fastened to one side and some stiffening plates are fastened to the other side of the main skirt.

In one aspect, the stiffening plates are located at a first distance from each other in a first direction.

The first distance is sufficiently long to allow folding of the main skirt.

In one aspect, the main skirt is provided with a number of first folding lines defined by the first distance between the stiffening plates.

In one aspect, the stiffening plates are located at a second distance from each other in a second direction different from the first direction.

The second distance is sufficiently long to allow folding of the main skirt.

In one aspect the respective third corners of the upper and lower lamellas are gathered in one single point.

In one aspect, the main skirt is provided with a number of second folding lines defined by the second distance between the stiffening plates.

In one aspect, the plurality of stiffening plates is arranged in a grid with rows and columns.

In one aspect, the stiffening plates are fastened to the main skirt between the lamellae.

In one aspect, the stiffening plates have a height being lower than the height between the lamellae.

In one aspect, the stiffening plates are inserted into pockets in the main skirt.

In one aspect, the stiffening plates are rectangular or square. Preferably, its corners are rounded, to prevent damages to the fabric of the main skirt, the lamella and/or other parts of the paravane. Alternatively, the stiffening plates may be triangular, polygonal, circular or semi-circular. Preferably, the stiffening plates are of the same size and shape. However, they may also be of different sizes and different shapes.

In one aspect, the stiffening plates are made of 2-20 mm thick polyethylene plates.

In one aspect, the paravane comprises a rear towing interface provided in the rear end of the floating body and/or in the rear end of the main skirt.

In one aspect, the rear towing interface comprises several connection points located continuously or at intervals between the rear top part of the floating body and the rear bottom part of the main skirt.

In one aspect, the rear towing interface is connected directly to the first end of the barrier. In this way, the paravane may be considered to be integrated with the barrier.

In one aspect, the front towing interface is connectable to the vessel and to a first end of the barrier. This may be the only towing interface needed for connecting the paravane to the vessel and to the first end of the barrier.

In one aspect, the front towing interface is connectable to the vessel, while the rear towing interface is connectable to the first end of the barrier.

In one aspect, the front towing interface is connected to the vessel via the first towing line and the first end of the barrier is connected to the front towing interface via a first additional towing line. In one aspect this first additional towing line is a bridle consisting of multiple lines for proper transfer of forces to the barrier. In one aspect this bridle consists also of a fabric.

In one aspect, the front towing interface is connected to the vessel via the first towing line and a second additional towing line, while the first end of the barrier is connected to the first towing line via the first additional towing line.

In this way, the paravane will be towed at a distance from the first end of the barrier. Hence, it is achieved that turbulence caused by the paravane being towed will occur outside of the barrier, i.e. the paravane will not cause turbulence inside the barrier, which will negatively impact for example oil spill collection.

Optionally, the rear towing interface may be connected to the barrier by means of an clastic towing line. Preferably, this elastic towing line is connected to the barrier a distance from where the first additional towing line is connected. It should be noted that the clastic towing line does not contribute during towing, its only purpose is to prevent the paravane from turning into the barrier opening in the initial towing phase, during stops in the towing or during deployment. Hence, the elastic towing line is preventing a wrong starting position for the paravane.

Optionally, a utility line with or without elastic properties may be connected to front of the floating body and or to the front of the skirt. The other end of the utility line may be fastened to one or several fixed points in first towing line. It should be noted that the utility rope does not contribute during towing, its only purpose is to enable optimal position during retrieval over a dock edge or over the stern on a vessel.

In one aspect, the paravane comprises at least one intermediate lamella having a first point secured to the front end of the main skirt between the upper lamella and the lower lamella, a second point secured to the rear end of the main skirt between the upper lamella and the lower lamella and a third point provided at a distance from the main skirt, wherein the third point is connected to the front towing interface.

In one aspect, the respective third corners of the upper, intermediate and lower lamellas are gathered in one single point.

In one aspect, the at least one lamella has a skirt facing edge defined as the edge between the first point and the second point, wherein the skirt facing edge is secured continuously or at intervals to the main skirt.

In one aspect, the lamellas have a first or leading edge, defined as the edge between the first point and the front towing interface. In one aspect, the leading edge is curved. In one aspect, the leading edge is tensioned during the towing operation. In one aspect the leading edge is provided with a semi-stiff flotation member ensuring that the front towing interface is kept at surface level and at a distance from the floating body to ensure correct tow starting position.

In one aspect, the lamellae have a second or trailing edge, defined as the edge between the second point and the front towing interface. In one aspect, the trailing edge is curved. In one aspect, the trailing edge is tensioned during the towing operation. In one aspect, the trailing edges is reinforced by a rope, webbing etc. to transfer forces to the rear towing interface.

In one aspect, the lamellas have a substantially triangular shape, wherein the first, second and third points are forming corners of the substantially triangular shape.

Alternatively, the lamellas may comprise a fourth point provided at a distance from the main skirt. Preferably, this fourth point is also connected to the front towing interface. In this case the interface between the third and fourth point and FTI may be through a bridle consisting of two or more lines.

In one aspect, the lamellae are non parallel.

In one aspect, the floating body is an elongated floating body defined with a longitudinal direction between its front end and its rear end.

In one aspect, the front end of the floating body projects a distance from the front end of the main skirt.

In one aspect, the paravane comprises an intermediate skirt connected between the floating body and the main skirt, wherein a front distance between the front end of the main skirt and the floating body is longer than a rear distance between the rear end of the main skirt and the floating body.

According to the above, the leading edge is lower than a trailing edge. Hence, the lamella will pull the paravane downwardly in the water during use, preventing the paravane from collapsing or surfacing.

Alternatively, this can be achieved by connecting the main skirt directly to the floating body while securing the first point of the lamellas to the main skirt at a point lower than the second point.

In one aspect, the longitudinal direction of the main skirt is aligned with the longitudinal direction of the floating body. The longitudinal direction of the main skirt may be substantially parallel with the longitudinal direction of the floating body.

In one aspect, the paravane comprises a skirt ballast secured to the lower end of the main skirt. In one aspect, the paravane comprises a lamella ballast secured to the lower lamella. In one aspect, the skirt ballast and the lamella ballast comprise a weight line, i.e. a line to which a number of weight elements, such as lead elements or other denser than water elements. The skirt ballast and the lamella ballast may be connected to or integrated with the skirt and lamellae respectively.

The present invention also relates to a barrier system towable by a vessel, wherein the barrier system comprises:a barrier having a first end and a second end, wherein the second end is connectable to the vessel;a paravane as defined above, wherein the front towing interface is connectable to the vessel;
wherein the first end of the barrier is either connected to the front towing interface of the paravane or to a rear towing interface of the paravane.

In one aspect, the first end of the barrier and the second end of the barrier is connectable to the same side of the vessel.

In one aspect, the barrier system comprises a boom reel from which the barrier system is reeled out from and reeled onto. In one aspect, the boom reel is located on the vessel.

In one aspect, the paravane may be reeled onto the core of the reel with the barrier reeled outside the paravane. In one aspect the paravane may be reeled radially outside of the barrier.

According to the above, it is achieved that the barrier can be towed by one vessel only while still maintaining the opening of the barrier, defined as the distance between the first end and the second end of the barrier, sufficiently large. This is achieved by the paravane being able to pull the first end sideways out from a vessel direction.

In one aspect, the barrier system comprises towing lines to provide a distance between the vessel and the paravane, and between the vessel and the barrier.

In one aspect, the barrier system comprises a drag anchor secured to an apex of the barrier.

The present invention also relates to a method for deploying a barrier from a boom reel, wherein the method comprises the following steps:reeling out the barrier from a boom reel by pulling an apex of the barrier away from the boom reel;reeling out a first end and a second end of the barrier;inflating the barrier;reeling out a paravane from the boom reel, wherein the first end of the barrier is connected to a front towing interface of the paravane or to a rear towing interface of the paravane;inflating a floating body of the paravane;reeling out a first and second towing lines from the boom reel, wherein the first towing line is connected to the front towing interface of the paravane and wherein the second towing line is connected to the second end of the barrier.

In one aspect, the method further comprises the initial step of:providing the boom reel on a vessel;connecting a drag anchor to the apex of the barrier;releasing the drag anchor into the water;controlling the vessel to move, thereby causing the drag anchor to reel out the barrier from the boom reel.

In one aspect, the method further comprises the step of:disconnecting the first towing line and the second towing line from the boom reel;connecting the first towing line and the second towing line to the vessel hull.

Further the method comprises retrieving the barrier system from the water to the vessel in the opposite way.

According to the above, it is further achieved that the barrier can be towed outside of a turbulence area behind the vessel. This is an advantage when the barrier is used as an oil boom for collecting oil spill, wherein it is important that the oil spill is floating on top of the water body. In the turbulence area, the oil spill tends to mix with the water, and is hence more difficult to collect.

According to the above, the paravane may be reeled out from and reeled onto a boom reel together with the barrier and towing lines. Hence, the deployment and retrieval of the paravane become more efficient, as less time and less equipment are needed. Hence, the deployment and retrieval will involve less operations which may reduce risk exposure to personnel. In particular, there is no need for a paravane deployment crane for lifting the paravane from the vessel and into the water and for lifting the paravane from the water and up to the vessel. The lifting operation by means of such paravane deployment cranes represents a considerable HSE risk.

The object of the invention is to provide a paravane for a barrier where the paravane may be reeled inside the barrier on a reel which compared to known technology reduce deployment time, reduce retrieval time, reduce operation complexity, reduce risk for personnel and eliminate the need for a paravane deployment crane on the vessel.

In addition, there is no need for a separate storage area for the paravane, as the paravane is now stored on the boom reel together with the towing lines and barrier.

As a further consequence, a smaller vessel without suitable located cranes may be used for handing the barrier system.

Definitions

The term “towing line” is used herein for any type of flexible line used for towing purposes, such as a rope, a wire, a chain, webbing etc.

The term “barrier” is used herein for any type of element being used to separate one element from other elements, the other elements typically being water. The barrier may be used to separate floating or semi-floating garbage from water, such a barrier may be referred to as a garbage collector. The barrier may be used to concentrate and or separate oil spill from water, such a floating barrier may be referred to as an oil boom or active oil boom. The barrier may be used to separate aquatic organisms from water, such a barrier may be referred to as a fishing net, a trawl etc. The barrier may be a floating barrier, a partially floating barrier, or a submerged barrier.

The term “paravane” is used herein for a device being able to control a first end of a barrier to be separated from a second end of the barrier when the barrier is towed by a vessel. The paravane is a non-motorized device.

The term “flexible” is herein referring to the property of being capable of bending without breaking. The term “bending without breaking” is here used relative to the outer diameter of the core of the boom reel, wherein something is considered to be flexible if it may be reeled onto and reeled out from the boom reel without breaking. The core of the boom reel is a cylindrical object having a diameter which is typically between 20 cm to 100 cm.

Initially, it is referred toFIG.1, where a barrier system1is shown. The barrier system comprises a substantially U-shaped barrier2defined with a first end2a, a second end2band an apex2c. The area between the first end2aand the second end2bis referred to as an opening2O of the barrier2. The barrier2is towed by means of a first towing line3aand a second towing line3bconnected between the respective ends2a,2bof the barrier and a vessel VE.

The barrier system1further comprises a paravane10, which, when the barrier system is towed by the vessel VE, is pulling the first end2aof the barrier2away from the second end2bof the barrier2for the purpose of maintaining the opening2O wide.

As shown inFIG.1, a boom reel5is installed on the stern of the vessel VE.

In the present embodiment, the barrier is an oil boom for collecting oil spill on a water surface.

It should be noted that the paravane10may be connected to the first end2aof the barrier2and/or to the first towing line3ain various ways. This will be described further in detail below. First, the paravane10will be described in detail.

Floating Body

As shown inFIG.3, the paravane10comprises an inflatable elongated floating body11defined with a longitudinal direction A11between its front end11aand its rear end11b. As shown inFIG.4, the front end11aof the floating body11projects a distance D11arelative other parts of the paravane10.

The material of the floating body11may consist of two fabric layers. First an inner airtight bladder fitted with a valve. Then an outer fabric protecting the inner bladder. The fabrics used in the inner and outer bladder may be a reinforcement weave covered on one or both sides with thermoplastics like polyurethane, polyvinyl chloride, etc. or rubber, nitrile, etc. One or more valves13are provided in the floating body11for inflating/deflating the floating body11.

In the rear end11b, the floating body11comprises a rear towing interface RTI (indicated as a dashed area inFIG.3andFIG.4). This rear towing interface will be described further in detail below.

It should be noted that in the front end11aof the floating body11, and in the rear end11bof the floating body11, handles indicated as11care shown. These handles11care used during manual handling of the floating body11.

Main Skirt

The paravane10further comprises a main skirt suspended in the water below the floating body11. As shown inFIG.2andFIG.5, the water level WL is indicated by a dashed line, wherein most of the floating body11is floating above the water level WL and wherein the entire main skirt20is submerged below the water level WL.

The main skirt20is substantially rectangular, and is defined with a longitudinal direction A20between its front end20aand its rear end20b.

In the present embodiment, the main skirt20is made of two layers of fabric joined together by a welding process. The fabrics used is consisting of a relatively strong reinforcement weave covered on both sides with a mixture of softened polyurethane and polyvinylchloride. The main skirt20is non-permeable.

In the present embodiment, the length of the main skirt20is 2 meters and height around 1.2 meters.

The rear end20bof the main skirt20may also form a part of the rear towing interface RTI, either alone or together with the rear end11bof the floating body11, as indicated by the dashed area RTI inFIG.3andFIG.4.

The paravane10further comprises a number of lamellas31,32,33. As shown inFIGS.2and3, the paravane10comprises an upper lamella31, a lower lamella33and three intermediate lamellae32between the upper lamella31and the lower lamella33.

In the present embodiment, the lamellas31,32,33are of substantially similar size and similar shape, and they are substantially triangular, as best shown inFIG.10a.

Here it is shown that each lamella31,32,33have a first point or corner31a,32a,32c, which is secured to the front end20aof the main skirt20, a second point or corner31b,32b,33b, which is secured to the rear end20bof the main skirt20, and a third point or corner31c,32c,33cprovided at a distance from the main skirt20.

As shown inFIG.2, the third corners31c,32c,33care gathered in one single point, referred to as a front towing interface FTI. By gathering the corners in one single point, the opening(s) between the lamellas (as seen from the front view inFIG.2and as seen from the rear view inFIG.3), through which the water flows during towing, has a triangular shape. In other variants, for example where there is used a bridle, the third point of corners31c,32c,33cmay not be one single point, but having a vertical and or horizontal distance. This front towing interface FTI is connectable to the first towing line3a, or connectable to the first end2aof the barrier2.

The edge of the lamellas between the first corners31a,32a,33aand the second corners31b,32b,33bmay be referred to as skirt facing edges31sfe,32sfe,33sfe.

These skirt facing edges31sfe,32sfe,33sfeare preferably secured continuously to the main skirt20, due to the relatively large forces transferred between the lamellas and the main skirt20during towing and to prevent main skirt20from collapsing.

The edge of the lamellas between the first corner31a,32a,33aand the front towing interface FTI, i.e. between the first corner31a,32a,33aand the third corners31c,32c,33cmay be referred to as a leading edge31le,32le,33le. These leading edges31le,32le,33leare preferably tensioned during towing. Preferably, the leading edges31le,32le,33leare curved, as indicated by the radius RA-FTI inFIG.10a. This may reduce vibrations in the leading edge during towing. In addition the relatively heavy forces are more distributed when being transferred into the front20aof the main skirt20. In addition, the upper leading edge31leis provided with a flexible, but semi stiff flotation member ensuring that the front towing interface FTI is kept at surface level and at a distance from the floating body to ensure correct tow starting position.

The edge of the lamellas between the second corners31b,32b,33band the front towing interface FTI, i.e. between the second corners31b,32b,33band the third corners31c,32c,33cmay be referred to as trailing edges31te,32te,33te. These trailing edges31te,32te,33teare preferably tensioned during towing. Preferably, also the trailing edges31te,32te,33teare curved, as indicated by the radius RB-FTI inFIG.10a. This may reduce vibrations in the leading edges during towing.

The trailing edges31te,32te,33temay be reinforced by a towing line, rope or webbing etc. to transfer forces between the front towing interface FTI and the rear towing interface RTI and further into barrier first end2a.

The lamellas31,32,33are in the present embodiment made of a heavy reinforced perforated fabric. The perforated fabric has 23% opening. Due to the perforations, water is allowed to flow through the lamellas during towing. This evens out pressure built up around the lamellae due to external wave action. It also evens out pressure due to standing waves set up by the paravane10itself in different towing speeds. This reduce the probability for the lamellae collapse. The perforation also allows for more water to hit the main skirt20and thereby improve the sideways drag efficiency.

Stiffening Plates

The paravane10further comprises a plurality of stiffening plates25fastened to the main skirt20. The purpose of the stiffening plates25is prevent vertical collapse of the main skirt10, especially at high towing speed. Practical tests at low towing speed shows that the paravane works without stiffening plates25. However, when the towing speed is increased above a critical level, the forces acing on the main skirt20between two lamellae cause the main skirt20to collapse in vertical direction and thereby significantly reducing the area used to produce sideways drag from the paravane. At the same time, the stiffening plates25are not considerably reducing the flexibility of the main skirt20, i.e. the main skirt20may still be reeled onto and out from the boom reel5and is hence considered flexible.

In the present embodiment, the stiffening plates25are of the same rectangular shape and of the same size, with a height H25of 16 cm, a width W25of 16 cm. The stiffening plates25are cut from an 8 mm thick polyethylene plate. The corners and edges of the rectangular plates25are rounded, to prevent them from damaging other parts of the paravane10when reeled onto and out from the boom reel5.

It is now referred toFIG.6a,FIG.6bandFIG.6c. Here it is shown that the stiffening plates25are arranged in four rows R25A, R25B, R25C, R25D, each row being located in the areas of the main skirt20between each of the lamellas31,32,33. As indicated inFIG.6a, the four rows are substantially oriented in a direction parallel to the longitudinal direction A20of the main skirt20. In each row, the stiffening plates25are located at a first distance D25A from each other. Between each row, the stiffening plates25are located at a second distance D25B from each other.

As illustrated schematically inFIG.6bandFIG.6b, the distances D25A, D25B allow the main skirt20to be folded 180° along folding lines FLA, FLB indicated inFIG.6a.

In the present embodiment, the stiffening plates25are built into the main skirt20between two layers of fabric, wherein the fabric of the main skirt20around the stiffening plates are formed by welding the fabrics together.

Intermediate Skirt

The paravane10further comprises an intermediate skirt40connected between the floating body11and the main skirt20. As indicated inFIG.2, there is a front distance D40abetween the front end20aof the main skirt20and the floating body11which is longer than a rear distance D40bbetween the rear end20bof the main skirt20and the floating body11.

Due to the main skirt20, the leading edges31le,32le,33leof the lamellas become lower than the trailing edges31te,32te,33teof the respective lamellas. Hence, the lamellas31,32,33will pull the paravane10downwardly in the water during use, preventing the paravane10from collapsing or surfacing. Of course, the downwardly directed pulling force created by the orientation of the lamellas due to the intermediate skirt are adjusted to not exceed the upwardly directed force created by the buoyancy of the floating body11.

As shown inFIG.3, the longitudinal direction A20of the main skirt20is not exactly in parallel with the longitudinal direction A11of the floating body11due to the intermediate skirt40. Still, the longitudinal direction A20of the main skirt20may be considered to be approximately parallel with the longitudinal direction A11of the floating body11.

Further Details of the Paravane

The paravane10may further comprise a skirt ballast29secured to the lower end of the main skirt20(shown inFIG.5), and the paravane10may further comprise a lamella ballast39secured to the lower lamella33(shown inFIG.5). The skirt ballast and the lamella ballast may comprise a flexible weight or lead line, i.e. a line to which a number of weight elements (lead or other denser than water elements) are connected or integrated. By connecting the weight elements spaced apart from each other, the skirt ballast and the lamella ballast are considered to be flexible.

It should be noted that the floating body11, the main skirt20, the upper lamella31and the lower lamella33are made of one or more flexible materials, making the entire paravane flexible when the floating body11is deflated. It should be noted that even though stiffening plates25are secured to the main skirt20, the paravane is considered flexible within the definition of “flexible” above.

Paravane10as Part of the Barrier System1

The barrier system1and the paravane10have been described above. It is now referred toFIG.1. Here, the front towing interface FTI of the paravane10is connected to the vessel VE via the first towing line3a, and the rear towing interface RTI of the paravane10is connected to the first end2aof the barrier2.

An alternative embodiment is shown inFIG.9a. Here, the front towing interface FTI is connected to the vessel VE via the first towing line3aand the first end2aof the barrier2is connected to the front towing interface FTI via a first additional towing line3a1. Optionally, the rear towing interface RTI may be connected to the barrier2by means of an elastic towing line3c. Preferably, this elastic towing line3cis connected to the barrier2a distance from where the first additional towing line3alis connected. It should be noted that the elastic towing line3cdoes not contribute during towing, its only purpose is to prevent the paravane10from turning into the barrier opening20in the initial towing phase or during stops in the towing. Hence, the elastic towing line3cis preventing a wrong starting position for the paravane10.

Yet an alternative is shown inFIG.9b. This embodiment is similar to the above embodiment, the differences being that the barrier system1comprises a second additional towing line3a2between the first towing line3aand the front towing interface FTI and that the first additional towing line3alis connected to the first towing line3ainstead of to the front towing interface FTI.

Optionally, the additional towing line3a2may, also in the form of a bridle with two or more lines, be connected directly from front towing interface FTI to the first end2aof the barrier. In this case the first towing line3ais also connected to the first end2aof the barrier, but not necessarily at the same point.

InFIG.9aandFIG.9b, the paravane10will be towed at a distance from the first end2aof the barrier2. Hence, it is achieved that turbulence caused by the paravane10being towed will occur outside of the barrier2, i.e. the paravane10will not cause turbulence inside the barrier, which could negatively impact for example oil spill collection. Hence, it is assumed that the embodiments shown inFIG.9aandFIG.9bcan be towed at higher speed than the embodiment ofFIG.1.

InFIG.1,FIG.9aandFIG.9b, turbulence areas are indicated with wavy lines. The vessel turbulence is indicated as a turbulence area TA. It is shown inFIG.1,FIG.9aandFIG.9bthat the barrier2may be towed outside of the turbulence area TA.

Deployment of Barrier System

It is now referred toFIGS.7and8. Here, the boom reel5is shown to comprise a boom reel core5awith flanges5bin each end thereof. The outer core diameter D5ais indicated inFIG.7and may be 20-100 cm.

InFIG.8, it is shown that the first towing line3aand the second towing line3bare reeled onto the core5afirst, i.e. the towing lines3a,3bare nearest the core5a. Then, the paravane10, the first end2aof the barrier2and the second end2bof the barrier2are reeled onto the core, the first end2aand the second end2bbeing reeled onto the core substantially in parallel (at least when assuming that the length of the first towing line3ais equal to the length of the second towing line3b). Due to the flexible properties of the main skirt20, the deflated floating body11and the lamellas31,32,33, schematically indicated inFIG.8as dotted lines, are folded around stiffening plates25. Hence, the entire paravane10is considered to be flexible. It should be noted thatFIG.8is a schematical illustration only, as the barrier2in practice will be tensioned more when reeled onto the core5a, reducing the space occupied by the paravane10inFIG.8and reducing the space between layers of the barrier2outside of the paravane.

Finally, the end2cof the barrier2is reeled onto the core5a. As indicated inFIG.8, a drag anchor6is connected to the end2cof the barrier2.

It should be noted that in the present embodiment of the method, the barrier2is deployed from the boom reel5on the stern of the vessel VE by means of the crew on the vessel VE only. The steps of deploying the barrier from the boom reel5will now be described.

In a first step, the drag anchor6is released to the water.

Then, vessel VE is moved slowly forward, allowing the drag anchor6to gradually pull the apex2cof the barrier2away from the boom reel5and out into the water. For each inflation valve of the barrier2, the barrier2is inflated.

As the vessel VE moves further forward, the barrier2is reeled out from the boom reel5and inflated until the first end2aand the second end2bof the barrier2are deployed into the water. The paravane10, as shown inFIG.7, is already connected to the first towing line3aand to the first end2aof the barrier2. The elastic towing line3cis also indicated inFIG.7. The floating body11is inflated and is also deployed into the water.

In a final step, the towing lines3a,3bare at least partially deployed to the water. The towing lines3a,3bmay be secured to the boom reel5during the towing. However, they may also be released and secured to the hull of the vessel VE, as indicated inFIG.1,FIG.9aandFIG.9c.

The paravane10will, as the barrier2and the paravane10are towed by the vessel VE, now pull the first end2aaway from the second end2band hence increase the opening2O of the barrier. As is apparent from the description of the method above, no crane is needed.

The opposite steps are performed when retrieving the barrier and paravane from the water. Again, no crane is needed.

According to the above, it is further achieved that the barrier2can be towed outside of a turbulence area TA behind the vessel VE. This is an advantage when the barrier2is used as an oil boom for collecting oil spill, wherein it is important that the oil spill is floating on top of the water body. In the turbulence area TA, the oil spill tends to mix with the water, and is hence more difficult to collect.

ALTERNATIVE EMBODIMENTS

Some further alternative embodiments will be described below.

In one embodiment, the skirt facing edges31sfe,32sfe,33sfeof the lamellas may be secured to the main skirt20at intervals instead of continuously.

It is now referred toFIG.10b. Here, it is shown that the lamellas31,32,33may comprise fourth corners or points31d,32d,33dprovided at a distance from the main skirt20. The fourth points31d,32d,33dare also connected to the front towing interface FTI. Hence, the lamellas are no longer true triangles. InFIG.10bit is also shown that the third point31cand the fourth point31care connected to the first towing line3avia a bridle (i.e. two towing lines). It is considered only a matter of definition whether the front towing interface FTI is formed by the points31c,31donly or if the front towing interface FTI is formed by the points31c,31dtogether with the bridle.

Similarly, the rear towing interface RTI may be connected to the barrier2by means of two or more towing lines, for example two lines connected between the barrier2and the rear end11bof the floating body11, and two lines connected between the barrier2and the rear end20bof the main skirt20.

It should be noted that the intermediate skirt40is not an essential feature. In an alternative embodiment, the main skirt20may be connected directly to the floating body11. The downwardly directed pulling force may still be obtained by securing the first points31a,32a,33aof the respective lamellas to the main skirt20at a point lower than the second point31b,32b,33bof the respective lamellas.

It should be noted that instead of using the drag anchor6, a further vessel (not shown) may be used to reel out the barrier from the boom reel5. Other means for providing drag in the barrier2may also be used.

It is now referred toFIG.11. Here it is shown that the paravane10further comprises foils35connected between the lamellas31,32,33at a distance from the main skirt20. The foils35reduces how far the lamellas can be pulled away from each other during towing. The foils35may be fitted with stiffening plates with equal properties as the stiffening plates25in the main skirt20. In this case the foils35will also establish a minimum distance between lamellas31,32and33. InFIG.11, it is shown that the foils35are oriented substantially in parallel with the main skirt20. The foils35are made of a flexible material, such as a permeable, a semi-permeable or a non-permeable material.

It should be noted that some of the stiffening plates25may be slightly bent during exposure to forces on the boom reel core5a. Tests show that this does not impact the paravane functionality negatively.

It should further be noted that the above paravane10is intended for use on a starboard side of the vessel. It should be noted that a mirrored paravane may be used on a port side of the vessel. Of course, the vessel may use one starboard type of paravane and one port side type of paravane simultaneously, to tow two separate barriers or to tow one wider barrier. It is also possible to use two paravanes10on the same side of the barrier, for example a first paravane10as shown inFIG.1(i.e. connected via the rear towing interface to the first end2aof the barrier) and a second paravane10as shown inFIG.9aor9b.

The embodiments described above are focused on the use of the paravane10for an oil spill boom such as high speed Current Buster®, a garbage collecting boom etc. However, the paravane may also be used during towing of other objects in water, for example fishing gear, such as a trawl.

The paravane10will work when operated with a relative speed to the water induced by a towing vessel VE as described above. This relative speed may also me induced by a sea current or river.