The invention relates to a subsea installation and to a bend limiter for such subsea installation, wherein the subsea installation a flexible subsea member, installed in a subsea structure e.g. a pillar or monopole of an offshore generator, such as a generator associated to a wind turbine structure or another energy harvesting structure.

BACKGROUND ART

There are various practical situations in which a flexible elongate member such as a power cable, an umbilical, or a pipeline needs to be routed along the seabed to enter a support structure through an opening in it.

For example when collecting power from offshore wind driven turbine generators it is known to connect a power cable through an opening in a subsea foundation of the generator e.g. a monopole.

The cable is for example connected at one end at a hang-off within the support pillar, which is generally embedded in the seabed, to somewhere above the sea- level, and pass through an opening in a wall of the support pillar, somewhere below the sea-level closer to the seabed, from a connection point inside the support pillar, and the cable rest on the seabed outside of the support pillar. Because the cable outside of the support pillar is subjected to movement as a result of tides and weather, the cable is vulnerable to damage as a result of movement of that part of the cable which comes into contact with the edge of the opening. In particular, contact with the edge of the opening can cause the cable to be bent around a sufficiently small bend radius to cause damage.

To reduce the risk of bending of undesired or excessive damaging bending of the flexible subsea member, it is well known to provide a bend limiter to surround the flexible subsea member at locations where such excessive bends are expected to occur. A bend limiter may for example be fitted to the flexible subsea member adjacent to an end-fitting of the flexible subsea member and/or to a connector used for connecting the flexible subsea member to another element, such a subsea well head, a vessel or a platform. The prior art bend limiters may for example consist of a single elastic body moulded in polyurethane and may alternatively comprise an internal reinforcing structure as described in WO 92/12376 or in GB-A-2,291,686. They may also comprise heat- dissipation means, as is recommended in GB-A-2,291,686.

US2012261017A discloses a stiffening cover with a relatively high flexural modulus for a flexible pipe where the flexible pipe has been provided with a stiffened length section by applying the stiffening cover to partially or totally surround the pipe in the stiffened length section. This stiffening cover is simple to mount on production site of the flexible pipe, however, it only provides a limited stiffening effect which often may not be sufficient.

GB 2,304,393 A discloses a bend limiter for cables and hoses comprising a tubular body which has one or more lines of profiled slotting dividing the tubular body into sections. The slotting has a width which allows the sections to move relative to each other. The slotting is shaped in a meander shaped pattern which provides an interlocking effect.

Even though such bend limiters provides an adequate protections of the flexible subsea member of a subsea installation, there is still a need for an improved protection of the flexible subsea member and the subsea installation, in particular where the subsea installation is located near the seabed, such as in water depths of O-lOOm. In these environment there is significant movement due to wave and current which over time may damage both the flexible subsea member as well as the entire subsea installation.

DISCLOSURE OF INVENTION

An objective of the present invention is to provide a subsea installation comprising a flexible subsea member, wherein the subsea installation has a high stability even when located at relative shallow water depths such as up to a height of 100 m from seabed, such as up to a height of 50 m from seabed, such as up to a height of 30 m from seabed.

In an embodiment, it is an objective to provide a subsea installation comprising a flexible subsea member wherein the drag affecting the flexible subsea member, due to wave and current on an unburied length section of the flexible subsea member is reduced compared to prior art installation.

In an embodiment, it is an objective to provide a subsea installation which provide an improved protection of the flexible subsea member when installed at relative shallow water depths such as up to a height of 100 m from seabed, such as up to a height of 50 m from seabed or in particular when at least in part installed in the shallow water between seabed and up to 30 m from seabed, such as up to 25 m from seabed.

In an embodiment, it is an objective to provide a bend limiter for such subsea installation.

In an embodiment, it is an objective to provide a protection system, which facilitates a simple and reliable installation, which may even be a diverless installation.

In an embodiment, it is an objective to provide a protection device, which is relatively cost effective and is simple to use.

These and other objects have been solved by the invention or embodiments thereof as defined in the claims or as described herein below.

It has been found that the invention or embodiments thereof have a number of additional advantages, which will be clear to the skilled person from the following description.

The inventors of the present invention has found that by providing the subsea installation and the flexible subsea member of the subsea installation with a bend limiter according to the invention, the bend limiter is not only acting as a bend limiter, but has the additional effect of stabilizing the entire subsea installation and reducing the risk of damaging drag in the flexible subsea member, It is believed that this surprisingly effective stabilizing effect is caused by the relatively high weight of the bend limiter relative to its relative small outer diameter, relative to the outer diameter of the flexible subsea member.

Before the present invention, it was desired to keep the bend limiter weight as low as possible, because it was believed the weight of the bend limiter could provide a damaging drag in the flexible subsea member and at the same time a low weight could ease installation. However, the inventors have found that the benefits of the stabilizing effect of the bend limiter far increases any risk of damaging from drag of the bend limiter. Indeed it has been found that the bend limiter of the invention add to the lifetime of the entire subsea installation.

The bend limiter of the invention is suitable for housing a length section of a flexible subsea member of a subsea installation.

A bend stiffener reduces bending stresses and curvature of a length section of the flexible subsea member to be installed to acceptable levels.

The bend limiter comprises a tubular wall having a length and a circumference and defining a through bore for housing the flexible subsea member length section. The bend limiter has a longitudinal centre axis and an inner diameter ID _b and an outer diameter OD _b . The tubular wall comprises a cut pattern comprising one or more through cuts through the bend limiter tubular wall. The through cuts are fully or partially extending along the circumference of the tubular wall. To ensure a desired stabilizing effect, the tubular wall of the bend limiter has a submerged weight of at least 40 kg/m of its length.

The desired weight depends largely on the location of the subsea installation. In particular where the subsea installation is located near the seabed, such as up to 250 m from the seabed, it is desired that the weight in at least a length section of the bend limiter is relatively high, since there in such environment may be significant movement due to wave and current. Especially where the installation is located at shallow water depths of 0-100 m from the seabed. Many installations are located directly on the seabed, e.g. fixed offshore wind foundations and the bend limiter provides a tremendous stabilizing effect when applied in such subsea installations.

Advantageously, the tubular wall of the bend limiter has a submerged weight of at least 40 kg/m, such as at least 50 kg/m, such as at least 60 kg/m, such as at least 75 kg/m as at least 100 kg/m, such as up to 400 kg/m, such as up to 300 kg/m such as up to 200 kg/m such as up to 175 kg/m, such as up to least 150 kg/m. The term "submerged weight" means herein the weight when fully submerged in water having a density of 1025 kg/m ³ . The actual density of sea water depends on salinity, pressure (and thereby depth) and temperature.

The range of density in the oceans is generally from about 1.020 to 1.070 g/cm ³ colder water more dense saltier water more dense higher pressure causes density increase - pressure increases with depth due to the mass of water above

In practice as well as herein, the submerged weight is determined setting the density to 1025 kg/m ³ .

It should be emphasized that the term "comprises/comprising" when used herein is to be interpreted as an open term, i.e. it should be taken to specify the presence of specifically stated feature(s), such as element(s), unit(s), integer(s), step(s) component(s) and combination(s) thereof, but does not preclude the presence or addition of one or more other stated features.

Throughout the description or claims, the singular encompasses the plural unless otherwise specified or required by the context.

The "an embodiment" should be interpreted to include examples of the invention comprising the feature(s) of the mentioned embodiment.

The term "about" is generally used to include what is within measurement uncertainties. When used in ranges the term "about" should herein be taken to mean that what is within measurement uncertainties is included in the range.

The term "substantially" should herein be taken to mean that ordinary product variances and tolerances are comprised. All features of the invention and embodiments of the invention as described herein, including ranges and preferred ranges, may be combined in various ways within the scope of the invention, unless there are specific reasons not to combine such features.

Any chemical or physical property is to be determined at standard conditions of 23 °C and 1 atm. unless otherwise specified. The term bend limiter normally refers to a bend restrictor or a bend stiffener, wherein a bend restrictor functions as a mechanical stop and limits the radius of curvature of a length section of the flexible subsea member to be installed to a minimum value and a bend stiffener functions by reducing bending stresses and curvature of a length section of the flexible subsea member to be installed to acceptable levels.

The bend limiter of the invention may advantageously functioning both as a bend limiter and a stiffener at the same time and thereby provides a very beneficial protection of the flexible subsea member.

In an embodiment, the bend limiter has a weight above water of at least 45 kg/m of its length, such as at least 50 kg/m, such as at least 60 kg/m, such as up to 400 kg/m, such as up to 300 kg/m such as up to 200 kg/m such as up to 175 kg/m, such as up to least 150 kg/m.

The difference between the submerged weight of the bend limiter and its weight above water may advantageously be as small as possible, such as less than 40 %, preferably less than 20 % or even less than 15 %. Thereby the bend limiter provides an even higher stabilizing effect.

The desired weight per m of the bend limiter may in addition depend on the diameter of the bend limiter. The bend limiter has an inner diameter ID _b and an outer diameter OD _b defining the thickness of the tubular wall thickness of the bend limiter.

The ID _b of the bend limiter may be selected in dependence of the flexible subsea member to be supported by the bend limiter. Generally it is desired to select the ID _b of the bend limiter to be from 5 to 100 mm larger than the flexible subsea member to be supported by the bend limiter. The ID _b may be equal or may vary along the length of the bend limiter e.g. to form a trumpet shape at an end section of the bend limiter furthest from a connection location.

The connection location of the bend limiter is a location where the bend limiter is adapted to be connected to another element, such as the flexible subsea member directly or indirectly or to a connector or a retainer or other element that may hold the bend limiter in its desired location. The bend limiter advantageously has a first free end and a second opposite end adapted to be connected and which thereby provides the connection location of the bend limiter.

The term "indirectly connected" means herein that the bend limiter is connected to the flexible subsea member via at least one other element, e.g. via a connector, an end fitting a flange or similar.

Advantageously, the bend limiter has a submerged weight of at least 100 kg per m OD _b per m length of the bend limiter, such as at least 150 kg/m ² , such as at least 200 kg/ per m OD _b per m length, such as at least 250 per m OD _b per m length.

The weight above water may advantageously be at least 110 kg per m OD _b per m length of the bend limiter, such as at least 165 kg/m ² , such as at least 220 kg/ per m OD _b per m length, such as at least 275 kg/m ² per m OD _b per m length.

The tubular wall of the bend limiter may conveniently have an average wall thickness of from 5 mm to 50 mm, such as at least 10 mm, such as at least 15 mm.

In an embodiment, the bend limiter has an average wall thickness of from 10 mm to 25 mm.

When determining the average thickness of the bend limiter, slots and windows (i.e. through openings without solid material) in the wall is not included. Only locations of solid material are included.

It is generally desired that the bend limiter has a relatively low thickness compared to its weight, thereby increasing the stabilizing effect. It is believed that the smaller the surface area of the outer surface of the bend limiter the less area of the bend limiter will be affected by waves and current and the higher the weight, the less effect will such waves and current acting on the bend limiter outer surface have.

The tubular wall of the bend limiter may in an embodiment, have equal wall thickness along its length.

In an embodiment, the tubular wall of the bend limiter has a first length section having a first wall thickness along its length and a second length section having a second wall thickness along its length. Advantageously, the bend limiter comprises a first length section having a first average thickness and a second length section having a second average thickness different from the first average thickness. Preferably the first length section has an average thickness at least 5 mm, such as at least 10 mm larger than the average thickness of the second length section, preferably the first length section is closer to a connection location than the second length section.

In an embodiment, the first length section has an average thickness of 10 mm and the second length section has an average length section of 20 mm.

In an embodiment, the wall thickness of at least a length section of the bend limiter is gradually increasing or decreasing along the length of the bend limiter, e.g. determined from a connection location.

In an embodiment, the bend limiter has a touch down location along its length, where it is adapted to touch down on the seabed such that an uppermost section of the bend limiter is connected e.g. retained at a subsea installation and extending downwards to touch the seabed at the touch down location and where a lowermost length section of the bend limiter is laying in contact with the seabed. In this embodiment a length section of for example 0.5 to 5 m, such 1-2 m comprising the touch down location may advantageously have a higher weight and a larger average wall thickness that the average values of the remaining parts of the bend limiter.

Thereby a very strong, durable and supporting bend limiter may be obtained which may result in a significant prolongation of the lifetime of the subsea installation.

Advantageously, the tubular wall of the bend limiter has an average material density of at least 2000 kg/m ³ , such as at least 4000 kg/m ³ , such as at least 6000 kg/m ³ , such as at least 7000 kg/m ³ , such as at least 7500 kg/m ³ , such as at least 8000 kg/m ³ .

In practice it is desired that the tubular wall of the bend limiter has an average material density which is a high as possible and preferably at least 5000 kg/m ³

The tubular wall of the bend limiter advantageously comprises or consist of metal. Preferably, the metal comprises steel, such as carbon steel or stainless steel. In an embodiment, the tubular wall of the bend limiter comprises at least one layer of metal optionally coated with a polymer material. By providing the tubular wall of the bend limiter to be partly or fully of metal a very strong a durable bend limiter is obtained and in addition, the submerged weight of the bend limiter may be relatively high, while still provide the desired flexibility.

In addition, the metal layer ensures a high submerged weight while simultaneously providing a high thermal conductivity, which as may reduce or even prevent risk of overheating of the flexible subsea member housed in the bend limiter after installing in a subsea installation.

In an embodiment, the metal of the tubular wall of the bend limiter comprises corrosion protection, e.g. in the form of one or more coatings and/or in the form of sacrificial anode material attached to or forming part of the tubular wall.

The length of the tubular wall of the bend limiter is also called the bend limiter length. The bend limiter may in addition comprise a mounting section for being mounted to a flexible subsea member directly or indirectly as described above.

The tubular wall of the bend limiter may in principle be as long as desired e.g. up to 50 m or even longer. For most applications a length of the tubular wall of the bend limiter up to 30 m is sufficient.

In some applications the length of the tubular wall of the bend limiter may be as short as 1-3 m. This may for example be the case for a bend limiter adapted to be located inside a monopole proximally to an opening in the monopole where a flexible subsea member is passing through.

Advantageously, the tubular wall of the bend limiter has a length of at least 1 m, preferably at least 2 m, such as from 3 to 30 m, such as from 4 to 25 m, such as from 5 to 20 m.

The bend limiter may advantageously, be produced from a metal tube having the desired wall thickness, inner diameter, outer diameter and length preferably as described above for the tubular wall of the bend limiter. Where the bend limiter should be provided to be relatively long two or more metal tube sections may be fixed together e.g. by being welded together or using nut and bolts. The cut pattern is hereafter provided in the metal tube in the form of one or more through cuts. One or more coatings and/or polymer layers may be applied before or after prociding the through cut(s).

In an embodiment, the cut pattern comprises at least one cut slot, the cut slot preferably provides a pair of opposite cut faces that are facing each other and having a distance of at least 1 mm, such as at least 2 mm, such as between 3 and up to the wall thickness of the cut.

The cut slot provides that edges on respective sides of the cut are not touching each other when the bend limiter is in straight and unloaded condition. This means that a fraction of the material of the tubular wall of the bend limiter is removed when providing the cut slot(s).

In an embodiment, the cut(s) may be slim cut(s) providing a pair of opposite cut faces that are facing each other and is immediately adjacent to each other, such as with a distance of less than 1 mm.

In an embodiment, the cut(s) may be slot cut(s) providing a pair of opposite cut faces that are facing each other and having a distance of at least 1 mm, such as at least 2 cm, such as 2 - 20 mm, e.g. 3-10 mm.

In an embodiment, the cut(s) may comprise a combination of slim cut(s) and slot cut(s).

Advantageously, the cut pattern is sufficient for allowing the tubular wall of the bend limiter to bend with a selected bending radius, wherein the selected bending radius is from 0.5 to 25 m, such as from 2 to 10 m. The MBR is determined as the minimum bending radius without plastic deformation of the tubular wall.

In an embodiment, the MBR is equal along at least 90 % of the length of the tubular wall of the bend limiter, such as along its entire length.

In an embodiment, the bend limiter has a varying MBR along its length, such as a gradually increasing and or decreasing MBR determined from its connection location.

In an embodiment, the tubular wall of the bend limiter has a first length section having a first MBR and a second length section having a second MBR. For example, the first length section may have a MBR of about 5 m and the second length section may have a MBR of about 10 m.

To ensure the desired bending stiffness it may be desired that the cut pattern comprises cut(s) extending in substantially the entire circumference of the tubular wall. The cut(s) extending in substantially the entire circumference may be in form of one or more helically cuts or in form of a plurality of offset cuts which together extends in the entire circumference.

Advantageously, the cut pattern comprising a meandering pattern, preferably extending partly or fully in the circumference of the metal wall.

In particular it is desired that the cut pattern comprises a helically meandering pattern, such as a helically meandering pattern having a trapezoid meandering pattern.

An isosceles trapezoid is a trapezoid where the base angles have the same measure. As a consequence the two legs are also of equal length and it has reflection symmetry. This is possible for acute trapezoids or right trapezoids (rectangles).

Preferably the trapezoid shape of the trapezoid meandering pattern is an isosceles trapezoid shape forming protrusions with a narrow waist.

Preferably the helically meandering pattern has a pitch of from 2 cm to 1 m, such as from 4 cm to 0.5 m. The pitch is advantageously larger than the width of the trapezoid meandering pattern, such as up to 10 times the width of the trapezoid meandering pattern, such as from 2 times to 5 times the width of the trapezoid meandering pattern.

In an embodiment, the helically meandering pattern extends helically along the circumference of the tubular wall, preferably with a pitch of at least 50 mm such as from 60 mm to 200 mm, such as from 70 mm to 150 mm.

The trapezoid meandering pattern may conveniently have a width of from 0.5 to 30 cm, such as from 1 to 15 cm, such as from 2 to 8 cm.

The cut(s), such as slot cut(s) may be provided substantially perpendicular to the centre axis of the tubular wall of the bend limiter (determined with the bend limiter in straight condition) or the cut(s), such as slot cut(s) may be provided with an angle to the centre axis of the tubular wall of the bend limiter, such as an angle up to about 55 °, thereby providing opposite cut faces that are inclined relative to the centre axis of the tubular wall.

To reduce the risk or fully avoid that sections between of the tubular wall are displaced laterally e.g. to partly overlap, it may be advantageously to provide the bend limiter with slots in which the faces have an inclination in respect of the centre axis. In an embodiment at least one of the lines defining the faces has an angle with the centre axis in the range of 10° to 55°, such as in the range of 15° to 45°.

In an embodiment the cut(s) forms a repeated trapezoid pattern. A trapezoid consists of straight lines in which at least two of the lines meet with an angle which differs from 90°.

In an embodiment the cut(s) form a helical pattern in the tubular wall. A helical pattern in which the cut line is continuous may be produced in a relatively simple manner.

The cuts, such as the cut slots in the tubular wall may be provided by several cuttings methods, such as by using a jig saw or by laser cutting.

In an embodiment, the cuts in the tubular wall is made by water jet cutting. Water jet cutting has proven to provide excellent and accurate cuts.

In an embodiment the cuts in the tubular wall is made by plasma cutting. Plasma cutting is very efficient in particular for cutting in steel having large wall thickness. Plasma cutting may be used for cutting steel plates having a thickness up to 150 mm.

In an embodiment, the cuts in the tubular wall is provided by use of oxy-fuel cutting using oxygen and a fuel gas.

The use of oxy-fuel cutting is especially advantageously where the tubular wall is of or comprises metal such as steel, since it is both fast and very accurate. The cutting process may for example applying a mixture of oxygen and fuel gas to preheat the metal to its 'ignition' temperature (bright red heat), which for steel is usually in the range 700°C - 900°C, but well below its melting point. A jet of oxygen is then directed into the preheated area instigating a vigorous exothermic chemical reaction between the oxygen and the metal to form iron oxide or slag. The oxygen jet blows away the slag enabling the jet to pierce through the material and continue to cut through the material.

In an embodiment, the bend limiter comprises an internal wear coating, such as a wear coating of a polymer or a polymer containing composition, such as a coating comprising one or more of polyurethane (PU), polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE) or polyvinyl idene fluoride (PVDF), e.g. in a thickness of from 5 pm to 5 mm, such as from 10 pm to 1 mm, such as from 25 pm to 0.1 mm. The wear coating is advantageously sprayed or painted on internal side of the tubular wall.

The tubular wall of the bend limiter may advantageously comprise an external polymer tube extending in at least a part of the length of the tubular wall.

The external polymer tube may be bonded to the metal layer or mechanically fixed to the metal layer. The external polymer tube may comprise the cut pattern or a part thereof. In an embodiment, the external polymer tube is free of the cut pattern.

The external polymer tube may extend in a part of the length of the tubular wall or in the entire length thereof. The external polymer tube may conveniently have a thickness of 0.5 mm to 5 cm, such as from 1 to 10 mm.

In an embodiment, the tubular wall of the bend limiter comprises an internal polymer tube extending in at least a part of the length of the tubular wall, the internal polymer tube may advantageously have a thickness of 0.5 mm to 5 cm, such as from 1 to 10 mm.

The internal polymer tube may comprise the cut pattern or a part thereof. In an embodiment, the internal polymer tube is free of the cut pattern.

The internal polymer tube may be bonded to the metal layer or mechanically fixed to the metal layer.

The internal polymer tube and/or the external polymer tube may advantageously comprise or consist of elastomeric polymer. The internal polymer tube and/or the external polymer tube may for example comprise one or more of the polymers olefin(s) such as polyethylene (PE) or polypropylene (PP), styrene, polyamide (PA) polyurethane (PU), polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE) or polyvinyl idene fluoride (PVDF).

The internal polymer tube and/or the external polymer tube may add a stiffening effect to the tubular wall of the bend limiter, which thereby may act both as a stiffener and a bend restrictor.

The internal polymer tube and/or the external polymer tube may be penetrated into the cut(s) of the cut pattern in the tubular wall, such as penetrating into a depth of up to 5 mm, such as up to 2 mm to the cut(s), preferably the slot cut(s). This penetration provides an even higher stiffening effect to the tubular wall of the bend limiter which thereby acts both as an effective stiffener and a bend restrictor. This ensures a very strong protection of a flexible subsea member located in the tubular wall of the bend limiter and thereby a very effective protection of the entire subsea installation.

In an embodiment, the bend limiter forms part of a protection system or a protection device as described in co-pending application DK PA 2021 00156 herby incorporated by reference.

The invention also comprises a subsea installation comprising a flexible subsea member and a bend limiter for housing a length section of the flexible subsea member, wherein the bend limiter preferably is as described above.

The subsea installation including at least a part of the flexible member is advantageously located at relative shallow water depth such as up to a height of 100 m from seabed, such as up to a height of 50 m from seabed, such as up to a height of 30 m.

The flexible subsea member may for example be a cable, such as a power cable and/or a cable comprising optical fibre(s), a pipe such as a flexible bonded or unbonded pipe, an umbilical or any combination comprising one or more of these.

The subsea installation advantageously comprises a subsea structure. The subsea structure may for example comprise a, monopole, a gravity Base Structure, a jacket structure and a tripod structure.

The subsea structure may conveniently be a subsea foundation. In an embodiment, the subsea structure comprises or consists of a guide tube, such as a J-tube or an I- tube and/or it may comprise or consist of a support pillar. The subsea structure may for example be a subsea foundation of an energy harvesting system comprising a generator e.g. a subsea foundation comprising a support pillar.

The flexible subsea member is advantageously connected to the subsea structure at a connection location of the flexible subsea member, wherein the bend limiter is located around the flexible subsea member adjacent to the connection location of the flexible subsea member to provide that a minimum distance between the bend limiter and the connection location of the flexible subsea member does not exceed 2 m determined along the length of the flexible subsea member. Preferably the distance between the bend limiter and the connection location of the flexible subsea member does not exceed 1 m determined along the length of the flexible subsea member.

The subsea structure advantageously comprises an opening for passage of the flexible subsea member. The flexible subsea member may be connected to and/or passing into or through to said subsea structure.

The opening in the subsea structure may be any opening providing a passage for the flexible subsea member, such that a length section of the flexible subsea member is located inside the subsea structure and another length section of the flexible subsea member is located outside the subsea structure.

The opening in the subsea structure may for example be a hole or aperture in the subsea structure, such as a hole or any kind of opening in a pillar or a monopole into a hollow portion of the pillar/monopole.

In an embodiment, the opening in the subsea structure is in the form of a passage through a guide tube, such as a J-tube or an I-tube.

In an embodiment, bend limiter is connected directly or indirectly to the flexible subsea member, the bend limiter preferably being connected to the flexible subsea member via an end fitting and/or via a connector connecting the flexible subsea member to the subsea structure.

In an embodiment, the bend limiter is connected directly or indirectly to said flexible subsea member, said bend limiter preferably being connected to said flexible subsea member via an end fitting and/or via a connector connecting the flexible subsea member to said subsea structure, preferably to provide that a minimum distance between said bend limiter and said subsea structure not exceed 2 m, preferably does not exceed 1 m determined along the length of the flexible subsea member.

Advantageously, the bend limiter is connected to a retainer located and retained in an opening of the subsea structure and forming a passage for the flexible subsea member wherein said bend limiter is located around said flexible subsea member adjacent to said retainer preferably to provide that a minimum distance between said bend limiter and said retainer does not exceed 2 m, preferably does not exceed 1 m determined along the length of the flexible subsea member.

In an embodiment, the bend limiter is connected to a connector connecting the flexible subsea member to the subsea structure, wherein the flexible subsea member is passed through and protected by the connector which is arranged to retain a length section of the flexible subsea member inside an opening in the subsea structure while a length section of the flexible subsea member is located outside the subsea structure.

In an embodiment, wherein a length section of the flexible subsea member extends into or through the subsea structure and a length section of the flexible subsea member is located outside the subsea structure, preferably the bend limiter is located outside the subsea structure, preferably within a distance of up to 2 m, such as up to 1 m from the bend limiter to the subsea structure determined along the length of the flexible subsea member.

Advantageously, inner diameter ID _b of the tubular wall of the bend limiter is larger than an outer diameter OD _f of the flexible subsea member, preferably the inner diameter ID _b of the tubular wall of the bend limiter is up to about 130 mm larger than an outer diameter OD _f of the flexible subsea member, such as from 5 mm to 100 mm, such as from 20 to 50 mm larger than an outer diameter OD _f of the flexible subsea member. All features of the inventions and embodiments of the invention as described herein including ranges and preferred ranges may be combined in various ways within the scope of the invention, unless there are specific reasons not to combine such features.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS AND ELEMENTS OF THE INVENTION

The above and/or additional objects, features and advantages of the present invention will be further elucidated by the following illustrative and non-limiting description of embodiments of the present invention, with reference to the appended drawings.

The figures are schematic and are not drawn to scale and may be simplified for clarity. Throughout, the same reference numerals are used for identical or corresponding parts.

Figure 1 illustrates an embodiment of a subsea installation according to the invention.

Figure 2 is a perspective illustration of an embodiment of a subsea installation according to the invention.

Figure 3 is a side view of the bend limiter of an embodiment of the invention.

Figure 4 is a close op view of cuts of a bend limiter of an embodiment of the invention.

Figure 5 illustrates further embodiment of a subsea installation according to the invention.

The subsea installation illustrated in figure 1 comprises a subsea structure comprising a monopole 6a, with a through opening 6b. The subsea structure comprises an internal connection platform 2 located a lower portion of the monopole with a upper portion of the monopole which may comprise or be connected to a generator, such as a generator associated to a wind turbine or a wave power farm. The monopole 6a is fixed at the seabed S, e.g. by being partly buried therein. At the internal connection platform 2 a number of connectors 3 are located, through which flexible members may be passes into the generator. A flexible member 9, is passing through the through opening 6b of the monopole 6a a first bend limiter 5 is located to house a length section of the flexible member 19 outside the monopole 6a and a second bend limiter 4 is located to house a length section of the flexible member 19 inside the monopole 6a, a retainer 1 is located between the first bend limiter 5 and the second bend limiter 4 for retaining the the first bend limiter 5 and the second bend limiter 4 in position. The the first bend limiter 5 and the second bend limiter 4 may advantageously be connected to the retainer 1. The retainer may advantageously, be as the retaining portion described in co-pending application DK PA 2021 00156, however, it should be understood that any suitable retainer may be applied.

The flexible member 9 extends from a location outside of the monopole 6b, where it is resting on the seabed S, through the first bend limiter 5, through the retainer 1, through the second bend limiter 4 and trough the connector 3 at the internal connection platform 2, where in is held in a temporarily or stationary fixed position.

Above the internal connection platform 2, the flexible member may be connected to its target position e.g. to the generator.

At least one of the first bend limiter 5 and the second bend limiter 4 is a bend limiter according to an embodiment of the invention.

The instalment of the flexible member 19 may comprise that an end portion of the flexible member 19 is arranged to be housed in a protection arrangement composed of the second bend limiter 4, the retainer 1 and the first bend limiter 5. A pull in head is temporarily mounted to the second bend limiter 4 and to the end portion of the flexible member 19. Thereafter the flexible member and the protection arrangement 4, 1, 5 is pulled through the through opening 6b of the monopole 6a until the retainer has passed sufficiently through the through opening 6b to retain the protection arrangement 4, 1, 5 from retreat, thereafter the pull in head is released from the second bend limiter 4 and the flexible member is polled further into the monopole 6b and through the connector 3 at the internal connection platform 2, where it is fixed temporarily or stationary. The high weight of the second bend limiter 4 according to an embodiment of the invention, has a stabilizing effect on the subsea installation and it ensures a safe and stable retaining of the retainer, i.e. it ensures that the retainer is not pulled, pushed or otherwise displaced from its desired location at the through opening of the monopole 6b.

The high weight of the first bend limiter 5 according to an embodiment of the invention, has a stabilizing effect on the entire subsea installation and it prevent damage of the system and the flexible member caused wave and current.

The subsea installation and especially at least a portion of the flexible member is located at shallow water e.g. within a depth h from seabed S, which may be as described above, e. x may be 200 or less, such a 150 or less, such as 100 or less, such a 30 or less, such as 30 or less.

It is especially desired that the first bend limiter 5, located outside the subsea structure is housing the flexible member at the touch down location 5a, where the flexible member 19 is touching down at the seabed S.

The first bend limiter 5, located outside the subsea structure is advantageously housing the flexible member from a location of up to 2 m from the retainer to a location where it is resting on the seabed S. The first bend limiter 5, located outside the subsea structure advantageously has a length of at least 5 m, preferably at least 10 m.

The second bend limiter 4, located inside the subsea structure, need not be too long, e.g. a length of from 1 to 5 m may suffice.

The subsea installation shown in figure 2 comprises a subsea structure comprising a monopole 16a, a protection arrangement composed of a second bend limiter 14, and a flexible member 19, wherein a portion of the flexible member 19 is housed in the protection arrangement 14, 11, 15.

The protection arrangement 14, 11, 15 has been installed through an opening 16b in the monopole 16a. The top part of the monopole 16a is not shown but may for example provide a support for a generator, such as a generator associated to a wind turbine or a wave power farm. The monopole is fixed at the seabed S, e.g. by being partly buried therein. The protection arrangement 14, 11, 15 comprises from its proximal end (inside the monopole 16a) to its distal end (outside the monopole 16a) the second bend limiter

14, the retainer 11, and the first bend limiter 15.

The first bend limiter 15 is composed of a first bend limiter portion 15a and a second bend limiter portion 15b, wherein the first bend limiter portion 15a and the second bend limiter portion 15b are connected to each other at connection flanges 15c. The connection flanges 15c, may for example be connected using not shown screws and bolts.

The retainer 11 may be as described above.

The protection arrangement 14, 11, 15 further comprises a number of sacrificial anodes 18a, 18b which in principle may be located at any location.

The flexible member has been pulled through the protection arrangement 14, 11,

15.

At least one of the first bend limiter 15 and the second bend limiter 14 is a bend limiter according to an embodiment of the invention.

Figure 3 show an example of a bend limiter 20 of an embodiment according to the invention having a submerged weight of at least 40 kg/m of its length. The bend limiter 20 is of a rigid material e.g. as described above and comprises a cut pattern 21 in the form of a helically meandering pattern having a desired pitch 22. The bend limiter 20 may be integrated with or connectable with a retainer of a protection arrangement as illustrated in figures 1 and 2.

Figure 4 show the shape of the meandering cut in more detail. The meandering cut has a trapezoid meandering shape with a height h, a platform p, a width w, a slope s, a radius r and a pitch 22 as shown in figure 3. A desired flexibility and/or minimum bending radius of the bend limiter 21 may be designed by selection of a height h, platform p, width w, slope s, radius r and pitch 22.

The installation shown in figure 5 comprises a number of bend limiters 34a, 34b,

34c, 34d, 34e coupled to each other via intermediate anode sections 37a, 37b, 37c, 37d. The respective bend limiters 34a, 34b, 34c, 34d, 34e comprises each a tubular wall and a through bore. A not shown cut pattern is provided in each of the respective tubular wall of the respective bend limiters 34a, 34b, 34c, 34d, 34e. The cut patterns may be as described above.

The cut patterns in the respective bend limiters 34a, 34b, 34c, 34d, 34e may be equal or different in dependence of the required or desired flexibility and MBR

The bend limiters 34a, 34b, 34c, 34d, 34e and the intermediate anode sections 37a, 37b, 37c, 37d.are coupled via flanges 38a.

Each of the respective intermediate anode sections 37a, 37b, 37c, 37d carries one or more sacrificial anodes 38.

The bend limiters 34a, 34b, 34c, 34d, 34e and the intermediate anode sections 37a, 37b, 37c, 37d are connected to form a protection tube of a protection arrangement, wherein a first end of the protection tube, provided by a first bend limiter 34a of the bend limiters 34a, 34b, 34c, 34d, 34e is pulled into an opening for a cable 39 which has been pulled through an opening 36 a of a j-tube 36 of a subsea structure.

A cable 39 has been pulled through the protection tube and into the j-tube 36 and thereby into the subsea structure.

The cable 39 is buried in the seabed S. A top layer of the seabed comprises an area of stones and rocks 31 onto which a part of the protection tube is laying. The protection tube is protecting the cable from being damaged by contact with and movements against or over the stones and rocks 31. At least one of the bend limiters 34a, 34b, 34c, 34d, 34e has a weight as described above and preferably, all of the bend limiter has a submerged weight of at least 40 kg/m of its length and preferably a weight above water of at least 45 kg/m of its length. In particular it id preferred that the bend limiter 34b located at the touch down location has a submerged weight of at least 40 kg/m of its length and preferably a weight above water of at least 45 kg/m of its length. The high weight of the bend limiters 34a,

34b, 34c, 34d, 34e ensures that movements of the protection tube is kept at a minimum thereby protecting the protection tube and the entire installation from damage caused by the area of stones and rocks 31.