WO2023175164A2

WO2023175164A2 - Cathodic protection device for use in an impressed current cathodic protection system

Info

Publication number: WO2023175164A2
Application number: PCT/EP2023/056931
Authority: WO
Inventors: Jacob Daniel VAN DER SPEK
Original assignee: Corrosion & Water-Control Shared Services B.V.
Priority date: 2022-03-18
Filing date: 2023-03-17
Publication date: 2023-09-21
Also published as: NL2031333B1; WO2023175164A3

Abstract

The invention relates to a cathodic protection device for use in an Impressed Current Cathodic Protection system for an offshore structure. The device comprises a spacer tube, a flange, and a tubular anode. According to the invention, the tubular anode axis coincides with the spacer tube axis of the spacer tube, and the anode radius is at most 1,35 times the spacer tube radius. In case the tubular anode is provided in an anode housing that is mounted to the spacer tube, the housing radius is at most 1,35 times the spacer tube radius. Thus, a cathodic protection device has a linear configuration to enable a flexible object to slide along the spacer tube, from the spacer tube onto, over and off the anode or anode housing, without getting stuck.

Description

Title: Cathodic protection device for use in an Impressed Current Cathodic Protection system

The invention relates to a cathodic protection device for use in an Impressed Current Cathodic Protection (ICCP) system for providing an offshore structure with cathodic protection, preferably for providing a wind turbine foundation, for example a wind turbine foundation pile, with cathodic protection.

It is known to provide offshore structures with ICCP systems to provide the construction with cathodic protection, and to thus prevent, or at least slow down, corrosion of the construction.

For example, offshore wind turbines are supported by steel structures in the form of foundation piles and jacket like structures. To protect these structures against corrosion they are provided with an ICCP system. The great benefit of ICCP systems over the more traditional protection systems that utilise sacrificial anodes is that with the ICCP systems the anodes can be used for a relatively long period.

An ICCP system typically comprises a control device, a power source, one or more anodes and one or more reference cells. The power source is connected to the structure to be protected and to the anodes to create a potential difference. The one or more reference cells monitor potential difference created by the ICCP system, and the control system controls the power source based on the information provided by the one or more reference cells.

Materials used for the anode are for example high silicon cast iron, graphite, mixed metal oxide (MMO), platinum and niobium coated wire.

Anodes for ICCP systems are available in a variety of shapes and sizes. Common anodes are disk shaped or rod shaped, and are mounted on a spacer frame or tube to set the anode at a distance from the surface to be protected. The disk shaped anodes are supported by a spacer tube such that the anode surface faces away from the structure, and away from the spacer frame or tube. When seen from the side, a disk shaped anode has a T-shaped configuration. Rod shaped anodes are typically provided in with two or more anodes supported by a single spacer frame or tube. The tube or spacer frame bifurcates into multiple branches, each supporting an anode. Such a cathodic protection device for example also has a T-shape, or may have a Y-shape. Publication EP3635179 discloses two tubular anodes that are supported by a spacer frame that is welded to the foundation pile. The anodes are set up parallel to each other and parallel to the longitudinal axis of a wind turbine foundation pile. Publication EP3064648 discloses rod like anodes that are set up at the end of a mooring structure. Again, the two anodes are provided that are set up parallel to each other. In both EP3635179 and EP3064648 the anodes extend in a direction perpendicular to the support frame, providing the cathodic protection device with a T-shape configuration. Publication CN203639561 discloses an ICCP system with disc shaped anodes. The discs shaped anodes are supported at the end of a spacer tube, providing the cathodic protection device with a T-shaped configuration.

It is submitted that the configuration of prior art anodes makes them prone to catching free floating objects such as ropes, nets and plastic sheets. These objects may get hooked behind the anodes and the spacer structures that support the anodes. These objects may hamper the functioning of the cathodic protection device. Furthermore, once an object is hooked behind the cathodic protection device, it increases the flow resistance of the cathodic protection device. This is in particular detrimental when the cathodic protection device is mounted near the splash zone, the movement of the waves, in addition to the flow of the water, further increase the load on the hooked object and thus on the anodes and the spacer frames they are mounted on. The increased load may cause damage to the anodes and/or to the spacer frame, for example may cause the spacer frame to bend or fracture.

It is an object of the invention to provide an improved cathodic protection device for use in an Impressed Current Cathodic Protection (ICCP) system for providing an offshore structure with cathodic protection, preferably for providing a wind turbine foundation, for example a wind turbine foundation pile, with cathodic protection. The invention furthermore aims to provide a cathodic protection device that enables a more effective ICCP system, more in particular a system that is less susceptible to interference caused by foreign objects. The invention furthermore aims to provide a cathodic protection device that allows for a more efficient manufacturing process.

The invention therefore provides a cathodic protection device for use in an Impressed Current Cathodic Protection system (ICCP system) for providing an offshore structure, for example a wind turbine foundation pile, with cathodic protection, according to claim 1. It has been found that objects that get stuck on the anode and/or the spacer frame supporting the anode, may hamper the functioning of the anode. In particular, the objects may interfere with the field generated by the anode, and thus reduce the protection provided by the anode, therefore a cathodic protection device according to the invention allows for a more effective ICCP system.

The invention provides a more efficient design of the cathodic protection device, in particular of the way the spacer tube and the anode are set up relative to each other. By providing a tubular anode that extends parallel to a linear spacer tube in combination with the anode radius being equal to, or smaller than, 1 ,35 times the spacer tube radius, floating products have a reduced grip on the anode and spacer tube. Thus, the chance of foreign objects getting stuck to the cathodic protection device, interfering with the field generated by the anode, is reduced.

Furthermore, by thus combining a tubular anode with a spacer tube, the design of the spacer tube can be more efficient, i.e. the design needs to be less robust. A lighter spacer tube can be used, potentially for less costs than prior art spacer frames. The invention therefore also enables the efficient use of synthetic material to form spacer tubes.

It is submitted that the anode of a cathodic protection device according to the invention faces in a direction substantially parallel to the surface to be protected. In the prior art, at least part of the anode faces away from the surface to be protected. It has been found that a cathodic protection device according to claim 1 is able to provide an adequate filed of protection.

A cathodic protection device according to claim 1 comprises:

- a spacer tube, the spacer tube having an outward facing spacer tube surface that extends along a linear spacer tube axis between a foot end and a head end of the spacer tube, the spacer tube having a spacer tube radius that extends between the spacer tube axis and the spacer tube surface;

- a flange, the flange having a mounting surface for mounting the cathodic protection device against a mounting surface of a mount of the offshore structure, wherein the flange is connected with the spacer tube at the foot end thereof, - a tubular anode, the tubular anode having an outward facing anode surface that extends along a linear anode axis between a foot end and a head end of the tubular anode, the tubular anode having an anode radius that extends between the anode axis and the anode surface; wherein the tubular anode is mounted to the spacer tube at the head end thereof, with the tubular anode axis coinciding with the spacer tube axis of the spacer tube, and wherein the anode radius is at most 1 ,35 times the spacer tube radius, such that a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode.

A cathodic protection device according to the invention is in particular useful for the protection of foundation piles and transition pieces that are used for supporting offshore wind turbines. These types of foundations typically have a cylindrical configuration. Prior art anodes mounted on such a construction typically are supported by spacer frames, to set the anode at a distance from the object. Objects can easily get stuck on the protruding spacer frames and anodes, that protrude outwards from the construction. However, a cathodic protection device according to the invention is configured to provide minimal grip for foreign objects, and to thus prevent objects from getting stuck behind the cathodic protection device.

According to the invention, the cathodic protection device comprises a spacer tube that sets the tubular anode at a distance from the object to be protected, wherein the tubular anode is mounted to the spacer tube with a anode axis parallel to a spacer tube axis of the spacer tube. Thus, the tubular anode extends in the longitudinal direction of the spacer tube. Because the anode radius is at most 1,35 times the spacer tube radius, the anode does not significantly extend beyond the radius of the spacer tube. Therefore, a cathodic protection device, more in particular the combined spacer tube and anode, according to the invention is substantially rod shaped. Thus, objects that hook around the spacer tube can slide along the spacer tube and off the end of the cathodic protection device, without getting stuck behind branches of the spacer tube, the anode, or the anode housing.

In an embodiment, the anode surface is recessed relative to the outer surface of the spacer tube, i.e. the anode radius is smaller than the spacer tube radius, and one or more guide rails are provided that extend parallel to the anode axis along the anode, wherein the one or more guide rails preferably extend parallel to the spacer tube axis, and wherein each of the guide rails has an outward facing guide surface that is similar to the outer circumference of the spacer tube at the head end thereof. In such an embodiment, an object is facilitated to slide from the spacer tube onto the guide rails and thus along the anode.

In an embodiment of a cathodic protection device according to the invention, the tubular anode is received in an anode housing, the anode housing comprising an anode cover, e.g. a mesh or one or more guide rails, which anode cover has an outward facing guide surface that extends parallel to the anode surface, for guiding an object over the anode surface, the anode housing having a housing radius that extends between the anode axis and the guide surface, and wherein the housing radius is at most 1 ,35 times the spacer tube radius.

In a further embodiment, the anode housing further comprises a base at a foot end of the housing, and a top at a head end of the housing, wherein the cover extends between the base and the top, wherein the anode housing is mounted with the base over the head end of the spacer tube, and wherein the base of the anode housing and the top of the anode housing each have an outward facing surface, and wherein the outward facing surfaces of the base and the top are flush with the guide surface of the cover. Thus, the anode housing has a protrusion free outer surface, and the a flexible object can slide onto and off the anode housing without getting stuck.

In a further embodiment, the base of the housing is conically shaped, providing a ramp between the spacer tube surface and the guide surface of the cover, to facilitate objects sliding along the spacer tube to slide onto, and over, the tubular anode.

In an embodiment, the anode is received in an anode housing and the anode housing comprises one or more guide rails that extend parallel to the anode axis along the anode. The one or more guide rails preferably extend parallel to the anode axis, wherein each of the guide rails has an outward facing guide surface that is similar to the outer circumference of the spacer tube at the head end thereof. Thus, the guide surface of the one or more guide rails have a radius that is similar to the spacer tube radius, and the guide surfaces of the one or more guide rails form a continuation of the surface of the spacer tube. Thus, an object can easily slide from the spacer tube onto the guide rails and off the cathodic protection device.

In an embodiment, the spacer tube has a protrusion free outer surface, seen in a direction from the foot end to the head end. The spacer tube has a continuous cross section along its longitudinal axis. In combination with the tubular anode being set up coaxial with the spacer tube, this further prevents objects from getting stuck on the cathodic protection device. In an embodiment, the tubular anode is mounted over the spacer tube near the head end thereof such that the anode surface is flush with, or is recessed relative to the outward facing spacer tube surface of the spacer tube, or is provided in an anode housing that is mounted to the spacer tube at the head end thereof, wherein the housing has an outer surface that is flush with the outer surface of the spacer tube, such that a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode or anode housing, without getting hooked behind a protrusion extending from the spacer tube, the anode or the anode housing. In such an embodiment, the anode radius preferably is at most the same, i.e. is at most 1 times the spacer tube radius, or, when the anode is received in an anode housing, the housing radius is at most the same, i.e. is at most 1 time, the spacer tube radius

In an embodiment, the length of the spacer tube is in the range of 120 - 160 cm, and the length of the tubular anode is in the range of 40 - 60cm. In an embodiment, the length of the spacer tube is at least 2,5 times the length of the tubular anode housing. For example is 3 about times the length of the tubular anode housing

In an embodiment, the spacer tube radius is in the range of 17 - 20 cm and the anode radius or the housing radius is in the range of 22 - 27 cm, It is submitted that, when the tubular anode is received in an anode housing, the anode radius is smaller than the housing radius. In an embodiment, the anode radius is smaller than the spacer tube radius and the housing radius is at most the spacer tube radius.

It is submitted that if the spacer tube is provided with a coating, the coating having an outward facing surface, the outward facing surface of the coating is herein understood to also be the outward facing spacer tube surface.

In a preferred embodiment, the spacer tube has, when mounted to the construction to be protected, an upward facing surface that slopes downward to the sides, i.e. when seen in a plane perpendicular to the longitudinal axis of the spacer tube. Thus, gravity may make an object that lands on the top surface, slide off the spacer tube. In an embodiment, the cross section is rectangular or triangular shaped, with one point of the respective rectangle or triangle forming the pinnacle of the cross section.

In a preferred embodiment, the spacer tube has a circular cross section. Thus, objects that are pushed for example in a horizontal direction to the side of the spacer tube by a sea current, will easily slide off the spacer tube as well. In an embodiment, the spacer tube axis of the spacer tube is provided at the center of a cross sections of the spacer tube. Thus, the cross sections are aligned relative to each other on the spacer tube axis.

The flange of the cathodic protection device according to the invention has a mounting surface for mounting the cathodic protection device against a mounting surface of a mount of the offshore structure. Thus, the cathodic protection device is secured with the mounting surface of the flange against the mounting surface of a mount on the offshore structure. Typically, the structure to be protected, e.g. a transition piece or foundation pile supporting wind turbines, is provided with mounts comprising a flange having a mounting surface similar to the mounting surface of the flange of the cathodic protection device. In such an embodiment, the cathodic protection device is, with its flange, bolted to the flange of the mount on the structure to be protected.

The flange of the cathodic protection device is connected with the spacer tube at the foot end thereof. The flange thus projects outward relative to the spacer tube. Preferably, the flange is provided with a smooth, for example a chamfered, transition between the spacer tube and the flange.

In an embodiment, the cathodic protection device comprises a tubular anode having a continuous or semi continuous anode surface that extends parallel to an anode axis and over 360 degrees about the anode axis.

In an embodiment, the shape of the cross section of the tubular anode is the same as the shape of the cross section of the spacer tube, e.g. for example both have an octagonal cross section. In a preferred embodiment, the spacer tube and the anode both have a circular cross section.

The tubular anode has an anode axis and an anode surface. The anode surface is cylindrically arranged about the anode axis, such that the anode surface is parallel to, and faces away from, the central anode axis. The tubular anode is mounted to the spacer tube at the head end thereof, with the central tubular anode axis parallel and preferably aligned with the spacer tube axis of the spacer tube.

In an embodiment of a cathodic protection device according to the invention, the cross section of the anode is similar to, or is located within the cross section of the spacer tube at the head end thereof, and has the anode axis aligned with the spacer tube axis. Thus, a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the anode.

In an embodiment, the anode extends between a foot end and a head end, and the cross section of the anode at the foot end is identical to the cross section of the spacer tube at the head end thereof. In such an embodiment, the tubular anode forms a continuation of the spacer tube, more in particular, the spacer tube and the tubular anode have a continuous cross section, seen along the spacer tube axis in the direction from the foot end to the head end, and the surface of the tubular anode forms a continuation of the outer surface of the spacer tube, i.e. there is no significant recess, set back or protrusion at the transition from the outer surface of the spacer tube and the outer surface of the tubular anode. The continuous cross section, and therefore the continuous, smooth outer surface, makes it more difficult for objects to get a grip and get stuck on the spacer tube.

In an embodiment, the anode housing is mounted onto the spacer tube such that the head end of the spacer tube is received inside the foot end of the anode housing. In such an embodiment, the foot end of the anode housing preferably is provided with a gradual increase in its cross section. Thus the anode housing provides a ramp, i.e. a gradual transition, between the spacer tube surface at the spacer tube radius, and the guide surface of the anode cover at the housing radius. This furthermore promotes products sliding along the length of the spacer tube to slide onto, over and of the anode housing.

In an embodiment, the spacer tube axis of the spacer tube is provided at the center of a cross sections of the spacer tube. Thus, the cross sections are aligned relative to each other on the spacer tube axis.

In an embodiment, the tubular anode extends in a longitudinal direction between a foot end and a head end, the tubular anode having a continuous cross section, seen in a direction from the foot end to the head end.

In an embodiment, the anode surface is recessed relative to the outer surface of the spacer tube, and a mesh is provided that extends parallel to the anode axis along the anode surface, wherein the mesh has an outward facing guide surface that is flush with the surface of the spacer tube, such that the spacer tube and the mesh form a continuous, protrusion free guide surface to enable a flexible object to slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto the mesh, and thus over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the mesh.

Thus, in such an embodiment, the guide mesh has an outer circumference that is similar to an outer circumference of the spacer tube at the head end thereof, and the outer surface of the mesh forms a continuation of the outer surface of the spacer tube. Furthermore, the spacer tube, guide mesh and anode extend along a single linear axis.

In another embodiment, the anode surface is recessed relative to the outer surface of the spacer tube, and one or more guide rails are provided that extend parallel to the anode axis along the anode surface, wherein each of the one or more guide rails has an outward facing guide surface that is flush with the surface of the spacer tube, such that the spacer tube and the guide surface of the one or more guide rails form a continuous, protrusion free guide surface to enable a flexible object to slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto the guide rails, and thus over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the guide rail. Thus, in such an embodiment, the one or more guide rails have an outer circumference that is similar to an outer circumference of the spacer tube at the head end thereof, and the guide surface of the one or more rails forms a continuation of the outer surface of the spacer tube. Furthermore, the spacer tube, guide rails and anode extend along a single linar axis. Thus, in such an embodiment, the guide surface of the one or more guide rails is aligned with an outer circumference, i.e. the outer surface, of the spacer tube at the head end thereof, and the guide surface of the one or more guide rails forms a continuation of the outer surface of the spacer tube.

In some embodiments, the mesh or the one or more guide rails extend along the anode, while the anode surface lies recessed relative to the outer surface of the mesh or the outer surface of the one or more guide rails. Thus, the mesh or guide rails form a guide surface for an object that slides over the tubular anode, and thus protect the anode surface, e.g. from getting scratched. In these embodiments, the radius between the guide surface of the guide rails or the guide surface of the mesh and the anode axis, is the housing radius. Thus, the guide surface of the guide rails or the mesh is at most 1 ,35 times the spacer tube radius.

In an embodiment, the one or more guide rails extend parallel to the spacer tube axis. In such an embodiment, the edges of the guide rails extend parallel to the longitudinal axis of the spacer tube and the anode axis, and thus further reduce the chance of an object sliding in the longitudinal direction of the cathodic protection device form getting stuck. When the cathodic protection device is mounted on the offshore structure, the cross section of the spacer tube has an upper most point at the head end that is at a twelve o clock position and has a lower most point of the cross section of the spacer tube that is at a six o clock position. When the cathodic protection device is provided with one or more guide rails along the tubular anode, preferably one of the one or more guide rails is located at the twelve o clock position. Thus, an object sliding along the cathodic protection device slides form the surface of the spacer tube onto the guide surface of the guide rail, and via the guide rail off the cathodic protection device.

As an alternative, or in addition, a guide rail can be provided at the ten o cloak position and a guide rail is provided at the two o clock position.

In an embodiment, the guide rails have a width such that the guide surface of the guide rails extends along at least three percent of the circumference of the spacer tube, for example extends over at least a eleven degree angle.

In case there is one guide rail provided, the rail preferably is provided at the 12 o clock position, when the cathodic protection device is mounted to the offshore structure, and preferably has a relatively wide guide surface. In an embodiment, the single rail has a width such that the guide surface of the guide rail extends along at least 10% of the circumference, i.e. the guide surface of the guide rail extends over at least an 36 degree angle. Providing the guide rails with a wide guide surface enhances the protection of the anode surface. When multiple guide rails are provided, the guide rails may have a guide surface that is relatively narrow, and still prevent an object from scratching the anode surface.

In a further embodiment, the one or more guide rails are part of an anode housing, the anode housing further comprising a base at a foot end, and a top at a head end of the housing, wherein the guide rails extend between the base and the top, wherein the anode housing is mounted with the base to the spacer tube at the head end thereof, and wherein the base of the anode housing has a cross section that preferably is similar to the cross section of the spacer tube at the head end thereof, such that an outer surface of the housing forms a continuation of the outer surface of the spacer tube.

Thus, the node housing protects the anode surface, and a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode housing, without getting hooked behind protrusion extending from the spacer tube or the anode housing. In a further embodiment, the anode housing and the spacer tube are modular components, that are combined to form a cathodic protection device. Such an embodiment, allows for providing spacer tubes of different lengths, and for example anode housings with one and anode housings with two or more tubular anodes, and combining these into a cathodic protection device that is configured for a particular object to be protected. For example, an ICCP system for a particular object might require the use of long spacer tubes while an ICCP system for another object requires short spacer tubes. Thus, during the production process modular anode housings can be combined with a short spacer tube or a long spacer tube to fit the first or the latter ICCP system respectively.

In an embodiment, the anode housing comprises a tubular anode support, and the anode material is a single sheet, which sheet is glued onto the anode support. This configuration allows for an efficient production of tubular anodes. In a further embodiment, the anode support is configured to be attached to a base part and a top part to form an anode housing. As an alternative, the base and/or the top may be an integral part of the anode support.

In an alternative embodiment, the tubular anode comprises a first anode element, and the first anode element is semi cylindrical, e.g. extends over an arc of at least 90 degrees, preferably over an arc of about 180 degrees. In a further preferred embodiment, when the cathodic protection device is mounted on the offshore structure, the first anode element faces downwards, i.e. is provided at a side of the cathodic protection device that faces a sea floor.

Thus, the tubular anode is a modular tubular anode, the anode comprising one or more modular anode elements. During the manufacturing process, the size of the anode can be decided on by mounting one or more of the modular anode elements. For example, in an embodiment the tubular anode may comprise one, two or three anode elements that each extend over an arc of 120 degrees.

In a further embodiment, the tubular anode comprises a first anode element and a second anode element, and the second anode element is also semi cylindrical, and the first anode element and the second anode element each extends over an arc of about 180 degrees, wherein, when the cathodic protection device is mounted on the offshore structure, the second anode element faces upwards, i.e. is provided at a side of the cathodic protection device that faces away from the sea floor.

In an embodiment, the tubular anode comprises multiple anode elements. In such an embodiment, one of the anode elements can be redundant, and is only to be used when the other anode element breaks, or anode elements break, down. In an embodiment, the second anode element is used when the first anode element does not provide a sufficiently strong field. In an alternative embodiment, both, or all, anode elements are active during use of the cathodic protection device.

In a further embodiment, the tubular anode comprises two or more anode elements, which anode elements are separately powered, such that if one anode element, or the power provision of one of the anode elements, fails, at least one other anode element is still powered. Thus, the anode still produces a field, also when part of the anode is no longer active.

In an embodiment, the tubular anode is a first tubular anode and the cathodic protection device is provided with a second tubular anode, similar to the first tubular anode, and the second tubular anode is mounted coaxial with the first anode on the spacer tube, or the first and the second anode are mounted coaxial in a single anode housing according to the invention, such that the anode axis of the second anode coincides with the anode axis of the first anode.

In an embodiment, the second tubular anode is redundant, and is only to be used when the first tubular anode breaks down, or the second tubular anode is used when the first tubular anode does not provide a sufficiently strong field. In an alternative embodiment, both anodes are active during use of the cathodic protection device.

In a further embodiment, the tubular anode comprises two or more anode elements of anode material, which anode lements are separately powered, such that if one anode element, or the power provision of one of the anode elements, at least one other anode elements is still powered. Thus, the anode still produces a field, also when part of the anode is no longer active.

In an embodiment, the spacer tube and at least part of the anode housing are a single piece, and the anode is mounted on a part of the anode housing that is an integral component with the spacer tube

In a preferred embodiment, the spacer tube is hollow, and a cable for connecting the anode with a power source and/or a control unit, is guided via the hollow spacer tube from the housing to the flange. For example the flange can be provided with a recess in the guide surface thereof, for guiding the cable from the inside of the spacer tube to the outside of the spacer tube. In an embodiment, the spacer tube is made out of metal, e.g. steel, and is provided with a coating that shields the spacer tube from the field generated by the anode. In such an embodiment, the coating has an outward facing surface, which is herein to be understood as the outward facing spacer tube surface.

In an embodiment, the spacer tube is made of a synthetic material, preferably a fibre reinforced synthetic material. Thus, the spacer tube is not conductive, and does not have to be provided with a coating. Furthermore, the spacer tube can thus be made of a relative light material, and the cathodic protection device can be kept light. In a further embodiment, the cathodic protection device comprises an anode housing that is at least partially made of a synthetic material.

In a further embodiment, the flange is a sperate component that is attached to the spacer tube during the manufacturing process. In a further embodiment, the flange is made of steel, and the spacer tube is made of a synthetic material.

In an embodiment, the flange is connected with the spacer tube with the mounting surface of the flange extending perpendicular to the longitudinal spacer tube axis of the spacer tube.

In a preferred embodiment, the flange is connected with the spacer tube with the mounting surface of the flange extending at an angle, i.e. an angle in the range of 1-8 degrees, to the spacer tube axis of the spacer tube, to enable the cathodic protection device to be mounted to the offshore structure at an angle to the horizontal. This configuration allows for the cathodic protection device to be mounted to a structure with the spacer tube axis pointing downwards, which promotes sliding of objects away from the flange and off the cathodic protection device. It is submitted that typically, offshore structures are provided with dedicated mounts for attaching an cathodic protection device, the dedicated mounts having a mounting surface that is substantially vertical.

It is noted that the mounts on the structure to be protected can be set at a slight angle to the vertical to obtain the same effect in combination with a cathodic protection device having it’s mounting surface at a right angle to the spacer tube axis. However, in such an configuration, the mount at the construction would protrude more relative to the surface of the structure, and therefore create a feature behind which foreign objects might get stuck. Thus, by setting the spacer tube at an angle to the mounting surface of the flange of the cathodic protection device, the mounting surface and therefore the flange of the mount of the structure to be protected can remain parallel, and thus close to, the surface of the structure to be protected. In an embodiment, the flange is an annular disc, preferably made out of steel, the annular disc having an inward facing annular surface that is fixed to the outer surface of the spacer tube at the foot end thereof. Thus a simple configuration of the flange is provided. In a further embodiment, the annular disc is along the opening provided with a wall feature, to enlarge the annular surface that is attached to the spacer tube. In yet a further embodiment, this wall, or at least the inner surface thereof, is configured such that the enclosed space, i.e. the space that receives the spacer tube, is at an angle to the mounting surface of the flange. Thus, the configuration provides a spacer tube that is set at an angle to the mounting surface of the flange.

It is submitted that the flange can be provided with a central inner space for receiving the spacer tube. In such an embodiment the outside surface of the spacer tube is mounted to the inward facing surface of the flange. As an alternative, a wall feature along the inner opening of the annular disc is configured to be inserted into the spacer tube. In such an embodiment, the outward facing wall surface is attached to the inward facing surface of a hollow spacer tube.

In an embodiment, the cathodic protection device further comprises a reference cell and a reference cell support bracket, and the reference support bracket is configured to be mounted to the flange, preferably is configured to be mounted between the flange and the dedicated mount of the offshore structure. By providing the reference cell on a bracket to be mounted against the mounting surface, instead of on the spacer tube, the reference cell can be mounted close to the anode, while the spacer tube can be kept free of protrusions.

In an embodiment, the cathodic protection device is provided with a reference cell that is mounted on the spacer tube. In such an embodiment, the reference cell preferably is provided close to the flange of the cathodic protection device, such that most of the spacer tube, i.e. the section of the spacer tube between the reference cell and the tubular anode, is free from protrusions. Thus, a flexible foreign object that comes into contact with the spacer tube, may still slide along most of the spacer tube, and onto and over the tubular anode, without contact the reference cell, and thus without the risk of getting stuck behind the reference cell.

In an embodiment, the reference cell is provided at the bottom side of the cathodic protection device, i.e. at the side that in use faces towards the sea floor, such that objects can not easily hook behind it. Furthermore, in this position, the reference cell or the support bracket thereof, can not prevent objects from sliding along the spacer tube towards the housing of the cathodic protection device. A cathodic protection device according to the invention is configured to reduce the chance of objects getting stuck on the cathodic protection device. Herein, a fflexible object, refers to an object that at least partially follows the shape of the contour of the spacer tube and anode, for example plastic sheets, discarded fishing nets, ropes, etc. It has been found that objects that get stuck on the anode and/or the spacer frame supporting the anode, may hamper the functioning of the anode. In particular the objects may interfere with the field generated by the anode, and thus reduce the protection provided by the anode. Therefore a cathodic protection device according to the invention allows for a more effective ICCP system. Furthermore, once an object is hooked behind the cathodic protection device, it increases the flow resistance of the cathodic protection device. This is in particular detrimental when the cathodic protection device is mounted near the splash zone. The movement of the waves, in addition to the flow of the water, further increase the load on the anodes and the spacer frames they are mounted on. The increased load may cause damage to the anode and/or the spacer frame, for example may cause the spacer frame to bend or fracture. The design of the cathodic protection device according to the invention reduces the grip of foreign objects on the cathodic protection device, and therefore the design of the cathodic protection device can be more efficient, i.e. needs to be less robust. For example, a lighter spacer tube can be used, potentially for less costs than prior art spacer frames. The invention therefore also enables the efficient use of synthetic material to form spacer tubes.

A cathodic protection device is configured to provide an offshore structure with cathodic protection. The offshore structure can be designed as a cylindrical foundation structure or a truss like jacket for supporting a wind turbine. However, the structure can also be designed to support a platform for accommodating electrical installations or as a platform for a crude oil or natural gas production facility or a crude oil or natural gas exploration facility, etc. It is furthermore submitted that the offshore structure may be an earthbound structure or a floating structure, for example a floating wind turbine support structure.

The invention furthermore provides an offshore structure, e.g. a transition piece for supporting a wind turbine, the offshore structure being provided with one or more cathodic protection devices according to the invention.

In a further embodiment, the offshore structure is a cylindrical offshore structure, e.g. a transition piece for supporting a wind turbine.

In yet a further embodiment, the one or more cathodic protection devices are attached with their mounting surfaces to mounts provided on the offshore structure, with the spacer tube axis and the anode axis extending in a direction at an angle relative to the outer surface of the off shore structure and at an angle to the horizontal, such that the cathodic protection device points downwards, to thus promote sliding of objects along the spacer tube and the anode, off the cathodic protection device. Thus, an object that gets hooked on the spacer tube slides downward along the spacer tube and the anode off the cathodic protection device.

The invention provides an Impressed Current Cathodic Protection system comprising a cathodic protection device according to the invention. The invention furthermore provides a transition piece provided with a cathodic protection device according to the invention, preferably with one or more spacer tubes of the cathodic protection device at an angle in the range of 1-8 degrees, to a plane perpendicular to a longitudinal axis of the transition piece.

The invention furthermore provides a cathodic protection device for use in an Impressed Current Cathodic Protection system (ICCP system) for providing an offshore structure, for example a wind turbine foundation pile, with cathodic protection, the cathodic protection device comprising:

- a spacer tube, the spacer tube extending along a spacer tube axis between a foot end and a head end, the spacer tube having a continuous cross section, with the spacer tube axis at the center of the cross section, seen in a direction from the foot end to the head end;

- a flange, the flange having a mounting surface for mounting the cathodic protection device against a mounting surface of a dedicated mount of the offshore structure, wherein the flange is connected with the spacer tube at the foot end thereof, preferably with the mounting surface of the flange extending at a small angle, i.e. an angle in the range of 1-8 degrees, to the spacer tube axis of the spacer tube;

- a tubular anode, the tubular anode having a central tubular anode axis, wherein the tubular anode is mounted over the spacer tube at the head end thereof, and wherein the cross section of the anode is located within the outer circumference of the spacer tube at the head end thereof, such that the outer surface of the anode is recessed relative to the outer surface of the spacer tube, and with the anode axis aligned with the spacer tube axis, such that a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the anode;

- an anode housing, the anode housing comprising:

- a base at a foot end, and a top at a head end of the housing; and

-one or more guide rails; wherein the anode housing is mounted with the base to the spacer tube at the head end thereof, and wherein the one or more guide rails extend parallel to the anode axis between the base and the top of the housing along the anode, wherein the anode surface is recessed relative to the outer circumference of the spacer tube at the head end thereof, and wherein each of the guide rails has an outward facing guide surface that is flush with the base of the housing and with the outer circumference of the spacer tube at the head end thereof, and wherein an outer surface of the housing, i.e. an outer surface of the base, the guide rails and the top of the housing, forms a continuation of the outer surface of the spacer tube.

The invention furthermore provides a cylindrical offshore structure, e.g. a transition piece for supporting a wind turbine or a foundation pile, the offshore structure being provided with one or more cathodic protection devices, the cathodic protection device comprising:

- a tubular anode, the tubular anode having a central tubular anode axis, wherein the tubular anode is mounted to the spacer tube at the head end thereof, and wherein the cross section of the anode is located within the outer circumference of the spacer tube at the head end thereof, with the anode axis aligned with the spacer tube axis,

- multiple guide rails that extend parallel to the anode axis along the anode, wherein the one or more guide rails preferably extend parallel to the spacer tube axis, and wherein each of the guide rails has an outward facing guide surface that is flush with to the outer circumference of the spacer tube at the head end thereof such that a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto one or more guide rails, and thus over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the anode; wherein the one or more cathodic protection devices are attached with their mounting surfaces to mounts provided on the offshore structure, and with the spacer tube axis and the anode axis extend in a direction at an angle relative to the horizontal, such that the cathodic protection device points downwards, to thus promote sliding of objects along the spacer tube and the anode, off the cathodic protection device.

In the above embodiments, the guide rails may be replaced with a mesh, wherein the mesh extends parallel to the spacer tube axis, and wherein each of the mesh has an outward facing guide surface that is flush with to the outer circumference of the spacer tube at the head end thereof such that a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto the mesh, and thus over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the mesh.

The invention furthermore provides a cathodic protection device for use in an Impressed Current Cathodic Protection system for an offshore structure, wherein the device comprises a synthetic spacer tube, a flange, and a tubular anode. In an embodiment of a cathodic protection device according to the invention, the spacer tube has a protrusion free outer surface and the tubular anode is mounted to the spacer tube near the head end thereof such that the anode surface is flush with or is recessed relative to the protrusion free outer surface of the spacer tube, or, as an alternative, the tubular anode is provided in an anode housing that is mounted to the spacer tube, wherein the housing has an outer surface that is flush with the protrusion free outer surface of the spacer tube. In such an embodiment, the outward facing guide surface of the guide rails of the housing are part of the outer surface of the housing. Thus, a flexible object can slide along the spacer tube, from the spacer tube onto, over and off the anode or anode housing, without getting stuck.

According to the invention, a tubular anode is mounted to a spacer tube at a head end thereof with an anode axis of the tubular anode coinciding with a spacer tube axis of the spacer tube, and with an anode radius or a housing radius being at most 1 ,35 times a spacer tube radius. By thus setting up the anode as a continuation of the spacer tube, a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode or the anode housing.

Thus, the invention relates to a cathodic protection device for use in an Impressed Current Cathodic Protection system for an offshore structure. The device comprises a spacer tube, a flange, and a tubular anode. According to the invention, the tubular anode axis coincides with the spacer tube axis of the spacer tube, and the anode radius is at most 1 ,35 times the spacer tube radius. In case the tubular anode is provided in an anode housing that is mounted to the spacer tube, the housing radius is at most 1 ,35 times the spacer tube radius. Thus, a cathodic protection device has a linear configuration to enable a flexible object to slide along the spacer tube, from the spacer tube onto, over and off the anode or anode housing, without getting stuck.

The invention furthermore provides an Impressed Current Cathodic Protection system comprising one or more cathodic protection devices according to the invention. The invention furthermore provides a method for providing an offshore construction with cathodic protection using a cathodic protection device according to the invention. The method may comprise mounting the kathodic protection device onto the offshore construction with the spacer tube axis at an angle to the horizontal.

The invention furthermore provides a method for manufacturing a cathodic protection device, the method comprising:

- providing a spacer tube, the spacer tube having an end wall at a top end;

- guiding one or more wires through the spacer tube and through one or more openings in the end wall of the spacer tube;

- mounting one or more anode elements in an anode housing;

- mounting the anode housing on a head end, such that a connector chamber is created at the top end of the spacer tube;

- connecting the one or more wires with the one or more anode elements;

- filling the connector chamber with a curing resin material to seal the connections between the wires and the anode elements and preferably to fix the anode housing relative to the spacer tube, for example by allowing the curing resin material to flow in a space between an outward facing spacer tube surface and the anode housing, at the end of the spacer tube.

The invention furthermore provides a cathodic protection device provided with the above method, preferably a cathodic protection device according to claim 1 having a connecting chamber that is filled with a curing resin material according to the method.

Advantageous embodiments of the cathodic protection device according to the invention and the method according to the invention are disclosed in the sub claims and in the description, in which the invention is further illustrated and elucidated on the basis of a number of exemplary embodiments, of which some are shown in the schematic drawing. In the figures, components corresponding in terms or construction and/or function are provided with the same last two digits of the reference numbers.

In the figures,

Fig. 1 shows a side view of a first cathodic protection device according to the invention;

Fig. 2 shows a side view in cross section of the cathodic protection device of fig. 1 ;

Fig. 3 shows a perspective view of a second cathodic protection device according to the invention;

Fig. 4 shows a frontal view of the cathodic protection device of Fig. 3; Fig. 5 shows a side view of the cathodic protection device of Fig. 3;

Fig 6 shows a perspective view of a third cathodic protection device according to the invention;

Fig. 7 shows a schematic side view of an offshore structure provided with a cathodic protection device according to the invention; and

Fig. 8 shows an exploded view of an anode housing for the cathodic protection device of fig. 1.

Whilst primarily presented for illustrative purposes with reference to one or more of the figures, any of the technical features addressed below may be combined with any of the independent claims of this application either alone or in any other technically possible combination with one or more other technical features.

Figure 1 shows a side view of a first cathodic protection device 1 for use in an Impressed Current Cathodic Protection system (ICCP system) to provide an offshore structure, for example a wind turbine foundation, with cathodic protection. Figure 2 shows a side view in cross section of the cathodic protection device 1 of figure 1.

The cathodic protection device 1 comprises a spacer tube 2, a flange 3, and a tubular anode 4. In both figure 1 and figure 2 a midsection of the spacer tube is omitted.

The spacer tube 2 has an outward facing spacer tube surface 26 that extends along a spacer tube axis 5 between a foot end 6 and a head end 7 of the spacer tube. The spacer tube 2 has a spacer tube radius 24 that extends between the spacer tube axis 5 and the spacer tube surface 26.

The flange 3 has a mounting surface 9 for mounting the cathodic protection device 1 against a mounting surface of a mount of the offshore structure. The flange 3 is connected with the spacer tube 2 at the foot end 6 thereof.

The tubular anode 4 has an outward facing anode surface 10 that extends along an anode axis 11 between a foot end 31 and a head end 32 of the tubular anode. The tubular anode 4 has an anode radius 34 that extends between the anode axis 11 and the anode surface 10

According to the invention, the tubular anode 4 is mounted to the spacer tube 2 at the head end 7 thereof with the tubular anode axis 11 coinciding with the spacer tube axis 5 of the spacer tube 2 and with the anode radius being at most 1 ,35 times the spacer tube radius. By thus setting up the anode as a continuation of the spacer tube, a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode.

In the embodiment shown in figures 1 and 2, the tubular anode 1 is received in an anode housing 12, The anode housing 12 comprises an anode cover 37, in the embodiment shown a mesh 35. The anode cover 37 has an outward facing guide surface 36, that extends parallel to the anode surface 10, for guiding an object over the anode surface 10. The anode housing 12 has a housing radius 25 that extends between the anode axis 11 and the outward facing guide surface 36 of the mesh 35. According to the invention, the housing radius 25 is less than 1 ,35 times the spacer tube radius 24.

Furthermore, in the exemplary embodiment shown in figures 1 and 2, the anode housing 12 further comprises a base 19 at a foot end 20 of the housing 12, and a top 21 at a head end 22 of the housing 12. The anode cover 37 extends between the base 19 and the top 21 , and the anode housing 12 is mounted with the base 19 over the head end 7 of the spacer tube 2.

The base 19 of the anode housing 12 and the top 21 of the anode housing 12 each have an outward facing surface, which surfaces are flush with the guide surface 36 of the mesh 35.

In the exemplary embodiment shown, the base 19 of the housing is conically shaped, providing a ramp between the spacer tube surface and the guide surface of the cover, to facilitate objects sliding along the spacer tube to slide onto, and over, the tubular anode.

In the exemplary embodiment shown, the tubular anode 4 comprises a first anode element 38 and a second anode element 39. Figure 8 shows an exploded view of the anode housing 12. The anode housing 12 comprises a top part 40 that forms the top 21 of the housing and comprises a base part 41 that forms the base of the anode housing. The base part 41 and the top part 40 are mounted on a cylindrical housing body 42 of the anode housing. A cylindrical mesh 35 is to be mounted between the base part 41 and the top part 40 of the anode housing 12.

In the exemplary embodiment shown, the first anode element 38 and the second anode element 39 are both semi cylindrical. They each extend over an arc of 180 degrees. When the cathodic protection device 1 is mounted on the offshore structure, the first anode element 38 faces downwards, i.e. is provided at a side of the cathodic protection device that faces a sea floor. Thus, in the exemplary embodiment shown, the tubular anode 4 comprises multiple anode elements. In the particular embodiment, the first anode element 38 and the second anode element 39 are each connected to a wire at the inside of the anode housing. A connector 43 protrudes through an opening in the anode housing, into a connector chamber 44. In the connector chamber 44, shown in cross section in figure 2, the connectors are connected with wires 45 coming from the spacer tube. The wires pass through a wall into an inner space of the spacer tube.

Thus, in the exemplary embodiment shown, the anode housing 12 is mounted on the spacer tube 2 such that the connector chamber 44 is formed. The anode housing 12, more in particular the cylindrical housing body 42 of the anode housing 12, comprises the head end 7 of the spacer tube 2 at the foot end 20 of the anode housing, and comprises the connector chamber 44 at the head end 22 of the anode housing. During the manufacturing of the cathodic protection device 1 , after the anode housing 12 is mounted on the spacer tube 2 and after the wires are connected with the connectors 43, the connector chamber is filled with a curing resin material that seals the connector room and thus the connections. For example a thermoset material can be used to fill the connector chamber.

In the embodiment shown, the connector elements 38, 39 are each connected with a dedicated wire. Thus, if one anode element, or the power provision of one of the anode elements, fails, at least one other anode element is still powered. Thus, the anode still produces a field, also when part of the anode is no longer active.

The cathodic protection device 1 , can be manufacture using a method according to the invention, wherein the method comprises:

- providing the spacer tube 2, the spacer tube having an end wall 46 at a head end 22;

- guiding wires 45 through the spacer tube 2 and through the opening 47 in the end wall 46 of the spacer tube 2 and sealing the wires in the opening;

- mounting the first and second anode elements 38, 39 in the anode housing 12;

- mounting the anode housing 12 on the head end 22 of the spacer tube 2, such that the connector chamber 44 is created at the head end 22 of the spacer tube 2;

- connecting the wires 45 with the anode elements 38,39;

- filling the connector chamber 44 with a curing resin material to seal the connections between the wires 45 and the anode elements 38,39 and to fix the anode housing 12 relative to the spacer tube 2 by allowing the curing resin material to flow into a space between the outward facing spacer tube surface 26 and the anode housing 12, at the head end 22 of the spacer tube 2. Figures 3 shows a perspective view of a second cathodic protection device 1 according to the invention for use in an Impressed Current Cathodic Protection system (ICCP system) for providing an offshore structure, for example a wind turbine foundation pile, with cathodic protection.

The cathodic protection device 1 comprises a synthetic spacer tube 2, a flange 3, and a tubular anode 4.

The synthetic spacer tube 2 extends along a spacer tube axis 5, depicted in the side view shown in Figures 5, between a foot end 6 and a head end 7. in the embodiment shown, the spacer tube has a protrusion free outer surface 8, seen in a direction from the foot end 6 to the head end 7.

The flange 3 has a mounting surface 9 for mounting the cathodic protection device 1 against a mounting surface of a mount of the offshore structure. The flange 3 is connected with the spacer tube 2 at the foot end 6 thereof,

The tubular anode 4 has an outward facing anode surface 10 that is parallel to a central tubular anode axis 11 , depicted in Figure 5.

In the embodiment shown, the tubular anode 4 is provided in an anode housing 12 that is mounted to the spacer tube 2 at the head end 7 thereof. The housing 12 has an outer surface 13 that is flush with the protrusion free outer surface 8 of the spacer tube 2, such that a flexible object can slide along the spacer tube 2 , from the foot end 6 to the head end 7, and from the spacer tube 2 onto, over and off the anode housing 12, without getting hooked behind a protrusion extending from the spacer tube 2, the anode 4, or the anode housing 12.

It is submitted that In an alternative embodiment, the tubular anode is mounted over the spacer tube near the head end thereof, such that the anode surface is flush with, or is recessed relative to the protrusion free outer surface of the spacer tube. Preferably, the anode surface is recessed relative to the protrusion free outer surface of the spacer tube, and a guide mesh or guide rails are provided to guide a sliding object over the outer surface of the anode.

Figure 7 shows a cathodic protection device 1 according to the invention mounted on a transition piece 14. The transition piece 14 is mounted on a foundation pile 15 and supports an offshore wind turbine 16. It is submitted that foundation piles, and therefore transition pieces, typically have a cylindrical configuration.

The flange 3 of the cathodic protection device 1 is connected with the spacer tube 2 at the foot end 6 thereof. The flange thus projects outward relative to the spacer tube. In the embodiment shown, the flange is provided with a chamfered transition between the protrusion free surface of the spacer tube and the flange

The transition piece 14 is provided with mounts 17 comprising a flange having a mounting surface similar to the mounting surface of the flange 3 of the cathodic protection device 1. The cathodic protection device 1 is, with its flange 3, bolted to the flange of the mount on the transition piece 14.

The cathodic protection device 1 has a protrusion free outer surface 8 of the spacer tube 2 and of the anode 4, when seen in a direction from the flange 3 towards the head 7 of the spacer tube 2, and is thus configured to provide minimal grip for objects, and to thus prevent objects from getting stuck behind the cathodic protection device.

The spacer tube 2 sets the tubular anode 4 at a distance from the object to be protected. The spacer tube 2 has a protrusion free outer surface 8, and has a continuous cross section along its longitudinal axis. The continuous outer surface, i.e. without protrusions, in combination with the tubular anode being set up coaxial with the spacer tube and the tubular housing having an outer surface that is flush with the outer surface of the spacer tube, prevents objects from getting stuck on the cathodic protection device.

In the preferred embodiment shown, the spacer tube has a circular cross section, and thus has, when mounted to the construction to be protected, has an upward facing surface that slopes downward to the sides, i.e. when seen in a plane perpendicular to the longitudinal axis of the spacer tube. Thus, gravity may make an object that lands on the top surface, slide off the spacer tube. Furthermore, the circular cross section also enables that objects that are pushed in a horizontal direction to the side of the spacer tube by a sea current, will slide off the spacer tube as well.

The cathodic protection device 1 comprises a tubular anode 4, i.e. an anode having a continuous or semi continuous anode surface 10 that extends parallel to an anode axis 11 and over 360 degrees about the anode axis. In the embodiment shown, the spacer tube and the anode both have a circular cross section. The anode surface 10 is cylindrically arranged about the anode axis such that the anode surface is parallel to, and faces away from, the central anode axis 11. The tubular anode is mounted to the spacer tube at the head end thereof, with the central tubular anode axis 11 parallel and aligned with the spacer tube axis of the spacer tube.

In an embodiment, the cross section of the anode is similar to, or is located within the cross section of the spacer tube at the head end thereof, and has the anode axis aligned with the spacer tube axis. Thus, a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the anode.

In the embodiment shown, the cross section of the anode is located within the cross section of the spacer tube at the head end thereof. The anode surface is thus recessed relative to the outer surface of the spacer tube.

Furthermore, in the embodiment shown, guide rails 17 are provided that extend parallel to the anode axis 11 along the anode surface 10. The guide rails 17 are part of the anode housing 12. The anode housing further comprises a base 19 at a foot end 20, and a top 21 at a head end 22 of the housing.

The guide rails 17 extend between the base 19 and the top 21. The anode housing 10 is mounted with the base 19 to the spacer tube 2 at the head end 6 thereof, and the base of the anode housing has a cross section that is similar to the cross section of the spacer tube at the head end thereof, such that an outer surface of the housing forms a continuation of the outer surface of the spacer tube.

Thus, the anode housing protects the anode surface, and a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode housing, without getting hooked behind protrusion extending form the spacer tube or the anode housing.

Each of the guide rails 17 has an outward facing guide surface 18 that is flush with the surface 8 of the spacer tube 2, such that the spacer tube and the guide surface of the guide rails form a continuous, protrusion free guide surface that enables a flexible object to slide along the spacer tube from the foot end 6 to the head end 7, and from the spacer tube 2 onto the guide rails 17, and thus over and off the anode 4, without getting hooked behind a protrusion extending from the spacer tube or the guide rail. Thus, in such an embodiment, the one or more guide rails have an outer circumference that is similar to an outer circumference of the spacer tube at the head end thereof, and the guide surface of the one or more rails forms a continuation of the outer surface of the spacer tube.

Furthermore, the spacer tube, guide rails and anode preferably extend along a single axis. Thus, in such an embodiment, the guide surface of the one or more guide rails is aligned with an outer circumference, i.e. the outer surface, of the spacer tube at the head end thereof, and the guide surface of the one or more guide rails forms a continuation of the outer surface of the spacer tube.

In an alternative embodiment, the anode extends between a foot end and a head end, and the cross section of the anode at the foot end is identical to the cross section of the spacer tube at the head end thereof. In such an embodiment, the tubular anode forms a continuation of the spacer tube, more in particular, the outer surface of the tubular anode forms a continuation of the outer surface of the spacer tube, i.e. there is no significant recess, set back or protrusion at the transition from the outer surface of the spacer tube and the outer surface of the tubular anode.

In another alternative embodiment, the anode surface is recessed relative to the outer surface of the spacer tube, and a mesh is provided that extends parallel to the anode axis along the anode surface, wherein the mesh has an outward facing guide surface that is flush with the surface of the spacer tube, such that the spacer tube and the mesh form a continuous, protrusion free guide surface to enable a flexible object to slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto the mesh, and thus over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the mesh.

In the embodiment shown, the guide rails 17 extend parallel to the spacer tube axis 5 in such an embodiment, the edges of the guide rails extend parallel to the longitudinal axis of the spacer tube and the anode axis, and thus further reduce the chance of an object sliding in the longitudinal direction of the cathodic protection device form getting stuck. Figure 7 shows a schematic side view of an offshore structure 23 provided with a cathodic protection device 1. The offshore structure 23 comprises a foundation pile 15, a transition piece 14 that is mounted on the foundation pile 14, and a wind turbine 16 having a mast 27 that is mounted on the transition piece 14.

In the embodiment shown, the cathodic protection device 1 is mounted on the transition piece 14.

At the head end of the spacer tube 2, an upper most point 28 of the cross section of the spacer tube 2 is at a twelve o clock position, i.e. faces upward. The lower most point 18 of the cross section is at a six o clock position. In the embodiment shown, a guide rail 17a is located at the twelve o clock position.

The surface of the guide rail 17a forms an extension of the surface of the spacer tube 2. The surface of the guide rail and the surface of the spacer tube thus form a protrusion free surface such that an object sliding along the cathodic protection device 1 can slide from the surface of the spacer tube onto the guide surface of the guide rail, and from the guide rail off the cathodic protection device.

In a further embodiment, as an alternative, or in addition, to the guide rail at the twelve o clock position, a guide rail is provided at the ten o cloak position and a guide rail is provided at the two o clock position

Preferably, the rail at the twelve o clock position has a width such that the guide surface of the guide rail extends along at least 10% of the circumference, i.e. the guide surface of the guide rail extends over at least an 36 degree angle. Providing the guide rails with a wide guide surface enhances the protection of the anode surface. When multiple guide rails are provided, the guide rails may have a guide surface that is relatively narrow, and still prevent objects from scratching the anode surface.

In the embodiment shown, the anode housing 12 and the spacer tube 2 are modular components, that are combined to form a cathodic protection device. Such an embodiment allows for providing spacer tubes of different lengths, and for example anode housings with one and anode housings with two or more tubular anodes, and combining these into a cathodic protection device that is configured for a particular object to be protected. For example, figure 6 shows a spacer tube 2 that is similar to the one of the cathodic protection device shown in figures 3-5, which spacer tube 2 is combined with an anode housing 12’ that comprises two tubular anodes 4a, 4b.

Figure 6 shows a cylindrical offshore structure 23, in the particular embodiment shown a transition piece 14 supporting a wind turbine 16. The transition piece is provided with two cathodic protection devices 1. The cathodic protection devices 1 each comprise a spacer tube 2, a flange 3 and a tubular anode 4.

The spacer tube 2 extends along a spacer tube axis 5 between a foot end 6 and a head end 7. The spacer tube 2 has a continuous cross section, with the spacer tube axis 5 at the center of the cross section, seen in a direction from the foot end to the head end.

The flange 3 has a mounting surface for mounting the cathodic protection device 1 against a mounting surface of a dedicated mount 30 of the transition piece 14, wherein the flange 3 is connected with the spacer tube 2 at the foot 6 end thereof, with the mounting surface of the flange extending at a small angle, i.e. an angle in the range of 1-8 degrees, to the spacer tube axis 5 of the spacer tube 2.

The tubular anode 4 has a central tubular anode axis 11. The tubular anode 4 is mounted to the spacer tube 2 at the head end 7 thereof, with a cross section of the anode 4 located within an outer circumference of the spacer tube 2 at the head end thereof and with the anode axis 11 aligned with the spacer tube axis 5.

In the embodiment shown, the cathodic protection device 1 is provided with multiple guide rails, which guide rails, similar to the guide rails of the embodiment shown in figures 3-6, extend parallel to the anode axis along the anode. The guide rails extend parallel to the spacer tube axis, and each of the guide rails has an outward facing guide surface that is flush with to the outer circumference of the spacer tube at the head end thereof such that a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto one or more guide rails, and thus over and off the anode, without getting hooked behind a protrusion extending from the spacer tube or the anode.

Furthermore, the cathodic protection devices 1 are attached with their mounting surfaces 9 to mounts 30 provided on the transition piece 14, and with the spacer tube axis 5 and the anode axis 11 extending in a direction at an angle relative to the horizontal. Therefore, the cathodic protection devices each point downwards, to thus promote the sliding of objects downward along the spacer tube and the anode off the cathodic protection device. Thus, in the embodiment shown in figure 6, the tubular anode 4 is a first tubular anode 4a and the cathodic protection device is provided with a second tubular anode 4b. in the embodiment shown, the first tubular anode 4a and the second tubular anode 4b are similar to the first tubular anode 4. The second tubular anode 4b is mounted coaxial with the first anode 4a in a single anode housing 12, such that a central anode axis 11 of the second anode 4b coincides with a central anode axis 11 of the first anode 4a.

In an embodiment, the second tubular anode is redundant, and is only to be used when the first tubular anode breaks down In addition or as an alternative, the second tubular anode is used when the first tubular anode does not provide a sufficiently strong field. In an alternative embodiment, both anodes are active during use of the cathodic protection device.

In the embodiments shown in figures 3-6, the spacer tube and the anode housing are separate components that are combined during assembly of the cathodic protection device. In an alternative embodiment, the spacer tube and at least part of the anode housing are a single piece, and the anode is mounted on a part of the anode housing that is an integral component with the spacer tube

In the embodiments shown, the spacer tubes are hollow, and one or more cables for connecting the anode with a power source and/or a control unit, are guided via the hollow spacer tube from the housing to the flange.

Furthermore, in the embodiments shown, the spacer tubes and the anode housings are made of a synthetic material, preferably a fibre reinforced synthetic material. Thus, the spacer tubes are not conductive. Furthermore, the spacer tube can thus be made of a relative light material, and the cathodic protection device can be kept light.

Furthermore, in the embodiments shown, the flanges of the cathodic protection devices are a sperate components that are attached to the spacer tube during the manufacturing process, in the embodiments shown, the flanges are made of steel, and the spacer tube is made of a synthetic material.

For each of the embodiments shown in figures 3-6, the flange is connected with the spacer tube with the mounting surface of the flange extending perpendicular to the longitudinal spacer tube axis of the spacer tube. In an alternative embodiment of a cathodic protection device 1 according to the invention, schematically shown in figure 7, the flange 3 is connected with the spacer tube 2 with the mounting surface 9 of the flange 3 extending at an angle, i.e. an angle in the range of 1-8 degrees, to the spacer tube axis 5 of the spacer tube 2, to enable the cathodic protection device 1 to be mounted to the offshore structure 23 at an angle to the horizontal. This configuration allows for the cathodic protection device to be mounted to the offshore structure, in this particular case to the transition peace, with the spacer tube axis of the spacer tube pointing downwards, which promotes sliding of objects away from the flange and off the cathodic protection device.

In an embodiment, the reference cell is provided at the bottom side of the cathodic protection device, i.e. at the side that in use faces towards the sea floor, such that objects can not easily hook behind it. Furthermore, in this position, the reference cell or the support bracket thereof, can not prevent objects from sliding along the spacer tube towards the housing of the cathodic protection device.

Reference signs

01 cathodic protection device

02 spacer tube

03 flange

04 tubular anode

05 spacer tube axis

06 foot end spacer tube

07 head end spacer tube

08 protrusion free surface spacer tube

09 mounting surface flange

10 outward facing anode surface

11 anode axis

12 anode housing

13 outer surface housing

14 transition piece

15 foundation pile

16 offshore wind turbine

17 guide rails

18 outward facing guide surface guide rails

19 base anode housing

20 foot end housing

21 top anode housing

22 head end housing

23 offshore structure

24 spacer tube radius

25 housing radius

26 outward facing spacer tube surface

27 wind turbine mast

28 upper most point of the cross section of the spacer tube

29 lower most point of the cross section of the spacer tube

30 mount on offshore structure

31 foot end anode

32 head end anode

34 anode radius

35 mesh

36 outward facing guide surface mesh

37 anode cover

38 first anode element

39 second anode element

40 top part anode housing

41 base part anode housing

42 cylindrical housing body anode housing

43 connector

44 connector chamber

45 wires

46 end wall

47 opening in end wall

Claims

C L A I M S

1. Cathodic protection device for use in an Impressed Current Cathodic Protection system (ICCP system) for providing an offshore structure, for example a wind turbine foundation, with cathodic protection, the cathodic protection device comprising:

- a spacer tube, the spacer tube having an outward facing spacer tube surface that extends along a spacer tube axis between a foot end and a head end of the spacer tube, the spacer tube having a spacer tube radius that extends between the spacer tube axis and the spacer tube surface;

- a flange, the flange having a mounting surface for mounting the cathodic protection device against a mounting surface of a mount of the offshore structure, wherein the flange is connected with the spacer tube at the foot end thereof,

- a tubular anode, the tubular anode having an outward facing anode surface that extends along an anode axis between a foot end and a head end of the tubular anode, the tubular anode having an anode radius that extends between the anode axis and the anode surface; wherein the tubular anode is mounted to the spacer tube at the head end thereof, with the tubular anode axis coinciding with the spacer tube axis of the spacer tube, and wherein the anode radius is at most 1 ,35 times the spacer tube radius, such that a flexible object can slide along the spacer tube, from the foot end to the head end, and from the spacer tube onto, over and off the anode.

2. Cathodic protection device according to claim 1, wherein the tubular anode is received in an anode housing, the anode housing comprising an anode cover, e.g. a mesh or one or more guide rails, which anode cover has an outward facing guide surface that extends parallel to the anode surface, for guiding an object over the anode surface, the anode housing having a housing radius that extends between the anode axis and the guide surface, and wherein the housing radius at most 1,35 times the spacer tube radius.

3. Cathodic protection device according to claim 2, wherein the anode housing further comprises a base at a foot end of the housing, and a top at a head end of the housing, wherein the cover extends between the base and the top, wherein the anode housing preferably is mounted with the base over the head end of the spacer tube, and wherein the base of the anode housing and the top of the anode housing each have an outward facing surface, and wherein the outward facing surfaces of the base and the top are flush with the guide surface of the cover.

4. Cathodic protection device according to one or more of the preceding claims, wherein the tubular anode comprises a first anode element, and wherein the first anode element is semi cylindrical, e.g. extends over an arc of at least 90 degrees, preferably over an arc of about 180 degrees, and preferably, wherein, when the cathodic protection device is mounted on the offshore structure, the first anode element faces downwards, i.e. is provided at a side of the cathodic protection device that faces a sea floor.

5. Cathodic protection device according to claim 4, wherein the tubular anode comprises a second anode element, and wherein the second anode element is semi cylindrical, and wherein the first anode element and the second anode element each extends over an arc of about 180 degrees, wherein, when the cathodic protection device is mounted on the offshore structure, the second anode element faces upwards, i.e. is provided at a side of the cathodic protection device that faces away from the sea floor.

6. Cathodic protection device according to one or more of the preceding claims, wherein the tubular anode is a first tubular anode and the cathodic protection device is provided with a second tubular anode, similar to the first tubular anode, and wherein the second tubular anode is mounted coaxial with the first tubular anode on the spacer tube, or wherein the first and the second anode are mounted coaxial in an anode housing according to claim 2.

7. Cathodic protection device according to one or more of the preceding claims, wherein the spacer tube is made of a synthetic material, preferably a fibre reinforced synthetic material.

8. Cathodic protection device according to one or more of the preceding claims, wherein the flange is connected with the spacer tube with the mounting surface of the flange extending at an angle, preferably an angle in the range of 1-8 degrees, for example at an angle of 5 degrees, to the spacer tube axis of the spacer tube, to enable the cathodic protection device to be mounted to the offshore structure at an angle to the horizontal.

9. Cathodic protection device according to one or more of the preceding claims, wherein the cathodic protection device further comprises a reference cell and a reference cell support bracket, and wherein the reference support bracket is configured to be mounted to the flange, preferably is configured to be mounted between the flange and the mount of the offshore structure.

10. Offshore structure, e.g. a transition piece for supporting a wind turbine, the offshore structure being provided with one or more cathodic protection devices according to one or more of the preceding claims.

11. Offshore structure according to claim 10, wherein the offshore structure is a cylindrical offshore structure, e.g. a transition piece for supporting a wind turbine.

12. Offshore structure according to claim 10 or claim 11 , wherein the one or more cathodic protection devices are attached with their mounting surfaces to mounts provided on the offshore structure, and with the spacer tube axis and the anode axis extending at an angle to the horizontal, such that the cathodic protection devices points downwards, to thus promote sliding of objects along the spacer tube and the tubular anode, off the cathodic protection device.

13. Impressed Current Cathodic Protection system comprising one or more cathodic protection devices according to one or more of the claims 1-9.

14. Method for providing an offshore construction with cathodic protection using a cathodic protection device according to one or more of the claims 1-9.

15. Method for manufacturing a cathodic protection device, preferably for manufacturing a cathodic protection device according to one or more of the claims 1-9, the method comprising:

- providing a spacer tube, the spacer tube having an end wall at a head end;

- guiding one or more wires through the spacer tube and through one or more openings in the end wall of the spacer tube and sealing the wires in the one or more openings;

- mounting one or more anode elements in an anode housing;

- mounting the anode housing on the head end of the spacer tube, such that a connector chamber is created at the head end of the spacer tube;

- connecting the one or more wires with the one or more anode elements;

- filling the connector chamber with a curing resin material to seal the connections between the wires and the anode elements and preferably to fix the anode housing relative to the spacer tube, for example by allowing the curing resin material to flow in a space between an outward facing spacer tube surface and the anode housing, at the head end of the spacer tube.