NL2016645A

NL2016645A - Pipeline comprising anodes and method of laying said pipeline.

Info

Publication number: NL2016645A
Application number: NL2016645A
Authority: NL
Inventors: Rose Boyd Helen
Original assignee: Heerema Marine Contractors Nl
Priority date: 2016-04-01
Filing date: 2016-04-21
Publication date: 2017-10-04
Also published as: NL2016535B1; NL2016535A; NL2016587A; NL2016645B1; NL2016587B1

Abstract

The present invention relates to method of connecting a sacrificial anode to a pipeline or to a pipe unit, wherein the pipeline or pipe unit comprises a steel pipe, wherein the anode is applied as a layer of metal which is more anodic than steel on a Field Joint Area prior to the application of thermal insulation coating on the Field Joint Area.

Description

Title: Pipeline comprising anodes and method of laying said pipeline FIELD OF THE INVENTION

The present invention relates to a pipeline comprising anodes and to a method of laying said pipeline. Pipelines comprising anodes are well known in the field of the art

BACKGROUND OF THE INVENTION

In the past decades, the technology of laying pipelines at sea has undergone a tremendous development. Driven by the continuous search for hydrocarbons, pipelay vessels have been developed which are capable of laying pipelines in ever deeper waters.

Various configurations have been developed for pipelay: S-lay, J-lay, reel lay and some other more exotic methods. The terms S-lay and J-lay refer to the shape of the pipeline between the seabed and the pipelay vessel. The term reel-lay refers to the reel from which the pipeline is spooled. Each of these configurations has its own advantages and disadvantages.

Various methods of holding the pipeline in each of these configurations have also been developed, more specifically the collar-based method and the methods based on tensioners.

Pipelines may be both single wall pipelines and double wall pipelines, also known as pipe-in-pipe.

Generally, a coating is provided around the pipeline. Often, an anti-corrosion coating such as Fusion Bonded Epoxy (FBE) protects the steel pipe, and a thermal insulation such as PP surrounds the anti-corrosion coating. The thermal insulation layer may be composed of multiple sub layers. Other materials and configurations are also possible. The thermal insulation serves to prevent the hydrocarbons flowing through the pipeline from cooling off which can potentially result in blockage of the pipeline. The thermal insulation also provides mechanical protection.

In the field of the art and this document, the combination of the anti-corrosion coating and the insulation is referred to as: coating. A pipeline is built from individual pipe sections, standardly 10 to 20 meters long. The coating is generally provided around the individual pipe sections on land. These individual pipe sections are delivered to the pipelay vessel or to a preassembly yard. Generally, only the coating at the connections between individual pipe sections is made on the pipelay vessel or on the preassembly yard. These are called Field Joint Coatings (FJC). Generally, the ends of two individual pipe sections which are to be connected are bare metal in order to facilitate welding and weld inspection. When the weld has been completed, the FJC is made at the joint. The FJC interconnects the coating on both pipe sections.

The term “coating” in this document are used as an umbrella term for both the FJC coating at the Field Joint Area and the coating which extends around the pipe units and around the pipeline in the other areas than the FJC. The latter is hereinafter referred to as “main pipe coating”.

At the preassembly yard, a number of individual pipe sections are joined together to form pipeline sections before they are transported to the pipelay vessel. The pipeline sections may be multi-joints which are used in J-lay and are generally in the order of 20 -100 meter long. The pipeline sections may also be pipe stalks of 1 to 2 kilometers long which are spooled onto a reel on a spool base. The pipe section may also be a pipeline section of several kilometers long which is formed of several interconnected pipe stalks spooled on a reel.

Because the pipe itself is generally made of steel, it is sensitive to corrosion. In order to limit the effects of corrosion, sacrificial anodes are generally attached to the pipeline. The anodes are often installed at intervals of about 150-300m, but other intervals are possible. The sacrificial anodes are made from a metal which is more anodic than steel, for instance zinc. When the steel pipe itself comes into contact with the water, the anode corrodes preferentially and the steel pipe becomes cathodic relative to the anode. The steel pipe only starts to corrode once the self sacrificing anode has been fully dissolved. Typically, an anode is designed to be dissolved over a period of at least the design lifetime of the pipeline, which is typically 20 to 30 years. The steel pipe is protected from corrosion during that period.

All this is well known in the field of the art. However, the anodes have a number of drawbacks for which there is no solution to date.

Problems associated with anodes in reel lay

In reel lay, the anodes cannot be attached to the pipeline before the pipeline is spooled onto the reel, because the anodes protrude from the pipeline and would damage other parts of the pipeline which the anode contacts on the reel.

Therefore, the anodes have to be attached to the pipeline after it is spooled from the reel and before it enters the water. The requires interruptions of the reeling process. The attaching of an anode to the pipeline may take 10-15 minutes. During this time, the anode must be mechanically connected to the pipeline, an opening must be made in the coating, the electrical conductor of the anode must be electrically connected to the steel pipe and the coating in the opening must be reinstated. The interruptions decrease the effective speed of laying of the pipeline and increase the cost of the pipeline. The attaching of the anodes also makes the pipelay process complex and requires personnel, equipment and space on the reel lay vessel.

In order to reduce the interruption time, brackets sticking through the coating are prewelded on the pipe stalks. The brackets reduce the time for creating the electrical connection between the anode and the steel pipe, as the brackets eliminate the need for making an opening in the coating and reinstating the coating in that opening. However, the brackets form a source of poor adhesion between the coating and the pipeline, and may form the starting point for cracks when the pipeline is bent during the spooling process onto the reel and from the reel and when the pipeline is launched into the water. After lowering, the cracks may allow water ingress of the pipeline, causing corrosion and loss of thermal insulation.

Problems associated with anodes in S-lay, J-lay

For S-lay and J-lay, the same problem of possible damage to other pipe sections would apply if the anodes would be pre-installed on land and outside the critical path. The pipe sections are generally stored and transported as a group, and the protruding anodes would make transport difficult and damage likely. Therefore, this is generally not done in practice.

When the anodes are attached to the pipeline, the installation of the anodes requires an extra activity in the pipelay process. If the activity is in the critical path, the same problem of interruptions in the pipelay process and reduced speed applies as it does in reel lay. The installation of the anodes in S-lay and J-lay also requires extra personnel, space and equipment on the pipelay vessel.

In the pipelay industry, there is a continuous desire to speed up the pipelay process, because pipelay vessels are complex and therefore expensive to operate.

It was recognized in the present invention that the anodes can be provided on the pipeline in a different way, which results in various advantages such as: a faster and/or simpler pipelay process and less corrosion and loss of thermal insulation.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a faster pipelay method.

It is another object of the present invention to provide a simpler pipelay method.

It is another object of the present invention to provide a pipelay method which has fewer steps on the critical path.

It is an object of the present invention to provide a pipelay method which requires less space, less personnel and/or less equipment on board.

It is an object of the invention to provide a way of attaching anodes to a pipeline in a way which leads to less ingress of water and less corrosion.

It is an object of the invention to provide an alternative way of attaching anodes to a pipeline.

It is an object of the invention to provide pipe units comprising anodes which do not damage other pipe units, in particular during transport and handling or when spooled on a reel.

SUMMARY OF THE INVENTION

In order to achieve at least one object, the invention provides a method of connecting a sacrificial anode to a pipeline or to a pipe unit, wherein the pipeline or pipe unit comprises a steel pipe, the method comprising: - providing a coating on the steel pipe, - providing a recess in the coating, - embedding the anode in the recess, wherein at least 80 percent of a volume of the anode is embedded in the recess, and wherein at most 20 percent of the volume of the anode protrudes from the recess and wherein the anode protrudes from the outer coating surface of the coating surrounding the anode over a distance of at most 20 mm, and - providing an electric conductor between the anode and the steel pipe.

The method according to the invention allows pre-installation of the anodes, resulting in a faster pipelay process and with little or no damage to adjacent pipe units.

The anode may protrude from the outer surface of the coating surrounding the anode over a distance of at most 20 mm, more preferably at most 10 mm. Obviously the less the anode protrudes from the coating the less damage to adjacent pipe units.

The anode may be fully embedded in the recess, and an outer anode surface of the anode may be flush with an outer coating surface of the coating surrounding the anode or countersunk relative to the outer surface of the coating surrounding the anode

The anode may be embedded in a Field Joint Coating (FJC) during the making of the FJC.

The anode may be embedded on shore in the pipe coating of a pipe unit which is configured to be connected in an end to end relationship with other pipe units by a pipelay vessel to form a subsea pipeline.

The anode may be embedded on shore in the pipe coating of a pipe unit which is configured to be connected in an end to end relationship with other pipe units to form a longer pipe unit to be spooled on a reel.

The anode may be positioned in place relative to the steel pipe before the coating material is applied to the steel pipe, wherein the recess is made during the step of providing the coating on the steel pipe, and wherein the coating material is provided around the positioned anode, in particular: - during a step of providing a Field Joint Coating on a pipeline, or - during a step of providing a main pipe coating on a pipe unit.

The anode may comprise one or more anchoring brackets which protrude inwardly from an inner side of the anode, wherein the anode is attached to the main pipe coating or to the FJC via the anchoring brackets.

The method may comprise the steps of: - temporarily connecting the anode to an inside of an FJC mould, - positioning the FJC mould around an FJ area, thereby creating an injection chamber, - filling the enclosed injection chamber with FJC material and letting the FJC material solidify, - disconnecting the anode from the FJC mould, - removing the FJC mould from the FJC zone and leaving the anode in place.

The outer surface of the anode may be positioned at a distance from the inner surface of the FJC mould at the circumferential edge of the anode, creating a space at the circumferential edge of the anode in which the FJC material flows to form an overlap of FJC material over the anode and wherein seals are provided between the anode and the FJC mould which extend around a central portion of the anode and delimit the overlap and prevent the FJC material to flow over a central part of the outer surface of the anode.

The recess usually does not extend all the way to the steel pipe, and a body of coating material is provided between the anode and the steel pipe.

The recess may be made after the coating has been provided on the steel pipe, wherein the recess is made: - in a main pipe coating of a pipe unit configured to be connected to other pipe units in order to form a pipeline, or - in a FJC of a pipeline after the FJC has been formed around a Field Joint Area.

Multiple anode sections may be connected to the pipeline or pipe unit at a distance from one another, wherein said multiple anode sections form a group and wherein said multiple anode sections share an electric conductor for creating electric contact with the steel pipe.

Said distance may be smaller than twice an axial length of the anode section, and wherein in particular each anode section has an axial length which is smaller than a diameter of the pipeline or pipe unit.

The multiple anode sections may be connected to the inside of the FJC mould.

The multiple anode sections may be spaced apart in an axial direction of the pipeline.

The multiple anode sections may be spaced apart in a circumferential direction of the pipeline.

The FJC mould may comprise at least a first mould part and a second mould part which are movable relative to one another, and wherein the anode comprises at least a first anode section and a second anode section, wherein the first anode section is connected to the first mould part and wherein the second anode section is connected to the second mould part.

Seals may be provided between the FJC mould and the main pipe coating on either side of the FJ Area to prevent FJC material to flow out of the injection chamber.

The electric conductor may be curved and attached to the steel pipe at one end and attached to the anode at an opposite end, wherein the curved electric conductor extends through the pipe coating, and wherein the curved electrical connector is in particular folded during the positioning of the anode. A length of the electric conductor may be longer than a thickness of the pipe coating, in particular longer than twice a thickness of the pipe coating.

The outer surface of the steel pipe is covered with an anti-corrosion layer prior to the positioning of the anode, and wherein an opening is made in said anti-corrosion layer, and wherein one end of the electrical connection is secured to the steel pipe at the opening. The opening may be made in the Field Joint area.

An outer diameter of the FJC may be greater than an outer diameter of the main pipe coating on either side of the FJC, and wherein in particular a field joint insulation coating layer forms an overlap over the line pipe insulation coating layer.

The FJC mould may comprise at least one protrusion protruding from an inside of the FJC mould, wherein the protrusion makes a recess in the FJC during the making of the FJC and wherein subsequently the sacrificial anode is mounted in the recess.

The sacrificial anode may have a helical shape and is spooled around the FJC.

The anode may form a part of the FJC mould or form the whole of the FJC mould, and wherein said FJC mould is permanent.

The permanent FJC mould may be positioned around the Field Joint Area, wherein the sacrificial anode is connected to said permanent mould or forms the entire FJC mould, wherein an outer anode surface of the anode protrude from the outer coating surface of the coating surrounding the anode over a distance of at most 20 mm and is preferably flush with an outer coating surface of the coating surrounding the anode or countersunk relative to the outer surface of the coating surrounding the anode.

The FJC mould may be positioned in a recess formed in the main pipe coating of the pipe units on either side of the Field Joint Area, more in particular in the thermal insulation coating of these pipe units.

The FJC mould may be flush with the outer surface of the main pipe coating.

The recesses may be elongate in an axial direction, and may in particular be parallel with the main axis of the pipeline or pipe unit.

The pipeline may be laid in J-lay or reel lay.

The method may comprise creating at least one groove in the coating, in particular the main pipe coating, and inserting at least one anode in the form of a strip in said groove and securing the anode. Multiple grooves and strips shaped anodes may be installed. A plurality of anodes may extend parallel to the main pipe axis. A plurality of anodes may be mounted circumferentially around the pipeline or pipe unit.

At least one anode may extend helically around the pipeline or pipe unit.

The anode may be applied as a layer of metal which is more anodic than steel on the Field Joint Area prior to the application of thermal insulation coating on the Field Joint Area. The method may comprise spraying said layer. The method may comprise applying the layer of the anodic metal directly on to the steel pipe. The layer may be applied over the toe of the chamfers in the field joint area. The anodic metal may be aluminium.

Pipeline or pipe unit

The present invention further relates to a pipeline or a pipe unit configured to be attached to other pipe units in an end to end relationship, the pipeline or pipe unit comprising: - a steel pipe, - a coating covering the outside of the steel pipe, - at least one recess in the coating, - at least one anode embedded in the recess, wherein at least 80 percent of a volume of the anode is embedded in the recess, and wherein at most 20 percent of the volume of the anode protrudes from the recess and wherein the anode protrudes from the outer coating surface of the coating surrounding the anode over a distance of at most 20 mm, and - an electric conductor between the anode and the steel pipe.

The pipeline or pipe unit has the same advantages as the method.

The anode may protrude from the outer surface of the coating surrounding the anode over a distance of at most 20 mm, more preferably at most 10 mm.

The anode may be fully embedded in the recess, and an outer anode surface of the anode is flush with an outer coating surface of the coating surrounding the anode or countersunk relative to the outer surface of the coating surrounding the anode

The pipeline or pipe unit may comprise a plurality of Field Joint Coatings (FJC) wherein the sacrificial anodes are embedded in the Field Joint Coatings.

At least one anode may be embedded in a main pipe coating surrounding the steel pipe.

The anode may comprise multiple anode sections which are embedded as a group in the coating of the pipeline or pipe unit at a short distance from one another, wherein in particular said distance is smaller than twice an axial length of the anode, and wherein in particular each anode has an axial length which is smaller than a diameter of the pipeline or pipe unit.

Multiple anodes may be embedded in a single FJC.

At least one anode section may not be directly connected to the steel pipe via the electrical connection, but only indirectly via an interlinking conductor which extends between said anode section and another anode section which is directly or indirectly connected to the steel pipe.

The anode may extend partially around the steel pipe, over a circumferential angle of at least 10 degrees, more preferably at least 30 degrees, more preferably at least 80 degrees.

The anode may extend fully around the steel pipe,

An outer surface of the anode may have a same radius of curvature as the outer surface of the coating.

The anode may have a thickness which is less than half a thickness of the coating.

The outer surface of the anode may be countersunk relative to the pipe coating over a distance of 0.1 mm - 30 mm.

The coating material of the coating may overlap the anode at the circumferential edge thereof.

The anode may comprise one or more anchoring brackets protruding from an inner side of the anode into the coating and wherein the anode is secured to the coating via the anchoring brackets.

An outer diameter of the FJC may be greater than an outer diameter of the main pipe coating on either side of the FJC.

The outer surface of the anode may be at least partially free of any coating in order to be directly exposed to the water when the pipeline or pipe unit is submerged,

In an axial direction the anode may have a non-straight shape, in particular an undulated, serrated or castellated shape. A length of the anode or the length of the individual anode sections in an axial direction may be less than a steel pipe diameter of the steel pipe and wherein a thickness of the anode or of the individual anode sections is greater than 0.1 times the length of the anode.

At least one Field Joint Coating may comprise a permanent FJC mould and wherein the sacrificial anode is connected to said mould with its outer surface exposed to the outside. The FJC mould may be flexible.

The FJC mould may be positioned in a recess wherein said recess is formed in the coating of the pipe units on either side of the Field Joint Area, more in particular in the thermal insulation coating of these pipe units.

The pipeline or pipe unit may comprise one or more FJCs comprising a layer of metal which is more anodic than steel, wherein said layer is located underneath the thermal insulation coating in the Field Joint Area.

The pipeline or pipe unit may comprise one or more FJCs in which the layer of the anodic metal is applied directly on to the steel pipe. The layer may in particular extend over a toe of chamfers in the field joint area.

The anodic metal may be aluminium.

The present invention further relates to a pipe unit comprising opposite ends having a section of steel pipe which is bare metal without any coating, and wherein the main pipe coating has a sloping section, in particular a conical section, in which the thickness of the main pipe coating increases in a direction away from the end of the pipe unit, and wherein at the wide end of the sloping section a resting section is provided for an end of a permanent FJC mould, and wherein an upstanding ridge is provided which delimits the resting section and forms a transition to the outer surface of the main pipe coating of the pipe unit. FJC mould

The present invention further relates to an FJC mould comprising at least one connector for connecting one or more anodes to the FJC mould at least during the making of the FJC.

The connector may be configured for connecting the anode to an inside of the FJC mould, wherein the connector comprises an operating member positioned on the outside of the FJC mould, which operating member is operable from the outside in order to allow the FJC to be disconnected from the anode after an FJC comprising an anode has been made.

The FJC-mould may comprise multiple connectors which are removable bolts.

The at least one connector may be a suction member.

The FJC-mould may comprise multiple connectors which are spaced apart over a distance and form multiple mounting positions allowing multiple anodes to be connected to the inside of the FJC.

The FJC mould may comprise seals which prevent FJC material to flow into a space between the anode and an inner surface of the FJC mould during filling of the injection chamber enclosed by the pipeline and the FJC mould.

The FJC mould may be permanent and the anode may be connected to the outside of the FJC mould or at least connected to the FJC mould with the outer surface of the anode being exposed.

The FJC-mould may comprise a recess in the outer surface of the FJC-mould into which the anode is placed, wherein the outer surface of the anode protrudes from the outer coating surface of the coating surrounding the anode over a distance of at most 20 mm, and is preferably flush with or countersunk in the outer surface of the surrounding FJC mould. The FJC-mould may be flexible.

The present invention further relates to a combination of an FJC mould according to the invention and one or more anodes connected to the FJC mould.

The at least one anode may be connected to the inside of the FJC mould.

The at least one anode may be permanently connected to the outside of the FJC mould.

The FJC mould may comprise at least one protrusion protruding from an inside of the FJC mould, wherein the protrusion is configured for making a recess in the FJC after completion of the FJC.

The protrusion may be an insert.

Variant with strips

In a further aspect, the present invention relates to a pipeline or pipe unit, wherein one or more anodes having a strip shape are attached to the outside of the coating.

The strips may extend axially and/or circumferentially and/or helically.

Each strip may be provided in a groove in the coating.

Each strip may be flush with or countersunk in the outer surface of the coating.

The anodes may be electrically connected to the steel pipe in a field joint area by electrical conductors.

One or more strip shaped anodes may extend parallel to the main pipe axis.

One or more strip shaped anodes may extend circumferentially around the pipeline or pipe unit.

One or more anodes may extend helically around the pipeline or pipe unit.

In a further aspect the present invention relates to a method of attaching one or more anodes to a pipeline or pipe unit, the method comprising: a. providing one or more anodes having a strip shape and b. attaching said anodes to a coating of the pipeline or pipe unit.

The anodes may be attached to the outer surface of the coating.

The method may comprise making grooves in the coating and inserting the anodes in the grooves.

The anodes may extend parallel to the main pipe axis.

The anodes may extend circumferentially around the pipeline or pipe unit.

The anodes may extend helically around the pipeline or pipe unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts.

Figure 1 shows a top view of a spool base according to the prior art.

Figure 2 shows a side view of laying a pipeline with a reel lay vessel according to the prior art.

Figure 3 shows a sectional side view of an anode according to the prior art.

Figure 4 shows a sectional side view of another anode according to the prior art.

Figure 5A shows an axial sectional view of an embodiment of the invention.

Figure 5B shows an axial sectional view of another embodiment of the invention.

Figure 6 shows a sectional side view of another embodiment according to the invention.

Figure 7 shows an axial sectional view of the embodiment of figure 6.

Figures 8, 10, and 12 show sectional side views of the embodiment of figure 6 in consecutive steps of installation.

Figure 9, 11 and 13 show axial sectional views associated with respectively figures 8,10 and 12.

Figure 14A shows a sectional side view of a further embodiment according to the invention.

Figure 14B shows a sectional side view of yet a further embodiment according to the invention.

Figure 15 shows a sectional view of another embodiment according to the invention.

Figures 16, 18, 20 and 22A show a side view of consecutive steps in the installation of the embodiment of figure 15.

Figure 17, 19, 21 and 23 show sectional views of the installation steps shown in respectively figure 16, 18, 20 and 22A.

Figure 22B shows a sectional side view of another embodiment according to the invention.

Figure 24 shows a sectional side view of another embodiment according to the invention.

Figure 25 shows a detailed side view of a variant of the embodiment of figure 24.

Figure 26 shows a detailed side view of another variant of the embodiment of figure 24.

Figure 27 shows a sectional side view of another embodiment according to the invention.

Figure 28 shows an axial sectional view of the embodiment of figure 27.

Figure 29A shows a sectional side view of another embodiment according to the invention.

Figure 29B shows a sectional side view of yet another embodiment according to the invention.

Figure 30A shows a sectional side view of yet another embodiment according to the invention.

Figure 30B shows a sectional side view of another embodiment of the invention.

Figure 31 shows a sectional view of a detail of the embodiment of figure 30A.

Figure 32 shows a sectional side view of again another embodiment according to the invention.

Figure 33 shows a sectional side view of yet another embodiment according to the invention.

Figure 34 shows a sectional side view of the embodiment of figure 33 after completion.

Figure 35 shows a sectional side view of another embodiment according to the invention.

Figure 36 shows a sectional side view of another embodiment according to the invention.

Figure 37 shows a sectional side view of another embodiment according to the invention.

Figure 38 shows a sectional side view of yet another embodiment according to the invention.

Figure 39A shows a sectional side view of again another embodiment according to the invention.

Figure 39B shows an axial view of the embodiment according to figure 39A.

Figure 40A shows a sectional side view of again another embodiment according to the invention.

Figure 40B shows an axial view of the embodiment according to figure 40A.

Figure 41 shows a sectional side view of yet another embodiment according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Turning to Figure 1, in preparation of laying a pipeline by the method of reel-lay, pipeline sections are pre-constructed at a pipeline construction yard 1, also called a spoolbase. In a pipeline construction facility 2, short pipe sections 3, typically with a length of 40 feet (12.2 meters) are welded together to long pipeline sections 4, also called stalks, typically with a length of 1 to 2 kilometers. Completed stalks are temporarily stored in a stalk storage area 5.

In order to spool a pipeline 20 on a reel, a vessel 6 carrying a reel 7 is moored along a quayside 8 at or near the spoolbase 1. A first pipeline section 9 is plastically bent over the reel by rotating the reel by a reel drive unit 10, at the same time asserting back-tension on the pipeline section by a tensioning device 11 and support to the pipeline by a supporting device 12. Once the tail end of pipeline section 9 has arrived at the tie-in station 13, the process of spooling is stopped. A next pipeline section 14 is transferred from the storage area 5 to the pipeline assembly area 15. The pipeline assembly area 15 is provided with rollers 16 over which the pipeline section 14 can be moved towards the tie-in station 13, until its lead end meets the tail end of pipeline section 9. Subsequently, the lead end of pipeline section 14 is connected to the tail end of pipeline section 9, usually by means of a circumferential weld 17. Once the weld has been completed and the coating in the weld area has been reinstated, the spooling process is resumed. In this way, a series of stalks is connected to each other and spooled to the reel until the reel is full.

In preparation of laying pipe by the method of J-lay, the long pipeline sections 4 are much shorter, being assembled to a length of 2 to 6 pipe sections 3, i.e. a total length of 24.4 to 73.2 meters. Such sections are also called multi-joints. Multi-joints are shipped to the pipelay vessel either stacked on the deck of a transport vessel or stacked in crates which are hoisted on board of the pipelay vessel.

Turning to Figure 2, when the pipeline 20 is installed by the reel-lay method, the pipeline 20 is reeled at sea from a reel 7 on the pipelay vessel 21 to the seabed 22. In the reeling process, the pipeline 20 is supported by a pipelay ramp 23. On the pipelay ramp, the pipeline passes successively: - an aligner unit 24, which re-bends the pipeline coming from different layers on the reel to a universal bending radius; - a straightener 25, which straightens the pipe to a straight configuration; - one or more tensioners 26 which hold the weight of the pipeline suspended from the ramp 23; - a work station 27 in which pipeline construction activities such as welding, weld inspection and coating are performed; - a holding clamp 28 in which the pipeline 20 can be suspended when for instance a structure must be welded to the end of the pipeline; and - a stinger 29 which prevents damage to the pipeline 20 as a result of vessel motions.

When the pipeline 20 is installed by J-lay, the pipeline 20 is hung off in the holding clamp 28. Subsequently, a new multi-joint section is supported on the pipelay ramp 23 and connected to the pipeline 20 in the work station 27. After the connection between the new multi-joint and the pipeline 20 has been completed, the pipeline 20 is lowered to the seabed over a distance equal to the length of the multi-joint section. The lowering operation can be completed by a lowering clamp or a set of one or more tensioners.

Turning to Figure 3, an offshore pipeline 20 usually consists of a steel pipe 30 containing the flow medium 31 flowing through it; the medium can be oil or gas produced from a hydrocarbons field or water injected into a hydrocarbons field. In order to protect the steel pipeline 30 from corrosion by the salt seawater 32, a layer of line pipe anti-corrosion coating 33 is applied to the outside of the steel pipe 30. The layer of line pipe anti-corrosion coating 33 is usually around 0.25 to 0.5 millimeters thick. A known anti-corrosion coating material is Fusion Bonded Epoxy (FBE).

On top of the anti-corrosion coating, sometimes a layer of insulation coating 34 is applied to the pipeline 20. The thickness of this layer may vary widely, depending on the amount of insulation required. Typical thicknesses of insulating coating layers are 40 to over 100 millimeters. The material is usually a polymer such as thermoplastic polypropylene (PP) or poly-ethylene (PE), or thermosetting polyurethane (PU), sometimes with additives to improve its insulating properties.

In addition to the line pipe anti-corrosion layer 33, often sacrificial anodes 35 are mounted on the pipeline 20 and electrically connected with the steel pipe 30 at regular intervals of typically 150 to 300 meters distance. Sacrificial anodes consist of zinc or aluminium or another alloy that oxidizes easier in seawater than steel. As a result, the anode and the steel pipe form a galvanic couple, creating an electric potential between them, making the anode to corrode first, before the steel pipe which is acting as the cathode starts corroding.

For providing electrical contact between the anode 35 and the steel pipe 30, an electrical conductor 36 is connected to the steel pipe 30 by means of an electrical connection 37. The electrical connection 37 usually is a welded connection. For making up the electrical connection 37, an opening 38 must be provided through the layers of line pipe insulation coating 34 and line pipe anti-corrosion coating 33, in order to connect the electrical conductor directly to the steel pipe 30 or to a doubler plate preinstalled on the steel pipe. After the electrical connection 37 has been provided, the line pipe anti-corrosion coating and line pipe insulation coating layers must be reinstated in the opening 38.

Turning to Figure 4, sacrificial anodes 35 are typically 40 to 50 millimeters thick and clamped to the pipeline. Typically, they protrude 40 to 50 millimeters outside the outer diameter of the insulation coating layer 34. When the pipeline is installed by the method of reel-lay, such anodes cannot be spooled on a reel 7, as the locally protruding anodes would cause damage to the pipeline when the pipe is plastically bent over the reel, in the worst case in the form of a local buckle.

The anodes 35 can only be mounted to the pipeline 20 and electrically connected to the steel pipe 30 in the work station 27, after the anode mounting zone 40 has been reeled off the reel and has passed the aligner 24, the straightener 25 and the one or more tensioners 26. For every anode to be mounted, the reeling process must be interrupted for clamping the anode 35 around the pipeline 20 and connecting the electrical conductor to the steel pipe 30.

The interruption time for mounting anodes during reeling is reduced by welding electrically conductive brackets 41 to the steel pipe 30 in the Field Joint Area 42. The Field Joint Area 42 is the area formed by two adjoining pipe ends which are kept free of any coatings in order to allow the two pipe ends to be connected by a weld 43 and the weld 43 to be inspected. After completion of the weld, the coating layers in the field joint area 42 are reinstated, first a field joint anti-corrosion coating layer 44 on the steel pipe 30 and then on top of the field joint anti-corrosion coating layer one or more layers of field joint insulation coating, in the following figures indicated as one single layer of field joint insulation coating 45. The entire package of anti-corrosion coating and insulation coating in the field joint area is called the Field Joint Coating 46 (FJC).

The conductive bracket 41 protrudes through the thickness of the Field Joint Coating 46 to the outside diameter 47 of the Field Joint Coating. The conductive bracket 41 allows to connect the electrical conductor 36 to be connected to the bracket by an electrical connection 48, which connection usually is a weld. In this way, the bracket saves offshore interruption time during the reeling process for making an opening in the coating, then welding the electrical conductor 36 directly to steel pipe 30 and finally reinstating the coating layers in that opening after the electrical conductor has been welded.

However, the brackets 41 form a source of poor adhesion of the coating layers to the pipe, which during bending of the pipeline 20 over the reel 7 may form cracks, the cracks allowing water to ingress into the coating, which water ingress forms a threat both for the integrity of the pipeline due to corrosion and for the insulation properties of the coating.

In the process of J-lay, clamped on anodes 35 protruding outside the outer diameter of the Field Joint Coating also have drawbacks. If preinstalled on the multi-joint sections, the protruding diameter of the anodes makes load-out and transport in crates more difficult, potentially damaging the sensitive line pipe insulation coating 34 or field joint insulation coating 45 of underlying layers of multi-joints. If installed on the pipelay vessel, they entail either extra vessel time for being mounted on the pipeline or extra space and personnel for carrying out this activity in parallel to the process of connecting the new multi-joint to the pipeline.

Turning to Figure 5A, in a first embodiment, a sacrificial anode 50 is fully embedded in the Field Joint Coating 46. The outer surface 51 of anode 50 has an outer diameter which is the same or slightly smaller than the outside diameter 47 of the Field Joint Coating 46.

The outer surface 51 of anode 50 is free of any coating and directly exposed to the seawater 32 once installed on the seabed.

Some of the advantages of the invention are already achieved when at least 80 percent of a volume of the anode is embedded in the recess, and wherein at most 20 percent of the volume of the anode protrudes, and the invention extends to this embodiment. More in particular the anode may protrude from the outer anode surface over a distance of at most 20 mm, preferably at most 10 mm, more preferably at most 5 mm. These embodiments result in less of damage to surrounding pipes.

However, it will be clear that the advantages are greater when the anode is fully embedded in the recess, and an outer anode surface of the anode is flush with an outer coating surface of the coating surrounding the anode or countersunk relative to the outer surface of the coating.

The combination of the anti-corrosion coating 44 and the insulation coating 45 is indicated as Field Joint Coating 46. The term coating 18 is used as a generic term for both the Field Joint Coating 46 and the main pipe coating 49 which will be discussed below.

Apart from its outer surface, the anode 50 is fully embedded in the layer of field joint insulation coating 45. The anode is positioned in a recess 39 in the coating 18. The recess has a size and shape, in particular a depth, which is sufficient to accommodate the entire anode. At the embedded side, the anode may be provided with anchoring brackets 53 in order to ensure a proper anchoring of the anode 50 in the layer of field joint insulation coating 45. A body 310 of coating material is provided between the anode and the steel pipe

The anode faces 54 may be further shaped in order to reduce crack forming during bending and straightening of the pipeline during the reeling process. Crack forming may be further reduced by giving the layer of field joint insulation coating 45 a slight overlap 55 over the edges 56 of the outside area 51 of the anode.

An electrical conductor 57 connects the anode 50 electrically with the steel pipe. Depending on the situation, the length of the electric conductor may be longer than a thickness 271 of the pipe coating 18, in particular longer than twice a thickness of the pipe coating 18.

The anode may extend partially around the steel pipe, over a circumferential angle of at least 10 degrees, more preferably at least 30 degrees. In another embodiment the anode may extend over an angle of at least 80 degrees. The anode may extend over a circumferential angle of 10-90 degrees, more in particular 20-70 degrees. In yet another embodiment, two of such partially circumferential anodes may be installed at either side of the pipeline.

The outer surface of the anode may be countersunk relative to the pipe coating over a distance of 0.1 mm - 30mm.

The anode may have a thickness 315 which is less than half the thickness 271 of the pipe coating 18.

Turning to Figure 5B, in a variant of the previous embodiment, a sacrificial anode 250 is fully embedded in a recess 39 in the main pipe coating 49 (usually line pipe coating) of a pipe unit 99. The term main pipe coating 49 is used for the combination of the anti-corrosion coating 33 and the thermal insulation coating 34 on the pipe unit 99.

The pipe unit 99 may be a short pipe section 3 or a long pipe section 4. It is noted that fig. 5B shows only a part of the pipe unit 99. Installing an anode on the line pipe and not in the field joint area has the advantage that the anode is remote from the weld. Due to stiffness differences between the two pipes joined by the weld, the strains in the field joint area 42 have the tendency to be higher than along the line pipe when the pipeline is bent over a reel. Another advantage of installing the anode on the line pipe is that the process of installing the anode does not interfere with the process of constructing the Field Joint Coating.

For installing the anode, the recess 39 is formed in the line pipe insulation coating layer 34, for instance by cutting or milling or by melting the coating by pressing a hot counter-mould into the surface of the line pipe insulation coating, or otherwise. In the bottom of the recess 39, an opening 265 is made through the line pipe insulation coating layer 34 and the line pipe anti-corrosion coating layer 33 on to the steel pipe 30 for making an electrical connection between the electrical conductor 257 of anode 250 and the steel pipe 30.

Subsequently, the anode 250 is mounted in the recess 39. This can be done using bolts 253 engaging in threaded holes 256 in the line pipe insulation coating 34. The bolts have sunken heads 255 which do not protrude outside the outer surface 51 (or outside diameter 251) of the anode, in order to provide a flush or countersunk surface of the anode. The anode 250 can also be mounted in the recess 39 in other ways, such as gluing the anode in the recess 39 or by providing thin corrosion resistant steel straps around the outer surface 59 of the main pipe coating at the location of the anode 250.

The outer surface 51 of anode 250 has an outer diameter 251 which is the same or slightly smaller than the outside diameter 247 of the main pipe coating 49 and is flush or countersunk relative to the outer surface 59 of the main pipe coating 49. The outer surface 51 of anode 250 is free of any coating and directly exposed to the seawater 32 once installed on the seabed.

The gap 261 between the anode 250 and the recess 39 is filled with elastic material, with the purpose to prevent crack forming between the anode and the main pipe coating 49 when the pipeline 20 is bent over a reel 7. The anode faces 254 may be further shaped in order to reduce crack forming during bending and straightening of the pipeline during the reeling process.

Figures 6 and 7 show the first step of a possible way of installing an anode 50 on the pipeline 20 in a Field Joint Coating 46. Figure 7 represents view A-A of Figure 6. After the field joint anti-corrosion coating layer 44 has been applied on the steel pipe 30, a mould 60 is used for applying the layer of field joint insulation coating 45. The anode 50 is detachably mounted to the inside surface 61 of the mould 60. The detachable connection can have connectors 300 in the form of bolts 62, but can also be provided otherwise. The bolts can be engaged and disengaged with the anode 50 from the outside 63 of mould 60 via the outer ends 301 of the bolts. Obviously other connections than bolts 62 and other operating members than the outer ends 301 of the bolts are foreseeable. In another variant, suction may be used to connect the anode to the mould. Suction members may be provided between the mould and the anode. For the purpose of this document, such suction members shall be regarded as connectors.

Tightening seals 64 may be provided between the outer surface 51 of the anode and the inside surface of the mould 61 along the circumference of the outer surface of anode 50. During the tightening of the bolts 62, the seals 64 are squeezed between both surfaces 51 and 61 in order to form a fluid-tight sealing. The seal can be rubber or another flexible material. The function of the seal 64 is to prevent fluid to flow into the space between the surfaces 51 and 61 when the mould is filled during injection of the insulation coating. When this material would solidify in the space between surfaces 51 and 61, it could adhere to the outer surface 51 of the anode, from where it then later must be removed for not endangering proper electrical contact between the anode outer surface and the seawater once the mould has been removed from the pipeline and the pipeline has been installed on the seabed.

One or more electrical conductors 57 (only one is drawn for clarity) are electrically connected with the anode 50. For making an electrical connection between the electrical conductor 57 and the steel pipe 30, an opening 65 is made in the field joint anti-corrosion coating layer 44 in the projected area 66 of the electrical connection. The electrical connection 67 is preferably welded, for instance by a cadweld. After the electrical connection 67 has been made, the field joint anti-corrosion coating 44 is reinstated over the area of opening 65.

As an alternative to this procedure, a doubler plate may be welded to the steel pipe 30 in the projected area of the electrical connection 66 (not shown), before the field joint anti-corrosion coating is applied. The doubler plate is subsequently coated with a field joint anti-corrosion layer 44 together with the rest of the field joint area 42. Before making the electrical connection, the field joint anti-corrosion coating is scraped off the doubler plate and the electrical connection 67 is made between the electrical conductor 57 and the doubler plate. Finally, the field joint anti-corrosion layer is reinstated over the doubler plate.

Figures 8 and 9 illustrate the second step of the possible way of installing an anode 50 on the pipeline 20. Figure 8 represents section B-B of Figure 9, partly as a section through the mould 60, pipe and coating, partly as a view on the backside of the mould with the anode 50 bolted at the inside of the mould. The mould 60 is engaged with pipeline 20 around the field joint area 42. Figure 9 shows a hingable mould, comprising two half cylindrical sections 70A and 70B, hingable about one or more hinges 71 and secured with one or more pins through holes 72 after engagement. It will be clear that multiple other solutions of a mould are possible.

After engagement of the mould 60, tightening seals 73 may provide a fluid-tight barrier between the inside of the mould and the outer surface 74 of the line pipe insulation coating 34. It will be clear that other sealing methods can provide a fluid-tight barrier between the mould and the line pipe insulation coating, such as strapping the mould around the main pipe coating or by injecting glue or kit into the seam between mould and main pipe coating or other methods. In this way, an enclosed injection chamber 75 is formed into which the field joint insulation material can be injected. The electrical conductor 57 is folded into the chamber 75. The mould 60 is provided with an injection valve 76 for filling the chamber 75 with fluid coating material.

Tightening seals 64 around the periphery of the outer surface 51 of anode 50 may keep the chamber 77 between the anode 50 and the mould 60 free of coating material when this is injected into chamber 75.

Figures 10 and 11 illustrate the third step of the possible way of installing an anode 50 on the pipeline. Figure 11 represents the cross-section C-C in Figure 10. The injection chamber 75 now is filled with field joint insulation coating material 78, injected through the injection valve 76. The tightening seals 73 may prevent the fluid insulation coating material to flow out of the mould through the annulus between the inside surface of the mould 61 and the outer surface of the line pipe insulation coating 74. At the same time, the seals 73 may be placed in a position to form an overlap 80 of the field joint coating insulation layer 45 with the line pipe insulation coating layer 34. The term coating 18 is used to denote the combination of field joint coating insulation layer 45 and anti-corrosion layer 44.

The anchoring brackets 53 and the electrical conductor 57 are encapsulated by the fluid coating material. The recess 39 in which the anode 50 is embedded is not formed in a separate step, but automatically during the making of the Field Joint Coating.

Tightening seals 64 may keep the chamber 77 free of coating material 78, such that no coating material is adhered to the outer surface of the anode 51. At the same time, the seals 64 may be placed in a position to allow the Field Joint Coating material 78 to form an overlap 55 over the edge 56 of the anode 50, which overlap prevents a crack to be formed between the anode and the field joint insulation coating 45 when the pipeline is bent over a reel.

Figures 12 and 13 illustrate the last step of the possible installation procedure of an anode 50. Figure 13 is a cross-section over the line D-D in Figure 12. After solidification of the field joint insulation coating layer 45, the bolts 62 are unbolted via the ends 301, such that the anode 50 is no longer connected to the mould 60. Then, the one or more pins 72 are unsecured and the mould 60 is hinged open and released from the Field Joint Coating.

The field joint insulation coating layer 45 may be left with an overlap 80 over the line pipe insulation coating layer 34 with a smooth transition edge 81 to the line pipe insulation coating layer. The field joint insulation coating layer 45 may also be left with an overlap 55 over the edge 56 of the anode 50 with a smooth transition edge 82 to the outer surface of the anode 51. In this way, the outer surface of the anode 51 is kept free of any field joint insulation coating material, in order to be exposed directly to the seawater when installed on the seabed.

In the J-lay process, it is acceptable to give the Field Joint Coating 46 a somewhat larger diameter than the main pipe coating with a small overlap 80 over the outer surface of the main pipe coating 74, as shown in Figure 12. In the reel-lay process, it may be preferred, to give the Field Joint Coating 46 the same outside diameter as the main pipe coating, so that the main pipe coating, the Field Joint Coating and the anode have a flush outside diameter as for instance illustrated further on in Figures 30 and 32. A flush shape makes the Field Joint Coating 46 and the anode 50 less vulnerable to be damaged when the pipe passes the rollers 16, the tensioning device 11 and the supporting device 12 when the pipeline 20 is spooled onto a reel 7, and passing the aligner 24, the straightener 25, the one or more tensioners 26 and the stinger 29 when the pipeline 20 is reeled off the reel 7 to the seabed 22.

Figures 5 to 13 show only one layer of field joint insulation coating 45, injected in one injection step, using a single mould. As an alternative, the field joint insulation coating layer 45 may be built up in multiple layers, each with their own stiffness and thermal insulation properties. In this way, the field joint insulation coating can be built up to have both optimal properties to be bent over a reel 7 without the forming of cracks and optimal insulation properties for matching the insulation properties of the main pipe coating. When the field joint insulation coating is built up in multiple layers, the anode 50 would be installed using the mould of the last layer and contained in the last and most outer layer of the field joint insulation coating.

Figure 14A shows a second embodiment of the invention for application in a Field Joint Coating 46, which is a variant of the embodiment shown in Figures 6 to 13. The single sacrificial anode 50 shown in Figure 6 is subdivided into multiple smaller sacrificial anode sections, in Figure 14 indicated as 50a to 50d. Shorter and smaller anode sections will reduce the stresses between the anode and the Field Joint Coating when the pipeline 20 is bent over a reel.

Each of the small sacrificial anode sections 50a to 50d is bolted to the mould 60 by one or more bolts 62a to 62d. Tightening seals 64a to 64d may be applied to ensure that the chambers 77a to 77d between each anode section and the inside surface of the mould 61 stay free of Field Joint Coating material when the mould is injected, in order to safeguard that no film of coating is formed on the anode and that the anode is exposed directly to the seawater when installed on the seabed.

The multiple anode sections 50a to 50d are preferably electrically connected as indicated in Figure 14. The first anode section 50a and the last anode section 50d are connected to the steel pipe by electrical conductors 57a and 57d. Mutually, the anode sections 50a to 50d are interconnected by short electrical conductors 83. Multiple variants on this preferred arrangement of electrical conductors are possible. So is it possible to connect each individual anode section 50a to 50d by own electrical conductors 57a to 57d to the steel pipe 30. Also is it possible, in the arrangement of Figure 14 to leave out one of the electrical conductors 57a or 57d. The electrical conductors 57a to 57d are folded into the mould 60 when the mould is engaged around the joint area 42.

Engagement of the mould, injection of the Field Joint Coating material and release of the mould are substantially the same as described for the first embodiment described in Figures 6 to 13.

As noted in relation to Figure 13, the field joint insulation layer may be built up in multiple layers, with the anode 50 installed using the mould of the last layer and contained in the last and most outer layer of the field joint insulation coating.

Figure 14B shows a variant of the second embodiment of the invention for application in main pipe coating. The single sacrificial anode 250 shown in Figure 5B is subdivided into multiple smaller sacrificial anode sections in Figure 14B shown as 250a to 250d. Shorter and smaller anode sections will reduce the stresses between the anode and the main pipe coating when the pipeline 20 is bent over a reel.

The anode sections can be installed in different ways. Either for each individual anode section 250a-d an individual recess 39 can be formed with an individual opening 265 on to the steel pipe 30 for making an electrical connection between the individual electrical conductor 257 of the anode and the steel pipe. Alternatively, a single recess 39 can be formed as shown in Figure 14B, in which the individual anode sections 250a to 250d are mounted, for instance by bolts as shown in Figure 5B.

One or more openings 265 will be provided for making the electrical connections between one or more electrical conductors 257 and the steel pipe 30. Anode sections not having their own electrical conductor 257 to the steel pipe 30 (as for instance anode sections 250b and 250c in Figure 14B) will be connected to adjacent anode sections by short electrical conductors 283 in order to ensure that each anode section has an electrical connection with the steel pipe, either directly or via one of the other anode sections.

After installation of the anode sections 250a-d and the electrical conductors 257 and 283 on the pipeline 20, the voids between the recess 39 and the anode sections 250 as well as the openings 265 are filled with elastic material, with the purpose to prevent crack forming between the anode sections and the main pipe coating 49 when the pipeline 20 is bent over a reel 7.

Figure 15 shows a third embodiment of the invention for application in a Field Joint Coating 46. A sacrificial anode 90 is surrounding the Field Joint Coating 46. The outer surface 91 of the anode 90 has an outer diameter which is the same or slightly smaller than the outer surface 47 of the Field Joint Coating 46. The outer surface of the anode is therefore flush with or countersunk to the outer surface of the Field Joint Coating surrounding the anode. The outer surface 91 of anode 90 is free of any coating and directly exposed to the seawater 32.

At the coating side, the anode 90 may be provided with anchoring brackets 92 in order to ensure a proper anchoring of the anode 90 in the layer of insulation coating 45. However, other means of securing the anode 90 to the Field Joint Coating 46 are possible, such as gluing, screwing into tap holes in the coating, strapping with steel bands around the coating, etc.

An electrical conductor 94 connects the anode 50 electrically with the steel pipe 30.

Figures 16 and 17 show the first step of a possible way of installing the anode 90 of Figure 15 on a pipeline 20. Figure 17 represents view E-E of Figure 16. The anode 90 is fitted to the inside of mould 60 used for injecting the field joint insulation coating layer 45. If the mould is a hingable mould consisting of two half cylindrical sections 70A and 70B, the anode 90 would be built in two half cylindrical sections 90A and 90B to be fitted to the inside of the half cylindrical sections of the mould.

Circumferential tightening seals 100 and longitudinal tightening seals 101 may be applied to tighten the chambers 102A and 102B between the inside surface 61 of the mould 60 and the outer surface 91 of the anode sections 90A and 90B, in order to keep the outer surface of the anode 90 free of coating material when the mould is injected. The anode 90 can be temporarily connected to the mould 60 in various ways, such as by screwing bolts from the outside of the mould through the mould into tap holes in the anode 90, or by providing an under-pressure in the chamber 102, or by magnets, or in another way.

An electrical conductor 94 is at one end connected to an electrical connection 103 on the inside surface of one of the anode sections 90A or 90B and at the other end to an electrical connection 67 on steel pipe 30. For making the electrical connection 67, an opening 65 is made in the field joint anti-corrosion coating layer 44 at the projected area 66 of the electrical connection. The connection can be a cadweld or otherwise. After the electrical connection 67 has been made, the field joint anti-corrosion layer 65 is reinstated over the opening 65. A second electrical conductor can be provided between the other anode section 90A or 90B and steel pipe 30 (not drawn). Alternative to this second electrical conductor, a short electrical conductor 104 can be provided between anode sections 90A and 90B and electrically connected to them.

As an alternative to this procedure, a doubler plate (not shown) may be welded to the steel pipe 30 in the projected area of the electrical connection 66, before the field joint anticorrosion coating is applied. The doubler plate is subsequently coated with a field joint anticorrosion layer 44 together with the rest of the field joint area 42. Before making the electrical connection, the field joint anti-corrosion coating is scraped off the doubler plate. Then, the electrical connection 67 is made between the electrical conductor 94 and the doubler plate. Finally, the field joint anti-corrosion layer is reinstated over the doubler plate.

Figures 18 and 19 illustrate a second step of the possible way of installing an anode 90 on a pipeline 20. Figure 18 represents section F-F of Figure 19, partly as a section through the mould 60, pipe and coating, partly as a view on the backside of the mould 60 with the anode 90 connected at the inside. The mould 60 is engaged around the field joint area 42. Figure 18 shows a hingable mould, consisting of two half cylindrical sections 70A and 70B, hingable about one or more hinges 71 and secured with one or more pins through holes 72 after engagement.

It will be clear that multiple other solutions of a mould are possible. After engagement of the mould 60, tightening seals 73 may provide a fluid-tight barrier between the inside of the mould and the outer surface 74 of the line pipe insulation coating 34. In this way, an enclosed injection chamber 105 is formed into which the field joint insulation material can be injected. The electrical conductors 94 and 104 are folded into the chamber 105. The mould 60 is provided with an injection valve 76 for filling the chamber 75 with fluid coating material.

Circumferential tightening seals 100 and longitudinal tightening seals 101 around the periphery of the outer surface 91 of anode 90 may be applied to keep the chambers 102 between the anode 90 and the mould 60 free of coating material when this is injected into chamber 105.

Figures 20 and 21 illustrate a next step of the possible way of installing an anode 90 on the pipeline. Figure 20 represents the section G-G in Figure 21. The injection chamber 105 now is filled with field joint insulation coating material 78, injected through the injection valve 76. Tightening seals 73 may prevent the fluid insulation coating material to flow out of the mould through the annulus between the inside surface of the mould 61 and the outer surface of the line pipe insulation coating 74. At the same time, the seals 73 may be placed in a position to form an overlap 80 of the Field Joint Coating insulation layer 45 with the line pipe insulation coating layer 34.

The anchoring brackets 92 and the electrical conductors 94 and 104 are encapsulated by the fluid coating material.

Circumferential tightening seals 100 and longitudinal tightening seals 101 may be applied to keep the chambers 102 free of coating material 78, such that no coating material is adhered to the outer surface of the anode 91. At the same time, the circumferential seals 100 may be placed in a position to allow the Field Joint Coating material 78 to form an overlap 106 over the edge 107 of the anode 90, which overlap prevents a crack to be formed between the anode and the field joint insulation coating 45 when the pipeline 20 is bent over a reel 7.

Figures 22A and 23 illustrate the last step of the possible installation procedure of an anode 90. Figure 23 is a cross-section over the line H-H in Figure 22A. After solidification of the field joint insulation coating layer 45, the anode 90 is disconnected from the mould 60. Then, the one or more pins 72 are unsecured and the mould 60 is disengaged and released from the Field Joint Coating. The field joint insulation coating layer 45 may be left with an overlap 80 over the line pipe insulation coating layer 34 with a smooth transition edge 81 to the line pipe insulation coating layer. The field joint insulation coating layer 45 may also be left with an overlap 106 over the edge 107 of the anode 90 with a smooth transition edge 108 to the outer surface of the anode 91. The outer surface of the anode 91 may be kept free of any field joint insulation coating material, in order to be exposed directly to the seawater when installed on the seabed.

In the J-lay process, it is usually acceptable, to give the Field Joint Coating 46 a somewhat larger diameter than the main pipe coating with a small overlap 80 over the outer surface of the main pipe coating 74 as shown in Figure 22A. In the reel-lay process, it may be preferred, to give the Field Joint Coating 46 the same outside diameter as the main pipe coating 49. Also, the anode 90 can be given the same outside diameter as the Field Joint Coating 46, so that the main pipe coating 49, the Field Joint Coating and the anode have a flush outside diameter as for instance illustrated further on in Figures 30 and 32. A flush shape makes the Field Joint Coating 46 and the anode 90 less vulnerable to damage when the pipe passes the rollers 16, the tensioning device 11 and the supporting device 12 when the pipeline 20 is spooled onto the reel 7, and passing the aligner 24, the straightener 25, the one or more tensioners 26 and the stinger 29 when the pipeline 20 is reeled off the reel 7 to the seabed 22.

As noted in relation to Figure 13, the field joint insulation layer may be built up in multiple layers, with the anode 90 installed using the mould of the last layer and contained in the last and most outer layer of the field joint insulation coating.

Figure 22B illustrates a variant of the third embodiment for application in main pipe coating. For installing an anode 290 on a pipeline 20, a recess 39 in the form of a circumferential recess is formed in the outside diameter 247 of the line pipe insulation coating 34 in the same manner as described in relation with Figure 5B. In the bottom of the recess 39, an opening is made through the line pipe insulation coating layer 34 and the line pipe anti-corrosion coating layer 33 on to the steel pipe 30 for connecting the electrical conductor 294 of anode 290 to the steel pipe 30.

The anode is dimensioned in such a way that the outer surface 291 of the anode 290 does not protrude beyond the outer surface 59 of the main pipe coating 49. The anode can be made up of two or more cylindrical sections, but may also be a single plate of zinc or aluminium wrapped around the recess 39 when the metal plate is thin enough to be bent to the proper shape. The anode sections are connected to the field joint insulation coating layer 34 either by bolting as described in relation with Figure 5B or by gluing or by providing thin corrosion resistant steel straps around the outside surface 59 of the main pipe coating at the location of the anode 290, or otherwise.

The gap 261 between the anode 290 and the recess 39 as well as the opening 265 are filled with elastic material, with the purpose to prevent crack forming between the anode and the main pipe coating 49 when the pipeline 20 is bent over a reel 7.

Figure 24 shows a fourth embodiment of the invention for application in a Field Joint Coating 46 which is a variant of the third embodiment as described in Figures 15 to 23. In order to improve the flexibility of anode 90 to enable the anode to better follow the deformations of the Field Joint Coating 46 when the pipeline 20 is bent over a reel, the anode has a non-straight, in particular an undulated shape 95. The anode 90 with undulated shape 95 is installed in the field joint area 42 in exactly the same manner as described for the third embodiment in Figures 15 to 23.

Many more shapes are possible to give the anode 90 more flexibility for accommodating the deformations of the Field Joint Coating 46 when the pipeline 20 is bent over a reel, such as a serrated shape 96 as illustrated in Figure 25, or a castellated shape 97 as illustrated in Figure 26, or another shape.

As for the third embodiment, alternatively, the Field Joint Coating 46, the main pipe coating and the anode can be given the same outside diameter, without overlaps 80 and 106, to give the pipeline 20 a flush outside diameter, which might be preferred in the reel-lay process.

It will be clear that the non-straight shape, in particular the undulated shape 95 as shown in Figure 24, the serrated shape 96 as shown in Figure 25, the castellated shape 97 as shown in Figure 26 and any other shape of the anode providing more flexibility to bending of pipeline 20 can also be applied to an anode 290 in main pipe coating 34 as shown in Figure 22B.

Figures 27 and 28 illustrate a fifth embodiment of the invention for application in a Field Joint Coating 46, which is a variant to the third embodiment as described in Figures 15 to 23. Figure 28 is a cross-section over the line l-l in Figure 27. Instead of the long and thin anode 90 as described in the third embodiment, the fifth embodiment entails a shorter and thicker, more ring shaped anode 90. The length (La) of the anode may be smaller than the steel pipe diameter 270 of the steel pipe 30. A thickness 272 of the anode may be greater than 0.1 times the length La of the anode. A shorter and thicker anode may involve lower stresses between the anode 90 and the field joint insulation coating layer 45 when the pipeline 20 is bent over a reel.

As for the third embodiment, alternatively, the Field Joint Coating 46, the main pipe coating and the anode can be given the same outside diameter, without overlaps 80 and 106, to give the pipeline 20 a flush outside diameter.

It will be clear that a shorter and thicker, more ring shaped anode 90 as shown in Figure 27 can also be applied to an anode 290 in main pipe coating as shown in Figure 22B, in order to generate lower stresses between the anode 290 and the line pipe insulation coating layer 34 when the pipeline 20 is bent over a reel.

Figure 29A shows a sixth embodiment of the invention for application in a Field Joint Coating 46, which is another variant of the third embodiment. This sixth embodiment entails multiple short sacrificial anode sections, in Figure 29A shown as 90a to 90c. Short anode sections may reduce the stresses between anode sections 90a to 90c and field joint insulation coating 45 when the pipeline 20 is bent over a reel.

Figure 29A also shows the preferred arrangement of electrical connections between the anode sections 90a to 90c and the steel pipe 30. Preferably, the first and the last anode sections, in Figure 29A indicated as 90a and 90c are connected to the steel pipe 30 by electrical conductors 94a and 94c and the individual anode sections mutually connected by short electrical conductors 109 between the anode sections 90a to 90c. As an alternative, in the arrangement of Figure 29A one of the electrical conductors 94a or 94c may be left out. As another alternative, each anode 90a to 90c may be individually connected to the steel pipe 30 by its own conductor 94a to 94c, leaving out the short electrical conductors 109.

As for the third embodiment, alternatively, the Field Joint Coating 46, the main pipe coating and the anode sections can be given the same outside diameter, without overlaps 80 and 106, to give the pipeline 20 a flush outside diameter, as might be preferred in the reel-lay process.

Figure 29B shows the variant of Figure 29A, but now for main pipe coating 49. For mounting the short anode sections on the pipeline 20, first a recess 39 is formed in the surface of the main pipe coating in the form of a circumferential recess. The recess 39 can be either a single wide recess as shown in Figure 29B in which subsequently the short anode sections 290a to 290c are mounted and electrically connected with the steel pipe 30 and to each other by electrical conductors 283, or multiple short recesses, one per short anode section in which the individual anode sections 290a to 290c are mounted and electrically connected to the steel pipe 30. The short anode sections are shaped in a way that the outer surfaces 291 a to 291 c do not protrude beyond the outer surface 59 of the main pipe coating 49.

Figure 30A shows a seventh embodiment of the invention for application in a Field Joint Coating 46. An hourglass shaped recess 110 is formed in the outer surface 52 of the field joint insulation coating layer 45 by a protrusion 137 in the mould 60.

Figure 30B shows how an hourglass-shaped recess 110 is formed by a protrusion 137 mounted to the inside surface 61 of a FJC mould 60. The mould can be a hingeable mold as shown and described in relation to Figure 6 to 13 or another type of mould. The mould has an injection valve 76 through which fluid field joint insulation coating material 78 is injected into the injection chamber 75. The protrusion may be integral with the FJC mould or be an insert piece.

Optionally, one or more electrical conductors 114 can be electrically connected to the steel pipe 30 and temporarily connected to the inside surface 138 of the protrusion by temporary connection means 139, for instance a bolt, before the mould 60 is engaged with the pipeline 20.

After the injection chamber 75 has been injected with coating material 78 and the coating material has solidified, the temporary connection means 139 are disengaged, where upon the mould 60 can be removed from the pipeline 20. The protrusion 137 leaves an hourglass-shaped recess 110 in the surface of the field joint coating 46 in which the anode 290 can be mounted. The tail end of the electrical conductor 114 is accessible in the bottom of the recess for being connected to the anode.

Returning to Figure 30A, after solidification of the field joint insulation coating and release of the mould, the anode 290 comprising a pair of anode half shells 111 is mounted in the hourglass shaped recess 110 and kept in place by straps 112 around the pair of anode half shells. Alternatives to fixing by means of straps are possible, such as gluing the anode half shells 111 to the Field Joint Coating 46, bolting the anode half shells to threaded holes in the Field Joint Coating 46 and other means. The pair of anode half shells 111 is shaped in a way that the outside diameter 113 of the anode sections does not protrude beyond the outside diameter 47 of the field joint insulation coating layer 45.

In the J-lay process, it would be acceptable that the Field Joint Coating has a slightly larger diameter than the main pipe coating. In the reel-lay process, however, it is preferred that the outer surface 74 of the line pipe insulation coating 34 and the outside diameter 47 of the field joint insulation coating 45 and the outside diameter 113 of the half shell anode sections all have the same outside diameter, such that the half shell anode sections 111 are flush with the field joint insulation coating 45 and the field joint insulation coating 45 is flush with the line pipe insulation coating 34.

The pair of anode half shells 111 is electrically connected with the steel pipe 30 by means of one or more electrical conductors 114. The electrical conductors 114 may be cast into the layer of field joint insulation coating 45 when it is injected in the mould, taking care that a long tail end protrudes into the hourglass shaped recess after the mould has been released. This tail end then is connected to the pair of anode half shells before the anode half shells are mounted on the pipeline 20.

As an alternative to casting the electrical conductor into the coating material, the electrical conductor 114 may be first connected to the pair of anode half shells 111. The other end is then connected to the steel pipe 30, either by making an opening through the field joint insulation coating 45 and field joint anti-corrosion coating 44, or an opening through the line pipe insulation coating 34 and the line pipe anti-corrosion coating 33, at a location adjacent to the anode 111; subsequently making an electrical connection between the electrical conductor 114 and the steel pipe 30; and finally reinstating the coating layers in the opening through coating layers 44 and 45 or 33 and 34.

As noted in relation to Figure 13, the field joint insulation layer may be built up in multiple layers. If that would be the case, the anode half shells 111 would be installed in an hourglass recess 110 formed by a protrusion in the mould used for injecting the last and most outer layer of the field joint insulation coating 45.

It will be clear that a pair of anode half shells 111 can also be applied to the main pipe coating 49. In that case, first an hourglass shaped space must be formed in the outer surface of the line pipe insulation coating, in a similar way as described in relation with Figure 22B. The resulting embodiment of the anode 290 and the electrical connection to the steel pipe 30 are similar to the embodiment described in relation with Figure 22B.

Figure 31 shows an alternative method of connecting the electrical conductor 114 to the steel pipe 30 in a field joint area 42. A doubler plate 116 is welded to the steel pipe 30 before the field joint anti-corrosion layer 44 is applied. Subsequently, the field joint anticorrosion layer 44 is applied, also covering the doubler plate 116 by an anti-corrosion coating layer 117. Before attaching the mould for injecting the field joint insulation coating material 78 in the Field Joint Coating area 46, a counter-mould 118 shaped in the form of a truncated cone is placed over the doubler plate and connected to the doubler plate. This connection can be by a bolt or otherwise.

The cone shaped counter mould keeps the outer surface 117 of the doubler plate free of field joint insulation material 78 when this is injected into the mould. After the field joint insulation coating layer 45 has solidified and the mould has been removed, the plug 118 can be taken away, whereupon an opening 119 gives access to the doubler plate 116 for making the electrical connection. The anti-corrosion coating layer 44 is removed from the outer surface 117 of the doubler plate and the electrical connection between the electrical conductor 114 and the double plate 116 is made. Finally, the anti-corrosion layer is reinstated over the doubler plate 116 and opening 119 filled with insulation coating material.

Figure 32 represents an eighth embodiment of the invention for application in a Field Joint Coating 46, which is a variant on the seventh embodiment. Instead of one long hourglass shaped recess 110 and one long pair of sacrificial anode sections 111, now several short hourglass shaped recesses are applied, indicated as 110a to 110c, in which an anode 290 comprising several short pairs of half shell sacrificial anode sections are mounted, indicated as 111a to 111c. Each pair of half shell anode sections 111a to 111c is individually strapped around the pipeline 20 by straps indicated as 112a to 112c.

Alternatives to connecting by straps are possible as described under Figure 30A.

Figure 32 also shows the preferred arrangement of electrical connections between the pairs of half shell sacrificial anodes 111a to 111c and the steel pipe 30. Preferably, the first and the last pairs of anode sections, indicated as 111a and 111c are connected to the steel pipe 30 by electrical conductors 114a and 114c and the individual anode sections mutually by short electrical conductors 115 between the anode sections 111 a to 111c. The short electrical conductors 115 may protrude outside the outer surface 52 of the Field Joint Coating. However, that would make them vulnerable to be damaged during the spooling or reeling process. It would be better to lay the short electrical conductors in grooves embedded in the outer surface 52 of the Field Joint Coating, such that they do not protrude outside the outer surface 52.

As an alternative, one of the electrical conductors 114a or 114c may be left out. As another alternative, each anode 111 a to 111c may be individually connected to the steel pipe 30 by a conductor 114a to 114c, leaving out the short electrical conductors 115.

It will be clear that short pairs of anode half shells 111 as shown in Figure 32 can also be applied to the main pipe coating 49. In that case, first one or multiple hourglass shaped spaces must be formed in the outer surface of the line pipe insulation coating, in a similar way as described in relation with Figure 29B. This hourglass shaped space can be either one single space in which then the multiple short pairs of anode half shells 111 are mounted and their electrical connection to the steel pipe 30 made, or multiple shorter hourglass shaped spaces, one for each pair of anode half shells. The resulting embodiment of the anode 290 and the electrical connection to the steel pipe 30 are similar to the embodiment described in relation with Figure 29B.

Figure 33 shows a ninth embodiment of the invention for application in a Field Joint Coating 46, which is another variant of the seventh embodiment as shown in Figure 30A. An hourglass shaped recess 110 is formed in the outer surface of the field joint insulation coating layer 45 with a protrusion 137 in the mould 60. In the hourglass shaped recess 110, a rope-shaped sacrificial anode 130 is wrapped around the field joint area 46. The diameter 131 of the anode is such that the anode 130 does not protrude beyond the outside diameter of the Field Joint Coating 47 and is preferably flush with the outside diameter of the Field Joint Coating 47.

In the J-lay process, the diameter of the Field Joint Coating may be slightly larger than the diameter of the main pipe coating. In the reel-lay process, the diameters of Field Joint Coating and main pipe coating are preferably the same, such that the main pipe coating, the Field Joint Coating and the anode are predominantly flush.

After the anode 130 has been wrapped around the field joint area 46 and fixed, the free end of the electrical conductor 114, which is cast into the field joint insulation coating layer 45, is connected to the rope-shaped anode 130 by means of an electrical connection 132.

Optionally, the rope-shaped anode 130 may be cast into a stabilization layer 133, in order to prevent the wrappings of the rope-shaped anode to be displaced when the field joint area 42 passes the rollers 16, the tensioning device 11 and the supporting device 12 when the pipeline 20 is spooled onto the reel 7, and passing the aligner 21, the straightener 25, the one or more tensioners 26 and the stinger 29 when the pipeline 20 is reeled off the reel 7 to the seabed 22. During the application of the stabilization layer 133, care is taken that no stabilization layer material is disposed on the outer surface of the rope-shaped anode 130, such that this area stays non-coated in order to make electrical contact with the seawater 32 after the pipeline 20 has been installed on the seabed.

It will be clear that the embodiment of Figure 33 can easily be adapted to an application in main pipe coating. In that case, the hourglass shaped recess is formed by cutting or milling it in the outer surface of the line pipe insulation coating or by melting the outer surface of the line pipe insulation coating and taking it away. Once the hourglass shaped recess has been formed, the application of the wrapped anode 130 as shown in Figure 33 is exactly the same for main pipe coating as for Field Joint Coating.

Figure 34 shows a tenth embodiment of the invention for application in a Field Joint Coating 46, which is a variant of the ninth embodiment as shown in Figure 33. Instead of wrapping the rope-shaped sacrificial anode 130 around an hourglass-shaped recess 110, the rope-shaped anode 130 is now mounted to the inside surface 61 of the mould 60.

Before engaging the mould, the electrical connection 132 is made between the anode and the electrical conductor 114. Then the mould is engaged and field joint insulation coating material 78 injected into the mould. The rope-shaped anode is cast into the field joint insulation coating layer 45. Care is taken when the rope-shaped anode is mounted into the mould 60, that no coating material can be deposited on the outer surface 134 of the ropeshaped anode 130, so that the anode 130 can later make proper electrical contact with the seawater 32 after the pipeline 20 has been installed on the seabed. For that purpose, the outside diameter 135 of the Field Joint Coating in the zone of the anode 136 may be retracted slightly with respect to the outside diameter 47 outside the zone of the anode.

Figure 35 shows an eleventh embodiment of the invention for application in a Field Joint Coating 46. A flexible permanent mould 120 is mounted over the field joint area 42 after the field joint anti-corrosion layer 44 has been applied. For mounting the mould, it is preferably built in the form of two cylindrical half shells which can be closed around the field joint area 46. The flexible permanent mould 120 has overlaps 121 with the line pipe insulation coating layer 34. The overlaps provide a fluid-tight barrier, either by permanent tightening seals or by steel straps tightened around the mould half shells in the area of the overlap, or by melting the flexible permanent mould to the line pipe insulation coating in the areas of the overlaps, or in another way.

The flexible permanent mould contains a sacrificial anode 122 with an outside diameter which does not protrude beyond the outer surface 123 of the flexible permanent mould. The sacrificial anode 122 is electrically connected with the steel pipe 30 by an electrical conductor 124. The electrical conductor 124 is connected to the steel pipe 30 before the flexible permanent mould is engaged and is cast into the field joint insulation coating layer 45 when the mould is injected. The mould contains an injection opening 125 for injecting field joint insulation coating material 78 into the mould.

The flexible permanent mould 120 is well capable of following the large strains in the Field Joint Coating when the pipe 20 is bent over the reel. In the manufacturing process of the mould a proper connection between the flexible permanent mould 120 and the sacrificial anode 122 can be constructed, capable of sustaining the large strains occurring during the bending of the pipeline 20 over the reel. The anode is connected to the FJC mould via connectors 300. The anode may be provided in a recess 302 in the outer side of the FJC mould.

After the solidification of the field joint insulation coating layer 45, the flexible permanent mould 120 stays in place and becomes a permanent part of the Field Joint

Coating 46. Accordingly, for the purpose of this document, the permanent mould 120 is considered to form part of the Field Joint Coating 46 and the coating 18.

As noted in relation to Figure 13, the field joint insulation layer may be built up in multiple layers. If that would be the case, the flexible permanent mould 120 containing the sacrificial anode 122 would be the mould of the last and most outer layer of the field joint insulation coating 45.

Figure 36 shows an twelfth embodiment of the invention for application in a Field Joint Coating 46, which is a variant of the eleventh embodiment. The chamfer 126 of the field joint insulation coating layer 45 is now provided with a recess 127 with the same depth 128 as the thickness of the flexible permanent mould 120 in the area of the overlap 121 and the same length as the overlap 121. The recess 127 ensures that the mould 120, the anode 122 and the field joint insulation coating layer 45 all have substantially the same outside diameter, which is an advantage when spooling the pipeline 20 onto the reel 7 and when reeling it off to the seabed, as described in relation to Figure 22.

The chamfer 126 may be a conical section. At the wide end of the sloping section 305 a resting section 306 is provided for an end of a permanent FJC mould. An upstanding ridge 307 is provided which delimits the resting section 306 and forms a transition to the outer surface 59 of the main pipe coating of the pipe unit 99. The upstanding ridge 307 is provided between the resting section and the outer surface 59 of the main pipe coating. The resting section is provided between the sloping section and the upstanding ridge. The upstanding ridge may be oriented at right angles to the pipe axis, but a different angle is also possible.

As the flexible permanent mould 120 eventually forms an integrated part of the Field Joint Coating assembly, the material of the flexible permanent mould shall preferably have similar heat insulation properties as the field joint insulation coating material 78.

Figure 37 shows an thirteenth embodiment of the invention for application in a Field Joint Coating 46, which is a variant to the twelfth embodiment. Instead of embedding the anode 122 in the flexible permanent mould 120, the anode 122 itself now is used as the mould 120. The anode is provided with an injection opening 125 for injecting field joint insulation coating material 78 into the mould 120 formed by the anode 122.

As the material of anode 122 has worse thermal insulation properties than the field joint insulation coating layer 45, the material of the field joint insulation coating layer 45 must have better insulation properties than the material of the line pipe insulation coating layer 34, in order to ensure that the Field Joint Coating area 42 has the same insulation properties as the main pipe coating outside the area 42.

Figure 38 shows a fourteenth embodiment of the invention for application in a Field Joint Coating 46, which is a variant to the thirteenth embodiment. The mould 120 formed by the anode 122 is now given an undulated shape 95 in order to give the anode more flexibility for better following the deformations of the Field Joint Coating 46 when the pipeline 20 is bent over a reel. As an alternative to the undulated shape, the anode 122 can be given another flexible shape such as a serrated shape 96 as shown in Figure 25 or a castellated shape 97 as shown in Figure 26 or another shape.

Figures 39A and 39 B show a fifteenth embodiment of the invention, for application either on main pipe coating 49 or on Field Joint Coating 46 or on both. Long strip shaped anodes 140 made out of anode metal (zinc or aluminium) are provided in longitudinal direction along the pipeline 20 or sections thereof. The strip shaped anodes are mounted on the outside diameter 142 of the insulation coating 141, which can be main pipe coating or Field Joint Coating. The strip shaped anodes are mounted on the insulation coating either by bolts engaging in threaded holes in the insulation coating 141 or by gluing or by straps tightened around the outside diameter 142 at regular distances along the pipeline 20.

Optionally, first longitudinal channels 143 are formed in longitudinal direction along the pipeline 20 or sections thereof, in which longitudinal channels the strip shaped anodes 140 can be embedded in order not to protrude beyond the outside diameter 142 of the insulation coating. In this case the recesses are elongate in an axial direction, and are in particular parallel with the main axis 320 of the pipeline or pipe unit.

Optionally, also circumferential channels (not drawn) can be formed at regular distances along the pipeline 20 or sections thereof in which circumferential channels the straps can be embedded in order not to protrude beyond the outside diameter 142 of the insulation coating.

The strip shaped anodes 140 are electrically connected to the steel pipe 30 by electrical conductors 144 at regular distances along the pipeline 20. The connection to the steel pipe 30 can be made in a field joint area, in a way as shown in Figure 31 or by an opening in the main pipe coating as for instance described in relation to Figure 5B.

Figure 40 shows a sixteenth embodiment of the invention, for application either on lined pipe coating or on Field Joint Coating or on both. Helically shaped anodes 150 made out of anode metal (zinc or aluminium) are provided along the pipeline 20 or sections thereof. The helically shaped anodes are mounted on the outside diameter 142 of the insulation coating 141, which can be main pipe coating or Field Joint Coating. The helically shaped anodes are mounted on the insulation coating either by bolts engaging in threaded holes in the insulation coating 141 or by gluing or by corrosion resistant steel straps tightened around the outside diameter 142 at regular distances along the pipeline 20.

Optionally, first helically shaped channels 153 are formed along the pipeline 20 or sections thereof, in which helically shaped channels the helically shaped anodes 150 can be embedded in order not to protrude beyond the outside diameter 142 of the insulation coating. Optionally, also circumferential channels (not drawn) can be formed at regular distances along the pipeline 20 or sections thereof in which circumferential channels the straps can be embedded in order not to protrude beyond the outside diameter 142 of the insulation coating.

The helically shaped anodes 150 are electrically connected to the steel pipe 30 by electrical conductors 154 at regular distances along the pipeline 20. The connection to the steel pipe 30 can be made in a field joint area, in a way as shown in Figure 31 or by an opening in the main pipe coating as for instance described in relation to Figure 5B.

The helically shaped anodes can be made very wide and thin. Ultimately, they can be made so wide that the wraps of the helix overlap each other, in this way entirely covering the outer surface of the pipeline 20 or sections thereof. Corrosion resistant steel straps may be provided around the overlapping anode wraps in order to keep the anode wraps in place.

Figure 41 shows a seventeenth embodiment of the invention. An aluminium spray layer 160 is sprayed directly on to the steel pipe 30 and over the toe 161 of the chamfers 126 in the field joint area 42. The aluminium spray layer acts both as the field joint anticorrosion coating and as the cathodic protection in case seawater would penetrate to the aluminium layer 160.

During the bending of pipeline 20 over a reel 7, the highest risk of crack forming occurs along the chamfers 126, which are the contact planes between the line pipe insulation coating layer 34 and the later installed field joint insulation coating layer 45. The cracks potentially form a path for water ingress through the insulation coating to the steel pipe 30. The penetrating seawater will first meet the barrier of the aluminium spray layer 160 blocking the way to the steel pipe 30. In case the seawater would succeed in penetrating the aluminium layer 160, making contact with the steel pipe 30, the aluminium layer will act as cathodic protection to the pipeline 20.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms "a" or "an", as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

It will be apparent to those skilled in the art that various modifications can be made to the device and method without departing from the scope as defined in the claims.

Claims

A method of joining an anode to a pipeline (20) or a pipe joint (99), wherein the pipeline or pipe joint comprises a steel pipe (30), the anode being applied as a layer (160) of metal that is more anodic than steel, the layer being applied to a Field Joint Area (42) prior to applying a heat insulating coating (45) to the Field Joint Area.

The method of claim 1, comprising spraying the layer (160).

Method according to claim 1 or 2, comprising applying the layer of the anodic metal directly on the steel pipe (30) and in particular on a toe (161) of chamfers (126) in the Field Joint Area (42).

The method of any one of claims 1-3, wherein no separate electrical conductor is buried between the anode and the steel pipe (30), because the layer (160) is in direct contact with the steel pipe (30).

The method of any one of claims 1-4, wherein the anodic metal is aluminum.

The method of any one of the preceding claims, wherein the anode is embedded in a Field Joint Coating (FJC) (46) during the making of the FJC.

A method according to any one of the preceding claims, wherein the anode on land is embedded in the pipe coating (18) of a pipe unit (99) configured to be connected to other pipe units in a end-to-end relationship by a pipe laying vessel to form a submarine pipeline.

The method of any one of claims 1-6, wherein the anode on land is embedded in the pipe coating (18) of a pipe unit (99) configured to be connected to other pipe units in an end-to-end relationship to a longer pipe unit wound on a spool.

A pipeline (10) or a pipe unit (99) adapted to be connected in an end-to-end relationship with other pipe units, the pipeline or pipe unit comprising: a. A steel pipe (30), b. a coaling (18) that covers the outside of the steel pipe, c. at least one anode in the form of a layer (160) of metal that is more anodic than steel, the layer being at least partially under a heat insulating coating (45) around the steel pipe.

The pipeline or pipe unit according to claim 9, comprising a plurality of Field Joint Coatings (FJC) (48), wherein the anodes (20) are embedded in the Field Joint Coatings.

A pipeline or pipe unit according to any of claims 9-10, wherein the layer is located under the thermal insulating coating (45) in a Field Joint Area.

A pipeline or pipe unit according to claim 11, comprising one or more FJCs, wherein the anodic metal layer is applied directly to the steel pipe (30).

A pipeline or pipe unit according to any of claims 9-12, wherein the layer is sprayed onto the steel pipe.

A pipeline or pipe unit according to claim 12 or 13, wherein the anodic metal layer extends over a toe (161) of chamfers (126) in the Field Joint Area (42).

The pipeline or pipe unit according to any of claims 9-14, wherein the anodic metal is aluminum.