WO2020128001A1

WO2020128001A1 - Flexible pipe for transporting a fluid in an underwater environment and associated method

Info

Publication number: WO2020128001A1
Application number: PCT/EP2019/086731
Authority: WO
Inventors: Frédéric DEMANZE
Original assignee: Technip France
Priority date: 2018-12-20
Filing date: 2019-12-20
Publication date: 2020-06-25
Also published as: FR3090793A1; FR3090793B1

Abstract

Flexible underwater pipe designed to transport fluids having a longitudinal axis (A) comprising an internal pressure sheath, an external sealing sheath (20), the pressure sheath and the external sealing sheath (20) defining an annular space of the flexible pipe, at least one tensile armour layer (18) being arranged in the annular space, characterised in that the external sealing sheath (20) has a thickness (E) of between 1/125 and 1/75 of the internal diameter of the external sealing sheath (20) and in that it also comprises a reinforcing strip (22) which comprises a woven material (24) comprising warp yarns (25) and weft yarns (26), the warp yarns (25) being wound in a helix at a short pitch relative to the longitudinal axis (A) of the pipe, and in that the reinforcing strip (22) is linked to the external sealing sheath (20).

Description

Flexible pipe for transporting a fluid in an underwater environment and associated method

The invention relates to the technical field of flexible pipes for the transport of a fluid. More particularly, the invention relates to unbound flexible pipes used for the transport of hydrocarbons in an underwater environment.

Flexible pipes for the transport of a fluid in an underwater environment are submerged within a body of water such as a lake, a sea, an ocean, at depths that can exceed 3000 m. They are particularly interested in the transportation of water, gas and / or hydrocarbons between a bottom installation and a surface installation. They can also be used to connect two downhole installations. Certain flexible pipes can also be used to connect two surface installations.

The structure of a flexible pipe is for example described in the normative documents API RP 17B “Recommended Practice for Flexible Pipe”, 5th edition, published in May 2014 and API 17J “Specification ofr Unbonded Flexible Pipe”, 4th edition, published in May 2014 by the American Petroleum Institute.

Typically, a flexible submarine pipe as described in the documents published by GARI comprises an internal sealing sheath also called pressure sheath in the technical field of the invention. The internal sealing sheath forms an internal passage for circulation of the fluid and thus ensures its transport in a sealed manner.

Significant tensile forces can be exerted on the flexible pipe, especially when it extends through deep bodies of water. Therefore, at least one layer of tensile armor is arranged around the internal sheath to take up these tensile forces. The at least one layer of tensile armor typically comprises metal wires wound in a helix in a long pitch, that is to say that the absolute value of the helix angle between the longitudinal direction of a metal wire and the longitudinal axis of the flexible pipe is less than 60 °, for example between 25 ° and 55 °.

In order to prevent any entry of water from the medium in which the flexible pipe is immersed inside the latter, the flexible pipe generally comprises a polymeric external protective sheath or external sealing sheath, arranged around the pair of tensile armor plies. The outer sheath generally has a thickness of 10 mm. The pressure sheath and the external sealing sheath define between them a volume called annular space. The at least one layer of tensile armor is arranged within the annular space.

The transported fluid is generally composed of crude hydrocarbons. These hydrocarbons can include corrosive acid gases such as carbon dioxide, methane or even hydrogen sulfide. The transported fluid also includes water and possibly sand particles.

The gases contained in the transported fluid diffuse through the pressure sheath and can accumulate within the annular space. The annular space may also include water in the liquid phase which may result from an accidental tearing of the external sealing sheath and / or the diffusion of the water vapor contained in the transported fluid having migrated through the pressure sheath and then having condensed in the annular space. The combined presence of liquid water and acid gases within the annular space is likely to cause corrosion phenomena of the metallic tack elements present in the annular space, in particular when these armor elements are made of steel. carbon. Carbon steel armor wires can, for example, undergo stress corrosion corrosion (“Stress Corrosion Cracking, SCC”).

To reduce the corrosion of armor wires, it is taught for example in the document API RP 17B mentioned above to increase the thickness of the outer sheath. This reduces the risk of tearing the outer sheath and thus reduces the probability of having water in the annular space and therefore inducing corrosion phenomena.

However, this solution is not entirely satisfactory. Indeed, although the risks of tearing of the external sheath are reduced, the water vapor contained in the transported fluid can diffuse through the internal sheath and risks condensing within the annular space, which can lead corrosion of the carbon steel armor wires in the case where the transported fluid also contains a significant content of acid gases, in particular carbon dioxide and / or hydrogen sulfide and / or methane. This corrosion problem can lead to the loss of integrity of the submarine flexible pipe.

Consequently, there is a need to provide a flexible pipe in which the metallic elements forming the at least one layer of tensile armor are preserved from corrosion as well as a method for manufacturing such a flexible pipe which is easy to install. and inexpensive. To this end, the invention provides a flexible underwater pipe intended for the transport of fluids having a longitudinal axis (A) comprising:

- an internal pressure sheath,

- an external sealing sheath, the pressure sheath and the external sealing sheath defining an annular space of the flexible pipe,

- at least one layer of tensile armor arranged in the annular space,

characterized in that the external sealing sheath has:

a thickness (E) of between 1/125 and 1/75 of the internal diameter of said external sealing sheath;

and in that it also includes:

a reinforcing strip comprising a woven material comprising warp threads and weft threads, said warp threads being wound in a helix with a short pitch relative to the longitudinal axis (A) of the pipe,

and in that the reinforcing strip is linked to the external sealing sheath.

The flexible pipe according to the invention has an external sealing sheath having a thickness of between 1/125 and 1/75 of the internal diameter of the external sealing sheath, which promotes the diffusion of gases such as carbon dioxide , hydrogen sulfide and / or methane included in the annular space, through the external sheath, towards the outside of the flexible pipe. The gas concentration within the annular space is thus reduced and the at least one layer of tensile armor is preserved from corrosion.

The thickness of the external sealing sheath having been markedly reduced compared to the practice of the prior art, the gases can diffuse much more easily through the external sealing sheath from the annular space towards the outside of flexible driving. The evacuation of corrosive acid gases to the outside of the pipe is therefore improved. In addition, the external sealing sheath is impermeable to liquids, and in particular to sea water, in order to prevent the at least one layer of armor from coming into contact with water, which would promote its corrosion.

Furthermore, during the manufacture of the flexible pipe, the latter is subjected to bending in particular during storage. In service, the pipe is also stressed in bending, in particular in the context of dynamic applications. Therefore, the outer layer must be sufficiently elastic to withstand the deformations during bending stresses of the flexible pipe. When the flexible pipe is bent, it is the outermost layer which undergoes the greatest deformations, which are deformations in tension on the upper surface and in compression on the lower surface. In the case of the external sealing sheath of a flexible pipe, the relative deformations can exceed 7%. The solution of the prior art consisted in producing a very thick external sealing sheath with a polymeric material capable of withstanding large deformations in tension and in compression. The large thickness of the sheath according to the prior art made it possible to avoid the formation of folds on the lower surface during bending of the pipe, by improving the buckling resistance of the sheath when it is stressed in axial compression. . However, it has been discovered that it is possible to significantly reduce the thickness of the external sheath while avoiding the risk of folds provided that the external sealing sheath is reinforced with a woven material bonded to the outer sealing sheath and having a particular orientation.

In addition, the outer layer must withstand the internal and external pressure forces.

Given such a thickness and the bending stresses that the flexible pipe is brought to undergo during its manufacture and during its use, it is necessary to mechanically reinforce the external sealing sheath. Indeed, the outer sheath must be able to resist the phenomenon of swelling of the at least one layer of tensile armor commonly known as the "bird cage" phenomenon. The outer sheath must also be capable of accommodating phenomena of surface deformation of folding caused by bending of the pipe.

Thus, according to the invention, the external sealing sheath is formed by a polymer matrix with a thickness between 1/125 and 1/75 of the internal diameter of the external sealing sheath, which is relatively thin compared to that which is recommended by the normative documents published by the American Petroleum Institute.

Also, the outer sheath comprises a reinforcing strip comprising a woven material. The woven material comprises a set of warp threads arranged in parallel and extending in a plane along the length of the woven fabric, as well as a set of weft threads arranged transversely to the length of the woven fabric, the weft threads intersecting with warp threads. Warp threads provide mechanical resistance in the long direction of the woven material, while warp threads weft ensure the connection and structural support of the woven material and provide flexibility to the latter in the transverse direction.

For the purposes of the present invention, the term “yarn” means the joining together of a set of continuous fibers assembled in particular by twisting or spinning.

The woven material of the reinforcing strip is wound in a short pitch helix around the at least one ply of tensile armor, then the external sealing sheath is then hot extruded onto the woven material so that the polymeric material melt penetrates and diffuses through the warp and weft threads of the woven material. The woven material is then at least partially impregnated with the polymeric material which makes it possible to mechanically anchor, together, the reinforcing strip and the external sealing sheath.

The fact that the warp threads of the woven material are wound at a short pitch plays an important role in preventing wrinkling when the pipe is bent. Indeed because of this particular orientation, the warp son prevent the swelling of the outer sheath and on the contrary have the effect of keeping the latter in contact with the underlying layer, which prevents the formation of folds.

Thus, the polymer matrix gives the elasticity required for the external sealing sheath and the woven material of the reinforcing strip provides mechanical resistance to the radial forces linked to the internal and external pressure as well as to the bending forces undergone by the conduct.

Preferably, the thickness of the external sealing sheath is between 3 mm and 5 mm for an internal diameter of the external sealing sheath between 250 mm and 600 mm.

Advantageously, the spacing between two warp threads of the woven material is greater than or equal to 3 mm. Such spacing between the warp threads of the woven material allows better penetration and diffusion of the molten polymeric material to form the reinforced outer sheath.

Advantageously, the spacing between two weft threads of the woven material is greater than or equal to 5 mm and in that the thickness of a weft thread is at most equal to 3 mm. Such a spacing between weft threads of the woven material makes it possible to further improve the impregnation of the molten polymeric material in the woven material.

Preferably, the woven material comprises a fusible polymeric material. The fusible polymer material makes it possible to improve the mechanical anchoring between the woven material of the reinforcing strip and the external sealing sheath. According to a preferred embodiment of the invention, at least one weft thread and / or at least one warp thread of the woven material is made of fusible polymer material, advantageously the at least one weft thread is of fusible polymer. Advantageously, at least one weft thread of the woven material is made of a fusible polymeric material. Thus, this improves the mechanical anchoring of the woven material with the external sealing sheath without the mechanical resistance of the woven material in the long direction being deteriorated.

According to an alternative of the preferred embodiment of the invention, the reinforcing strip comprises a support layer of fusible polymer material with a thickness at most equal to 1 mm, the support layer being arranged on at least one of the faces of the woven material. The support layer of fusible polymer material improves the mechanical anchoring between the woven material of the reinforcing strip and the external sealing sheath. Preferably, the support layer is arranged on the internal face of the woven material. Thus, the woven material is sandwiched between the support layer and the external sealing sheath, once the latter is extruded, which has the effect of improving the mechanical anchoring.

Preferably, the fusible polymer material is identical to the polymer material of the outer sealing sheath. To obtain good mechanical anchoring between the woven material of the reinforcing strip and the outer sheath, a fusible polymer material belonging to the same family of polymers as the polymer material selected to produce the outer sealing sheath is selected. Advantageously, the fusible polymeric material and the polymeric material of the external sealing sheath are identical, further improving the mechanical anchoring.

The invention also relates to a method for manufacturing a flexible pipe having a longitudinal axis (A), comprising in order the following steps:

- extrusion of an internal pressure sheath;

- winding of at least one layer of tensile armor around the pressure sheath;

- helical winding at short pitch with respect to the longitudinal axis (A) of a reinforcing strip, the reinforcing strip comprising a woven material, the woven material comprising warp threads and weft threads, the chain being wound in short pitch with respect to the longitudinal axis (A);

hot extrusion around the reinforcing strip of an external sealing sheath of polymer material of thickness (E) between 1/125 and 1/75 of the internal diameter of said external sealing sheath so that 'once the outer sealing sheath is cooled, the reinforcing strip is linked to the outer sealing sheath.

The short-pitch winding of the warp threads of the woven material makes it possible on the one hand to avoid swelling of the at least one layer of tensile armor and on the other hand to keep the said armor elements flat and in place of the at least one layer of tensile armor. Indeed, the warp threads provide mechanical resistance in the longitudinal direction of the woven material. The woven material being wound up at short pitch, the warp threads thus make it possible to take up the radial forces undergone by the pipe.

During the extrusion step of the external sealing sheath, the polymeric material in the molten state penetrates and diffuses between the warp and weft threads of the woven material of the reinforcing strip. Once cooled, the polymeric material at least partially permeates the woven material, thereby making it possible to mechanically anchor, together, the reinforcing strip and the external sealing sheath. The external sealing sheath is therefore linked to the reinforcing strip to create an external reinforced sealing strip.

The process according to the invention can include the following characteristics:

- the thickness of the external sealing sheath is between 3 mm and 5 mm for an internal diameter of the external sealing sheath between 250 mm and 600 mm.

- the spacing between two warp threads of the woven material is greater than or equal to 3 mm.

- the spacing between two weft threads of the woven material is greater than or equal to 5 mm and in that the thickness of a weft thread is at most equal to 3 mm.

- the woven material comprises a fusible polymer material.

- At least one weft thread and / or at least one warp thread of the woven material is made of fusible polymer material, advantageously the at least one weft thread is of fusible polymer.

the reinforcing strip comprises a support layer of fusible polymer material with a thickness of at most 1 mm, the support layer being arranged on at least one of the faces of the woven material.

According to a preferred embodiment of the method according to the invention, the method further comprises, before the step of winding the reinforcing strip, the helical winding with a short pitch relative to the longitudinal axis (A) a support ring made of fusible polymer material whose diameter is between 1 mm and 3 mm, the support rod forming a bearing surface for the woven material of the reinforcing strip.

The support rod is rolled up in a short pitch to provide a stable support surface for the reinforcement strip.

Advantageously, the support rod makes it possible to raise the reinforcing strip to prevent it from being directly supported on the at least one layer of tensile armor. Thus, the impregnation of the woven material by the molten polymer material during the extrusion of the external sealing sheath is facilitated.

The support ring is made of a fusible polymer material in order to improve the mechanical anchoring between the woven material of the reinforcing strip and the external sealing sheath.

Preferably, the fusible polymer material is identical to the polymer material of the outer sealing sheath. To obtain good mechanical anchoring between the woven material of the reinforcing strip and the external sealing sheath, a fusible polymer material belonging to the same family of polymers as the polymer material selected to produce the external sealing sheath is selected. Advantageously, the fusible polymeric material and the polymeric material of the external sealing sheath are identical, further improving the mechanical anchoring.

Other features and advantages of the invention will emerge on reading the description given below of particular embodiments of the invention, given by way of non-limiting indication, with reference to the accompanying drawings in which:

[Fig. 1] is a partially cutaway perspective view of a section of a flexible pipe according to the invention,

[Fig. 2] schematically represents a view in longitudinal section of the flexible pipe illustrated in FIG. 1,

[Fig. 3a] and [Fig. 3b] schematically represent a perspective view of exemplary embodiments of a reinforcing strip according to the invention,

[Fig. 4a], [Fig. 4b] and [Fig. 4c] schematically represent a view in longitudinal section of an embodiment of an external sealing sheath according to the invention.

[Fig. 5a], [Fig. 5b], [Fig. 5c], and [Fig. 5d] schematically represent a view in longitudinal section of a preferred embodiment of an external sealing sheath according to the invention.

In what follows and unless otherwise stated, the terms "exterior" or "exterior" and "interior" or "internal" are generally understood to mean radial with respect to the longitudinal axis of the submarine flexible pipe, the term “exterior” or “external” being understood as being relatively more radially distant from the longitudinal axis and the term “interior” or “internal” is understood as relatively closer radially to the longitudinal axis of the flexible submarine pipe.

In Figure 1 is illustrated an example of a flexible underwater pipe 10 according to the invention.

The flexible pipe 10 is intended to be immersed in a body of water. The body of water can be a lake, sea or ocean. Generally, the depth of the body of water is at least 50 m, and more particularly between 500 m and 4000 m.

The flexible pipe 10 routes a fluid through the body of water between a first installation and a second installation. The first installation is for example an underwater installation such as a well head or a collector (called "manifold" in English). The second installation is, for example, a surface installation such as a floating production, storage and unloading unit (FPSO for “Floating Production Storage and Offloading” in English) or a taut anchoring platform (TLP for “Tension Leg Plaftorm "in English). The flexible pipe 10 ensures the transport of the fluid between two surface installations or between an underwater installation and a surface installation or between two underwater installations.

The fluid transported by the flexible pipe 10 is for example water and / or an oil and / or gas fluid. The petroleum and / or gas fluid is formed from a multiphase mixture comprising a liquid part formed mainly of linear and / or cyclic, saturated and / or unsaturated carbon compounds, of variable density and of water, a gaseous part composed for example of methane (CH4), carbon dioxide (C02), hydrogen sulfide (H2S) and other gases and finally, a solid part generally composed of sand particles. The temperature of the fluid within the flexible pipe 10 is typically between 50 ° C and 200 ° C, more particularly between 50 ° C and 130 ° C. The temperature of the fluid varies during transport between the first installation and the second installation, the temperature variation is all the greater the greater the length of the flexible pipe 10.

As shown by way of example in FIG. 1, the flexible pipe 10 comprises a plurality of concentric layers arranged around a longitudinal central axis A. According to the invention, the flexible pipe 10 comprises a sheath of pressure 14, at least one layer of tensile armor 18 and an external sealing sheath 20.

The flexible pipe 10 is preferably a flexible pipe of the unbound type. By unbound, it is understood in the sense of the present invention a flexible pipe 10 in which the at least one layer of tensile armor 18 is free to move relative to the pressure sheath 14 during bending of the flexible pipe 10. Preferably all the layers of flexible pipe 10 are free to move relative to one another. This makes the pipe 10 more flexible than a pipe in which the layers are linked to each other.

The flexible pipe 10 advantageously comprises a pressure vault 16 arranged around the pressure sheath 14. The pressure vault 16 is arranged between the at least one layer of tensile armor 18 and the pressure sheath 14.

Preferably, the flexible pipe 10 also includes an internal carcass 12 arranged inside the pressure sheath 14.

The internal carcass 12 reinforces the flexible pipe 10 against the forces of external pressure. It limits the risk of collapse of the flexible pipe 10 when the pressure outside the flexible pipe 10 is greater than the pressure inside the flexible pipe 10.

The internal carcass 12 comprises at least one profiled metal strip, wound in a spiral. The at least one metal strip is wound in a helix in a short pitch thus forming a succession of turns. The expression “wound in short pitch” indicates that the absolute value of the helix angle formed by the metal wire with the longitudinal axis A of the flexible pipe 10 is close to 90 °, and is typically between 60 ° and 90 °.

The section of the profiled metal strip has for example an S-shaped geometry. To reinforce the resistance of the carcass to external pressure forces, the turns of the metal strip are stapled to each other.

The material of the metal strip is typically carbon steel, preferably stainless steel.

When the internal carcass 12 is present, the flexible pipe 10 is said to have a non-smooth passage (“rough bore” in English). When the flexible pipe 10 does not have an internal carcass 12, it is said to have a smooth passage (“smooth bore” in English). The pressure sheath 14 is extruded on the internal carcass 12 when the latter is present. The pressure sheath 14 forms a fluid circulation passage. It ensures the transport of the fluid through the body of water in a sealed manner.

The pressure sheath 14 is advantageously formed from a thermoplastic polymeric material, for example based on a polyolefin such as polyethylene or polypropylene, based on a polyamide such as PA1 1 or PA12, or based a fluoropolymer such as polyvinylidene fluoride (PVDF).

Alternatively, the pressure sheath 14 is formed on the basis of a high performance polymer such as a polyaryletherketone (PAEK) such as polyetherketone (PEK), polyetheretherketone (PEEK), polyetheretherketone ketone (PEEKK), polyetherketoneketone (PEKK) ) or polyetherketoneetherketoneketone (PEKEKK), polyamideimide (PAI), polyetherimide (PEI), polysulfone (PSU), polyphenylsulfone (PPSU), polyethersulfone (PES), polyarylsulfone (PAS), polyphenylene (PPE), phenylene polysulfide (PPS) liquid crystal polymers (LCP), polyphthalamide (PPA), fluorinated derivatives such as polytetrafluoroethylene (PTFE), perfluoropolyether (PFPE), perfluoroalkoxy (PFA) or l ethylene chlorotrifloroethylene (ECTFE) and / or mixtures thereof.

The polymer material is chosen according to the nature and the temperature of the fluid transported.

The thickness of the pressure sheath 14 is for example between 5 mm and 20 mm.

The pressure vault 16 strengthens the resistance of the flexible pipe 10 against the internal pressure.

The pressure vault 16 limits the risks of the flexible pipe 10 bursting, in particular when the pressure inside the flexible pipe 10 is greater than the external pressure.

In the example shown, the pressure vault 16 is located between the pressure sheath 14 and the at least one layer of tensile armor 18.

The pressure vault 16 is advantageously formed of a metallic profiled wire wound helically around the pressure sheath 14. The profiled wire preferably has a geometry in the form of Z, T, U, K, X or I.

The pressure vault 16 is wound in a short pitch helix around the pressure sheath 14.

The material of the metallic profiled wire is, for example, carbon steel. The at least one layer of tensile armor 18 is intended to reinforce the flexible pipe 10 against the longitudinal tensile forces.

The at least one layer of tensile armor 18 is located outside the pressure sheath 14, around the pressure vault 16.

The at least one layer of tensile armor 18 typically comprises a sheet of internal tensile armor 18a and a sheet of external tensile armor 18b. Each tensile armor ply 18a, 18b comprises a plurality of tensile armor elements wound in a long pitch. The expression “coiled in long pitch” indicates that the absolute value of the helix angle formed by the plurality of armor elements with the longitudinal axis A of the flexible pipe 10 is less than or equal to 60 °, and is typically between 25 ° and 55 °.

The section of the tensile armor elements is for example rectangular or circular.

The tensile armor elements are for example formed by metallic wires, the metallic material is for example carbon steel.

When the flexible pipe 10 is intended for applications in a particularly corrosive environment, the metallic material forming the armor elements of the armor plies 18a, 18b is chosen from stainless steels such as duplex steels.

The tensile armor elements of the internal tensile armor ply 18a are wound with a helix angle opposite to the helix angle of the tensile armor elements of the external tensile armor ply 18b . The tensile armor elements belonging to the same tensile armor ply 18a, 18b are substantially contiguous.

The external sealing sheath 20 is arranged around the at least one layer of tensile armor 18. The external sealing sheath 20 is impermeable to liquids and forms a protective barrier against the ingress of water from the outside. from the flexible pipe 10, in particular from the body of water to the annular space.

The external sealing sheath 20 is advantageously formed from a thermoplastic polymeric material, for example based on a polyolefin such as polyethylene or polypropylene, based on a polyamide such as PA1 1 or PA12, or based on a fluorinated polymer such as polyvinylidene fluoride (PVDF).

As a variant, the outer sheath is formed based on a high performance polymer such as a polyaryletherketone (PAEK) such as polyetherketone (PEK), polyetheretherketone (PEEK), polyetheretherketoneketone (PEEKK), polyetherketoneketone (PEKK) or polyetherketoneetherketoneketone (PEKEKK), polyamide-imide (PAI), polyether-imide (PEI), polysulf (poly) ), polyethersulfone (PES), polyarylsulfone (PAS), polyphenylene ether (PPE), phenylene polysulfide (PPS) liquid crystal polymers (LCP), polyphthalamide (PPA), fluorinated derivatives such as polytetrafluoroethylene ( PTFE), perfluoropolyether (PFPE), perfluoroalkoxy (PFA) or ethylene chlorotrifloroethylene (ECTFE) and / or mixtures thereof.

The external sealing sheath 20 and the pressure sheath 14 define between them a volume called the annular space. The annular space comprises, according to the example shown in FIG. 1, the pressure vault 16 and the at least one layer of tensile armor 18.

Acid gases such as carbon dioxide and / or methane and / or hydrogen sulfide and water vapor contained in the fluid diffuse through the pressure sheath 14 and risk accumulating within the annular space. These compounds can cause corrosion of the armor element wires of the at least one layer of tensile armor 18 and of the profiled metal wires of the pressure vault 16, in particular when the annular space contains both a high concentration. into acid gases and water in the liquid state, for example condensed water vapor.

To reduce the concentration of acid gas within the annular space, the external sealing sheath 20 has a very thin thickness, as shown in FIG. 2.

The external sealing sheath 20 is arranged outside the at least one layer of tensile armor 18.

The external sealing sheath 20 has a thickness E of between 1/125 and 1/75 of the internal diameter D of the external sealing sheath 20. In FIG. 2, the internal radius D / 2 of the internal sheath is shown with reference to the longitudinal axis A of the flexible pipe.

The internal diameter D of the external sealing sheath 20 is advantageously between 150 mm and 600 mm.

Preferably, the thickness E of the external sealing sheath 20 is between 3 mm and 5 mm for an internal diameter D of the external sealing sheath 20 between 250 mm and 600 mm According to the invention, the thickness E of the external sealing sheath 20 and the internal diameter D of the external sealing sheath 20 are measured in the same units, in millimeters.

Such a thickness promotes the diffusion of gases, in particular carbon dioxide and / or methane and / or hydrogen sulfide through the external sealing sheath 20 and therefore reduces the concentration of these gases within the annular space. Corrosion of the metallic elements of the at least one layer of tensile armor 18 and of the pressure vault 16 is thus reduced.

As illustrated in FIG. 2, the external sealing sheath 20 is arranged externally to the at least one layer of tensile armor 18.

The external sealing sheath 20 has a total thickness E.

The external sealing sheath 20 of the flexible pipe 10 further comprises a reinforcing strip 22 of thickness E1, less than the total thickness E. The external sealing sheath 20 is advantageously mechanically reinforced over a thickness E1 advantageously included between 0.1 mm and 2 mm and preferably between 0.4mm and 2mm.

The reinforcing strip 22 has a length L advantageously between 10 m and 5000 m.

The reinforcing strip 22 has a width L ′ advantageously between 30 mm and 200 mm, preferably between 50mm and 150mm.

The thickness of the strip (22) is between 0.1 mm and 2 mm.

The external sealing sheath 20 and the reinforcing strip 22 are linked together by mechanical anchoring. The manner of mechanically anchoring the reinforcing strip 22 with the external sealing sheath 20 will be explained below, in the passage of the description relating to the method of manufacturing the flexible pipe according to the invention.

The reinforcing strip 22 comprises a woven material 24 visible in FIGS. 2, 3a and 3b.

The woven material 24 is produced from an assembly of a plurality of warp threads 25 with a plurality of weft threads 26. The warp threads 25 are arranged in parallel and they extend in a plane in the longitudinal direction of woven material 24. The weft threads 26 are arranged transversely to the longitudinal direction of the woven material 24, the weft threads 26 intersect with the warp threads 25.

The warp threads 25 provide the mechanical resistance in the long direction of the woven material 24, while the weft threads 26 ensure the connection and the maintenance structural of the woven material 24 and provide flexibility to the latter in the transverse direction.

The reinforcing strip 22 is wound in a short pitch helix, forming a succession of turns around the at least one ply of tensile armor 18. In this way, the warp threads 25 of the woven material 24 forming the reinforcing strip 22 are also wound in a short pitch helix. This prevents swelling of the outer sealing sheath 20 and prevents the formation of folds when the flexible pipe is bent. This also makes it possible to limit the swelling of the at least one layer of tensile armor and to keep plated and in place said tensile armor.

To improve the resistance to internal pressure, the reinforcing strip 22 and therefore, the woven material 24, is wound with an absolute helix angle between 60 ° and 90 ° relative to the longitudinal axis A of the flexible pipe 10.

The turns of the reinforcing strip 22 are wound edge to edge without overlap.

Alternatively, the reinforcing strip 22 is helically wound, voluntarily leaving a clearance between the turns. The play between each turn is for example between 1 mm and 2 mm.

The external sealing sheath 20 also has a thickness E2, less than the total thickness E and advantageously greater than the thickness E1, which is not mechanically reinforced. The unreinforced zone of thickness E2 provides the elasticity necessary for the external sealing sheath to accommodate the bending forces. Advantageously, the reinforced zone of thickness E1 is situated on the internal side of the external sealing sheath, 20, while the unreinforced zone of thickness E2 is situated on the external side.

FIG. 3a illustrates a first example of a reinforcing strip 22 according to the present invention. The reinforcing strip 22 comprises a woven material 24 comprising warp threads 25 and weft threads 26.

The warp threads 25 and the weft threads 26 are obtained by bringing together a set of continuous fibers assembled in particular by twisting or spinning.

The warp threads 25 are arranged in the longitudinal direction of the woven material.

The continuous fibers forming the warp threads 25 are selected from the fibers having a tensile elastic modulus greater than 10 GPa, advantageously greater than 30 GPa and preferably between 50 GPa and 150 GPa.

The weft threads 26 are arranged in the transverse direction of the woven material. The weft threads 26 intersect with the warp threads 25 to form the structure of the woven material 24.

The continuous fibers forming the weft threads 26 are selected from the fibers having an elongation at the threshold greater than 5%, more advantageously greater than 7% and preferably greater than 10%. The elongation at the threshold is the maximum elongation in the elastic range of deformation.

The continuous fibers used to form the warp threads 25 and the weft threads 26 are selected from the family of organic fibers, mineral fibers or metallic fibers.

The organic fibers are for example aramid fibers such as Kevlar® or polyethylene terephthalate or high molecular weight polyethylene fibers.

The mineral fibers are, for example, carbon, basalt or glass fibers.

The metallic fibers are for example formed from boron, alumina or any other metallic material suitable for the present invention.

The spacing between two warp threads 25 of the woven material 24 is advantageously greater than or equal to 3 mm, preferably greater than 5 mm.

The spacing between two weft threads 26 of the woven material 24 is advantageously greater than or equal to 5 mm.

The thickness of a weft thread 26 is at most equal to 3 mm.

According to a second example of a reinforcing strip 22 according to the invention (not shown), the reinforcing strip 22 differs from the previous one in that the woven material 24 comprises a fusible polymeric material.

The meltable polymeric material is typically a thermoplastic polymeric material. Preferably, the fusible polymer material is selected from a polymer cited above and from the same family as that used to produce the pressure sheath 14 and / or the external sealing sheath 20. Advantageously, the fusible polymer material selected is exactly identical to the polymer material used to make the external sealing sheath 20.

In this second example, at least one warp thread 25 and / or at least one weft thread 26 of the woven material 24 of the reinforcing strip 22 is produced from a fusible polymeric material. Advantageously, it is preferable that it be the at least one weft thread 26 which is made of a fusible polymer material. Thus, the mechanical properties of the reinforcing strip 22 in the longitudinal direction are preserved since they are provided by the warp threads 25.

A third embodiment of a reinforcing strip 22 is illustrated in FIG. 3b. In this example, the reinforcing strip 22 comprises an additional support layer 30.

The support layer 30 is placed and glued on at least one of the faces of the woven material 24, typically at the level of the internal face of the woven material 24.

The support layer 30 has a thickness at most equal to 1 mm.

The support layer 30 is advantageously made from a fusible polymeric material such as a thermoplastic polymeric material of the type of those mentioned above for producing the pressure sheath 14 or the external sealing sheath 20 .

In a fourth embodiment of a reinforcing strip 22 (not shown), the woven material 24 comprises both at least one weft thread 26 and / or at least one warp thread 25 made of a fusible polymer material and , a support layer 30 also made of a fusible polymer material.

The use of a fusible polymer material in the reinforcing strip 22 makes it possible to improve the mechanical anchoring between the reinforcing strip 22 and the external sealing sheath 20 when it is extruded on said strip 22. The connection between the reinforcing strip 22 and the external sealing sheath 20 is improved when the fusible polymer material used is identical to the polymer material used to extrude the external sealing sheath 20.

The flexible pipe 10 can comprise additional layers such as anti-wear strips arranged between the pressure vault 16 and the at least one layer of tensile armor 18, or between the sheet of internal tensile tack 18a and the sheet of external traction armor 18b. The anti-wear strips limit the wear of the pressure vault and of the at least one layer of tensile armor 18 under the effect of friction.

The flexible pipe 10 can comprise a pair of plies of additional tensile armor when the tensile forces are particularly high.

Advantageously, the flexible pipe 10 comprises thermal insulation strips. For example, thermal insulation strips are wound in a short pitch between the external sealing sheath 20 and the tensile armor ply external 18b. The thermal insulation strips are for example formed from a polymeric polypropylene matrix.

The method of manufacturing the flexible pipe 10 will now be described with reference to Figures 4a to 4c and Figures 5a to 5d.

Initially, the pressure sheath 14 is extruded on a mandrel or, if it is present, directly on the metal carcass 12.

Optionally, the pressure vault is then wound in a short pitch around the pressure sheath 16. The expression “wound in short pitch” indicates that the absolute value of the helix angle is close to 90 °, and is typically between 75 ° and 90 °.

A first embodiment of the flexible pipe 10 is illustrated in FIGS. 4a to 4c.

As illustrated in FIG. 4a, at least one layer of tensile armor 18 is wound around the pressure vault 16 in a long pitch. The expression "wound in long pitch" indicates that the absolute value of the angle helix is less than or equal to 60 °, and is typically between 25 ° and 55 °.

Next, as can be seen in FIG. 4b, a reinforcing strip 20 comprising a woven material 24 which comprises warp threads 25 and threads is wound at short pitch relative to the longitudinal axis A of the flexible pipe 10. weft 26. The warp threads 25 being arranged in the longitudinal direction of the woven material 24, they are also wound at short pitch relative to the longitudinal axis A.

Finally, as illustrated in FIG. 4c, a thermoplastic polymeric material is hot extruded in the molten state on the reinforcing strip 22, typically at the melting point of the thermoplastic polymeric material, on the one hand for forming the external sealing sheath 20 and, on the other hand, for binding the reinforcing strip 22 and the external sealing sheath 20 together.

In the molten state, the polymeric material is very little viscous and it can penetrate and diffuse through the spaces between the warp threads 25 and the weft threads 26 of the woven material to impregnate it at least partially.

During the cooling of the polymeric material of the external sealing sheath 20, a phenomenon of shrinking of the material occurs, so that the external sealing sheath 20 tends to compress radially and come to press against the au minus a layer of tensile armor 18.

At the same time, the polymeric material having penetrated into the woven material 24 solidifies and traps the latter. Mechanical anchoring occurs natural between the reinforcing strip 22 and the external sealing sheath 20. The reinforcing strip 22 is thus linked to the external sealing sheath.

The external sealing sheath 20 thus formed has a reinforced thickness E1, less than the total thickness E.

The total thickness E is between 1/125 and 1/75 of the internal diameter of the external sealing sheath.

Advantageously, the external sealing sheath formed has a thickness E of between 3 mm and 5 mm for an internal diameter of the external sealing sheath 20 of between 250 mm and 600 mm.

Advantageously, the spacing between two warp threads (25) of the woven material (24) is greater than or equal to 3 mm.

Advantageously, the spacing between two weft threads (26) of the woven material (25) is greater than or equal to 5 mm and in that the thickness of a weft thread (26) is at most equal to 3 mm.

According to an alternative (not shown), the woven material 24 of the reinforcing strip 22 comprises a fusible polymeric material. Advantageously, at least one weft thread (26) and / or at least one warp thread (25) of the woven material (24) is made of fusible polymeric material, advantageously the at least one weft thread (26) is made of polymer fuse. Preferably, it is the at least one weft thread 26 which is made from a fusible polymeric material.

According to another alternative (not shown), the woven material 24 of the reinforcing strip 22 comprises a support layer 30 an additional support layer 30.

The support layer 30 has a thickness at most equal to 1 mm.

The support layer 30 is advantageously made from a fusible polymeric material such as a thermoplastic polymeric material of the type of those selected for producing the pressure sheath 14 or the external sealing sheath 20.

A second embodiment of a flexible pipe 10 according to the present invention which is the preferred mode, will now be described, FIGS. 5a to 5d supported.

As illustrated in FIG. 5a, at least one layer of tensile armor 18 is wound around the pressure vault 16 in a long step. The expression “wound long pitch "indicates that the absolute value of the helix angle is less than or equal to 60 °, and is typically between 25 ° and 55 °.

According to the preferred embodiment, before the step of winding the reinforcing strip 22, there is wound in a helix at a short pitch, in particular around the at least one layer of tensile armor 18, a support ring 40 , as seen in Figure 5b.

The support ring 40 has a diameter between 1 mm and 3 mm.

The support ring 40 makes it possible to form a support surface for the woven material 24 of the reinforcing strip 22 when it is subsequently wound in a short pitch on the ring 40.

Preferably, the support ring 40 is made from a fusible polymeric material such as a thermoplastic polymeric material.

Then, as can be seen in FIG. 5c, there is wound at short pitch relative to the longitudinal axis A of the flexible pipe 10, a reinforcing strip 20 comprising a woven material 24 which comprises warp threads 25 and threads weft 26. The warp threads 25 being arranged in the longitudinal direction of the woven material 24, they are also wound at short pitch relative to the longitudinal axis A.

Finally, the external sealing sheath 20 is hot extruded on the reinforcing strip 22 resting on the support ring 40, as illustrated in FIG. 5d.

During the extrusion step of the external sealing sheath 20, the polymeric material is in the molten state and has a generally low viscosity, so that it is able to penetrate and diffuse through the spaces between the warp threads 25 and the weft threads 26 of the woven material to at least partially impregnate it.

When the polymeric material of the external sealing sheath 20 cools, a phenomenon of shrinking of the material occurs, so that the external sealing sheath 20 tends to compress radially and to press against the at least a layer of tensile armor 18.

At the same time, the polymeric material having penetrated into the woven material 24 solidifies and traps the latter. A natural mechanical anchoring takes place between the reinforcing strip 22 and the external sealing sheath 20. The reinforcing strip 22 is thus linked to the external sealing sheath.

When the thermoplastic polymeric material is extruded on the reinforcing strip 22, the heat of the material is such that, when the material in the molten state comes into contact with the support ring 40 of fusible polymeric material, this last bottom and mixes with the thermoplastic polymeric material of the external sealing sheath 20.

The fact of using a fusible polymeric material in the woven material 24, replacing at least one warp thread 25 and / or at least one weft thread 26, or for producing a support layer 30 bonded to the at least one of the faces of the woven material 24, or even to produce a support rod 40, makes it possible to improve the mechanical anchoring of the connection between the reinforcing strip 22 and the external sealing sheath 20.

The mechanical anchoring is improved when the fusible polymeric material is chosen from the same families of thermoplastic polymeric material used to form the external sealing sheath 20. Advantageously, the mechanical anchoring between the reinforcing strip 22 and the sheath is further improved external sealing 20 by selecting a fusible polymer material identical exactly to the thermoplastic polymer material selected to produce the external sealing sheath 20.

Of course, it is not incompatible to provide in the steps of the method of manufacturing the flexible pipe 10 according to the invention, a step of winding a support rod 40 before the step of winding a reinforcing strip 22 comprising a woven material 24 comprising a fusible polymeric material, the fusible material possibly being either at least one weft thread 26, or a support layer 30 or else a combination of at least one weft thread 26 and a support layer 30.

According to a third embodiment of a flexible pipe according to the invention (not shown), the reinforcing strip is wound, not before the step of hot extrusion of the external sealing sheath, but after the extrusion step.

Advantageously, the reinforcing strip is wound in a short pitch around an external sealing sheath whose polymeric material is still hot.

Preferably, the reinforcing strip is wound just after the end of the extruder head, at the extrusion outlet of the external sealing sheath.

Claims

1. Flexible submarine pipe (10) intended for the transport of fluids having a longitudinal axis (A) comprising:

- an internal pressure sheath (14),

- an external sealing sheath (20), the pressure sheath (14) and the external sealing sheath (20) defining an annular space of the flexible conduit (10),

- at least one layer of tensile armor (18) arranged in the annular space, characterized in that the external sealing sheath (20) has:

a thickness (E) of between 1/125 and 1/75 of the internal diameter of said external sealing sheath (20);

and in that it also includes:

a reinforcing strip (22) comprising a woven material (24) comprising warp threads (25) and weft threads (26), said warp threads (25) being wound in a helix with a short pitch relative to the longitudinal axis (A) of the pipe,

and in that the reinforcing strip (22) is linked to the external sealing sheath (20).

2. Flexible pipe according to claim 1, characterized in that the thickness of the external sealing sheath (20) is between 3 mm and 5 mm for an internal diameter of the external sealing sheath (20) between 250 mm and 600 mm.

3. Flexible pipe according to claim 1 or 2, characterized in that the spacing between two warp threads (25) of the woven material (24) is greater than or equal to 3 mm.

4. Flexible pipe according to any one of claims 1 to 3, characterized in that the spacing between two weft threads (26) of the woven material (24) is greater than or equal to 5 mm and in that the thickness of a weft thread (24) is at most equal to 3 mm.

5. Flexible pipe according to one of claims 1 to 4, characterized in that the woven material (24) comprises a fusible polymeric material.

6. Flexible pipe according to claim 5, characterized in that at least one weft thread (26) and / or at least one warp thread (25) of the woven material (24) is made of fusible polymer material, advantageously the at least one weft thread (26) is made of fusible polymer.

7. Flexible pipe according to claim 5 or 6, characterized in that the reinforcing strip (22) comprises a support layer (30) of fusible polymer material with a thickness at most equal to 1 mm, the support layer (30) being disposed on at least one of the faces of the woven material (24).

8. Flexible pipe according to one of claims 5 to 7, characterized in that the fusible polymeric material is identical to the polymeric material of the external sealing sheath (20).

9. Method for manufacturing a flexible pipe (10) having a longitudinal axis (A), comprising the following steps in order:

- extrusion of an internal pressure sheath (14);

- winding of at least one layer of tensile armor (18) around the pressure sheath (14);

- helical winding with short pitch relative to the longitudinal axis (A) of a reinforcing strip (22), the reinforcing strip (22) comprising a woven material (24), the woven material (24) comprising warp threads (25) and weft threads (26), the warp threads (25) being wound up at short pitch relative to the longitudinal axis (A);

hot extrusion around the reinforcing strip (22) of an external sealing sheath (20) made of polymer material of thickness (E) between 1/125 and 1/75 of the internal diameter of said external sheath sealing (20) so that once the outer sealing sheath (20) has cooled, the reinforcing strip (22) is linked to the outer sealing sheath (20).

10. The method of claim 9, wherein the thickness of the external sealing sheath (20) is between 3 mm and 5 mm for an internal diameter of the external sealing sheath (20) between 250 mm and 600 mm.

11. The method of claim 9 or 10, wherein the spacing between two warp threads (25) of the woven material (24) is greater than or equal to 3 mm.

12. Method according to any one of claims 9 to 1 1, wherein the spacing between two weft son (26) of the woven material (25) is greater than or equal to 5 mm and in that the thickness of a weft thread (26) is at most equal to 3 mm.

13. Method according to one of claims 9 to 12, wherein the woven material (24) comprises a fusible polymeric material.

14. The method of claim 13, wherein at least one weft thread (26) and / or at least one warp thread (25) of the woven material (24) is made of fusible polymeric material, advantageously the at least one thread weft

(26) is made of fusible polymer.

15. Method according to any one of claims 9 to 14, in which the reinforcing strip comprises a support layer (30) of fusible polymeric material with a thickness at most equal to 1 mm, the support layer (30) being arranged on at least one of the faces of the woven material (24).

16. A method according to any one of claims 9 to 15, further comprising, before the step of winding the reinforcing strip (22), helically winding at a short pitch relative to the longitudinal axis (A) of a support rod (40) of fusible polymer material whose diameter is between 1 mm and 3 mm, the support rod (40) forming a bearing surface for the woven material (24) of the reinforcement strip (22).

17. Method according to any one of claims 9 to 16, in which the fusible polymeric material is identical to the polymeric material of the external sealing sheath (20).