AU2013292000B2

AU2013292000B2 - Flexible pipe for conveying fluid, cannula and associated method

Info

Publication number: AU2013292000B2
Application number: AU2013292000A
Authority: AU
Inventors: Jean-Christophe BOURGET; Thomas EPSZTEIN
Original assignee: Technip France SAS
Current assignee: Technip Energies France SAS
Priority date: 2012-07-20
Filing date: 2013-07-17
Publication date: 2016-06-30
Anticipated expiration: 2033-07-17
Also published as: FR2993629B1; FR2993629A1; BR112015001223B1; WO2014012971A1; MY172887A; DK2874807T3; EP2874807B1; BR112015001223A2; AU2013292000A1; EP2874807A1

Abstract

This pipe comprises a first sheath (20) made of polymer material, a second sheath (22) made of polymer material arranged around the first sheath (20), and at least one tensile armour layer. It comprises, at each end of the pipe (16), an end fitting (14). At least one of the end fittings (14) comprises a cannula (58) positioned between the first sheath (20) and the second sheath (22) in contact with at least one of said sheaths (20, 22). The cannula (58) is provided with at least one chemically active product able to react with the acidic compounds originating from the fluid present in the central bore (16) through the first sheath (20).

Description

FLEXIBLE PIPE FOR CONVEYING FLUID, CANNULA AND ASSOCIATED METHOD

The present invention relates to a flexible pipe for conveying fluid, delimiting a central bore tor circulation of the fluid, comprising: a first sheath made of polymer material; a second sheath made of polymer material arranged around the first sheath; at least one tensile armour layer and. at each end of the pipe: an end fitting.

Such a pipe is in particular a flexible pipe of a type that is not bonded ("unbonded") intended tor use for the conveying of gaseous or biphase hydrocarbons comprising a gaseous phase.

Such a flexible pipe is made for example produced in accordance with the documents relating to the standards API 17J (Specification for Unbonded Flexible Pipe) and API RP 17B (Recommended Practice for Flexible Pipe) established by the American Petroleum Institute.

Such a flexible pipe is generally formed of an assembly of concentric and superposed layers. It is considered "unbonded” for the scope and purposes of embodiments of the present invention since at least one of the layers of the pipe is capable of moving longitudinally in relation to the adjacent layers during flexion of the pipe. In particular, an unbonded pipe is a pipe that is free of bonding materials that connect the layers forming the pipe.

In a known manner, fluids conveyed in the pipes of the abovementioned type can be maintained under high pressure, for example greater than 100 bar and/or at high temperatures, for example higher than 70'C for long periods of time that may extend over several years.

The petroleum fluid conveyed by the pipe contains not only hydrocarbons, but may also include other compounds, in particular acidic and corrosive compounds, such as hydrogen sulfide (1-12S) and carbon dioxide (C02).

On account of the high pressure and the high temperature of the fluid flowing through the pipe, the acidic compounds have the tendency to diffuse through the internal pressure sheath, and to accumulate in the intermediate space that accommodates the tensile armour layers.

These layers being generally constituted of metal filaments or wires, the acidic compounds are likely to cause an accelerated corrosion of these layers. Such corrosion may degrade the mechanical integrity of the pipe, which is typically quite highly stressed by the longitudinal tensile and/or compressive stresses.

In order to overcome this problem, the documents EP 0S44429 and WO 2009/153451 describe pipes in which at least one active sheath intended to react with the acidic compounds is interposed between the fluid flow passage and the armour layers.

This active sheath is for example formed of a polymer matrix having dispersed therein a chemically active product that is capable of reacting with the acidic compounds passing through this sheath in order to neutralise them.

Thus, the acid compounds are converted into other neutral compounds as they pass through the active sheath. This reduces the risk of corrosion of the armour layers when the treated compounds emerge out of the active sheath.

Such solution therefore greatly improves the resistance of the armour layers. It could however be even further improved. In effect, in order to ensure the connection of the flexible pipe, it is necessary to provide for end fittings at the ends of the pipe.

The mounting of the end fittings requires the creation of a seal at the level of each polymer sheath present in the conduit.

For this purpose. It is generally necessary to interpose a metal cannula between the pressure sheath and the active sheath in order to crimp the active sheath.

The cannula locally detaches the active sheath from the pressure sheath and creates, upstream of the cannula, a potential zone for accumulation of corrosive gases. In this zone, the gases that have passed through the pressure sheath at the level of the cannula migrate and accumulate, which results in some cases in a localised over consumption of the active sheath.

This phenomenon is observed particularly when the total pressure in the central bore of the pipe is low, that is to say less than 100 bars, more precisely when it is comprised between 5 bars and 60 bars. Typically, such pressure levels are encountered during the phase of maintenance ofthe pipe. In this case, a gap of a few tenths of a millimetre is likely to appear between the pressure sheath and the active sheath, which facilitates the migration of acidic compounds from the rear end of the cannula to its front end.

It is therefore necessary to substantially increase the thickness of the active sheath in order to overcome this problem of localised over consumption of the active sheath. This increases the cost ofthe pipe and the weight thereof.

An object of embodiments ofthe invention is therefore to obtain a flexible pipe in which the risk of corrosion ofthe armour layers is particularly low, the pipe then being lighter and less expensive than the currently known pipes. A first aspect of the invention provides a flexible pipe for conveying fluid delimiting a central bore for circulation ofthe fluid, comprising a first sheath made of polymer material; a second sheath made of polymer materia! arranged around the first sheath; at least one tensile armour layer and, at each end of the pipe: an end fitting end; wherein at least one of the end fittings includes a cannula positioned between the first sheath and the second sheath in contact with at least one of the said sheaths; the cannula being provided with at least one chemically active product that is capable of reacting with the acidic compounds originating from the fluid present in the central bore through the first sheath, the cannula comprising a metal support base and an insert applied onto the base, said insert being permeable to gas and containing the at least one chemically active product.

The pipe according to embodiments of the invention may include one or more of the following characteristic features, taken into consideration individually or in accordance with any technically possible combination: at least one of the first sheath and the second sheath includes a chemically active product, that is capable of reacting with the acidic compounds originating from the fluid present in the central bore; at least a part of the cannula includes a polymer matrix, the active product being dispersed in the form of particles in the polymer matrix; at least a part of the cannula includes a matrix of porous ceramic material, advantageously sintered, the active product being disposed in the form of a layer at the surface of the matrix; the cannula comprises a metal support base and an insert that is permeable to gases, applied on to the base, the insert containing the active product; the cannula delimits an axial gas discharge conduit, the axial gas discharge conduit being arranged in the base without passing through the insert, or being arranged through the base and the insert; the cannula has an end portion tapering longitudinally, the tapered end portion being at least partially formed by the insert; the base delimits a housing for accommodating the insert, the insert being fully accommodated in the housing; the base delimits a housing for accommodating the insert, the insert comprising a portion that is accommodated within the housing and a portion protruding out longitudinally beyond the base, out of the housing; the insert is disposed completely on the exterior of the base in the axial extension of the base; the insert and the base are fastened to one another by means of interlocking; the cannula delimits at least one axial gas flow conduit; the cannula has a conically tapered end portion; the axial conduit opens out axially into the conically tapered end portion. A second aspect of the invention provides a cannula designed to be positioned between a first sheath made of polymer material and a second sheath made of polymer material, of a flexible fluid conveying pipe. the cannula being provided with at least one chemically active product, that is capable of reacting with the acidic compounds originating from the fluid conveyed by the pipe through the first sheath, the cannula comprising a metal support base and an insert applied onto the base, said insert being permeable to gas and containing the at least one chemically active product.

The cannula may include one or more of the following characteristic features, taken into consideration individually or in accordance with any technically possible combination: it comprises a metal base and an insert that is permeable to gases applied on to the base and containing the chemically active product. it delimits an axial conduit for the passage of gases. the cannula delimits an axial gas discharge conduit, the axial gas discharge conduit being arranged in the base without passing through the insert, or being arranged through the base and the insert; the cannula has an end portion tapering longitudinally, the tapered end portion being at least partially formed by the insert; the base delimits a housing for accommodating the insert, the insert being fully accommodated in the housing; the base delimits a housing for accommodating the insert, the insert comprising a portion that is accommodated within the housing and a portion projecting out longitudinally beyond the base, out of the housing; the insert is disposed completely on the exterior of the base in the axial extension of the base; the insert and the base are fastened to one another by means of interlocking; the cannula has a conically tapered end portion; the axial conduit opens out axially into the conically tapered end portion. A third aspect of the invention provides a method for conveying fluid, comprising of the following steps: provision of a pipe according to the first aspect; circulation of fluid through the central bore delimited by the first sheath made of polymer material: permeation of an acidic compound through the first sheath; treatment processing of the acidic compound by the active product present in the cannula.

Tlie present invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Figure 2 is a view, represented in partial cross section along a median axial plane, of the end fitting of the pipe as in Figure 1, comprising a cannula according to embodiments of the invention;

Figure 3 is a three quarter frontal perspective view of a first cannula according to embodiments of the invention;

Figure 4 is a cross sectional view taken along an median axial plane of the cannula as in Figure 3;

Figure 6 is a view similar to that in Figure 3 of a second cannula according to embodiments of the invention;

Figure 7 is a view similar to that in Figure 4 of the second cannula according to embodiments of the invention;

Figure 8 is a view similar to that in Figure 3 of a third cannula according to embodiments of the invention;

Figure 9 is a view similar to that in Figure 4 of the third cannula according to embodiments of the invention;

Figure 10 is a view of a detail marked X in Figure 9;

Figure 11 is a view similar to that in Figure 3 of a fourth cannula according to embodiments of the invention;

Figure 12 is a view similar to that in Figure 4 of the fourth cannula according to embodiments of the invention.

In the remainder of this description, the terms "upstream" and "downstream" are generally understood to be in relation to the normal direction of flow of a fluid. A first flexible pipe 10 according to embodiments of the invention is partially illustrated through Figure I and Figure 2.

The flexible pipe 10 comprises a central section 12 illustrated in part in Figure 1, It includes, at each ofthe upstream and downstream ends of the central section 12. an end fitting 14 (not visible in Figure 1), the relevant parts of which are shown in Figure 2.

The pipe i 0 delimits a central bore 16 for circulation of a fluid, advantageously a petroleum fluid. The central bore 16 extends along an axis A-A1 between the upstream end and the downstream end ofthe pipe 10 and opens out through the end fittings 14.

The flexible pipe 10 is meant to be arranged through a body of water (not shown) in an operational installation for exploitation of fluids, in particular hydrocarbons.

The body of water is, for example, a sea, a lake or an ocean. The depth of the body of water to the right ofthe fluid exploitation installation is for example between 500 m and 3000 m.

The fluid exploitation installation includes a surface assembly and a bottom assembly (not shown) which are generally connected to each other by the flexible pipe 10.

The flexible pipe is preferably an "unbonded" (as per the accepted English terminology) pipe.

At least two adjacent layers of the flexible pipe 10 are therefore free to move longitudinally relative to each other upon the pipe undergoing flexion or bending. Advantageously, all ofthe layers of the flexible pipe are free to move relative to each other. Such pipe is for example described in the documents relating to the standards published by the American Petroleum Institute (API) API 17J and API RP17B.

As illustrated in Figure 1, the pipe 10 delimits a plurality of concentric layers which extend continuously along the central section 12 up until the end fittings 14 situated at the ends of the pipe.

According to embodiments of the invention, the pipe 10 comprises at least a first sheath 20 made of a polymer material advantageously constituting a pressure sheath, and at least a second sheet 22 made of polymer material, disposed around the internal sheath 20. The second sheath 22 advantageously constitutes an active sheath for chemical treatment of corrosive gases that are likely to be present in the central bore 16 and thus likely to pass through the first sheath 20.

The pipe 10 further comprises at least one tensile armour layer 24 A, 24B disposed on the exterior in relation to the second sheath 22.

Advantageously, and according to the desired use, the pipe 10 in addition comprises an internal carcass 26 disposed on the interior of the first sheath 20, a pressure vault 28 interposed between the first sheath 20 and the or each tensile armour layer 24A, 24B and an external sheath 30, designed for the protection of the pipe 10.

In a known manner, the first sheath 20 is intended to confine in a sealed manner the fluid conveyed in the pipe bore 16. It is formed of polymer material, for example based on a polyolefin such as polyethylene, based on a polyamide such as PA 12 or PA 1 I, or based on a fluorine polymer such as polyvinylidene fluoride (PVDF).

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

The carcass 26, when it present, is formed for example of a profiled metal strip wound spirally. The spiral windings of the strip are advantageously interlocked into each other, which enables the capacity to absorb the radial crushing loads.

In this example, the carcass 26 is disposed within the interior of the first sheath 20 and the second sheath 22. The pipe is of the "rough bore" type.

By way of a variant (not shown), the flexible pipe 10 has no internal carcass 26, it is then referred to as "smooth bore" as per the accepted English terminology.

The helical winding of the profiled metal strip forming the carcass 26 is short pitched, that is to say that it has a helix angle having an absolute value close to 90°, typically comprised between 75° and 90°. in this example, the pressure vault 28 is designed to absorb the loads associated with the pressure prevailing within the interior of the first sheath 20 and second sheath 22. It is for example formed of a meta! profiled wire helically wound around the second sheath 22. The profiled wire generally has a complex geometry, in particular having a form shaped like Z, T, U, K, X or I.

The pressure vault 28 is helically wound with a short pitch around the second sheath 22.

The flexible pipe 10 according to embodiments of the invention comprises at least one armour layer 24A, 24B, formed of a helical winding of at least one elongated armour element, in the example shown in Figure 1, the flexible pipe 10 includes a plurality of armour layers 24A. 24B.

Each armour layer 24A, 24B comprises longitudinal armour elements wound with a long pitch around the axis A-A’ of the pipe.

The term "wound with a long pitch", is used to indicate that the absolute value of the helix angle is less than 60°, and is typically comprised between 25° and 55°.

The armour elements of a first armour layer 24A are generally wound at an angle in the opposite direction relative to the armour elements of a second armour layer 24B. Thus, if the winding angle of the armour elements of the first layer 24A is equal to + a, a being comprised between 25° and 55°, the winding angle of the armour elements of the second armour layer 24B disposed in contact with the first armour layer 24A is for example - a, with a comprised between 25° and 55°.

The armour elements are for example formed by metal wires, or strips.

The externa! sheath 30 is intended to prevent the permeation of fluid from the exterior of the flexible pipe into the interior. It is advantageously made of polymer material, in particular based on a polyolefin, such as polyethylene, based on a polyamide, such as PA 11 or PA 12, or based on a fluorine polymer such as polyvinylidene fluoride (PVDF).

The thickness of the external sheath 30 is for example comprised between 5 mm and 15 mm.

According to embodiments of the invention, the second sheath 22 when it is present is an active sheath. It has a reduced permeability to acidic compounds. Thus, the second sheath 22 has a matrix 40, preferably made of polymer material, and at least one chemically active product 42 present on this matrix 40 and capable of reacting chemically with the acidic compounds originating from the fluid present in the central bore 16 in order to block their diffusion within the second sheath 22.

Advantageously, the active product is capable of irreversibly neutralising the corrosive effects of the acidic compounds and limiting their corrosive effect on the armour layers 24A, 24B.

The matrix 40 is advantageously made of a polymer material similar to that of the first sheath 20, for example based on a polyolefin, such as polyethylene, based on a polyamide, such as PA11 or PA12, or based on a fluorine polymer such as polyvinylidene fluoride (PVDF).

The chemically active product that is capable of reacting with acidic compounds is for example selected from among the products described in the European patent application EP 0844429.

The chemically active products may be selected from the metal oxides. The chemically active products may also be selected from among metal carbonates, metal chlorides, hydrated forms of metal carbonates and metal chlorides, the hydroxylated forms of metal carbonates and metal chlorides, alkali metal carbonates, alkaline earth carbonates, alkali chlorides, alkaline earth chlorides, hydrated forms of the alkali metal carbonates, alkaline earth carbonates, alkali metal chlorides, alkaline earth chlorides, and hydroxylated forms of alkali metal carbonates, alkaline earth carbonates, alkali metal chlorides, alkaline earth chlorides.

The second sheath 22 may comprise, in addition, fillers of lamellar form having a shape coefficient greater than 20, the mass concentration of the said lamellar fillers in the sheath being at a maximum equal to 10%.

The second sheath 22 may comprise, in addition, absorbent fillers which trap the acidic compounds, the absorbent fillers being selected from among activated carbons, zeolites and aluminas.

The second sheath 22 advantageously includes additives for improving the mechanical properties of the matrix, the additives being selected from among poly (ethylene-octene), poly(ethylene-propylene), poly( ethylene-butene), and poly(styrene/ethylene butylene/styrene). The chemically active products may be chemically surface treated with silanes. The sheath may include maleic anhydride grafted polyolefins.

In particular, the chemically active products are advantageously selected from among metal oxides of the type (Fe203, PbO, ZnO, NiO, CoO CdO, CuO, Sn02, Mo03, Fe304, Ag20 Cr02, Cr03, Cr203, TiO, Ti02 and Ti203) or the alkali or alkaline earth oxides (CaO, Ca(OH)2, MgO), or compounds containing amine functional groups such as polyamines and polyethylene polyamines.

In one embodiment, the matrix comprises a single type of active product. By way of a variant, the matrix contains a combination of different active products, for example a combination of several metal oxides, a combination of metal oxides with alkali or alkaline earth oxides.

The chemically active products may also be selected from among metal carbonates (for example ZnC03), or metal chlorides (for example, ZnC2), as well as the hydrated and/or hydroxylated forms of metal carbonates and metal chlorides (for example 2ZnC03.3H20, Zn(OH)2, Zn5(C03)2(0H)6 or [Zn(0H)2]3.(ZnC03)2). The chemically active products may also be selected from among alkali metal carbonates, alkaline earth carbonates, alkali metal chlorides and alkaline earth metal chlorides (for example, Na2C03 or CaC03), as well as the hydrated and/or hydroxylated forms of alkali metal carbonates, alkaline earth carbonates, alkali metal chlorides and alkaline earth chlorides.

For the active products mentioned here above, the reaction principle generally consists of converting oxidised derivatives, carbonate derivatives, chlorine derivatives (possibly in hydrated and or hydroxylated forms) into sulfide derivatives (in the case of a reaction with H2S) or carbonate derivatives (in the case of a reaction with C02). In the case where only C02 is present, the carbonate forms of metal derivatives, derivatives of alkali and alkaline earth derivatives are not selected.

Advantageously, the mass proportion of the chemically active product in the matrix is comprised between 10% by mass and 50% by mass. The active product preferably has a specific surface area that is greater than 5 m2/g and in particular at least greater than 20 m2/g. In a preferred manner, the specific surface area of the active product may be less than 50 m2/g.

The active product is for example dispersed in the form of particles. It then has advantageously a specific surface area that is greater than 5 m2/g. The particles have in particular a particle size that is greater than 0.02 pm.

According to another embodiment of the invention, the second sheath 22 is a polymer sheath having reduced permeability to water molecules (H20) or a water resistant sheath, whereof the matrix 40 is advantageously made of a polymer material based on a polyolefin, such as polyethylene, or based on a fluorine polymer such as polyvinylidene fluoride (PVDF). According to yet another embodiment of the invention, the second sheath 22 is a polymer sheath whereof the matrix 40 is advantageously made of a polymer material similar to that of the first sheath 20, for example based on a polyolefin, such as polyethylene, based on a polyamide, sucli as PA 11 or PA 12, or based on a fluorine polymer such as polyvinyiidene fluoride (PVDF).

As illustrated in Figure 2, each end fitting 14 has an end vault 50 and an external connecting cover (not shown), delimiting with the end vault 50 an internal annular space 52.

The end fitting 14 further comprises a first crimping assembly 54 for crimping the first sheath 20, a second crimping assembly 56 for crimping the second sheath 22 and interposed between the crimping assembly 54 and the crimping assembly 56, an active cannula 58 according to embodiments of the invention.

The end fitting 14 further comprises a fastening assembly (not shown) for fastening the armour layers 24A, 24B, and a third crimping assembly (not shown) for crimping the external sheath 30.

The end fitting 14 further comprises, preferably, a gas discharge assembly 60 for discharging the gases that have passed through the first sheath 20. By way of a variant, the assembly 60 is meant to be for a measurement of pressure as described in the patent application PCT/EP2012/052774 of the Applicant.

In this example the end vault 50 is adapted to connect the pipe 10 to another connection end fitting 14 or to terminal equipment units. This end vault 50 has a central hole 62 designed to receive the end of the first sheath 20 and to permit the flow of the fluid flowing through the central bore 16 towards the exterior of the pipe 10.

The central hole 62 is delimited, in front of the crimping assembly 54, by an internal surface 63 converging axially towards the axis A-A' by moving towards the exterior of the pipe 10. The internal surface 63 is conical for example.

The crimping assembly 54 of the first sheath 20 in this example comprises a first crimping ring 64 and an intermediate vault 66 for axially clamping the first ring 64.

The first ring 64 is adapted to be interposed between the first sheath 20 and the converging surface 63 in order to be inserted by deformation in the first sheath 20 when the intermediate vault 66 is thrust to the end vault 50 by pressing on the ring 64.

The intermediate vault 66 includes an interior portion 68 meant for the axial thrusting of the first ring 64, an intermediate support portion 70 for supporting the crimping assembly 56 of the second sheath 22, and an upper fastening portion 72 for fastening on to the end vault 50.

The intermediate portion 70 delimits a surface 74 converging towards the axis A-A’ by moving towards the exterior of the pipe. The surface 74 is intended to cooperate with the crimping assembly 56. The intermediate portion 70 further defines a transverse end stop surface 76 for the crimping assembly 56.

The upper portion 72 of the intermediate arch 66 is fastened on to the end arch 50 in the cavity 52, for example by screws.

The crimping assembly 56 of the second sheath 22 includes in this example a second ring 80 and a clamping flange 82 for clamping the second ring 80.

The clamping flange 82 comprises an internal portion 84 defining a clamping surface 86 for clamping the second ring 80 and an upper portion (not shown) intended to be fastened on to the upper portion 72 of the intermediate vault 66 and/or on to the end vault 50.

The clamping surface 86 converges towards the axis A-A' by moving towards the interior of the pipe 10.

The second ring 80 here has a biconical shaped form. It is inserted between the intermediate vault 66 and the clamping flange 82 during the tightening of the flange 82 on to the vault 66.

The second ring 80 is disposed axially so as to be lacing the cannula 58, with interposing of the second sheath 22.

Thus, during tightening of the crimping flange 82 against the intermediate vault 66 the surfaces 74, 86 push the cones of the second ring 80 into the second sheath 22 by a wedge effect, in order to bring about the sealing and crimping of this sheath 22, bearing against the cannula 58.

As illustrated in Figures 2 to 5, the cannula 58 has a generally tubular shaped form. It comprises a central portion 90 that is substantially cylindrical, and an interior end portion 92, tapered towards a free edge 94. The cannula 58 further comprises, opposite the free edge 94, a retaining portion 96 formed in this example by a neck flange.

The cannula 58 delimits a central lumen 98 having an axis A-A', through which is inserted the first sheath 20.

According to embodiments of the invention, the cannula 58 is provided with at least one chemically active product that is capable of reacting with the acidic compounds originating from the fluid present in the central bore through the first sheath 20. The active product is as previously described above in the context of the active sheath 22.

In this example, and as illustrated by Figures 2,3 and 4, the cannula 58 thus includes a support base 100, advantageously made of metal, and an insert 102 permeable to gas, applied on to the base 100 and that receives the chemically active product, which is capable of reacting with the acidic compounds.

In this example, the base 100 extends over the entire length of the cannula 58 o the exterior of the insert 102. It defines an exterior surface 104 of the cannula 58.

The base 100 internally defines a housing 106 for receiving the insert, having a form shaped to be complementary to that of the insert 102.

The housing 106 is of substantially annular shape. It is bounded axially towards the interior of the pipe 10 by a shoulder 108 for axial locking of the insert 102. The shoulder 108 is advantageously situated axially to be facing the tapered end portion 92.

As illustrated in Figure 5, the housing 106 has a locking cavity 109 for locking the insert 102 that is advantageously circumferential opening towards the axis A-A’. The cavity 109 is located in the vicinity of the retaining portion 96.

The insert 102 includes a sleeve 110 that is advantageously cylindrical positioned in the internal housing 106. The sleeve 110 has a form shaped to be substantially complementary to that the housing 106. Thus the sleeve 110 is positioned flush with the internal surface of the base 100 to be facing the shoulder 108.

The sleeve 110 has an exposed internal surface, meant to be placed so as to face the gap defined between the cannula 58 and the internal sheath 20.

In this example, the insert 102 is entirely accommodated within the base 100 without axially protruding out therefrom. Thus, the length of sleeve 110 is less than the length of the cannula 58.

In a first embodiment, the insert 102 comprises a polymer matrix, with the chemically active product being dispersed within the polymer matrix. In this embodiment, the polymer matrix is for example selected from among one of the polymers previously defined for the matrix for the internal sheath, in particular based on a polyolefin such as polyethylene, based on a polyamide such as PA12 or PA11, or based on a fluorine polymer such as polyvinylidene fluoride (PVDF).

The active product is as previously defined above for the second sheath 22. It will therefore not be described in further detail.

The weight content of chemically active product in the polymer matrix is for example comprised between 10% and 50% by weight.

The active product is advantageously dispersed in the form of particles having a surface area greater than 5 m2/g, as described in the patent application WO 2009/153451 for the active sheath 22.

In a second embodiment, the matrix of the insert 102 is formed out of a porous ceramic based material that is advantageously sintered. The active product is then disposed in the form of a layer borne by the matrix of the insert 102. This layer is for example an interior layer disposed on an interior surface of the matrix. The active product is for example one of the compounds previously defined above for the active sheath.

The insert 102 is axially secured within the base 100 by means of interlocking, and by being locked in over the axial shoulder 108.

The insert 102 includes at least one radially projecting piece for locking 119 having a shape that is complementary to that of the cavity 109. The projecting piece 119 gets inserted into the cavity 109. The thickness of the insert 102 is less than that of the base 100, at the level of the central portion 90 of the cannula 58.

With reference to Figure 2 the gas discharge assembly 60 for discharging the gas comprises at least one internal conduit 120 arranged axially through the cannula 58, at least one intermediate channel 122 arranged through the intermediate vault 66 and a downstream channel 124 arranged through the end vault 50.

In the example shown in Figures 3, 6 and 11, the cannula 58 includes a plurality of internal conduits 120 spaced angularly about the axis A-A’. Each conduit 120 extends axially along the cannula 58 and opens out upstream into the tapered end portion 92, to be facing the intermediate space between the first sheath 20 and second sheath 22.

Each conduit 120 opens out downstream into the intermediate channel 122. Advantageously, the conduit 120 opens transversely out of the cannula 58 through the retaining portion 96.

The intermediate channel 122 extends axially through the intermediate vault 66 between the interior portion 68 and the intermediate portion 70. It is connected downstream to the downstream channel 124.

The downstream channel 124 extends through the end vault 50. It opens out downstream out of the end fitting 14 through an outlet port (not shown).

This outlet port can be fitted with a differential drainage valve as described in the document WO 95/56045. Such a valve is designed to open when the pressure prevailing in the downstream channel 124 is greater than a predetermined value. By way of a variant, the outlet port is connected to a gas analyzer, of a known type, in a manner so as to quantify the composition of gas at the level of the gap between the polymer sheaths 20, 22, in particular with a view to determining the presence or absence of acidic compounds such as hydrogen sulfide or carbon dioxide.

By way of a variant or additional aspect, the outlet port is connected to a system for measuring the flow rate of gases and/or the temperature of the gases, such as a sensor for measurement of the temperature of the gases. It can also be connected to a known pressure measurement system for measuring the differential pressure of the gases between this outlet port and the internal passage 16 of the pipe.

According to an variant embodiment of the invention, the assembly 60 for discharging the gases including at least one internal conduit 120 formed axially through the cannula 58, at least one intermediate channel 122 formed through the intermediate vault 66 and one downstream channel 124 formed through the end vault 50, is optional.

The mounting of the end fitting 14 of the pipe 10 will now be described.

In order to bring about the sealing at the level of the end fitting 14 of the pipe 10, the first ring 64 of the crimping assembly 54 is first of all introduced between the end vault 50 and the first sheath 20. Then, the intermediate vault 70 is inserted.

The cannula 58 is positioned between the first sheath 20 and second sheath 22. The tapered end portion 92 is disposed at the level of the point of separation between the first sheath 20 and the second sheath 22.

Then, the second ring 80 of the crimping assembly is disposed between the second sheath 22 and the intermediate vault 66.

The clamping flange 82 is then mounted between the second sheath 22 and the armour layers 24A, 24B so as to be placed in contact with the ring 80.

Subsequently, the crimping flange 82 is tightened against the intermediate vault 68. This causes, by means of a wedge effect on the surfaces 74, 86, the penetration of the cones of the ring 80 in the second sheath 22.

The clamping of the intermediate vault 66 against the end vault 50 moreover also causes an axial thrust of the first ring 64 against the end vault 50 and its partial insertion into the first sheath 20 by means of a wedge effect on the surface 63.

The armour layers 24A, 24B are then secured to the exterior of the intermediate vault 70 and the crimping flange 82.

The external sheath 30 is then crimped by the third crimping assembly and the end fitting cover is mounted over the vault 50 around the assemblies 54, 56, in order to seal off the end fitting.

In operation, a fluid flows through the central bore 16 of the pipe 10. When acidic gases originating from the fluid pass through the first sheath 20, at the level of the gap present between the first sheath 20 and the cannula 58, they come into contact with the chemically active product present within the insert 102.

The corrosive gases are thus treated over their passage to the region of separation of the second sheath 22 from the first sheath 20. Then, the treated gas are collected in each internal conduit 120 and are discharged out of the pipe 10 through the internal conduit 120, the intermediate channel 122 and the outlet channel 124.

The presence of chemically active products in the insert 102 ensures that the gases extracted through the first sheath 20 do not accumulate at the level of the region of separation, and therefore do not induce any localised over consumption of the active sheath 22.

The thickness of the active sheath 22 may thus be reduced, which would lighten the pipe 10 and reduces its cost. This outcome is achieved in a simple manner by maintaining the integrity of the armour layers 24A, 24B. A second cannula 58 according to embodiments ot the invention is illustrated through the Figures 6 and 7. Differently from the first cannula 58 illustrated in Figure 3, the base 100 extends over only a part of the length of the cannula 58, The housing 106 opens out axially towards the interior ot the pipe, and delimits an external shoulder 130 towards the exterior of the pipe.

The insert 102 at least partially protrudes out beyond the housing 106, towards the interior of the pipe 10, and thus delimits a section of the tapered portion 92 that extends up to the free edge 94.

In this cannula 58, the internal conduit 120 is delimited in the insert 102 between the end portion 92 and the retaining portion 96, and then in the base 100 at the level of the retaining portion 96.

By way of a variant, a metal tube 126 is advantageously inserted into each conduit 120 so as to reinforce the mechanical structure of the insert 102, and to axially secure the insert 102 on to the base 100. Preferably, the metal tube 126 is welded to the external shoulder 130 of the cannula 58.

In this configuration, the interior end of the insert 102 is thus placed directly in the region of separation between the first sheath 20 and the second sheath 22. This ensures the efficient consumption of any corrosive gases that may possibly accumulate in this region, and prevents the localised over consumption of the active sheath 22. A third cannula 58 according to embodiments of the invention is represented in Figures 8 to 10. The insert 102 here is located at the end of the base 100 and is secured by means of interlocking on the base 100.

For this purpose, the insert 102 delimits an exterior lip 140 having an increasing cross sectional area while moving axially towards the base 100.

The exterior lip 140 thus defines an interior surface 142 inclined towards the axis A-A'ofthe pipe 10 while moving towards the exterior of the pipe 10.

The interior surface 142 is bevelled at its free interior end 144.

The base 100 delimits an interior lip 150 to be used for engaging in the exterior I ip 140 of the insert 102.

The interior lip 150 has an increasing cross sectional area while moving towards the insert 102.

It thus defines an exterior surface 152 diverging away from the axis A-A' of the pipe 10 while moving towards the insert 102. The exterior surface 152 is bevelled at its free end 154.

Thus, the insert 102 is secured axially on to the base 100 by means of interlocking of the exterior lip 140 around the interior lip 150. The retention in place of the insert 102 is ensured by means of cooperation between the surfaces 142, 152 that are in contact over the lips 140, 150, The insertion and the assembling of the insert 102 on the base 100 is facilitated by the presence of the bevels on the free edges 144, 154 respectively.

Advantageously, in this embodiment, the cannula 58 does not have the internal gas discharge conduit 120. The walls of the base 100 and the insert 102 are solid. A fourth cannula 58 according to embodiments of the invention is represented in Figures 11 and 12.

In contrast to the first cannula 58 represented in Figures 3 and 4, the insert 102 is disposed completely on the exterior of the base 100. Thus, the insert 102 is mounted in axial extension of the base 100, by being applied on to an end annular surface of the base 100.

The insert 102 therefore forms an interior section of the central portion 90 of the cannula 58, and the tapered end portion 92 of the cannula 58.

The internal conduit 120 is delimited partly in the base 100, and partly in the insert 102. A metal tube 126 is inserted into each internal conduit 120 in order to ensure the reinforcement of the insert 102 at the level of the internal conduit 120, and the axial securing of the insert 102 relative to the base 100. The metal tube 126 thus also makes it possible to drain the gases present upstream of the tapered portion 92.

The operation of this cannula 58 is similar to that of the cannulas 58 previously described above.

The insert 102 may be manufactured in accordance with various means of operational implementation. The insert 102 may be extruded, injected or applied by means of thermal spraying over the surface of the exterior shoulder 130 of the cannula 58. Furthermore, an additional step of machining or welding of the insert 102 may be required in order to ensure that it is properly fitted to the cannula 58. This means of implementation of the insert 102 may be used alone or in combination with the steps of machining or welding.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification i elates.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A flexible pipe for conveying fluid delimiting a central bore for circulation of the fluid, comprising a first sheath made of polymer material; a second sheath made of polymer material arranged around the first sheath: at least one tensile armour layer and, at each end of the pipe: an end fitting end; wherein at least one of the end fittings includes a cannula positioned between the first sheath and the second sheath in contact with at least one of the said sheaths; the cannula being provided with at least one chemically active product that is capable of reacting with the acidic compounds originating from the fluid present in the central bore through the first sheath, the cannula comprising a metal support base and an insert applied onto the base, said insert being permeable to gas and containing the at least one chemically active product.
2. A pipe according to claim 1, wherein at least one of the first sheath and the second sheath includes a chemically active product, that is capable of reacting with the acidic compounds originating from the fluid present in the central bore.
3. A pipe according to any one of the preceding claims, wherein at least the insert of the cannula includes a polymer matrix, the active product being dispersed in the form of particles in the polymer matrix.
4. A pipe according to any one of the preceding claims, wherein at least the insert of the cannula includes a matrix of porous ceramic material, advantageously sintered, the active product being disposed in the form of a layer at the surface of the matrix.
5. A pipe according to claim any one of the preceding claims, wherein the cannula delimits an axial gas discharge conduit, the axial gas discharge conduit for discharging gas being arranged in the base without passing through the insert, or being arranged through the base and the insert.
6. A pipe according to any one of the preceding claims, wherein the cannula has an end portion tapering longitudinally, the tapered end portion being at least partially formed by the insert.
7. A pipe according to any one of the preceding claims, wherein the base delimits a housing for accommodating the insert, the insert being fully accommodated in the housing.
8. A pipe according to any one of the preceding claims, wherein the base delimits a housing for accommodating the insert, the insert comprising a portion that is accommodated within the housing and a portion protruding out longitudinally beyond the base, out of the housing.
9. A pipe according to any one of the preceding claims, wherein the insert is disposed completely on the exterior of the base in the axial extension of the base.
10. A pipe according to any one of the preceding claims, wherein the insert and the base are fastened to one another by means of interlocking.
11. A cannula designed to be positioned between a first sheath made of polymer material and a second sheath made of polymer material, of a flexible fluid conveying pipe, the cannula being provided with at least one chemically active product, that is capable of reacting with the acidic compounds originating from the fluid conveyed by the pipe through the first sheath, the cannula comprising a metal support base and an insert applied onto the base, said insert being permeable to gas and containing the at least one chemically active product.
12. A cannula according to claim 11, delimiting an axial conduit for the passage of gases,
13. A cannula according to claims 11 or 12, comprising a central portion that is substantially cylindrical, and an interior end portion tapered towards a free edge.
14. A cannula according to claim 13, comprising, opposite the free edge, a retaining portion formed by a neck flange.
15. A method for conveying fluid, comprising of the following steps: provision of a pipe according to any one of claims 1 to 10; circulation of fluid through the central bore delimited by the first sheath made of polymer material; permeation of an acidic compound through the first sheath; treatment processing of the acidic compound by the active product present in the cannula.