AU2014294864B2

AU2014294864B2 - Method and installation for fabrication of an instrumented pipe

Info

Publication number: AU2014294864B2
Application number: AU2014294864A
Authority: AU
Inventors: Claudio Da Silveira CARVALHO; Victor Viana CHAVES; Olivier DELCROIX; Pascal Estrier; Olivier MESNAGE
Original assignee: Technip France SAS
Current assignee: Technip Energies France SAS
Priority date: 2013-07-26
Filing date: 2014-07-21
Publication date: 2018-06-28
Anticipated expiration: 2034-07-21
Also published as: AU2014294864A1; EP3024641A1; WO2015011394A1; EP3024641B1; BR112016001618A2; BR112016001618B1; FR3009014A1; DK3024641T3; FR3009014B1

Abstract

The invention concerns a method and a facility for producing a flexible instrumented pipe (10). Said facility has an entrance (50) opposite an exit (52) in order to be able to pull through a tubular structure (54) comprising a support sheath made from polymer material having a free cylindrical outer surface, said facility comprising a movable storage support (60) capable of storing at least one optical fibre sensor (64), so as to be able to wind said at least one optical fibre sensor (64) helically around said support sheath. The facility further comprises a transformation device (68) for supplying and for applying a holding sheath coaxially on said support sheath, so as to be able to hold said at least one optical fibre sensor (64) in a fixed position against said cylindrical outer surface.

Description

The invention concerns a method and a facility for producing a flexible instrumented pipe (10). Said facility has an entrance (50) opposite an exit (52) in order to be able to pull through a tubular structure (54) comprising a support sheath made from polymer material having a free cylindrical outer surface, said facility comprising a movable storage support (60) capable of storing at least one optical fibre sensor (64), so as to be able to wind said at least one optical fibre sensor (64) helically around said support sheath. The facility further comprises a transformation device (68) for supplying and for applying a holding sheath coaxially on said support sheath, so as to be able to hold said at least one optical fibre sensor (64) in a fixed position against said cylindrical outer sur face.

(57) Abrege : L'invention conceme un precede et une installation de fabrication d'une conduite flexible instrumentee (10). Ladite installation presente une entree (50) opposee a une sortie (52) pour pouvoir entrainer une structure tubulaire (54) comprenant une gaine de support en materiau polymere presentant une surface exteme cylindrique libre, ladite installation comprenant un support de stockage mobile (60) apte a stacker au moins un capteur a fibre optique (64), de maniere a pouvoir enrouler helico'idalement ledit au moins un capteur a fibre optique (64) autour de ladite gaine de support. L'installation [Suite sur la page suivante]

WO 2015/011394 Al llllllllllllllllllllllllllllllllllllllllllllllllll^ comprend en outre un dispositif de transformation (68) pour foumir et pour appliquer une gaine de maintien coaxialement sur ladite gaine de support, de lacoii a pouvoir maintenir ledit au moms un capteur a fibre optique (64) en position fixe contre ladite surface exteme cylindrique.

Method and installation for fabrication of an instrumented pipe

The present invention relates to a method and an installation for fabrication of an instrumented flexible pipe for the transport of hydrocarbons and an instrumented flexible pipe obtained by said method.

One application field envisaged is that of underwater flexible pipes for conveying hydrocarbons between an underwater installation situated on the seabed and a surface installation above the underwater installation. Multiple movements of the sea between the seabed and the surface exert stresses on underwater pipes.

Such underwater flexible pipes are notably described in the standards API 17J “Specification for Unbonded Flexible Pipe” and API RP 17B “Recommended Practice for Flexible Pipe” published by the American Petroleum Institute.

Known instrumented flexible pipes are equipped with optical fiber sensors deployed along the entire length of the pipe. These sensors make it possible to measure locally deformations of the pipe and notably bending, elongation and twisting thereof as well as swelling thereof.

The movements of the sea are more pronounced near the surface and the mechanical loads on flexible pipes are greater. Also, it is necessary to monitor deformations thereof in real time. It is notably necessary to detect critical damage to the pipes and the associated equipments.

For example, the rupture of a bend stiffener or a bend limiter following agitation of the marine environment can lead to a large reduction in the radius of curvature of the pipe and therefore damage it. Then again, partial rupture of the tensile armour layers of a flexible type can for its part cause both elongation and twisting of the pipe. Furthermore, rupture of the anti-swelling bands can lead to serious local swelling of the external sheath of the flexible pipe. Such swelling can also be caused by an abnormal increase in the pressure in an annular space of the flexible pipe.

Also, by recording the aforementioned deformations of the flexible pipe over time, it is possible to evaluate and to update its durability during its period of service. As a result, sudden ruptures are avoided, which makes it possible not only to set up an optimum and therefore more economical organization for replacing the pipes but also to provide technical improvements taking account of the damage suffered.

Optical fibres can be used both as sensors for effecting various measurements and as a transmission channel for transmitting the measurement signals.

In the present application, the term “optical fibre sensor” denotes an optical fibre used as a sensor for effecting measurements, for example measurements of deformation, temperature or chemical composition.

Optical fibre sensors have properties that make them very suitable for instrumentation of structures of great length in a severe environment, notably underwater flexible pipes. First of all, an optical fibre sensor can be very long, up to several tens of kilometres long, which makes it possible to instrument a structure of great length. Then, each optical fibre sensor can include a large number of measurement areas disposed or distributed over the entire length of the optical fibre, which makes it possible with a single optical fibre sensor to obtain measurements coming from numerous measurement areas disposed along the pipe. It is also possible to locate the measurement areas at a great distance from the signal acquisition and processing unit. Furthermore, optical fibre sensors are intrinsically explosion-proof, which makes it possible to use them in an explosive environment. They are also insensitive to electromagnetic interference. Finally, optical fibre sensors are compact because of the small diameter of the optical fibres, which facilitates their integration into the wall of the flexible pipes.

There are known optical fibre sensors in which the optical fibre has been modified locally to form sensors, the modified areas producing the measurements and the rest of the fibre serving to route the measurement signals to the acquisition and processing equipment. This applies in particular to optical fibre sensors including Bragg gratings produced by a photo-etching process, which may notably be used to effect measurements of elongation or temperature.

There are also known optical fibre sensors that are not locally modified and where the whole of the optical fibre serves both as sensor and as signal

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2014294864 28 May 2018 transmission channel. This applies in particular to sensors based on reflectometry methods, notably Rayleigh, Raman or Brillouin reflectometry methods. The Raman reflectometry method makes it possible to effect a distributed measurement of temperature along an optical fibre that is not locally modified. The Brillouin reflectometry method, for its part, makes it possible to effect a distributed measurement of temperature and/or deformation along an optical fibre that is not locally modified.

In accordance with the prior art, an optical fibre sensor is installed over the entire length of the flexible pipe and an optoelectronic device for generating and acquiring optical signals is mounted at one of the ends of the pipe so as to be able to acquire and process the signals transmitted by the sensors. As a result, it is possible to measure the elongation of the optical fibre in real time at a plurality of measurement areas along it, for example, and to deduce therefrom the deformation of the pipe. For the elongation measured locally by the optical fibre sensor to correspond to the local deformation of the pipe, it is important for the optical fibre sensor to be correctly fastened to the pipe in the elongation measurement areas.

The document W02009/068905 discloses an instrumented flexible pipe comprising in the direction from the interior toward the exterior a polymer material pressure sheath, a pressure armour wire wound with a short lay around the pressure sheath, tensi le armour wires wound with a long lay around the pressure armour wire and a protective sheath. The pressure sheath or the external sheath is equipped with a helically wound optical fibre sensor, this optical fibre sensor being coupled to this sheath so as to be able to effect measurements of deformation.

The use of such an optical fibre sensor gives rise to technical difficulties. First of all, the elongation at rupture of optical fibres is much less than that of polymer material sheaths. Moreover, the fibre must be fastened to the sheath to which it is coupled over its entire length so as to follow its deformation. Also, an optical fibre is relatively fragile and its position relative to the sheath must be precisely defined.

It is desirable that embodiments of the present invention provide a method of fabricating an instrumented flexible pipe that makes it possible not only to adjust the position of an optical fibre sensor relative to a sheath accurately but also to fasten the optical fibre sensor firmly to the sheath.

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According to a first aspect of the present invention, there is provided a method of fabricating an instrumented flexible pipe for the transport of hydrocarbons, said fabrication method being of the type including the following steps: a tubular structure is procured including a polymer materia! support sheath having a free cylindrical external surface; at least one optical fibre sensor is procured; said at least one optical fibre sensor is wound helically around said support sheath so as to be able to fasten said at least one optical fibre sensor to said support sheath; wherein a retaining sheath is further procured and wherein said retaining sheath is applied coaxially to said support sheath so as to retain said at least one optical fibre sensor in a fixed position against said cylindrical external surface, wherein said polymer material retaining sheath is formed around said support sheath so as to be able to apply said retaining sheath coaxially against said cylindrical external surface, and wherein the retaining sheath is extruded directly around the support sheath.

Accordingly, one feature of the invention lies in the use of the optical fibre sensor between the support sheath and the retaining sheath. Accordingly, the optical fibre sensor is held and gripped between the support sheath and the retaining sheath. In this case it is fastened to the external surface of the support sheath. As a result, the optical fibre sensor can be adjusted into a precise position on the external surface of the support sheath. Moreover, the optical fibre sensor being fastened to the support sheath, it can be used to measure deformation of the support sheath in order to deduce therefrom deformation of the pipe and notably bending, elongation, twisting or swelling thereof.

Such use of the optical fibre sensor on the surface of the support sheath is much easier than embedding it in the thickness of a sheath. Embodiments of the present invention notably make it possible to avoid having to guide the optical fibre sensor between the exit lips of the extrusion head during extrusion of a sheath and thereafter to have to retain it within the thickness of this sheath as it cools.

Embodiments of the present invention are easier to implement than the solution that would consist firstly in machining a groove along the external face of the support sheath, secondly deploying the optical fibre sensor at the bottom of this groove and thirdly filling this groove with a molten polymer that becomes welded to the polymer constituting the support sheath so as to fasten the optica] fibre sensor to the support sheath.

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The optical fibre sensor is wound in a spiral and applied against the cylindrical external surface of the support sheath, so as to form a helix with a particular lay, and the retaining sheath is then applied coaxially to the cylindrical external surface, trapping the optical fibre sensor.

Furthermore, said at least one optical fibre sensor is advantageously wound helically with a 5 helix angle relative to the axis of the tubular structure between 45.5° and 54.5° or between 55° and 66.5°. As a matter of fact, it is has been discovered that the choice of such a helix angle makes it possible to effect precise measurements of the deformation of the tubular structure at the same time as avoiding the risk of damaging the optical fibre sensor if the tubular structure is coiled with a small radius of curvature.

Accordingly, if the tubular structure is coiled with its minimum bending radius, the axia!

deformation of the support sheath can routinely reach 8%.

Now, the only optical fibre sensors capable of withstanding such elongation in the long term are those constituted of a polymer optical fibre, for example a polymethylmethacrylate (PMMA) optical fibre or a poly-perfluorobutenyl-vinyl-ether optical fibre (the latter polymer is sold under the trademark Cytop®). However, these polymer optical fibres have a number of drawbacks. First of all, their optical attenuation is high, typically between 30 dB/km and 150 dB/km. Consequently, polymer optical fibre sensors have a maximum length between 100 metres and 500 metres, which may be insufficient for some applications. The second drawback of polymer optical fibres is their inability to withstand temperatures greater than approximately

100°C. Now, the temperature inside an extrusion head is very much higher than this limit, so that such optical fibres cannot withstand passage through the interior of an extrusion head.

Glass optical fibres can for their part withstand passage through the interior of an extrusion head. As a matter of fact, some glass optical fibres, notably those coated with carbon and polyimide, are capable of withstanding a temperature of 300°C for long periods, while the extrusion temperature of a polyethylene or polyamide sheath is of the order of 200°C. Another advantage of glass optical fibres is their very low optical attenuation (<3 dB/km/ which makes it possible to use them to effect remote measurements at distances of more than 5 km, routinely up to more than 15 km.

However, the major drawback of glass optical fibres is their lack of ductiliity and their low elongation at rupture. In practice, it is recommended that their relative elongation should be

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2014294864 28 May 2018 limited to a value less than 2% and preferably less than 1 %, failing which there would be a risk of premature rupture, notably in the case of cyclic loading that could lead to fatigue.

Consequently, embodiments of the present invention are advantageously implemented using a glass optical fibre sensor so as to overcome the temperature problem. Moreover, the elongation problem is overcome thanks to the helical winding of the optical fibre sensor, whereby the elongation of the optical fibre sensor is much less than that of the support sheath to which it is fastened.

Now, a surprising phenomenon has been discovered concerning the choice of the helix angle of the optical fibre sensor. As a matter of fact, it has been discovered that when the tubular structure is deformed in bending, the optical fibre sensor suffers virtually no elongation if its helix angle is between 54.7° and 54.8°, advantageously approximately equal to 54.74°, and this is the case even if the tubular structure is bent sharply, for example coiled with its minimum radius of curvature.

Moreover, it has been discovered that when the tubular structure is deformed in bending, the maximum elongation along the optical fibre sensor decreases progressively from a first maximum value to zero as the helix angle increases from 0° to approximately 54.75° and that this elongation then increases progressively from zero to a second maximum value as the helix angle increases from approximately 54.75° to 90°. Moreover, the second maximum value is virtually equal to half the first maximum value, i.e. the maximum elongation along the optical fibre sensor when the helix angle is equal to 0° is virtually twice that when the helix angle is equal to 90°.

This phenomenon seems to be linked to the high Poisson’s coefficient of the polymers from which the support sheaths may be made, i.e. the fact that if an area of the support sheath is loaded axially in tension (for example an area located on the outside when the sheath is bent), this area tends to contract strongly in a circumferential direction.

The discovery of this phenomenon has made it possible to define ranges of helix angles that may be suitable for glass optical fibre sensors.

The first criterion is that the helix angle must be between 44.5° and 66.5°, and preferably between 49.5° and 60.3°, to prevent excessive elongation of the io optical fibre sensor when the tubular structure is coiled with its minimum radius of curvature.

The second criterion, which is applicable only if it is wished to be able to effect measurements of bending, is to eliminate helix angles between 54.7° and 54.8°, failing which the optical fibre sensor would be insensitive to the phenomenon to be measured. Furthermore, to improve the accuracy of the bending measurement, it is advantageously desirable to eliminate helix angles between 54.5° and 55°. Also, to obtain a high accuracy of bending measurement, it is preferable to eliminate helix angles between 53.9° and 55.8°.

The combination of these two criteria leads to choosing a helix angle between 45.5° and 54.5° or between 55° and 66.5°. Moreover, the helix angle is preferably between 49.5° and 53.9° or between 55.8° and 60.3°.

Furthermore, in accordance with one advantageous embodiment of the invention, the optical fibre sensor is a deformation measurement sensor, typically a sensor making it possible to measure the elongation of the optical fibre parallel to the axis of the optical fibre. As a result, it is possible to deduce from measurements the various modes of deformation of the tubular structure and notably bending, elongation, swelling and twisting thereof.

The flexible pipe can advantageously be instrumented with a plurality of optical fibre sensors having different helix angles and/or crossing one another so as to obtain sufficient measurements to be able to decorrelate and deduce accurately the deformations (bending, tension, swelling, twisting) of the tubular structure. Thus an optical fibre sensor wound with an angle of 54.75°, for

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2014294864 28 May 2018 example, is insensitive to bending of the flexible pipe but can provide information on its other modes of deformation, namely elongation, swelling and twisting. On the other hand, an optical fibre sensor wound with a helix angle between 45.5° and 54.5° or between 55° and 66.5° is sensitive to all modes of deformation of the flexible pipe.

Moreover, by comparing measurements obtained in different areas situated along the flexible pipe, either with the same optical fibre sensor or with different optical fibre sensors, it is possible to deduce the modes of deformation of the flexible pipe more accurately.

Accordingly, if the flexible pipe has a dynamic area situated in the immediate vicinity of a static area, for example, it is advantageous to compare the measurements obtained in these two areas to deduce therefrom, by virtue of their difference, the variations of bending in the dynamic area, other stresses (tension, swelling, twisting) being assumed to be substantially identical in the two areas compared. This solution can notably be employed in the upper part of a riser, when the flexible pipe is deployed via an I-tube to the bottom of which a stiffener is fixed. In this configuration, the upper area of the flexible pipe inside the 1-tube is a static area in which the pipe is virtually immobile whereas the area situated a little lower down at the level of the stiffener is a dynamic area in which the pipe may be subject to large variations of bending.

Moreover, embodiments of the present invention are preferably implemented using an optical fibre sensor including at least one Bragg grating, advantageously at least ten Bragg gratings.

In accordance with a preferred embodiment of the invention, said at least one optical fibre sensor that is procured is buried inside a longitudinal body. Accordingly, the optical fibre sensor is protected from the external environment inside a longitudinal body. For example, the latter is constituted of a rod inside which the optica! fibre sensor extends axially. Moreover, said longitudinal body is advantageously wound helically around said support sheath so as to be able to fasten said at least one optical fibre sensor to said support sheath. As a result, the optical fibre sensor is protected when the longitudinal body, previously wound onto a spool, is paid out and then passed through guide members and then applied against the cylindrical external surface. Said longitudinal body and said cylindrical external surface are preferably joined. For example, it is joined over its entire length to the surface of the support sheath, by gluing, welding or mechanical anchoring. As a result, the optical fibre sensor is perfectly fastened to the support sheath by way of the longitudinal body and their relative position is perfectly determined before the retaining sheath is applied. The latter then traps the longitudinal body and holds it applied against the cylindrical external surface of the support sheath. The optical fibre sensor is therefore able to withstand movements of the support sheath and the flexible pipe without damage.

Said at least one optical fibre sensor that is procured is advantageously buried inside a longitudinal body of trapezoidal section. In accordance with one variant, said trapezoidal section has a wide base opposite a narrow base and the longitudinal body is flattened and has two opposite wide faces relative to two opposite bevelled edges. As explained in more detail hereinafter in the remainder of the description, the wide base of the longitudinal body is applied against the cylindrical surface of the support sheath so that the two opposite bevelled edges form respective angles greater than 90° with the cylindrical surface. This feature makes it possible to improve the passage of the tubular structure through a fabrication installation as described hereinafter.

In accordance with a preferred embodiment of the invention, a tubular structure further including at least one tensile armour layer is procured. In the context of the present application, a tensile armour layer includes a set of reinforcing wires wound in a helix along the axis of the tubular structure with a helix angle having an absolute value between 15° and 60°, so as to be able to withstand traction forces effectively. The reinforcing wires are generally metal wires. They may also consist of a composite material, for example a carbon fibre composite.

In accordance with an advantageous variant of the present invention, the support sheath is situated on the outside of said at least one tensile armour layer. Moreover, the retaining sheath is preferably the outermost layer of said tubular structure. Also, the tubular structure advantageously includes another polymer material sheath inside said at least one tensile armour layer.

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Accordingly, the tubular structure includes, for example, in the direction from the interior toward the exterior, at least an internal sheath referred to as the pressure sheath and intended to provide a seal against hydrocarbons circulating in the pipe, a crossed pair of tensile armour layers, a support sheath surrounded by an optical fibre sensor and finally a retaining sheath. In this variant, the support sheath and/or the retaining sheath also serve as an external sheath protecting the tubular structure.

in accordance with another variant of the present invention, the support sheath is situated inside said at least one tensile armour layer. In accordance with this variant, the support sheath may be the innermost layer of the tubular structure, for example, i.e. the support sheath and the pressure sheath are then combined. This variant may also employ as the support sheath an intermediate sheath disposed between the pressure sheath and the tensile armour layers.

Another embodiment of the present invention provides an instrumented flexible pipe for the transport of hydrocarbons, said pipe being fabricated in accordance with the fabrication method described above.

According to a second aspect of the present invention, there is provided an installation for the fabrication of an instrumented flexible pipe for the transport of hydrocarbons, said installation including an entry opposite an exit so as to be able to drive from said entry to said exit a tubular structure including a polymer material support sheath having a free cylindrical external surface, said installation including a mobile storage support adapted to store at least one optical fibre sensor so as to be able to wind said at least one optical fibre sensor helically around said support sheath so as to be able to fasten said at least one optical fibre sensor to said support sheath; wherein it further includes a transformation device for supplying and for applying a retaining sheath coaxially to said support sheath so as to be able to retain said at least one optical fibre sensor in a fixed position against said cylindrical external surface, and wherein said transformation device includes an annular extrusion head so as to be able to form said polymer material retaining sheath around said support sheath.

As a result, the optical fibre sensor is wound beforehand in a helix around the support sheath to be applied against the cylindrical external surface, after which the tubular structure passes through the extrusion head that forms the retaining sheath around the tubular structure.

After this, and as the tubular structure advances, the retaining sheath is applied to the support

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2014294864 28 May 2018 sheath so as thereafter, on cooling, to clamp the optical fibre sensor against the cylindrical surface.

Preferably, the installation advantageously includes a sealed chamber situated between said entry and said annular extrusion head so as to be able to create a reduced pressure around said tubular structure. As a result, by creating a reduced pressure around the tubular structure, to be more precise between the latter and the retaining sheath being applied, the retaining sheath is naturally applied against the cylindrical external surface of the support sheath.

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

Figure 1A is a diagrammatic partial cutaway perspective view of an instrumented flexible 10 pipe obtained in accordance with a fabrication method conforming to an embodiment of the invention;

Figure IB is a diagrammatic view of an instrumented flexible pipe in service;

Figure 2 is a diagrammatic view of a detail from Figure 1;

Figure 3 is a diagrammatic view of an installation for fabrication of an instrumented 15 flexible pipe conforming to a first embodiment;

Figure 4 is a diagrammatic view of an installation for fabrication of an instrumented flexible pipe conforming to a second embodiment;

Figure 5 is a diagrammatic view of a detail from Figure 4;

Figure 6 is a diagrammatic detail view in cross section of an element in accordance with a 20 first variant employed in the installations represented in Figures 3 and 4; and,

- Figure 7 is a diagrammatic detail view in cross section of an element in accordance with a second variant employed in the installations represented in Figures 3 and 4.

Figure 1A shows an instrumented flexible pipe 10 for the transport of 5 hydrocarbons. It is made up of different layers.

The flexible pipe 10 firstly includes an internal pressure sheath 12 in the interior 14 of which the hydrocarbon circulates. The pressure sheath 12 is intended to confine the fluid transported in the passage 14 in a sealed manner. It is produced in a polymer material, for example based on a polyolefin such as io polyethylene, a polyamide such as PA11, PA12 or PA6-12 or a fluorinated polymer such as polyvinylidene fluoride (PVDF). The thickness of the pressure sheath is between 5 mm and 20 mm, for example.

Around the pressure sheath 12 is disposed a pressure armour layer 18, the function of which is to withstand forces linked to the pressure inside the 15 pressure sheath 12. The pressure armour layer 18 is formed of at least one profiled metal wire wound in a helix with a short lay around the pressure sheath

12. The profiled wire generally has a complex geometry, notably in the shape of a Z, T, U, K, X or I, making it possible to clip adjacent turns to each other. In the present application, the expression “with a short lay” means that the absolute value of the helix angle is close to 90°, typically between 75° and 90°.

Two superposed tensile armour layers 20, 22 are wound around the pressure armour layer 18 with opposite long lays. In the present application, the expression “with a long lay” means that the absolute value of the helix angle is less than or equal to 60°, typically between 15° and 55°.

The flexible pipe 10 is an “unbounded” pipe of the type described in API standard 17J, and the pressure sheath 12, the pressure armour layer 18, the tensile armour layers 20, 22 and the external sheath 24 are free to move longitudinally relative to one another when the pipe bends.

The flexible pipe 10 may also include an internal carcass, not shown in

Figure 1A, disposed inside the pressure sheath 12. When present, the internal carcass is formed of a profiled metal tape, for example, clipped and wound in a spiral. The principal function of the internal carcass is to withstand radial crushing forces. A flexible pipe with no internal carcass, of the type shown in

Figure 1A, is referred to as a “smooth bore” pipe. A flexible pipe including an internal carcass is referred to as a “rough bore” pipe.

In the embodiment of the invention shown in Figure 1A, the sealed external sheath 24 and the support sheath onto which an optical fibre sensor is wound are combined. The support sheath 24 has a cylindrical external surface 26 to which is applied an instrumented tape 28 forming a longitudinal body. This instrumented tape 28 extends along the cylindrical external surface 26 in a spiral with a long lay.

Furthermore, and as described in detail hereinafter, the instrumented tape io 28 includes within its thickness at least one optical fibre sensor making it possible to measure elongation of the optical fibre so as to measure deformations of the support sheath 24 so as to be able to determine and track bending, elongation, twisting or swelling of the flexible pipe 10. A plurality of types of optical fibre sensor may advantageously be used to effect deformation measurements, notably those including Bragg gratings and those in which the measurement principle is based on Brillouin reflectometry.

Other known types of optical fibre sensor could be employed, notably those based on Raman or Rayleigh reflectometry, and the optical fibre sensor could be used to measure other physical magnitudes, for example the temperature of the flexible pipe 10 or the chemical composition of the fluids in contact with the instrumented tape 28.

The instrumented tape 28 is advantageously made from polymer, for example polyamide or polyethylene, which surrounds the optical fibre sensor to protect it, notably from abrasion during fitting. As a matter of fact, the instrumented tape 28 is driven in movement and rubs against guides during its application, as explained in the remainder of the description.

What is more, the instrumented tape 28 is trapped between the support sheath 24 and a retaining sheath 30 installed around the support sheath 24. The retaining sheath 30 therefore grips the support sheath 24 and thus exerts a radial pressure on the thick tape 28, which is then held in a fixed position against the cylindrical external surface 26.

Figure 2 shows in cross section the instrumented tape 28 gripped between the retaining sheath 30 and the support sheath 24, which are partially represented. In this variant, the instrumented tape 28 has a rectangular section of thickness T having a value between 10% and 20% of its width L, for example. Inside the instrumented tape 28 there is buried an optical fibre sensor 29 that extends longitudinally at the heart of the instrumented tape 28.

The optical fibre sensor 29 is coupled to the instrumented tape 28 and the instrumented tape 28 is itself coupled to the support sheath 24 and to the retaining sheath 30 that grips it. The expression “coupled” means that any elastic deformation of one of the elements is transmitted entirely to the other element coupled to it without any relative movement at the interfaces.

io The instrumented tape 28, also referred to as a rod or cable, is obtained by extrusion or pultrusion, for example. In the former case the thermoplastic polymer rod is extruded directly around the optical fibre sensor 29. There is advantageously a layer of primer between the optical fibre sensor 29 and the polymer to improve adhesion and thus the coupling of the optical fibre sensor and the instrumented tape. In the latter case, a unidirectional composite, for example glass fibre and epoxy resin, rod is pultruded and the optical fibre is inserted into the rod during pultrusion.

The optical fibre sensor 29 is therefore perfectly coupled to the materials of the instrumented tape 28 and therefore, thanks to the retaining sheath 30, perfectly coupled to the support sheath 24. As a matter of fact, the retaining sheath 30 mechanically immobilizes the instrumented tape 28 on the one hand in an axial direction, i.e. in a direction parallel to the axis of the pipe, and on the other hand in a radial direction. As a result, the retaining sheath 30 makes it possible to prevent slippage between the instrumented tape 28 and the support sheath 24 in the aforementioned two directions. Accordingly, the helix angle of the optical fibre sensor relative to the axis of the pipe is fixed, as is the lay.

Furthermore, the retaining sheath 30 also makes it possible to protect the instrumented tape 28 and the optical fibre sensor 29 throughout the service life of the instrumented flexible pipe.

Also, the instrumented tape 28 is held in a fixed position along its longitudinal axis relative to the support sheath 24 and/or the retaining sheath

30. To this end, the instrumented tape 28 is advantageously stuck or welded to the support sheath 24, the effect of which is to prevent these two parts sliding relative to each other in a direction parallel to the longitudinal axis of the instrumented tape 28. Sticking or welding the instrumented tape 28 to the support sheath 24 may be replaced or complemented by using mechanical anchoring means between the instrumented tape 28 and the retaining sheath

30, the function of these means being to prevent the instrumented tape 28 sliding relative to the retaining sheath 30 in a direction parallel to the longitudinal axis of the instrumented tape 28. For example, these longitudinal anchoring means may consist in geometrical irregularities on the external face and/or the lateral faces of the instrumented tape 28, for example transverse io striations or local variations of the width L or the thickness T, the retaining sheath 30 espousing these irregularities.

The bottom face 31 of the instrumented tape 24 is substantially plane (before it is wound around the support sheath 24) so as to increase the area of contact between the instrumented tape 28 and the support sheath 24, which makes it possible to increase the adhesion between these two parts.

It is clear that the instrumented tape 28 must have a stiffness less than the stiffness of the support sheath 24 to which it is coupled so that the presence of the instrumented tape does not significantly affect the deformations of the support sheath 24. Also, the product of the thickness T of the instrumented tape 28 and the modulus of elasticity in traction of the instrumented tape 28 is advantageously less than the product of the thickness of the support sheath 24 and the modulus of elasticity in traction of the support sheath 24. If the instrumented tape 28 and the support sheath 24 are made of the same polymer material, the thickness of the instrumented tape 28 is preferably very much less than the thickness of the support sheath 24, for example one tenth of the thickness and preferably one thirtieth of the thickness.

Ways of fabricating the flexible pipe in accordance with the invention are described in detail hereinafter, to be more precise ways of associating the instrumented tape 28 and the support sheath 24.

Before describing these fabrication methods, the conditions of service of the instrumented flexible pipe in a marine environment are explained with reference to Figure 1B.

Thus Figure 1B shows a marine environment including a seabed 32 and an opposite sea surface 34. A seabed installation 36 on the seabed 32 is connected to a surface installation 38 floating on the surface 34 via an instrumented flexible pipe 40. The latter is extended at the surface by an optical cable 42 connected to an acquisition and processing device 44 controlled by a computer 46.

Direct reference will be made to Figure 3, which shows an installation for fabricating an instrumented flexible pipe in accordance with a first embodiment.

The installation includes an entry 50 opposite an exit 52. At the entry 50, a io tubular structure 54 is wound on a drum 56. The tubular structure 54 includes, in the direction from the interior toward the exterior, a pressure sheath, a pressure armour layer, two tensile armour layers and a polymer material external sheath forming the support sheath. The tubular structure 54 passes first through a taping machine 58. This includes a rotating frame 60 on which is installed a spool 62 of an instrumented tape 64 as described hereinabove with reference to Figures 1 and 2. The rotating frame 60 has a rotation axis substantially coinciding with the axis of the tubular structure 54. The spool 62 is arranged on the rotating frame 60 so that its axle is inclined to the rotation axis of the rotating frame 60. As a result, when the tubular structure 54 is driven in movement in the direction of the arrow F from the entry to the exit and the rotating frame 60 is simultaneously driven in rotation, the instrumented tape 64 is applied in a helix 66 to the cylindrical external surface of the external sheath forming the support sheath.

The speed of advance of the tubular structure 54 and the speed of rotation of the rotating frame 60 determine the lay and the angle of the helix 66 relative to the longitudinal axis of the instrumented flexible pipe.

The instrumented tape 64 includes an elongation measurement optical fibre sensor. This sensor includes a glass optical fibre the cladding of which advantageously consists of carbon and polyimide, which makes it possible for this optical fibre sensor to withstand temperatures of the order of 300°C. As explained above, such an optical fibre is relatively fragile and withstands with difficulty elongations greater than 2% without deteriorating. The optical fibre is therefore wound in a helix around the support sheath so as not to suffer excessive stresses. On the other hand, it has been discovered that if the helix angle relative to the longitudinal axis of the pipe is equal to precisely 54.74°, the optical fibre is not subjected to any stress if the pipe is deformed. It is therefore necessary to find an optimum angle as a function on the one hand of the maximum deformation possibilities of the optical fibre sensor and on the other hand the elongation measurement sensitivity of the optical fibre sensor.

In practice the helix angle is advantageously between 45.5° and 66.5° to avoid subjecting the optical fibre sensor to a relative elongation of the order of 2% or more. To avoid subjecting the optical fibre sensor to a relative elongation io of the order of 1% or more the helix angle is preferably between 49.5° and

60.3°.

Furthermore, to enable measurement of the bending of the flexible pipe, the helix angle is advantageously not between 54.5° and 55°. To enable more accurate measurement of the bending of the flexible pipe the helix angle is preferably not between 53.9° and 55.8°.

The combination of these criteria leads to choosing a helix angle between 45.5° and 54.5° or between 55° and 66.5°. Furthermore, the helix angle is preferably between 49.5° and 53.9° or between 55.8° and 60.3°.

The instrumented tape 64 is preferably coated with glue by means of a 20 glue applicator that is not shown before being applied to the external surface of the support sheath. As a result, the helix 66 remains in a fixed position on the support sheath of the tubular structure 54.

The tubular structure 54 equipped in this way with the instrumented tape 64 then passes through an annular extrusion head 68 to extrude the retaining sheath around the support sheath and thereby to clamp the instrumented tape 64 against the support sheath of the tubular structure 54. The instrumented flexible pipe produced in this way then passes through a cooling enclosure 70 before being wound around a receiving drum 72.

The installation shown in Figure 3 moreover includes an ultrasound sensor

74 for detecting the turns of the instrumented tape 64 so as to measure accurately the lay of the helix 66 after cooling and thermal shrinkage. This measurement is effected through the retaining sheath. It makes it possible to slave the rotation speed of the rotating frame 60 accurately as a function of the speed of advance of the tubular structure 54 so as to obtain a precise and stable helix angle over the entire length of the flexible pipe.

Figure 4 shows a fabrication installation in accordance with a second embodiment. Elements analogous or functionally analogous to those of the installation shown in Figure 3 bear the same reference with a prime symbol:

Accordingly there is again shown a tubular structure 54' wound on a drum

56' and situated at the level of an entry 50'. The installation includes a taping machine 58' equipped with a rotating frame 60' and a spool 62' on which is wound an instrumented tape 64' made from a thermoplastic polymer. As io explained in more detail hereinafter, an optical fibre sensor is buried at the heart of the thick tape 64'. The thermoplastic polymer is polyethylene, for example, or polyamide. This type of polymer has the advantage of being heatweldable. Also, the taping machine 58' includes a device 76 for heating the instrumented tape 64' and the installation includes, between the entry 50' and the taping machine 58', an oven 78 through which the tubular structure 54’ passes. Accordingly, the oven 78 softens the polymer material external sheath serving as the support sheath and the heating device 76, for its part, makes it possible to soften the thermoplastic polymer before the instrumented tape 64' is applied to the surface of the polymer material support sheath of the tubular structure 54' so that it can be welded thereto.

Moreover, a hot-air heating device 80, such as that shown in Figure 5, in which the tubular structure 54’ is seen, the instrumented tape 64’ being applied against the external sheath, makes it possible to input additional thermal energy. This is even more favourable to the welding of the instrumented tape

64’ to the support sheath of the tubular structure 54’.

In the same way as in the previous embodiment shown in Figure 3, the instrumented flexible pipe produced in this way passes, after the annular extrusion head 68’, through a cooling enclosure 70’ before being wound around a receiving drum 72’.

It will be seen that the glass optical fibre sensor is advantageously coated with carbon and polyimide making it possible to protect it durably from the rise in temperature during the welding and extrusion phases.

The annular extrusion head 68, 68’ advantageously includes a reducedpressure chamber, not shown, through which the tubular structure 54, 54’ equipped with the instrumented tape 64, 64' passes. As a result, a reduced pressure is created by means of a vacuum pump between the support sheath and the retaining sheath being formed, so that the latter is applied freely against the cylindrical external surface of the support sheath. The instrumented tape 64, 64' is therefore held forcibly against the cylindrical external surface, which enables improved fastening together of the instrumented tape 64, 64' and the support sheath. Fastening them together is important so that io movements of the sheaths are mechanically transmitted in their entirety to the optical fibre sensor.

Such a chamber includes an opening situated at the entry of the annular extrusion head and this opening is equipped with a seal making it possible to reduce air leaks between the tubular structure 54, 54’ equipped with the instrumented tape 64, 64' and said opening. This seal strongly compresses the tubular structure 54, 54’, which is driven through in translation, and there is a high risk of the instrumented tape 64, 64' being damaged, notably by abrasion.

Also, to attenuate this risk, the instrumented tape 64, 64’ has a trapezoidal general shape, as explained with reference to Figures 6 and 7.

Figure 6 shows in cross section an instrumented tape 82 of trapezoidal cross section in accordance with a first particular embodiment. The instrumented tape 82 has two opposite faces, a lower face 84 adapted to come to bear on the support sheath of the tubular structure and an opposite upper face 86 adapted to be covered by the retaining sheath.

Furthermore, the instrumented tape 82 here has at its heart three parallel optical fibre sensors 88, 90, 92. What is more, it has two opposite sides 94, 96 symmetrical with respect to each other. Each side forms with the lower face 84 an acute angle less than 45°, for example close to 30°.

As a result, the friction driving the instrumented tape 82 applied to the sealed sheath through the seal does not cause damage to or unsticking of the instrumented tape 82.

In accordance with a second particular embodiment, as shown in Figure 7, an instrumented tape 98 of trapezoidal general cross section includes an upper

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2014294864 28 May 2018 face 99 featuring a shallow longitudinal groove the extremum 100 of which is situated in line with the optical fibre sensor 102. The upper face 99 thus features two bearing surfaces 104, 106 on opposite sides of the extremum 100. As a result, the elements driving the tubular structure, such as rollers or caterpillar tracks, do not damage the optical fibre sensor,

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 relates.

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2014294864 28 May 2018

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

!. Method of fabricating an instrumented flexible pipe for the transport of hydrocarbons, said fabrication method being of the type including the following steps:

a tubular structure is procured including a polymer material support sheath having a free

5 cylindrical external surface;

at least one optical fibre sensor is procured;

said at least one optical fibre sensor is wound helically around said support sheath so as to be able to fasten said at least one optical fibre sensor to said support sheath;

wherein a retaining sheath is further procured and wherein said retaining sheath is applied

10 coaxially to said support sheath so as to retain said at least one optical fibre sensor in a fixed position against said cylindrical external surface, wherein said polymer material retaining sheath is formed around said support sheath so as to be able to apply said retaining sheath coaxially against said cylindrical external surface, and wherein the retaining sheath is extruded directly around the support sheath.

15
2. A method of fabrication according to claim 1, including the step of creating a reduced pressure between the tubular structure and the retaining sheath when so applied such that the retaining sheath is applied against the cylindrical external surface of the support sheath.
3. Fabrication method according to Claim 1 or 2, wherein said at least one optical fibre sensor is wound helically with a helix angle between 45.5° and 54.5° or between 55° and 66.5° relative to

20 the axis of the tubular structure.
4. Fabrication method according to any one of Claims 1 to 3, wherein the optical fibre sensor is a deformation measurement sensor.
5. Fabrication method according to any one of Claims I to 4, wherein the optical fibre sensor includes at least one Bragg grating.

25
6. Fabrication method according to any one of Claims 1 to 5, wherein said at least one optical fibre sensor that is procured is buried inside a longitudinal body.
7. Fabrication method according to Claim 6, wherein said longitudinal body is wound helically around said tubular structure so as to be able to fasten said at least one optical fibre

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2014294864 28 May 2018 sensor to said support sheath.
8. Fabrication method according to Claim 7, wherein said longitudinal body and said cylindrical external surface are joined.
9. Fabrication method according to any one of Claims 6 to 8, wherein said at least one optical

5 fibre sensor that is procured is buried inside a longitudinal body of trapezoidal section.
10. Fabrication method according to Claim 9, wherein said trapezoidal section includes a wide base opposite a narrow base.

1 i. Fabrication method according to any one of Claims 1 ίο 10, wherein a tubular structure is procured further including at least one tensile armour layer.

10 12. Fabrication method according to Claim 11, wherein said support sheath is situated outside said at least one tensile armour layer.
13. Fabrication method according to Claim 12, wherein said retaining sheath is the outermost layer of said tubular structure.
14. Fabrication method according to Claim 12 or 13, wherein a tubular structure is procured
15 further including another polymer material sheath inside said at least one tensile armour layer.

15. Instrumented flexible pipe for the transport of hydrocarbons, wherein it is fabricated in accordance with the fabrication method according to any one of Claims 1 to 14.
16. Installation for the fabrication of an instrumented flexible pipe for the transport of hydrocarbons, said installation including an entry opposite an exit so as to be able to drive from

20 said entry to said exit a tubular structure including a polymer material support sheath having a free cylindrical external surface, said installation including a mobile storage support adapted to store at least one optical fibre sensor so as to be able to wind said at least one optical fibre sensor helically around said support sheath so as to be able to fasten said at least one optical fibre sensor to said support sheath;

25 wherein it further includes a transformation device for supplying and for applying a retaining sheath coaxially to said support sheath so as to be able to retain said at least one optical fibre sensor in a fixed position against said cylindrical external surface, and

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2014294864 28 May 2018 wherein said transformation device includes an annular extrusion head so as to be able to form said polymer material retaining sheath around said support sheath,
17. An installation according to claim 16, including a sealed chamber situated between said entry and said annular extension head so as to be able to create a reduced pressure around said

5 tubular structure.

50’

Fig.6