GB2330394A

GB2330394A - Elongate streamlined element capable of changing its curvature and method for making same

Info

Publication number: GB2330394A
Application number: GB9901047A
Authority: GB
Inventors: Jean Hardy; Maso Fabrice Dal; Francois Grosjean
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 1997-05-16
Filing date: 1998-05-05
Publication date: 1999-04-21
Also published as: BR9804916A; AU7659898A; FR2763380B1; FR2763380A1; GB9901047D0; WO1998053237A1

Abstract

The invention concerns an abrasionproof elongate streamlined element in composite material capable of changing its bend. The streamlined element comprises an elongate hollow body (1) and means (9) made of a composite material stabilised inside the elongate body. The elongate hollow body comprises one or several mechanical fixing means (24) which serve to maintain the composite, material means inside the elongate body, while allowing the means to move axially relative to the elongate element.

Description

1 ELONGATE SHAPED ELEMENT CAPABLE OF CHANGING ITS CURVATURE AND METHOD FOR

MANUFACTURING THE SAME The present invention relates to an elongate shaped element of a long length made from composite and a method of manufacturing it, the shaped element having high mechanical characteristics along the longitudinal axis and in particular being capable of withstanding local stress and/or abrasion.

Such shaped elements specifically lend themselves to applications involving the manufacture of flexible pipelines or elements of flexible pipelines made by helical winding techniques, these pipes having particularly high resistance characteristics and is lightness qualities.

In most cases, the shaped elements used to manufacture flexible piping have a support, inside which a core is placed.

During manufacture and during their service life, for example where these elements are used to provide reinforcements made up of several layers, shaped elements will have to be capable of withstanding: local lloverbendingll which might be caused by the support on which the element is placed, alternate bending stresses, during which the core must remain in the support whilst retaining a certain amount of freedom relative to the support, and abrasion and friction, since the pipe may be made up of several layers of elements arranged one on top of the other.

The prior art describes various embodiments which allow the core to be retained in the interior of the support regardless of the stress to which the pipe is

2 subjected and withstand abrasion. Certain methods involve placing an anti- abrasion material on at least one surface of the shaped element to be protected or sheathing the entire shaped element once it has been manufactured. Such operations require an additional process, which increases the cost of manufacturing the shaped element to a not inconsiderable degree. Furthermore, the anti-abrasion material must have adhesion characteristics with regard to the shaped element, which restricts the choice of materials that can be used. Another approach is to use a bonding substance to stick the anti-abrasion coating to the shaped element, This being the case, the nature of the bonding substance must be compatible both with the material from which the element is made and the anti-abrasion coating. This dual constraint limits the range of materials which can be used still further and increases the cost of the elements. 20 Furthermore, the fact of using a bonding substance will not allow the desired degree of axial freedom required of the core relative to the support to be conserved. Patent FR 2.494.401 describes different embodiments of a shaped element. A first approach consists in using a mould made from an anti-abrasion material and filling it with an armoured plastic adhering to the inner wall thereof, the nature of the material being selected so as to ensure that the core will be securely retained in the mould. This choice restricts the materials which can be used for the mould since it also requires the materials used for the mould to be compatible with each other. In addition, the degree of axial freedom between the core and the support is non- existent and bending stress causes cracks in the material 3 forming the core.

Another approach to ensuring that there is a certain degree of axial freedom between the core and the support is to deposit vaseline on the interior of the support. This will conserve a degree of axial freedom between the core and the support. However, if the element is subjected to bending, for example, the core tends to "work loose", coming apart from the support.

The objective of the present invention is to overcome the drawbacks of the prior art and in particular to provide a shaped element and a method of manufacturing it, having the following characteristics:

ability to withstand changes of curvature in the shaped element as a result of the degree of axial freedom maintained between the core and the support, resistance to abrasion.

In the description of the invention given below, by "composite material" is meant a material which may incorporate fibres, such as glass fibres, carbon fibres, aramide fibres, embedded in a matrix such as a thermosetting or cross- linkable matrix, or any other material which requires processing to bring it to its final state.

The expressions "elongate body" and "hollow elongate body" used throughout the description denote the same element, for example a body which is preferably resistant to abrasion due to the actual nature of the material from which it is made and/or due to the geometric characteristics of this mould, for example its thickness, allowing sufficient resistance to abrasion to be conserved. The term "core" refers to the stabilised composite material.

The invention therefore relates to an elongate shaped element made from a composite material, this element being likely to be subjected to bending, and preferably capable of withstanding abrasion, the shaped is 0 4 element consisting of a hollow elongate body and a core made from a stabilised composite material inside the elongate body. It is characterised in that the hollow elongate body has one or more mechanical fixing means which allow the core of composite material to be secured inside the hollow elongate body whilst nevertheless allowing the core some freedom for axial movement inside the elongate element. 10 This will prevent core from becoming loose from the body in the event of any changes in curvature of the shaped element and a certain degree of axial freedom will be retained, essentially in the longitudinal or axial direction of the element. is The elongate body may have at least one groove and the mechanical fixing means may be located on at least one of the walls of this groove, for example the wall forming the base of the groove and/or at least one of the side walls of the groove. 20 These mechanical f ixing means may have an 11 i shaped part on the side walls of said elongate body which will be inserted in the core of composite material, for example, the core being of a width In" and the value of,, ill being within a range of between 0.05n and 0.25n, for example, and preferably between 0.08n and 0.13On. The mechanical fixing means are formed by one or more elongate elements, for example, which extend across at least a part of the length of one or more of the walls of the groove. In another embodiment, the fixing means are formed by one or more elongate elements which extend across at least a part of at least one of the walls of the groove, for example, slots of a depth llrll, for example. The ratio of the value of the depth of the slot relative to the thickness llell of the groove is within the range of 1 between 0.1 and 0.4, for example.

The mechanical fixing means may also be formed by one or more parts of the hollow elongate body, by means of a forming process, for example.

The mechanical fixing means may also be of a "TIIshaped design with a base width of 11 and a width at the head of 12, the width 12 being less than 0.5n, for example, and the value 11 being such that (12)/3>1,>0.1n, where 'In" is the width of the core of composite material.

The mechanical fixing means may also be localised elements such as recesses and/or contact pieces distributed over at least a part of the length of at least one of the walls.

If the recesses are of a depth 11p11 and a wall of the 15 hollow elongate body is of a thickness llell, the ratio p/e is between 0.1 and 0.5, for example.

The present invention also relates to a method used to manufacture a shaped element susceptible to changes in curvature and capable of withstanding abrasion.

The method is characterised in that the following steps are performed:

a hollow elongate body is preferably adapted so as to be capable of withstanding abrasion, the elongate body having at least one mechanical fixing means and/or a means enabling a mechanical fixing means to be formed, the mechanical fixing means permitting an axial movement between the core and the elongate body, and said hollow elongate body is filled with a composite material.

By virtue of one mode of implementing the method, the hollow elongate body filled with the composite material is put through a process which will change it to its final state, this processing being applied before or after manufacture of the element.

9 6 The mechanical fixing means may be formed before or after the step during which the composite material assumes its final shape.

The present invention lends itself particularly well to applications involving the manufacture of flexible pipe having at least one elongate shaped element as proposed by the invention and in particular for the manufacture of a flexible pipe such was would be used in the petroleum industry.

As compared with the known prior art, the shaped element having the characteristics outlined above as well as the method used to manufacture it offer numerous advantages and overcome various problems, in particular those listed below: the fact of using mechanical fixing means or mechanical retaining means as opposed to the chemical means conventionally used, such as bonding substances, means that the core can be held securely in place whilst at the same time leaving a certain degree of axial freedom, i.e. allowing it to move or slide axially relatively to the elongate body forming the support, consequently, the materials used for the support can be selected from a much wider range than the range conventionally available for use with the prior art, this means that cheaper materials can be used than those conventionally used and/or which are easier to process. Other features and advantages of the method and device proposed by the invention will become clear from the description of embodiments below, given by way of illustration and not restrictive in any respect, with reference to the appended drawings, in which: figure 1 is a schematic illustration of a method 35 used to manufacture a shaped element as proposed by

0 7 0 0 0 0 0 0 the invention, figure 2 is a schematic illustration in crosssection of the features of the mechanical fixing means distributed over a section of a hollow elongate body which are then inserted in the core with which the body is filled, figure 3 illustrates an embodiment in which the mechanical fixing means, such as slots, extend across practically the entire length of the two walls of the groove, being inserted in the core, figure 4 illustrates an embodiment of mechanical fixing means which is in the form of recessed slots extending across the walls of the groove, figures 5 and 6 illustrate a specific example of a mould having mechanical fixing or retaining mans formed from a section of the wall of the hollow elongate body, figure 7 illustrates a different embodiment in which the mechanical f ixinq means are provided in the form of a T-shaped rail, which is inserted in the core, figure 8 depicts an embodiment in which the mechanical fixing means are provided in the form of a recessed rail in the wall of the mould and figure 9 illustrates a flexible pipe of the prior art provided with a resistance consisting of mechanical hooking means reinforcement In order to provide a clearer understanding of the invention, the example described below by way of illustration, although this is not restrictive, relates to a method of manufacturing a shaped element such as that described in detail in patent FR 2.494.401 filed by the applicant and only those steps which are essential and necessary to an understanding of the method proposed by the invention and its implementation are described and are so with reference to figure 1.

8 A hollow elongate body 1 is unwound from a reel 2, for example, in readiness for winding on a drum or mandrel 3. It is fed, for example, between guide rollers 4 and tension rollers 5. The shaft of the mandrel 3 is connected to drive means such as those described in the abovementioned patent or to any other conventional means capable of driving the shaft.

The shaped element made on the mandrel 3 initially has a radius of curvature Ro. This element is then stored, for example on a reel with a radius R,, before being unwound onto a core of flexible pipe with a radius R., for example. The shaped element changes from radius R2 to radius R-. passing through an infinite radius.

The shaped element comprises a hollow elongate body 1, for example, in the form of a longitudinal groove 6, having one or more mechanical means for securing or hooking the composite material in the groove, the mechanical fixing means being described in more detail with reference to figures 2 to 7 and indicated by references 24, 25, 26, 27, 28, 29, 30, 31 and 32.

This longitudinal groove is preferably 11Ull-shaped, consisting of three walls, one wall forming the base together with two side walls, the angles between each of the side walls and the wall forming the base of the groove ranging between 80 and 1000 and preferably close to 900.

As it is wound around the drum, the groove 6 is filled with high-resistance filaments 8 or rovings, for example, previously impregnated with a curable resin, the filaments and matrix together forming the composite material or core 9 (f igure 2) of the section or shaped element.

Having been filled as above with the uncured composite material, the elongate body is then f ed through a processing device 10 designed to bring about A i 9 stabilisation of the composite material.

The mechanical fixing or retaining means 24, 25, 26, 27, 28, 29, 30, 31 can then be formed from a part of the mould, for example a part 31, 32 of the mould wall, as illustrated in figures 6 and 7 as an example, although this is not restrictive.

The method of manufacturing the shaped profile may incorporate an additional shaping step, known to those skilled in the art, in order to form the mechanical hooking means 32. This step is generally performed after the composite material has been cured but it would not be a departure from the scope of the invention if it were performed during or alternatively after the step during which the shaped profile is made. They may also be preformed.

If used as a mould-support, it is preferable to adapt the hollow elongate body so that it will withstand abrasion, particularly that caused as a result of friction between the different layers. Consequently, it may be shaped from a material whose nature exhibits abrasion resistance itself, for example, or it may be given geometric characteristics that will impart sufficient resistance to it to withstand the occurrence of abrasion. For example, in the mould used, those walls likely to be in contact with other walls will be of a thickness which is preferably selected to suit the nature of the material enabling it to withstand abrasion.

This being the case, the elongate body will be made, for example, from a material selected from the following list: polyamide 11, high-density polyethylene, polypropylene, filled or not with carbon black, polytetrafluoroethylene or any other abrasion- resistant material. The nature of the material selected will, in any case, be compatible with the chosen curing process.

Other materials which may be used, plasticized or not, filled or not, are set out in the list below:

PVW: polyvinylidene difluoride PSU: polysulphone PES: polyethersulphone PPS: polyphenylene sulphide PEI: polyetherimide PEEK: polyetheretherketone PAI: polyamide imide PFA: polyfluoroalkoxy.

The design of the fixing means described below with reference to the drawings as well as their number and distribution in relation to the hollow elongate body will be specifically selected to suit the materials used, the material of the mould-support and/or the material forming the core.

The choice of parameters, such as shape, number and distribution of the fixing means may also depend on the stress to which the shaped element may be subjected during its service life and/or during its manufacture. The element may, in effect, be used alone or may be integrated in a flexible pipe such as that described with reference to figure 9, producing by winding one or more layers of shaped elements having at least one fixing means of the mechanical type. In practice, the strain to which the flexible pipe will be subjected, depending in particular on how it will be used, will create stress in the directions of low resistance such as the transverse directions in the case of uni-directional composite materials, which will also affect the choice of fixing means.

various examples of fixing means which satisfy the criteria listed above are described in relation to figures 2 to 8.

Figure 2 is provided as an illustration, though not restrictive, of the preferred geometric and dimensional characteristics which the mechanical fixing means must satisfy, partiCularly in terms of their dimension relative to the thickness of the wall of the hollow elongate body. The mechanical fixing means are protrusions 24, for example, extending across a certain length relative to one of the walls of the hollow elongate body and which are inserted in the composite or core 9.

In this case, it is desirable to limit the portion of means 24 which is inserted in the core in order to retain a maximum compression section.

In effect, the pressure applied to the shaped is element is inversely proportional to the surface area to which it is applied.

If a hollow elongate body does not have mechanical fixing mens, the surface area or width to which pressure is applied corresponds substantially to the internal width of the groove, i.e. the distance 1 separating the interior of the two side walls 21 and 22 of the groove.

The width of the fixing means 24 of figure 2 which is inserted in the composite material is "ill and the width of the groove is 1,111, which means that the width across which pressure is applied is substantially equal to 1-2i. It is important to reduce the width,i,, of the contact piece which penetrates the core to a minimum whilst at the same time conserving a sufficient value to ensure that the core is retained in the mould. This choice is of particular importance if the moulds have a low modulus of compression and the cores have a high modulus.

The width,ill of the fixing means inserted in the composite material is preferably between 0.05n and 0.25n, 12 In" being the total width of the core substantially corresponding to the internal width of the groove, and preferably between 0.08 and 1.30n.

If there are shear stresses, the minimum radii of curvature of the fixing means 24 will preferably be in excess of 0.2 mm so as to minimise the onset of potential cracking in the planes parallel with the fibres.

The fixing means are preferably distributed in a symmetrical pattern in order to balance the core of composite material inside the hollow elongate body and distribute it as uniformly as possible.

The material of the fixing means may be of the same nature as that used for the hollow elongate body or of a different nature but compatible with the material of the is elongate element.

Figure 3 shows a preferred embodiment of an element proposed by the invention in which the fixing means are formed by means of protrusions 28, 29, for example, preferably located on each of the side walls 21, 22 of the groove 6 and extending at least along a part of the length thereof, such as rails.

These rails are preferably distributed in a symmetrical design along the side walls of the groove 6, i.e. the rail corresponding to projection 28 located on the side wall 21 of the groove 6 faces the rail shown by reference 29 on the opposite side wall 22.

The rail may extend continuously across the entire length of the groove.

Advantageously, the effective width of these projections 28, 29 is between 0.05n and 0.25n, where 'In', is the total width of the core, and preferably between 0.08 and 0,130 n.

The advantage of this design is that it permits axial displacement or sliding of the core in the groove, the axis referred to being the longitudinal axis of the 13 groove corresponding to that of the elongate element.

In another embodiment, it is also possible to distribute several portions or rails or projections of a type similar to those sown by reference 28 or 29 in f igure 3 at a same height or alternating one with the other across different heights. The lengths of the different portions of rail and the intervals separating these portions of rail may have different values, which will of course be selected so as to ensure that the core is securely held in the groove.

The shape and dimension of these projections will depend on their position in the groove 6, for example, in particular on the wall or walls on which they are disposed.

is In figure 4, the mechanical fixing means are formed by two recesses such as furrows or slots 25 and 26, which by preference extend across the entire length of the side walls 21, 22 of the groove 6.

The composite material forming the core penetrates these furrows at least partially, so that they will be retained in the groove. The shape, number and dimension of these slots are selected to suit their relative position in the groove 6, for example, relative in particular to the wall or walls on which they are disposed. They are also chosen as a function of the number of slots distributed in the groove, for example.

The depth of the grooves llrll is fixed relative to the thickness llell of the wall of the groove, the value of ratio r/e being preferably between 0.1 and 0.4 in order to ensure that the core is retained in the mould without it being embrittled.

Figures 5 and 6 illustrate an example of an elongate body having mechanical fixing means which are formed by a part 31 of the side walls of the elongate body. The fixing means are shaped during or after the stabilisation 14 process of the composite material or the process whereby the core will be cured to assume its final state forming the core.

optionally, they may be preformed before the groove is filled with the composite material and fibres which form the core, their final shaping being carried out after the filling step.

To this end, the hollow elongate body has at each of the upper parts of its walls 21, 22, for example, a section 31, which may or may not be bulged, which acts as a base from which the mechanical fixing means are created 32 (Fig. 6).

Figure 6 illustrates the mould and its mechanical fixing means 32 after the shaping step.

The embodiment has the advantage of retaining a freedom of axial movement of the core relative to the hollow elongate body.

Figure 7 illustrates another embodiment of the shaped element proposed by the invention in which the mechanical fixing means are in the form of a projection 30 formed on a level with the base or wall of the groove extending across a part of the length of the shaped element, such as a rail.

The rail 30 is of a 'IT"-shaped design, for example, having a leg of a height 'It", and is of a width 1-, at the base and a width 12 at the head.

The width values L, 1- are selected as a function of the width of the core 1InvT, for example, and are preferably as follows:

1,<0.5n and (1,,)/3>1-_>0,1n.

Figure 8 illustrates an example of an embodiment of the shaped element proposed by the invention in which the groove has a single slot 27 located in its bottom wall 23. The slot 27 extends across the entire length of the hollow elongate body, for example, and is of a depth "h',.

is In order to ensure that the core is securely retained in the groove, the ratio h/e, where llell is the thickness of the wall, is preferably between 0.2 and 0.5. This range of values will ensure that the core is retained in the groove whilst preventing the projection created thereby in the wall of the groove f rom causing it to become embrittled.

Clearly, the various embodiments of f ixing means described above with reference to the drawings may be combined with one another and distributed in one of the layouts described above relative to the shaped element, without departing from the scope of the invention. Advantageously, they may be used to manufacture a pipe such a that described in relation to figure 5.

The examples outlined above by way of illustration, but not restrictive, with reference to the drawings represent hollow elongate bodies with side walls and a base wall substantially perpendicular to one another.

The present invention may also be applied to hollow elements whose walls subtend angles of any value.

Clearly, the thicknesses of the walls forming the hollow shaped element may be different.

The shaped element described above consisting of a mould-support and provided with mechanical fixing means is advantageously used to manufacture sealed flexible pipes such as described by way of illustration, but not restrictively, with reference to figure 5, the tensile resistance reinforcement being provided as proposed by the prior art, for example.

Such pipes may be subjected to high tensile stress. This pipe is made up as follows, starting from the nterior and moving towards the exterior: a flexible internal sheath or tubular core 51, made from a plastics material such as a thermoplastic or an elastomer, for example, 16 0 0 0 a flexible metallic reinforcement 52 surrounding the tubular core 51 and resistant to the forces created by the pressure prevailing inside and outside the flexible pipe, which may be formed by helically winding at a low pitch a self-clamping shaped element of an S, Z or T shaped design; consequently, the pressure will not act directly on the tubular core 51, a flexible and sealed sheath 53 made from a plastic material such as an elastomer and covering the reinforcement 52, thereby protecting it from attack from outside, and a tensile resistance reinforcement 54. The tensile resistant reinforcement is made up of two layers 55 and 56, helically wound in opposite directions with a large winding pitch.

17

Claims

1) An elongate shaped element made from a composite material, said element being susceptible to changes in curvature and preferably capable of withstanding abrasion, the shaped element having a hollow elongate body and a core made from a stabilised composite material inside the elongate body, characterised in that the hollow elongate body has one or more mechanical fixing means (24, 25, 26, 27, 28, 29, 30, 31, 32) which enable the core of composite material to be held inside the elongate body whilst allowing the core the possibility of axial displacement relative to the elongate body.

2) A shaped element as claimed in claim 1, characterised in that said hollow elongate body has at least one groove (6) and in that the mechanical fixing means are located on at least one of the walls of said groove (6) such as the wall forming the base of the groove and/or the side walls of the groove.

3) A shaped element as claimed in claim 2, characterised in that the fixing means (24) has a part "ill of a width 'In" on the side walls of said elongate body which is inserted in the composite material and in that "ill is between 0.05n and 0.25n and preferably between 0.08n and 0.13On.

4) A shaped element as claimed in claim 3, characterised in that said mechanical fixing means comprise one or more elongate elements (28, 29) extending across at least a part of the length of one or more of the walls of the groove.

5) A shaped element as claimed in claim 2, 18 characterised in that said mechanical fixing means consist of one or more elongate elements (25, 26) of a depth llrll extending across at least a part of the length of one of the walls of the groove, such as slots, and in that the ratio r/e where llell is the thickness of the wall of the groove on which the slot is disposed is preferably between 0.1 and 0.4.

6) A shaped element as claimed in one of claims 1 and 2, characterised in that the mechanical fixing means are formed from at least a part of the hollow elongate body.

7) A shaped element as claimed in claim 4, characterised in that said fixing means (30) are of a TIT" shaped design having a width 1, at the base and a width 1- at the head and in that the width 12 is less than 0.5n and in that (1-)/3>1->0,1n, where 'In" is the width of the core of composite material.

8) A shaped element as claimed in claim 1, characterised in that said mechanical fixing means (24) are localised elements such as recesses and/or contact pieces distributed across at least a part of the length of at least one of the walls of the hollow body (21, 22, 23).

9) A shaped element as claimed in claim 8, characterised in that if the depth of a recess is "p" and the wall of the hollow elongate body is of a thickness "ell, the ratio p/e is between 0.1 and O.S.

10) A method of manufacturing a shaped element susceptible to changes in curvature and capableof withstanding abrasion, characterised in that it comprises 19 0 the following steps: a hollow elongate body is adapted to withstand abrasion, the elongate body having at least one mechanical fixing means and/or a means enabling a mechanical fixing means to be formed, the mechanical fixing means allowing a degree of axial movement to be left between the core and the elongate body and said hollow elongate body is filled with a curable composite material.

11) A method as claimed in claim 10, characterised in that said hollow elongate body filled with the composite material is treated so that it changes to its final state, said treatment process being applied during or after manufacture of said body.

12) A method as claimed in one of claims 10 and 11, characterised in that said mechanical f ixing means is formed before or after the step during which the composite material is processed to assume its final form.

13) A flexible elongate body such as a flexible pipe, having at least one elongate shaped element as claimed in one of claims 1 to 8.

14) Application of the method as claimed in one of claims 10 to 12 and the shaped element as claimed in one of claims 1 to 9 to the manufacture of a flexible pipe used in the petroleum industry.