FR2904992A1 - Smooth-bore type flexible conduit for use in sea-bed, has axial blocking tubular layer with link coils with sectioned wires wound in helical manner, where coils are formed of wires of same section forming parallelogram - Google Patents

Abstract

The conduit has an axial blocking tubular layer (40) placed under armor webs (48, 50) and with link coils (42) with sectioned wires wound in a helical manner. Each wire has an inner surface (70) opposite to an outer surface (72), where the surface (70) defines an inner medium surface plane. Lateral flanges define medium planes inclined with respect to the surface plane of the surface (70) for allowing relative transversal movement of the coils along joint surfaces. The coils are formed of wires of same section forming a parallelogram, where the wire is wound against the flanges.

Description

1 Stabilized flexible pipe resistant in axial compression The

  The present invention relates to a flexible pipe for transporting hydrocarbons or other fluids under high pressure, and to a method for producing such a pipe. More particularly, the invention relates to a flexible pipe having a high resistance to axial compression. The flexible hydrocarbon transport pipes are already well known, and they generally comprise, from the inside towards the outside of the pipe, a metal carcass, to take up the radial crushing forces, covered with a sealing sheath. polymer interior, a pressure vault to withstand the internal pressure of the hydrocarbon, plies of armor to take the axial tension forces and an outer sheath of polymer to protect the entire pipe and in particular to prevent sea water to penetrate into its thickness. The metal casing and the pressure vault consist of longitudinal elements wound with short pitch, and they give the pipe its resistance to radial forces while the plies of armor are made of metal wires wound in long steps to resume axial efforts. It should be noted that in the present application, the concept of short-pitch winding designates any helical winding at a helix angle close to 90, typically between 75 and 90. The concept of winding with a long pitch covers the propeller angles of less than 55, typically between 25 and 55 for the armor plies. These pipes are intended for the transport of hydrocarbons, particularly in the seabed, and at great depths. More precisely they are called unbonded type and are thus described in the normative documents published by the American Petroleum Institute (API), API 17J and API RP 17B.

2904992 2 Where a pipe, whatever its structure, is subjected to an external pressure which is higher than the internal pressure, compression forces oriented parallel to the pipe axis occur in the wall of the pipe. and which tend to shorten the length of the pipe. This phenomenon is called the reverse end-cap effect in English. The intensity of the axial compression forces is proportional to the difference between the external pressure and the internal pressure. This intensity can reach a very high level in the case of a flexible pipe immersed at great depth, owing to the fact that the internal pressure can, under certain conditions, be much lower than the hydrostatic pressure. In the case of a flexible pipe of conventional structure, for example in accordance with the normative documents of the API, the inverse bottom effect tends to induce a longitudinal compressive force in the son constituting the armor layers, and to shorten the length of the flexible pipe. In addition, the flexible pipe is also subjected to dynamic stresses especially during installation or in service in the case of a rising pipe (riser in English). All of these constraints can cause the armor plies to flare up and irreversibly disrupt the armor plies, thus causing the flexible conduit to fail. WO 03/083343 discloses a solution for increasing the axial compressive strength of armor plies of a flexible pipe. This solution consists of wrapping reinforced tapes, for example aramid fibers, around the armor plies. In this way we limit and control the swelling of the armor layers. However, if this solution solves the problems related to the radial buckling of the son constituting the armor plies, it only makes it possible to limit the risk of lateral buckling of said threads that lasts. The document WO 96/17198 describes, in particular in FIG. 18, a flexible pipe comprising a tubular axial blocking layer 2904992 3 able to take up the axial compression forces and limit the shortening of the pipe, which makes it possible to avoid damaging the tablecloths of armor. Also, a problem which arises and which the present invention aims to solve is to provide a flexible pipe which not only can withstand high axial compression without being shortened, but which can also sustainably withstand repeated cycles of alternating flexion. while maintaining its flexibility and integrity. In addition, it is desirable that this conduit be bent at small bending radii. In order to solve this problem, the present invention provides a stabilized flexible hydrocarbon transport pipe, said pipe comprising at least two armor plies and a tubular axial blocking layer located under said armor plies, said tubular layer axial locking device comprising contiguous turns of profiled wire of substantially quadrilateral section and wound helically with a short pitch, said contiguous turns being adapted to axially block said pipe in compression, the profiled wire of said turns having an inner surface opposite to an outer surface and two opposite side flanks, said inner surface defining a middle plane of internal surface and said lateral flanks defining lateral planes of lateral flanks inclined with respect to said middle plane of internal surface, said contiguous turns defining seam surfaces inclined with respect to axis of said pipe, e simultaneously allowing the transverse relative movement of said contiguous turns following said inclined joint surfaces and the deflection of said pipe; according to the invention said contiguous turns are formed of profiled wire of the same section substantially forming a parallelogram, said profiled wire being wound lateral flank against side flank.

Thus, the tubular blocking layer is formed from one or more son of single geometry. The uniqueness of the geometry simplifies the supply of the wires and the manufacture of the tubular blocking layer. In addition, and advantageously, said lateral flanks are inclined with respect to said internal surface by an angle of between 50 and 70, which makes it possible to improve the compressive strength of the pipe, while maintaining good flexibility. . In the present application, by convention, the angle of inclination between two concurrent lines is the absolute value of the angular aperture of the smallest of the four angular sectors defined by the intersection of the two lines. It is therefore always between 0 and 90. In addition, said tubular axial blocking layer preferably comprises two profiled son of the same section wound together, side flanks against lateral flanks. In this way, the speed of realization of the axial blocking tubular layer is increased.

Other features and advantages of the invention will appear on reading the following description of particular embodiments of the invention, given by way of indication but not limitation, with reference to the appended drawings in which: Figure 1 is a partial schematic perspective view of a flexible pipe according to the invention; FIG. 2 is a partial diagrammatic view in axial section of a portion of the flexible pipe illustrated in FIG. 1; - Figure 3 is a partial schematic view in axial section of detail of a portion of the flexible pipe; and Figure 4 is a partial schematic view of the pipe members shown in Figure 3 in an operative position. Figure 1 illustrates a flexible pipe 10 according to the invention of the smooth-boron type and which here, from the inside of the pipe 12 to the outside 14, an inner sealing sheath 16 made of plastic material, an arch 18, a tubular locking layer 20, two crossed armor plies 22, 24 separated from the tubular locking layer 20 by an intermediate sheath 25, and an outer sealing sheath 26. The flexible pipe 10 thus extends longitudinally along the axis A. The stapled pressure vault 18 and the tubular blocking layer 20 are made by means of longitudinal elements wound helically at short pitch, forming non-contiguous turns for the pressure vault 18 and joined for the tubular blocking layer 20, while the crossed armor plies 22, 24 are formed of helical windings long pitch of metal son. In other types of rough-boron type structures a metal carcass is mounted within the inner sealing sheath 16 and the intermediate sheath 25 is removed. This is the case of the pipe portion 28 shown in axial hemiclage and illustrated in FIG. 2. It has an inside 32 towards the outside 32, a carcass 34 formed of a profiled metal strip and wound in stapled turns. to each other and making it possible to take up the radial crushing forces, a sealing sheath 36 of plastics material, a pressure vault 38 made of a zeta-shaped wire wound helically with a short pitch and stapled; a tubular blocking layer 40 having a profiled wire section substantially forming a parallelogram 42 which will be detailed below, a first anti-wear band 46, two armor son 48 and 50 separated by a second anti-wear band wear 52 and an outer sheath 54 of plastic separated from the armor son by a retaining band 56. The anti-wear bands have the function of limiting wear and friction between adjacent metal layers. Advantageously, such a layer may also be interposed between the pressure vault 38 and the tubular locking layer 40. The sole purpose of the retention band is to maintain the armor plies during the manufacture of the pipe, until the outer sheath is laid. This retention band is different in structure and function from the aramid fiber reinforced tapes described in WO 03/083343. It has a much lower mechanical strength and would not be able to limit or control in service the swelling of the armor plies under conditions similar to those described in WO 03/083343. As for the tubular locking layer 40, shown only in FIG. 3, it consists of a profiled wire 42 of non-rectangle parallelogram-shaped section and having two parallel lateral flanks 44. When the pipe is in the rest position the turns are contiguous and they delimit joint planes inclined relative to the axis of the pipe A, close to 60. In addition, the profiled wire 42 has an inner surface 70 and an opposite outer surface 72. As soon as the pipe is bent, the turns slide against each other along their joint plane, flanks against flanks as shown in FIG. This Figure 4 shows a portion of the tubular locking layer 40 corresponding to the inner portion of the curvature. Thus, the turns of the profiled wire 42 approach each other, the wire tending to pivot on itself as the turns slide relative to each other so that the parallel side flanks 44 come closer together. of a plane perpendicular to the axis of the pipe. In contrast, in the elongation portion of the tubular blocking layer 40, which is not shown, the wires swing in the opposite direction so that the lateral flanks 44 incline more with respect to the axis of the pipe A, the turns also sliding against each other. The bending of the pipe is accompanied by a rotation of the plane of the turns of the profiled wire 42. Thus, the average plane in which each turn is inscribed then tends to rotate along an axis perpendicular to the plane of curvature of the pipe. away from the position substantially perpendicular to the axis of the pipe, position it occupies when the pipe extends longitudinally. This rotation is accompanied by a relative axial sliding between the internal 70 and outer surfaces 72 of the profiled wire 42, and the internal and external tubular structures at their contact surfaces with the layer. tubular blocking 40.

In a particularly advantageous manner, the angles of the profiled wire 42 are chamfered or rounded to facilitate their pivoting while avoiding damage to the inner and outer tubular layers at their contact surface with the tubular locking layer 40.

As shown in Figure 2, the pipe 28 extends longitudinally in a rest position. Note that in this rest position, the profiled wire 42 which forms turns around the pressure vault 38, has its inner surface 70 resting on the turns of the pressure vault 38, while the armor son 48 , 50 and the first anti-wear strip 46 are they, bearing on the outer surface 72. Advantageously, the turns of the profiled wire 42 are supported on the pressure vault 38 via a layer of synthetic material having a low coefficient of friction so as to facilitate the axial relative sliding between the tubular locking layer 40 and the pressure vault 38. A layer of the same kind can also be provided as a replacement for the anti-wear band 46, in the The purpose of this invention is to facilitate axial relative sliding between the tubular blocking layer 40 and the first armor ply 48. Another embodiment of the invention, according to which the tubular layer of Blocking is substituted for the internal carcass 34 and plays both a role in the resumption of radial compression forces and in the recovery of axial forces. Furthermore, thanks to this tubular blocking layer 40 it is understood that any axial stress tending to retract the pipe 25 as illustrated in Figure 1 would be taken up by the turns of the profiled wire 42 in flanks against flanks. The blocking layer is designed such that these stresses never exceed the elastic limit of the profiled wire, so that the deformations remain reversible and weak. In practice, under the application of axial compression, the blocking layer and the pipe can reversibly shorten by a relative value of less than 0.3%, advantageously 0.15%. Under these conditions, the swelling of the armor plies remains lower, in relative value, at approximately 0.6%. Thus, the radial movements of the armor son remain significantly lower than their own thickness, which avoids any risk of disorganization of the armor plies. 5

Claims (3)

  A stabilized flexible hydrocarbon transport pipe (10), said pipe comprising at least two armor plies (22, 24) and a tubular axial blocking layer (20, 40) located beneath said armor plies, said layer axial blocking tubular comprising contiguous turns of profiled wire (42) of substantially quadrilateral section and helically wound with a short pitch, said contiguous turns being adapted to axially lock in compression w said pipe (10), the profiled wire of said turns having a surface internal (70) opposed to an outer surface (72) and two opposite lateral flanks (44), said inner surface defining an inner surface mean plane and said lateral flanks defining lateral sidewall planes inclined with respect to said middle surface plane internal, said contiguous turns defining seals surfaces inclined relative to the axis (A) of said pipe, so as to allow r simultaneously the transverse relative movement of said contiguous turns along said inclined joint surfaces and the deflection of said pipe (10); characterized in that said contiguous turns are formed of profiled wire (42) of a same section substantially forming a parallelogram, said profiled wire being wound lateral flank (44) against lateral flank (44).   2. Flexible pipe according to claim 1 characterized in that said lateral flanks (44) are inclined relative to said inner surface by an angle of between 50 and 70.   3. stabilized flexible pipe according to claim 1 or 2, characterized in that said tubular axial blocking layer comprises two profiled son wound together, side flanks against lateral flanks.