FR2844022A1 - FLEXIBLE PIPELINE WITH MULTI-LAYER CORRUGATED METAL TUBE - Google Patents

Abstract

The flexible pipe has an inner impermeable metal tube (1), a shield (2), an optional polymer sealing sleeve (3), reinforcing layers (4, 5) and an outer protective sleeve (6). The metal tube is in two coaxial layers made from spiral-wound corrugated metal strip with three crests and two troughs, wound so that the crests of one winding fit into the troughs of another and welded together. The strip is wound so that its corrugations lie at an angle of over 80 degrees to the axis of the pipe.

Description

The present invention relates to the field of flexible pipes.

  used by the petroleum industry. More particularly, the present invention provides a flexible pipe comprising a multilayer corrugated metallic internal tube. Flexible pipes are used in particular by the petroleum industry to convey oil from a wellhead located at the bottom of the sea to a treatment installation located on the sea surface. The pipes laid on the seabed, commonly called "flow line", 10 mainly undergo static mechanical stresses, on the other hand, the pipes connecting the sea floor to the surface, commonly called "riser",

  are mechanically stressed statically and dynamically.

  The flexible pipes used must be able to withstand

  internal pressures and / or at strong external pressures and also withstand longitudinal bending or twisting without risk of rupture.

  API 17B and API 17J describe flexible pipe structures and establish general criteria for the construction of

flexible lines.

  The document FR 2756605 proposes to produce a flexible pipe comprising from the inside to the outside: - an internal metallic corrugated tube. The tube is continuous and gas tight, - a metal reinforcement commonly called a "pressure vote", - an intermediate polymer sheath for sealing, - at least one layer of tensile armor,

  - an external polymer protection and sealing sheath.

  The presence of the internal corrugated tube prevents the diffusion of the acid gases contained in the conveyed fluid towards the vote and the layers of tensile armor. Thus the metallic materials of the vote and of the tensile armor plies can be chosen without respecting the criterion of resistance to

  corrosion as defined by API standards.

  The corrugated tube is a continuous monolayer tube. It is made by making a cylindrical tube, then forming corrugations on the cylindrical tube. The present invention aims in particular to improve the internal metallic corrugated tube. It proposes to produce a corrugated tube 10 comprising several layers, the sum of the thicknesses of each layer

  which may be equal to the thickness of the single-layer tube of the prior art.

  The present invention relates to a flexible pipe comprising a sealed metal tube, the wall of which comprises corrugations, and a vote of resistance to pressure of metal wire wound helically around said metal tube, characterized in that said wall of the tube comprises

minus two layers.

  According to the invention, the waterproof metal tube can comprise an undulating strip helically wound around the axis of the pipe, the turns of the strip covering the adjacent turns over at least one period of undulations. According to a first embodiment, the ripple period can consist of a crest and a hollow, the undulating strip having three ridges and two recesses, the turns of the strip covering two ridges and a hollow of the adjacent turns and a helical weld bead can join three

superimposed turns.

  According to a second embodiment, the undulation period can consist of a crest and a hollow, the undulating strip having four ridges and three recesses, the turns of the strip covering two ridges and three recesses of the adjacent turns and a helical weld bead can

  securing four superimposed turns.

  The weld bead can be placed in a hollow or on a ridge.

  The strip may have a first face made of a first material and a second face made of a second material which resists

  better corrosion than said first material.

  The corrugations can be helical forming an angle greater than 15 80 relative to the axis of the pipe.

  According to a third embodiment, the sealed metal tube

  may include a first tube and a second coaxial tube.

  The shape of the voting thread can cooperate with the shape of the undulations.

  An extruded polymer sealing sheath can be placed around

said vote.

  The present invention also relates to a first method of manufacturing a flexible pipe comprising the steps: a) imposing a movement in advance on a strip, b) plastically deforming the strip by profiling to obtain a profiled strip, the cross section profiled strip comprising at least two periods of undulations, c) the strip is wound around a helix around the axis of the pipe to produce an undulating tube, at least one period of undulations of said profiled strip covering the end of said corrugated tube so that said tube comprises at least two layers, d) a weld bead is produced between said layers, e) a metallic wire is wound around a helical tube

to vote.

  In step d), the weld bead can be made continuously 10 and following a helix. In step d), the bead can be made on a free end of the profiled strip. In step c), the winding angle by

  relation to the axis of the pipe can be greater than 80.

  The invention also relates to a second method of manufacturing a flexible pipe comprising the steps: a) a first cylindrical tube is manufactured, b) A second cylindrical tube is coaxial with the first tube to obtain a two-layer cylindrical tube, c) Corrugations are formed on the cylindrical tube with two layers. In the case of winding of the flexible pipe at a given radius of curvature, the layers of a multilayer corrugated tube are subjected to a lower rate of elastic or plastic deformation than that generated in a monolayer corrugated tube of the same overall thickness. The rate of deformation 25 designates the ratio between the value of the elongation of a dimension and the initial value of this dimension. The lowering of the tube deformation rate is favorable with regard to the fatigue strength of the corrugated tube. However, during the winding-unwinding operations inherent in the manufacturing mode and the installation mode of the flexible pipes (the internal corrugated tube sees all the subsequent stages of the pipe manufacturing process) and in service ("riser" subject dynamic stresses), the corrugated tube is subjected to numerous fatigue cycles. Consequently, the multilayer corrugated tube has a longer service life than a monolayer corrugated tube. By retaining the same overall thickness, the multilayer tube exhibits corrosion resistance and resistance properties.

  static mechanics identical to those of a single-layer tube.

  In addition, the best fatigue strength of a multilayer corrugated tube makes it possible to select a material whose mechanical fatigue strength is

  0 lower but with better corrosion resistance.

  Other characteristics and advantages of the invention will be better

  understood and will appear clearly on reading the description given below

  by way of example with reference to the drawings in which: - Figure 1 is a perspective and partial view of a flexible pipe according to the invention, - Figure 1A shows a section of a corrugated tube surrounded by a vote, - FIG. 2 represents the external shape of a corrugated tube, - FIG. 3 shows schematically a first method of manufacturing the corrugated tube, - FIG. 3A represents a strip, - FIGS. 4 and 5 represent structures of the corrugated tube obtained according to the method described in relation to Figure 3, 25 - Figure 6 shows a section of a corrugated tube, - Figure 7 shows a second method of manufacturing the corrugated tube. The flexible pipe with axis AA ′, as shown in FIG. 1, comprises from the inside towards the outside, an internal metallic corrugated tube 1, a vote 2, possibly a polymer sheath 3 for sealing, possibly two plies of tensile armor 4 and 5 and possibly a sheath 6 of external protection. Vote 2 consists of rolled up profiled metal wires

  according to a pitch helix (that is to say with a winding angle greater than 80 relative to the axis of the pipe) around the corrugated tube.

  The wires are separated by a clearance, for example of the order of 5% to 8% of the width of the wire, allowing flexibility in voting, and therefore in conduct. The sons

  metal can be non-staplable or have a T, Z or U shape allowing stapling. The metallic vote ensures in particular the resistance to bursting when the pipe is subjected to a strong internal pressure and participates in the resistance to crushing when the pipe is subjected to a strong external pressure.

  The sheath 3 is generally made of thermoplastic material with

  high melting point, for example of the polyamide type. The sheath 3 is extruded around the vote 2. It is in particular intended to ensure the tightness of the pipe and to prevent the pipe from being crushed by pressing on the vote, during strong external pressures exerted on the conduct.

  The armor plies 4 and 5 consist of metallic wires wound in a long pitch helix (that is to say with a winding angle less than 60 relative to the axis of the pipe) around the sheath 3 The tensile armor plies in particular ensure the tensile strength of the pipe. The wire section can be rectangular. The tablecloth threads

  of armor 5 can be crossed with respect to the wires of armor ply 4.

  According to another embodiment, the sealing sheath 3 can also be extruded between two armor plies 4 and 5, the armor ply 4 being

  made up of wires wrapped around vote 2.

  The sheath 6 can be made of extruded polymer around the armor ply 5. It provides external protection for the pipe and possibly

the tightness of the pipe.

  2 shows a section of a corrugated tube along a plane containing the axis AA 'of the flexible pipe (only the middle line of the corrugated tube is shown). The average distance Dm which separates the corrugated tube from the axis AA 'is constant over the entire length of the tube. The undulations are formed by a succession of ridges and valleys. A crest 10 10 designates the parts of the tube whose distance from the axis AA ′ is greater than the average distance Dm. A recess 11 designates the parts of the tube whose distance from the axis AA 'is less than the average distance Dm. The corrugations are helical, i.e. a hollow or crest forms a helix on the wall of the corrugated tube. Two successive recesses can be arranged on a single helix. Two successive recesses can also be arranged on two separate propellers. The corrugated tube has periodic undulations, i.e. the shape of the undulations is identical over the entire length of the tube. A ripple period is defined by the unit form of the ripples. A ripple period can be characterized by the distance P which separates two successive peaks or two valleys, the distance P being measured in a direction parallel to the axis AA '. The shape of the undulations can be sinusodal, circular or other. The shape of the ridges

  may or may not be symmetrical with respect to the shape of the recesses 11.

  The wires constituting vote 2 can also have shapes as described by document FR 2756605 in relation to FIGS. 3 to 9. FIG. 1A, cut along the axis AA ′, represents the mean line of an undulating tube and of a vote. The vote is made up of the metal wire 8 surrounded around the undulating tube 9. The part of the wire 8 which is opposite the tube 9 has a shape which cooperates with the tube 9, that is to say that the shape of the wire 8 follows the undulations of the tube 9. The orthogonal section of the metal wire 8 has

  a stud Sa which is housed in a hollow 9a of the tube 9.

  According to the present invention, the corrugated tube 1 consists of several layers, that is to say that the corrugated tube consists of at least

  two separate and overlapping layers.

  FIG. 3 shows schematically a method of manufacturing the internal metallic corrugated tube 10 1. A metal strip 24 is available in the form of a reel 21. By unwinding the reel 21, one obtains the scrolling in the direction V of the strip 24 of planar surface and defined width. The width ú of the strip can be between 0.01 m and 1 m, the thickness e of the strip can be greater than 0.1 mm. The strip 24 is introduced into the profiling machine 22 to form corrugations. The profiling machine 22 is composed of pairs of rollers whose shapes are complementary. The cross section (perpendicular to the direction of travel) of the strip 25 leaving the profiling machine 22 has undulations. The generator of the undulations of the strip 25 is parallel to the direction of travel V. The shape of the undulations of the cross section of the strip 25 is

  substantially identical to the shape of the corrugations of the corrugated tube 1 seen in a section passing through the axis AA 'of the tube. The undulations of the strip 25 comprise at least two unitary forms of undulations, that is to say at least two periods of undulation (two peaks and two valleys). Rollers and 25 rollers guide and impose the advance movement on the strips 24 and 25.

  Then, the corrugated strip 25 is wound around the axis of the pipe AA '.

  The winding is carried out according to a helix with pitch not around the axis AA '.

  The winding angle can be greater than 80 relative to the axis AA 'of the pipe. To facilitate winding, the direction of travel V of the strip makes an angle of with respect to the axis AA ', the angle ac being equal to the winding angle of the strip 25. The strip 25 covers the last turn formed over at least one period of the ripple (or at least an axial distance P). For example, a successive peak and trough of a turn overlaps a successive crest and trough of the adjacent turn. The tool 23 produces a continuous weld bead to secure a turn with the turn or the adjacent turns and to seal the corrugated tube. The weld bead has the shape of a helix which is substantially identical to the shape of the helix of the strip winding. It can be placed close to the free ends of the strip 25 and can be produced on a ridge or in a hollow of the

  undulations. The weld secures all the layers which are superimposed.

  To carry out the welding, it is possible, for example, to use an electrical process such as seam welding or a high energy density process such as laser welding. The tube 20 can be animated by a helical movement around the axis AA ', the coil 21, the profiling machine 22 and the tool 23 being fixed.

  According to a variant, the coil 21, the profiling machine 22 and the tool 23 are driven in a rotational movement around the axis AA ′ and the tube 20 is driven in a forward movement in the direction of axis AA '. After manufacture of the corrugated tube, the distance, measured in a radial direction of the tube, separating two parts of superimposed turns may be less than five times the thickness e of the strip, preferably less than once the thickness e of the strip. The strip 24 shown in FIG. 3A has two sides X and Y, the material of the side X being different from that of the side Y. The strip 24 25 can be constituted by two sheets of different materials, one sheet being glued and covering the other sheet. Thus, the X face of the strip is made of a corrosion-resistant steel, for example an austenitic-ferritic steel. The Y side of the strip is composed of a steel whose mechanical strength is greater than that of the A side. The method described in relation to FIG. 3 can be implemented using a strip described in relation to FIG. 3A for obtain a corrugated tube whose internal wall is composed of the material of the face X and whose external wall is composed of the material of the face Y. FIG. 4 represents a section of a corrugated tube 30 according to a plane passing through the axis AA 'of driving. The tube 30 has two layers of strip. It consists of the winding of a strip comprising two recesses and three ridges. For example, the turn 32 has the recesses C and E, as well as the ridges B, D and F. A turn covers two ridges and a recess of the adjacent turn 10. The coil 32 covers the ridges B and D, as well as the hollow C of the coil 31. The coil 32 is covered by the ridges D and F, as well as by the hollow E of the coil 33. The weld bead 34 is helical shape. It is placed on the top of the ridges and secures three superimposed turns. On the

  crest D, the weld bead 34 secures the turns 31, 32 and 33.

  FIG. 5 represents a section of a corrugated tube 30 according to a plane

  passing through the axis AA 'of the pipe. The tube 40 has three layers of strip. It consists of the winding of a strip comprising three hollows and four crests. One turn covers three ridges and two hollows of the adjacent turn. The weld bead is placed on the bottom of the recesses and secures four superimposed turns.

  The materials constituting the internal corrugated tube are metal alloys resistant to corrosion by petroleum effluents in order to guarantee the maintenance of the seal during the life of the pipe. For example austenitic-ferritic steel (UNS S31803), austenitic steel (UNS S31254), or nickel-based steel (N 06625). The weld bead must also resist corrosion. Finite element calculations, in the case of a symmetrical circular wave profile, illustrate the advantage of the corrugated tube with two layers by comparison with a monolayer corrugator of the same overall thickness. We compare the lifetime of a tube formed by a single layer of 1.2 mm thick e and the lifetime of a two-layer tube formed of two corrugated strips of 0.6 mm thick each. The pitch P is 30 mm and the depth H 8 mm with identical radii R1 and R2 9 mm (see Figure 6). Alternating bending cycles are applied at more or less twice the maximum radius of curvature of the tube. We deduce the variation of the plastic deformation accumulated over a quarter cycle. The two surfaces of the layers of the bilayer tube are, in this example, considered in contact but can

slide one over the other.

  The lifetime N (in number of cycles) as a function of the plastic deformation (applied to each cycle) p is calculated with a Manson law 15 Coffin obtained from fatigue tests in traction-compression. This law is of the form:

  úp = K x Na o K and ac are constants.

  For an identical situation of mechanical stress on the flexible pipe, the maximum cumulative plastic deformation on the external surface of the two-layer corrugated tube is reduced by more than 40% compared to the single-layer corrugated tube of the same total thickness. By relying on experimental Manson-Coffin curves established on an austenitic alloy, this results in a 150% increase in fatigue life. This lifetime gain increases with the number of layers making up the tube

  wavy because the deformation rate decreases with the thickness of the layers.

  The most requested location is the same in the two cases studied: it is the crest of the wave. If the weld is positioned at this location, it is necessary to choose welding conditions and / or a filler product such that the weld bead has a mechanical resistance at least equal to that of the base metal. Otherwise, the weld can be positioned in a less stressed area, by

example in the hollow of a wave.

  FIG. 7 shows diagrammatically a second method of manufacturing the internal metallic corrugated tube 1. The cylindrical tube 51 of axis AA ′ is first manufactured. The tube 51 can be manufactured from a continuous strip welded according to a longitudinal bead or in a helix. Then a second tube 52 is placed around the first tube 51. The tube 52 can be produced and then fitted onto the tube 51 or produced directly around the tube 51. The second tube 52 may not be welded to the first tube 51. The material of the first tube 51 may be different from the material of the second tube. For example, the material of the first tube 51 resists corrosion better than the material of the second tube 52. All of the tubes 51 and 52 constitute the bilayer tube 50. The tube 50 is introduced into the tool 53 which forms undulations. Tool 53 can be

  consisting of pinch rollers and a rotating core.

  The tool 53 can also be a hydroforming tool. The tube 50 is inserted into a mold. The internal wall of the tube 50 is subjected to a uniform pressure by means of a fluid (for example water). The pressure is chosen to be high enough to deform the tube 50 so that it

follows the shape of the mold.

  The corrugated tube can also be produced according to the second

process with three or more tubes.

Claims (13)

  1) Flexible pipe comprising a watertight metal tube, the wall of which has corrugations, and a vote of resistance to pressure made of metal wire helically wound around said metal tube, characterized   in that said tube wall has at least two layers.   2) flexible pipe according to claim 1, characterized in that said sealed metal tube comprises an undulating strip helically wound around the axis of the pipe, the turns of the strip   covering the adjacent turns over at least one period of undulations.   3) flexible pipe according to one of the preceding claims,   characterized in that the ripple period consists of a ridge and a trough, the undulating strip having three ridges and two troughs, the turns of the strip covering two ridges and a trough of the adjacent turns and in that a helical weld bead secures three superimposed turns. 20   4) flexible pipe according to one of claims 1 and 2, characterized in   that the ripple period consists of a ridge and a trough, the undulating strip having four ridges and three troughs, the turns of the strip covering two ridges and three troughs of the adjacent turns and in that a bead of helical welding secures four superimposed turns.   ) Flexible pipe according to one of claims 3 and 4, characterized in   that said weld bead is disposed in a hollow.   6) flexible pipe according to one of claims 3 and 4, characterized in   that said weld bead is disposed on a ridge.   7) flexible pipe according to one of claims 2 to 6, characterized in that said strip comprises a first face made of a first material and a second face made of a second material which resists   better corrosion than said first material.   8) flexible pipe according to one of the preceding claims, characterized in that the corrugations are in a helix forming an angle   greater than 80 relative to the axis of the pipe.   9) flexible pipe according to claim 1, characterized in that said   sealed metal tube comprises a first tube and a second coaxial tube.   ) Flexible pipe according to one of the preceding claims,   characterized in that the shape of said voting thread cooperates with the shape of said undulations.   11) Flexible pipe according to one of the preceding claims,   characterized in that an extruded polymer sealing sheath is arranged around said vote.   12) Method of manufacturing a flexible pipe comprising the steps: a) imposing a movement of advance on a strip, b) plastically deforming the strip by profiling to obtain a profiled strip, the section of the profiled strip comprising at least two periods of undulations, c) the strip is wound around a helix around the axis of the pipe to produce an undulating tube, at least one period of undulations of said profiled strip covering the end of said undulating tube so that said tube has at least two layers, d) a weld bead is produced between said layers, e) a metal wire is wound around a helix around said undulating tube to vote.   13) The manufacturing method according to claim 11, characterized in that in step d), the weld bead is made continuously and following a helix.   14) manufacturing method according to one of claims 11 and 12,   characterized in that in step d), the bead is made on a free end of the profiled strip.   ) Manufacturing method according to one of claims 11 to 13   characterized in that in step c), the winding angle with respect to the axis of the driving is greater than 80.   16) Method for manufacturing a flexible pipe comprising the steps: a) a first cylindrical tube is manufactured, b) A second cylindrical tube is coaxial with the first tube to obtain a cylindrical tube with two layers,   c) Corrugations are formed on the cylindrical tube with two layers.