OA12259A

OA12259A - Flexible pipe with a winding of a wire or strip for restraining the armour wires.

Info

Publication number: OA12259A
Application number: OA1200200337A
Authority: OA
Inventors: Philippe Espinasse
Original assignee: Coflexip
Priority date: 2000-05-10
Filing date: 2001-04-05
Publication date: 2006-05-11
Also published as: EP1154184B1; WO2001086184A1; EP1154184A1; AU2001248467A1; BR0108836B1; DK1154184T3; EP1154184B2; DK1154184T4; BR0108836A

Abstract

The pipe consists of a series of layers: an inner plastic sleeve (4) between two metal short-pitch windings (3, 5) with engaging coils, at least one layer of long-pitch traction armoring (6, 7) and an outer sealing sleeve (8). It has at least one continuous short-pitch spiral winding (9) over the outer armoring layer (7) so that its coils lie at least partially in the gaps (12) in the armoring layer and compressed partly into the outer sealing sleeve.

Description

1 012259

Flexible pipe with a winding of a wire or strip for restraining thearmour wires

The présent invention relates to a flexible pipe for transporting, over longdistances, a fluid which is under pressure and possibly at a hightempérature, such as a gas, petroleum, water or other fluids. The inventionrelates most particularly to a pipe intended for offshore oil exploration. Itrelates especially, first, to the flow lines, that is to say flexible pipesunwound from a barge in order to be laid generally on the bottom of the seaand connected to the subsea installations, such pipes working mainly instatic mode, and, secondly, to the “risers”, that is to say flexible pipes whichare unwound from a surface installation such as a platform and areconnected to the subsea installations and most of which do not lie below theseabed, such pipes working essentially in dynamic mode.

The flexible pipes used offshore must be able to resist high internaipressures and/or extemal pressures and also withstand longitudinal bendingor twisting without the risk of being ruptured.

They hâve various configurations depending on their précisé use but ingeneral they satisfy the constructional criteria defined in particular in thestandards API 17 B and API 17 J drawn up by the American PetroleumInstitute under the title “Recommended Practice for Flexible Pipe” and“Spécification for Unbonded Flexible Pipe”. Reference may also be made todocuments FR 2 654 795 A, WO 98/25 063 A, FR 2 727 738 A andFR2 744 511 A. A flexible pipe comprises in general, from the inside outwards: a structural assembly able to resist radial forces, composed of a sealing sheath made of a plastic, generally a polymer, able to resist to agreater or lesser extent the Chemical action of the fluid to be transported,and of a winding of a métal element wound in a hélix with a short pitch; at least one ply (and generally at least two crossed plies) of tensile armour wires wound with a long pitch, that is to say the lay angle measured along the longitudinal axis of the pipe is less than 60°; and 2 012259 an extemal protective sealing sheath made of a polymer.

In certain pipes, the said structural assembly is formed by a carcassconsisting of an interlocked métal strip surmounted by the said sheath.

In pipes called “smooth-bore” pipes, the said structural assembly consistsof: the said internai sealing sheath; and a pressure vault résistant mainly to the pressure developed by thefluid in the sealing sheath and consisting of the winding of one or moreinterlocked profile métal wires (which may or may not be self-interlockable) wound in a hélix with a short pitch (that is to say with awinding angle of close to 90°); the profiled wires hâve a cross section in theform of a Z or a T or dérivatives thereof (teta or zêta) or in the form of a U,or more advantageously in the form of an I (cf. document WO 00/09899).

In pipes called “rough-bore” pipes, there is also, inside the internai sealingsheath, a carcass consisting of an interlocked métal strip which serves toprevent the pipe ffom collapsing under the extemal pressure. However, thepressure vault also helps to withstand the crushing forces.

It is known, for example from the document WO 92/11487 in the name ofthe Applicant, to provide, between the armour plies and the outer sheath, anadhesive tape wound over the upper ply in order to make it easier for it tobe restrained, at least temporarily, during manufacture while waiting for theextemal sheath to be placed over it. This restraining is especially necessarywhen the armour wires are Iubricated in order to protect them fromcorrosion. It is also known to wind around the armour wires, after theadhesive tape, a Kevlar® tape or a tape of another similar high-strengthmaterial, intended to resist the end cap effect (bird-cage deformation).

Flexible-pipe laying Systems, illustrated for example by the document “Recommended Practice for Design of Risers for Floating Production

Systems and Tension-leg Platforms”, drawn up by the American Petroleum

Institute, generally include a System for taking up the tension, or tensioner, 3 012259 of the linear contact (Caterpillar track) type, which grips a length of flexiblepipe by means of at least one pair of opposed endless belts, the objectivebeing to transfer the gripping force to the ply of outer armour wires. Theforces exerted are designed in order to take account of the minimal frictioncoefficient which exists between the various layers of the pipe between theCaterpillar track blocks and the armour wires of the flexible pipe: thisminimal coefficient occurs at the interface between the external armour plyand the superjacent adhesive, with a value taken into account of less than0.1. This very low value means that the flexible pipe has to be greatlycompressed so as to be able to transfer reasonable tangential retainingforces. This large axial compression may consequently mean that the crushrésistance of the pipe must be increased, and therefore the pressure vaultsmust be reinforced; this increases the suspended weight and thereforeincreases the radial pressure to be exerted by the tensioners.

In addition, nor must the forces exerted by the blocks be increased too muchwith the risk of damaging the sheath where it cornes into contact with theblocks, the limit adopted being set to forces of about 120 metric tonnes permétré.

The objective of the invention is to provide a flexible pipe which has theoverall structure mentioned above but is designed so as not to hâve theselimitations due to the excessively low friction coefficient between theexternal armour ply and the superjacent layer (defined around the externalarmour ply by a winding of adhesive tape and/or a winding of a tape ofstrong material and/or the external sheath itself).

The objective of the invention is achieved by virtue of a flexible tubularpipe comprising, from the inside outwards, at least: a sealed structuralassembly résistant to radial forces, composed of a sealing sheath made of aplastic, generally a polymer, able to withstand to a greater or Iesser extentthe Chemical action of the fluid to be transported, and of a winding of amétal element wound in a hélix with a short pitch; and at least one ply oftensile armour wires wound with a long pitch and an external protectivesealing sheath, characterized in that at least one strong continuous elongateelement with a déformable jacket (peripheral région) is wound helically 4 012259 with a short pitch directly around the said armour ply, preferably in theopposite winding direction to that of the armour ply, so that the spiralledcontinuous elongate element, crossed or not with respect to the ply, ispartially inserted between the gaps between the tums of the ply and blocksthe latter. Optionally, the armour ply blocked by the spiralled continuouselongate element may be covered with an adhesive tape and/or a strongaramid fibre tape (for example Kevlar® tape), even though under certainconditions the continuous elongate element according to the inventionmakes it possible to dispense with these layers. The continuous elongateelement is a wire or a tape; in the fîrst case, it is advantageous for thewinding to be done with non-touching tums; in the second case, thewinding may be done with touching tums and even with partial overlapbetween one tape turn and another. The wire (or tape) increases the frictioncoefficient at the armour/superjacent layer interface from a value of lessthan 0.1 to a value which exceeds 0.2 or even 0.4. This is because, whereaswithout the wire of the invention the force at the interface between theextemal armour ply and the superjacent layer is transmitted by pure friction,with the low coefficient mentioned, the said force is transferred, when thewire of the invention is présent, partially by positive mating(complementary shapes) and by shear at the wire, which pénétrâtes both thearmour ply and the superjacent layer. The wire can also serve to preventbird-cage deformation due to the reverse end cap effect. A material with thenecessary strength is chosen and the winding pitch is reduced as required, inorder to allow this effect. The wire may then replace the Kevlar® tape usedpreviously for this purpose. The winding angle measured along thelongitudinal axis is not critical and is, for example, between about 50° and85°.

The spiralled wire may consist of a single material combining both thestrength property and the deformability property, for example an aluminiumwire, or else a wire with a core providing the strength (made of Steel, carbonfibre, aramid fibre such as Kevlar®, etc.) surrounded by a déformablesheath (for example made of a thermoplastic). 5 012259

By virtue of the invention, it is possible to reduce the gripping forces exerted by the pads and/or to lay heavier pipes or to lay pipes at greater depth.

Further advantages and features will become apparent upon reading thedescription which follows, with reference to the appended schematicdrawings showing, by way of example, one embodiment of a flexible pipeaccording to the invention. In these drawings:

Figure 1 is a longitudinal sectional view of a pipe of the “rough-bore”type to which the invention is applied;

Figure 2 is a simplified perspective view with partial cut-away of thesame pipe.

The pipe 1 of axis 2 comprises, from the inside outwards, a carcass 3 madeof an interlocked métal strip, a polymeric internai sealing sheath 4, a métalvault 5 consisting of the winding of at least one profiled métal wire (here, aself-interlockable zêta wire) wound in a hélix with a short pitch, an armourlayer able to resist the axial tension in the longitudinal direction of the pipeand consisting of a pair of crossed armour plies 6, 7 wound in oppositedirections with a long pitch, and a polymeric extemal sealing sheath 8.Other layers (not shown) may be provided, according to the type and thepurpose of the pipe, such as, for example, a hoop layer consisting of awinding with a short pitch of a rectangular wire interposed between thepressure vault 5 and the First armour ply 6, other pairs of armour plies andintermediate sheaths placed between various armour plies.

According to the invention, wound around the outermost armour ply 7, w.ma short pitch, preferably in the opposite direction to that of the ply and witha certain gripping force, is a rod or wire 9 consisting of a strong core 10 andof a pliant sheath 11 which meets, more or less transversely, the armourwires of the ply 7 and partially pénétrâtes the helical gaps 12 existingbetween two armour wires. Ail the gaps 12 are thus blocked by the sinking-in of the sheath 11, thereby stabilizing the armour wires. The pliancy of thesealing sheath 8, constituting the layer superjacent to the annour ply and to 6 012259 the wire 9, allows the wire 9 to be at least partially impressed thereinto,contributing to the positive blocking and the increase in the frictioncoefficient at the interface.

Claims

7 012259 CLAIMS

1. Flexible tubular pipe comprising, from the inside outwards, atleast: a sealed structural assembly résistant to radial forces, composed of aninternai sealing sheath (4) made of a plastic, generally a polymer, able towithstand to a greater or lesser extent the Chemical action of the fluid to betransported, and of a winding (3, 5) of a métal element wound in a hélixwith a short pitch; at least one ply of tensile armour wires (6, 7) wound witha long pitch and an extemal protective sealing sheath (8), characterized inthat at least one strong continuous elongate element (9) with a déformablejacket is wound helically with a short pitch directly around the said armourply (7) so that the jacket of the continuous elongate element (9) is partiallyinserted into the gaps (12) between the armour wires of the said ply (7).
2. Pipe according to Claim 1, characterized in that the jacket of thecontinuous elongate element (9) is partially impressed into the extemalsheath (8).
3. Pipe according to either of Claims 1 and 2, characterized in thatthe continuous elongate element (9) is wound in the opposite windingdirection to that of the armour ply (7).
4. Pipe according to any one of the preceding claims, characterizedin that an adhesive tape and/or a strong aramid fibre tape is wound over thearmour ply (7) blocked by the said continuous elongate element (9).
5. Pipe according to any one of the preceding claims, characterizedin that the continuous elongate element (9) is made of a single strongdéformable material.
6. Pipe according to any one of Claims 1 to 4, characterized in thatthe continuous elongate element (9) has a strong core (10) surrounded by adéformable sheath (11). 8 012259
7. Pipe according to any one of the preceding daims, characterizedin that the continuons elongate element is a wire.
8. Pipe according to Claim 7, characterized in that the wire (9) is5 wound with non-touching tums.
9. Pipe according to any one of Claims 1 to 7, characterized in thatthe elongate element is a tape.
10. Pipe according to Claim 9, characterized in that the tape is wound with overlapping tums.
11. Pipe according to any one of the preceding claims, characterizedin that the structural assembly consists of an internai sealing sheath (4) and 15 a cylindrical pressure vault (5) consisting of the winding of an interlockedprofiled métal wire wound in a hélix with a short pitch.
12. Pipe according to any one of the preceding claims, characterizedin that the structural assembly consists of a carcass made of an interlocked 2 0 métal strip (3) surmounted by an internai sealing sheath (4).