WO1998016774A1

WO1998016774A1 - Method and device for connecting a flexible pipe

Info

Publication number: WO1998016774A1
Application number: PCT/FR1997/001827
Authority: WO
Inventors: Anh Tuan Do; Joël LE NOUVEAU
Original assignee: Coflexip
Priority date: 1996-10-16
Filing date: 1997-10-13
Publication date: 1998-04-23
Also published as: EP0932788A1; FR2754585A1; CA2268985A1; FR2754585B1; ZA979260B; AU4709397A; AU725395B2

Abstract

The connecting device for connecting a joining piece to the end of a flexible pipe comprises a cannula (7) and a sleeve tube (23) having over a certain length undulations (28), characterised in that the undulations are constituted by separate rings (28) which extend over a length at least equal to the internal diameter of said flexible pipe (2), and the cannula (7) has indentations (34) arranged on its external surface in a straight line with the internal sheath (3).

Description

Method and device for connecting a flexible pipe

The present invention relates to a method and a device for connecting a nozzle to one end of a flexible pipe, and more particularly to a flexible pipe which undergoes high mechanical and thermal stresses during the transport of a fluid such as gas or crude oil.

Various connection devices, generally designated as a whole by the term end piece, have been proposed for several decades.

A flexible pipe, in a simplified version, comprises from the inside to the outside, at least one internal sealing sheath, a pressure vault formed by armor and an external sealing sheath.

A commonly used endpiece comprises a certain number of elements which are connected and which cooperate with each other and in particular a hollow internal end element whose end face abuts against the internal sealing sheath of the flexible pipe, a special element which is arranged under, and connected to the pressure vault and a cover or external clamping and holding sleeve which is arranged outside the flexible pipe, over an axial length to envelop, on the one hand, the area of junction between the end faces of the internal element and the internal sealing sheath, and on the other hand, part of the flexible pipe. Means are also provided for fixing the external sleeve. However, the installation of such a nozzle requires partially stripping the end of the pipe to be connected and removing the armor from the pressure vault in order to insert the special element, otherwise it would be impossible introduce anything into the end of the flexible pipe. Another type of end piece also developed by the applicant, requires in the same way as previously a prior preparation of the end of the flexible pipe to be connected, in order to be able to put an internal element in the pipe.

FR-A-2 728 049 and FR-A-2 728 051 relate to a connection device for plastic tubes, consisting of a sleeve clamping, internally threaded and capable of being screwed onto reverse pitch threads provided on each end of the tubes to be connected. A seal is interposed between the end faces of the tubes and it is housed in a central groove made in the sleeve. This type of nozzle can only be used if the ends of the tubes are threaded since the connection is essentially made by screwing. For tubes which do not have threads on the external protective sheath, it is essential to provide said tubes with appropriate threads beforehand, which is not easy when the connection must be made at the place of exploitation; moreover, this type of connection requires special tools.

FR-A-2 729 206 relates to a method for producing a connection between a rigid tubular part and the end of a flexible tube. The tubular part must have two parts separated by a collar provided with a circumferential groove, one of the parts having circumferential grooves into which a layer of thermoplastic material penetrates. A metal sleeve, one end of which is extended and folded down into the groove and the other end of which is folded radially inwards beyond the end of the tubular part, is mounted for maintaining the connection. The connection method consists in introducing heating means into the flexible tube in order to deform the latter by flaring it before the introduction of the tubular part, then in heating the tubular part while compressing the metal sleeve so as to melt the thermoplastic material and tighten the tubular part and the flexible tube in their connection position. In addition to the fact that the tubes capable of being connected to the tubular part must be flexible enough to be able to be deformed by heating and to allow the introduction of the tubular part, it should be noted that the recommended connection still requires either special parts such as the tubular piece (groove and circumferential grooves) or prior preparation. Finally and above all, such a connection device cannot be used for flexible pipes in which a fluid under high pressure circulates, for example of the order of 40 bar and more, and strong stresses develop, such as the background effect which is the traction exerted on the end-pipe connection, the constraint of the background effect possibly being of the order of 10 tonnes. US-A-2 262 228 discloses a method of placing a nozzle on a plastic hose which is flexible enough and deformable so that its end can be forced into the nozzle with a large reduction in its outside diameter. ; this operation is followed by a new compression of the thickness of the pipe by expansion of a central sleeve. The pipe is therefore crushed and pinched, but not otherwise deformed. Such a method is inapplicable to the pipes concerned by the invention which are too rigid to be thus introduced into a nozzle with an internal diameter much smaller than the external diameter of the pipe. US-A-4 653 779 discloses a method of fitting a nozzle in which an outer sleeve provided with inner rings compresses and deforms the pipe as far as its reinforcing plies.

However, in this process, the internal passage of the pipe has a diameter which varies greatly at the end piece, so that the flow can be disturbed.

Document US-A-2,146,756 relates to a permanent nozzle for unarmoured pipe.

The object of the present invention is to remedy the aforementioned drawbacks and to propose a connection device which can be used in any type of pipe to be connected, provided that the end of the pipe is suitable for being expanded.

The expansion which is referred to in the present invention is the operation by which one flares at least the end of a pipe over a certain length, to allow the introduction of an element of a part, in this case the cannula of a connecting piece.

When reference is made to the drawing operation, this means that the workpiece is subjected to tightening by radial compression leading to a reduction in the external diameter.

When referring to the hooping operation, this means that a mechanical connection is made between two elements by pressure exerted on one or both elements.

The subject of the present invention is a device for connecting a flexible pipe of the type comprising at least one internal sheath, a reinforcement constituted by assembled wires and an external protective sheath, said nozzle comprising a cannula and a sleeve having on a certain length of the corrugations and which is characterized in that the corrugations consist of separate rings which extend over a length at least equal to the internal diameter of said flexible pipe, and in that the cannula has serrations formed on the face external opposite the internal sheath.

According to another characteristic, the sleeve is under radial tensile stress.

According to another characteristic, the cannula is under radial compression stress. According to another characteristic, the sleeve and the cannula are tightened towards each other through said end of the flexible pipe, with a tightening rate of between 15 and 20%.

According to another characteristic, the tightening produces a penetration of the corrugations of the sleeve in the external sheath and of the serrations of the cannula in the internal sheath.

According to another characteristic, the method for connecting a nozzle to one end of a flexible pipe is of the type according to which the nozzle comprises on the one hand, a cannula, one end of which is introduced into the free end of the flexible pipe, said cannula having an external diameter equal (to the tolerances near manufacture of the pipe) or slightly greater (of the order of 1%) than the internal diameter of said pipe (the cannula being able to be tapered at its end in order to allow a primer to 'introduction), and on the other hand, a sleeve which is arranged around the external sheath of the pipe, and it is characterized in that it consists in: - introducing (possibly by force) the cannula into the end of the pipe, over a predetermined length;

- move the sleeve to bring it above the length of cannula inserted;

- radially deforming the length of the cannula introduced by means of a mandrel previously disposed in the flexible pipe until the internal diameter of the cannula is substantially equal to the internal diameter of the non-flared flexible pipe;

- Pass the sleeve and the corresponding pipe portion in a clamping device, wherein said sleeve is tightened radially at the same time as said pipe portion under the sleeve. According to another characteristic, the sleeve and the pipe portion are tightened according to a predetermined tightening rate.

According to another characteristic, the tightening rate is between 15 and 20%. Other advantages and characteristics will appear on reading the description relating to a preferred embodiment of the invention as well as the appended drawings in which:

FIG. 1 is a schematic view in longitudinal section of the pipe to be connected, FIG. 2 shows the positioning of the sleeve around the pipe of FIG. 1,

FIG. 3 shows the positioning of the cannula in the pipe of FIG. 2,

FIG. 4 shows the result of the expansion of the pipe in FIG. 3,

FIG. 5 shows the fitting of the sleeve around the expanded part of the pipe of FIG. 4,

- Figure 5A shows an enlargement of the section of the pipe of Figure 5, - Figure 6 shows the pipe of Figure 5 after drawing,

FIG. 6A shows an enlargement of the section of the pipe of FIG. 6,

- Figure 7 is a partially sectional view of the connection end piece, - Figures 8 to 10 are partial elevation views of the installation allowing the various stages of connection between the end piece and a flexible pipe.

The pipe 2 to be connected (FIG. 1) to an inside diameter Dj and an outside diameter D ₀ . Its thickness is zero, and consists of at least one internal sheath, layers of armor and an external sheath.

We pass around the pipe 2 a sleeve 23 (Figure 2) whose inner diameter D _M0 (taken at the teeth 28) is at least equal to the outer diameter D, of the pipe after expansion (Figure 4).

Is inserted into the end of the pipe 2 over a length L preferably greater than the width of the sleeve 23 (Figure 3), a cannula 7 of _CI0 inside diameter D and of outside diameter D _CE0 equal to or slightly greater than the diameter D [within the conduit.

In order to promote its penetration into line 2, the cannula 7 preferably ends in a tapered shape 20 (here shown simplified but more exact in FIG. 7). The outer surface of the cannula 7 carries undulations or indentations not shown in this figure. After insertion of the cannula 7 into the pipe 2, the outside diameter D ₀ of the latter is not substantially modified.

Thanks to a swelling mandrel not shown, we just (Figure 4) forcefully widen the cannula 7 (at least its end) so that its new internal diameter D _cπ is equal to or very close to the diameter Dr of the pipe 2 not deformed , its outside diameter becoming D _CE1 . The extreme part 2 ′ of the pipe therefore widens to take an internal diameter equal to D _CE1 and a new external diameter Dj. The rate of additional expansion by expansion [(D _r D ₀ ) / D _o ] is greater than 1% and preferably greater than or equal to 3%.

During this enlargement by expansion, there is formed between the enlarged part 2 'and the non-enlarged part a flare 2a (called "dogleg"); the thickness e of the pipe is not very significantly different between the part 2 ′ and the part 2, and the flaring 2a itself has this thickness. In other words, the slight reduction in thickness results only from the increase in the perimeter of the pipe, but not from an overwriting of the thickness of the pipe.

We then come (Figure 5) to move the sleeve 23 which was on hold so that it surrounds the expanded part 2 ', which is possible thanks to the sufficient diameter D _M0 of the sleeve 23. Alternatively, it would have been possible, depending on the tool chosen, to immediately dispose the sleeve around the part 2 '.

The pipe in this region 2 'has the shape that can be seen in FIG. 5A, namely that the internal sheaths 3 and external 5 and the armor ply 4 are not substantially deformed (apart from their widening subsequent to expansion ). There was, approximately, only one displacement of matter, but no compression.

By a drawing operation (FIG. 6), the diameter of the sleeve 23 is reduced, which leads to its internal diameter (and the diameter outside of part 2 ') to take a value D ₂ less than D, and D _M0 . During this operation, the cannula 7 is designed to resist drawing and its new internal diameter D _CI2 is very slightly different from D ,. Optionally, it is possible to have kept in the cannula 7 the expansion tool to prevent its collapse during the drawing. You can also iron the expansion tool if the diameter D _CI2 was too small.

During the drawing operation, it should be noted that the flare 2a remains, even if it is slightly reduced.

As shown in FIG. 6A, the pipe 2 ′ is locally deformed under the effect of the depression of the teeth 28 of the sleeve 23 (and incidentally reliefs 34 of the cannula 7 whose function is essentially to prevent sliding), so that the armor ply 4 is corrugated.

We will now describe in more detail in a particular application which is that of the connection of a nozzle 1 to a flexible pipe 2 in which a pressurized fluid circulates, for example a gas or crude oil. The flexible pipe 2 generally comprises, from the inside to the outside, at least one internal sealing sheath 3, of given internal diameter D, one or more plies of armor 4 wound around the internal sealing sheath 3, made of a material identical or different from that of an external protective sheath 5, arranged around the armor 4. The structure of such a pipe is well known to specialists and will not be described in detail. However, the application more particularly relates to a pipe in which the armor plies 4 are each constituted by a winding of "Kevlar" ribbons, which are the subject of the documents

WO 97/13091 and WO 97/12753 in the name of the applicant.

The end piece 1 comprises on the one hand, a vault comprising in particular the cannula 7 intended to be introduced into the end 14 of the pipe 2 and, on the other hand, the sleeve or cover 23 disposed around the end of the line 2 to be connected (figure 7).

The arch comprises a rear part 6 and a distal part or cannula 7 proper. The rear part 6 is fixed and centered by a centering ring 9 in a pulling flange 8 secured to a pushing or pulling member 10 movable on a frame 1 1 of the wire drawing bench 12 (Figure 8). In the cannula 7 is mounted a draw rod 13 which is integral with the traction flange 8. The flexible pipe 2 is held in a support designated as a whole by the reference 15 and comprising in particular a support plate 16, a spacer 17 and a clamp 18. In a first step, the cannula 7 of the arch is introduced into the end 14 of the pipe 2 so as to widen (very slightly) said end 14 over a predetermined length L, for example of 250 mm, such deformation being in fact very limited (otherwise, it would require considerable force to drive the cannula 7 into line 2). The end 14 of the pipe 2 may have, as shown in FIG. 1, a chamfer 14a to allow easier introduction of the tip of the cannula 7 into said end 14. This introduction is carried out without prior preparation of the pipe 2 , that is to say without separation and / or removal of part of the constituent members of the structure of the pipe 2. This introduction is carried out using the cannula 7 which has a sufficient thickness to also withstand the residual stresses resulting wire drawing. The tests carried out have shown that a thickness of 5 mm of the cannula 7 is perfectly suitable for a hose with an internal diameter equal to three inches. The cannula 7 comprises a thick cylindrical part 19 which is extended forward by a tapered point 20. The dotted line 21 is an imaginary line which divides the thickness of the distal part 7 into two zones, the upper zone of approximately 3 mm corresponding to the expansion and the lower zone corresponding to what will be hooped later to ensure that the internal diameter D _C12 of the cannula 7 is equal, after hooping, to the internal diameter D, of the pipe 2. In the second phase, shown in FIG. 9, the cannula is detached from the traction flange 8 so as to be advanced and made integral with the support 15 by means of screws 22. In this advanced position of the cannula 7 and of the pipe 2, the sleeve or cover 23 previously fitted on the pipe 2 opposite the cannula 7 and which, with reference to FIG. 7, comprises a zone 24 raised relative to the main body

25, the difference in thickness in the cover being materialized by a fictitious dotted line 26. On the underside 27 of the cover 23, undulations are provided in the form of separate rings 28 which must, during subsequent tightening, penetrate into the outer sheath 5. An end part 29 of the cover rests on a flat 30 formed on the rear part 6 of the arch. The rings 28 are formed over a predetermined length of the sleeve, which is at least equal to the internal diameter D, of the pipe and more particularly, equal to approximately 250 mm, and they are spaced at least one pitch of 4 mm. The height of each ring is approximately 8 mm so that the rings can penetrate into the outer sheath 5 and cause, during the subsequent drawing, an undulation of the armor wires.

When the cover 23 is put in place, a mandrel 33, previously disposed in the pipe, is moved to force it inside the cannula 7. Such introduction of the mandrel 33 deforms the cannula 7 of the arch up to 'that the sections of said cannula 7 and of line 2 are aligned, that is to say that a continuity is obtained between line 2 and cannula 7 since the diameters D] and D _CII are equal. It is the operation of the expansion.

The cannula 7 comprises, on its external face, serrations 34, with a structure different from the rings 28, a small number of which is shown in FIG. 7. The serrations 34 are intended to provide hooping between the cannula 7 and the internal sheath 3 opposite as well as the hooping between the cannula 7 and the armor 4. After hooping, the end of the pipe is located in a confined space, which makes it possible to limit the creep over time of the internal sheath 3 and consequently ensure a lasting seal at the end of the pipe. In an exemplary embodiment, the pitch between the serrations is of the order of a millimeter and the height of each serration is of the order of 0.5 mm.

In a following step, the end-pipe assembly is moved back towards the rear position on the chassis 11 and a die 31 with its die holder 32 is put into place in the wire drawing bench 12. This being done, the previous one is moved together through the die 31, this drawing operation having the effect of ensuring the tightening of the cover 23 on the external sheath 5 and of completing the shrinking of the cannula 7 on the internal sheath 3 and the armor 4 of the pipe 2, so that at the outlet of the die 31, the diameters D, and D _CI2 are equal, which ensures continuity between the connected elements and eliminates any obstacle for a circulation of the fluid.

The tests carried out showed that a thickness of 5 mm for the cannula 7 was sufficient to withstand the traction during the introduction, the expansion and the residual compression effect after the drawing, for the considered internal diameter of the pipe.

With regard to the tightening rate, it has been empirically determined that it is between 15 and 20% and more particularly of the order of 16.5, that is to say approximately 2 to 3 times the conventional tightening implemented in the prior art.

The tightening rate is defined by the ratio between the thickness of the free pipe and the thickness of the flared end of the pipe.

Likewise, the drawing length is linked to the internal diameter D _! of the pipe and it essentially depends on the background effect which is known in principle, on the internal friction coefficients of the pipe structure (of the order of 0.2) and on the nature of the materials used to carry out the pipe (sealing sheaths and armor) as well as the material from which the cover is made. Tests have shown that this drawing length is at least about 3 times the internal diameter D of the pipe.

At the outlet of the die, the cover 23 is under radial tensile stress and the cannula 7 is under radial compression stress, the stress state σ of the cover and of the cannula being able to be expressed by the relation: σ = E thermoplastic x tightening rate in which E thermoplastic is the Young 's modulus of the outer thermoplastic sheath of the pipe.

It should be noted that the drawing action also makes it possible to secure the armor 4 because of the rings 28 of the cover 23 which, by non-uniform crushing of the external sheath 5 of the pipe 2, causes a undulation of the plies of wires constituting said armourings 4, combined with compression between the two external and internal thermoplastic sheaths of the pipe 2.

In summary, the method of connecting a nozzle to a flexible pipe consists of: a) - introducing into a end 14 of the flexible pipe 2 a mandrel 33 whose diameter is equal to the internal diameter D] of the pipe, b ) - arrange around the pipe 2 a sleeve or cover 23, c) - introduce into the end 14 the cannula 7 of the vault of the nozzle whose internal diameter D _CI0 nominal is less than the diameter internal D _n of the pipe and whose external diameter D _CE0 is slightly greater than or equal to the internal diameter D, of the flexible pipe 2, d) - continue said introduction over a determined length of pipe L, with possibly a slight flaring of said end 14 along said length, e) - move the cover 23 to bring it above or opposite the cannula 7 of the arch, f) - move the mandrel 33, previously introduced, to bring it into the cannula 7 of the vault, which causes, by expansion, a radial deformation of said cannula 7, until the nominal diameter D _CI0 becomes D _CI1 , equal to the internal diameter D [of the non-expanded pipe; this expansion operation ensures hooping between the cannula 7 and the internal sheath 3 and therefore the seal between the end piece and the flexible pipe, g) - drawing the cover 23 and the end 14 of the corresponding pipe, in order to reduce the outside diameter of said cover and compress the pipe portion located between the cover and the distal part according to a determined tightening rate.

As we saw above, step e) could be placed after step f) -

Finally, it should be noted that the effects of hooping and wire drawing persist. Indeed, the relaxation of plastics will tend to cancel the initial constraints imposed by hooping and wire drawing. The fact that it is a reinforced tube considerably increases the relaxation times of the layers of the thermoplastic sheaths; moreover, after drawing, the end of the pipe thus compressed between the cannula and the sleeve is, after crushing, in a confined space which has the effect of making the relaxation times of the thermoplastic sheaths practically infinite and therefore eliminating almost creep phenomena. This gives a seal and a hooking of the pipe on the durable nozzle.

Claims

1. Device for connecting a nozzle (1) to one end (14) of a flexible pipe (2) comprising at least one internal sheath (3), a frame (4) constituted by assembled wires and an external sheath protective (5), said tip comprising a cannula (7) and a sleeve (23) having over a certain length of corrugations (28), characterized in that the corrugations (28) are constituted by separate rings (28) and which extend over a length at least equal to the internal diameter (D,) of said flexible pipe (2), and in that the cannula (7) has serrations (34) formed on the external face opposite the sheath internal (3).

2. Device according to claim 1, characterized in that the sleeve (23) is under radial tensile stress.

3. Device according to claim 1, characterized in that the cannula (7) is under radial compression stress.

4. Device according to any one of claims 1 to 3, characterized in that the sleeve (23) and the cannula (7) are clamped towards each other through said end (14) of the flexible pipe ( 2) and with a tightening rate between 15 and 20%.

5. Device according to claim 4, characterized in that the tightening produces a penetration of the rings (28) of the sleeve (23) in the external sheath (5) and of the serrations (34) in the internal sheath (3).

6. Method for connecting a nozzle (1) to one end (14) of a flexible pipe (2) according to claim 1, of the type according to which the nozzle (1) comprises on the one hand, a vault comprising a cannula (7) which is introduced into the free end (14) of the flexible pipe, said cannula (7) having a nominal internal diameter (D _CI0 ) less than the internal diameter (DT) of said pipe (2) and an external diameter (D _CE0 ) slightly greater than or equal to the internal diameter (Dr), and on the other hand, a sleeve (23) which is arranged around the external sheath (5) of the pipe, characterized in that it consists of:

- Introducing, possibly by force, the cannula (7) into the end (14) of the pipe (2), over a predetermined length; - move the sleeve (23) to bring it above the length of cannula inserted;

- radially deform the length of the cannula (7) introduced by means of a mandrel (33) previously disposed in the flexible pipe, until the internal diameter of the cannula (7) is substantially equal to the internal diameter of the flexible flared pipe;

- Passing the sleeve (23) and the corresponding pipe portion in a clamping device (31, 32), in which said sleeve is tightened radially at the same time as said pipe portion under the sleeve.

7. Method according to claim 6, characterized in that the sleeve (23) and the pipe portion are tightened according to a predetermined tightening rate.

8. Method according to claim 7, characterized in that the tightening rate is between 15 and 20%.

9. Method according to claim 6, characterized in that the step of moving the sleeve (23) is made after the step of radial deformation.