GB2535925A

GB2535925A - Connection end-fitting of a flexible pipe with the armour threads anchored by trapping

Info

Publication number: GB2535925A
Application number: GB1609767.7A
Authority: GB
Inventors: Deleau Fabrice; Papon Gérard
Original assignee: IFP Energies Nouvelles IFPEN; Technip France SAS
Current assignee: IFP Energies Nouvelles IFPEN; Technip Energies France SAS
Priority date: 2013-12-03
Filing date: 2014-11-26
Publication date: 2016-08-31
Anticipated expiration: 2034-11-26
Also published as: FR3014165B1; GB201609767D0; GB2535925A9; WO2015082275A1; GB2535925B; FR3014165A1; BR112016012426B1; BR112016012426A2; DK179648B1

Abstract

The present invention relates to a connection end-fitting for a flexible pipe, in which the armour threads (4) are anchored by trapping between at least two jaws (7, 8). The jaws (7, 8) have more or less a tapered shape and are formed in such a way that the armours (4) have a continuous radius of curvature. In that way, the armour does not have any singular point in the end-fitting.

Description

FIELD OF THE INVENTION

The present invention relates to a connection end fitting of a flexible pipe, notably for transporting a fluid in a marine environment. It more particularly relates to an unbonded type flexible pipe used for offshore exploitation of oil and/or gas reservoirs.

BACKGROUND OF THE INVENTION

These flexible pipes, generally tubular, consisting of an assembly of different concentric and superposed armour wire layers, are referred to as unbonded because the armours and the layers have a certain freedom to move relative to one another.

These flexible pipes can meet, among other things, the recommendations of the normative documents API 17J "Specification for Unbonded Flexible Pipe" and API RP 17B "Recommended Practice for Flexible Pipe" established by the American Petroleum Institute.

In general, the constituent layers notably comprise sheaths made from polymer material generally providing a sealing function and reinforcement layers designed to take up the mechanical stresses. These reinforcement layers are formed by winding strips, metal wires, various tapes or hollow structural sections made from composite materials.

Figure 1 shows an unbonded type flexible pipe used for offshore exploitation of oil and gas reservoirs. Such a flexible pipe generally comprises, from inside to outside, an inner carcass (1) consisting of a clipped strip intended to withstand collapse of the pipe under the effect of the external pressure, an internal pressure sheath (2), a pressure vault (3) consisting of at least one clipped metal wire helically wound with a short pitch, said pressure vault (3) being intended to take up the radial stresses caused by the internal pressure, at least one tensile armour ply (4) (four plies as illustrated in Figure 1) consisting of long-pitch helical windings of wires, strips, metal or composite tapes, said armour plies (4) being intended to take up the longitudinal stresses undergone by the pipe, and an outer sealing sheath (5) intended to protect the reinforcement layers from the sea water.

The pipe illustrated in Figure 1 is of rough bore type, i.e. the fluid circulating in the pipe is in contact with inner carcass (1), said inner carcass (1) being indeed the first layer, starting from the inside. However, the flexible pipe can also be of smooth bore type, and in this case, the first layer of the pipe, starting from the inside, is an additional sealing sheath made from polymer material for example.

Flexible tubular pipes comprise, at each end, a connection end fitting intended to provide connection of the pipes with one another, or with terminal equipments. These end fittings need to be made under conditions ensuring good fastening and good sealing.

Indeed, end fittings must fulfill several functions, notably tensile armour anchoring, as well as crimping and sealing of the free ends of the various sheaths, and in particular crimping at the free end of the inner pressure sheath. An essential function of a rigid end fitting of a flexible pipe is to transmit a tensile stress and, among the various layers that make up the flexible pipe, this stress is taken up by the armour layers, therefore armour anchoring conditions the static resistance and fatigue strength of the system.

An example of a connection end fitting is notably described in patent application FR-2,816,389 Al. In this embodiment, the armours are folded and unfolded, and anchoring of the armours is achieved by means of an epoxy type resin. General shaping of the armour wires induces concentration factors due to the particular geometry and to local plastic and elastic deformations.

When it is used under severe conditions, the fatigue strength of this system is not sufficient. Indeed, for this end fitting, the manufacture and the production (notably with folding/unfolding) induce during operation a high stress on the wires in a zone close to the entry in the end fitting (at the separation of the armours); the wire is subjected to a tractive force, a normal and transverse bending stress with a state of high residual stresses.

To overcome this drawback, the present invention relates to a connection end fitting for a flexible pipe where anchoring of the armour wires is achieved by wedging between two jaws. The jaws have a substantially conical shape and they are formed in such a way that the armours have a continuous radius of curvature. Thus, the armour has no singular point in the end fitting and provides good fatigue strength. Furthermore, the geometric form required for the wires in the end fitting is preferably close to the free form thereof so as to avoid to the maximum introducing plastic and elastic residual stresses (notably due to the folding/unfolding stage).

SUMMARY OF THE INVENTION

The invention relates to a connection end fitting of a flexible pipe, said flexible pipe being of unbonded type and comprising notably an internal pressure sheath and at least one ply of tensile armours wound around said pressure sheath, each of said tensile armour plies comprising a tip length anchored in said end fitting. Anchoring of each of said tip is achieved by wedging said tip between two jaws, so that said tip length has no singular point, said jaws being arranged in said end fitting and being substantially conical.

According to the invention, said tip length has a substantially continuous radius of 20 curvature.

Advantageously, said jaws have the shape of a cone of revolution whose generatrix is substantially a straight line forming an angle with the axis of revolution of said flexible pipe smaller than 20°, preferably smaller than 10° and more preferably substantially equal to 5°, an arc of a circle or a portion of an ellipse, of a parabola or of a hyperbola, or made up of two consecutive radii of curvature.

According to an embodiment of the invention, said flexible pipe comprises at least two tensile armour plies wound around said pressure sheath, said tips of said tensile armour plies being arranged one above the other and wedged between two jaws.

According to another embodiment of the invention, said flexible pipe comprises at least two tensile armour plies wound around said pressure sheath, each tip of said tensile armour plies being wedged individually between two jaws.

Preferably, said flexible pipe comprises two tensile armour plies wound around said pressure sheath and said end fitting comprises three jaws, among which an intermediate jaw in contact with each one of said tips of said tensile armour plies.

Advantageously, at least one of said jaws is moved by means of at least one threaded rod.

According to an aspect of the invention, at least one of said jaws is made from mild steel.

Furthermore, at least one of said jaws can have a polymer layer at the contact point with said tip length of one of said tensile armour plies.

Preferably, said polymer layer is made from an elastomer material.

Advantageously, one of said jaws is fastened to said end fitting or to one of the layers of said flexible pipe.

According to a variant embodiment of the invention, at least one of said jaws is grooved for prepositioning said tip length of a tensile armour ply.

Advantageously, the clamping pressure exerted by said jaws on said tip length ranges between 3 and 100 MPa, and it is preferably substantially equal to 50 MPa.

Furthermore, the invention relates to an unbonded type flexible pipe comprising notably an internal pressure sheath and at least one ply of tensile armours wound around said pressure sheath. Said flexible pipe comprises at least at one of its ends a connection end fitting according to the invention.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the method according to the invention will be clear from reading the description hereafter of embodiments given by way of non limitative example, with reference to the accompanying figures wherein: - Figure 1, already described, illustrates a flexible pipe, - Figure 2 is a cross-sectional view of an end fitting according to a first embodiment of the invention, -Figure 3 is a cross-sectional view of a connection end fitting according to a second embodiment of the invention, - Figure 4 is a three-dimensional cross-sectional view of a connection end fitting according to the second embodiment of the invention, - Figure 5 is a cross-sectional view of the second embodiment of the invention, -Figure 6 illustrates the stresses exerted on an armour in an end fitting according to the invention, -Figure 7 illustrates a stage prior to the manufacture of the end fitting according to the second embodiment of the invention, - Figure 8 illustrates the sealed areas of the end fitting according to the second embodiment of the invention, - Figure 9 illustrates a variant embodiment of the jaws for the two embodiments of the invention, and - Figure 10 illustrates the winding angle of an armour wire.

DETAILED DESCRIPTION

The present invention relates to a connection end fitting of a flexible pipe where the rigid end fitting is notably designed to take up the axial mechanical tension undergone by the flexible pipe. The invention therefore consists in anchoring in the connection end fitting armour plies included in the flexible pipe by wedging (pinching) the tips of the armour plies between jaws so as to secure them to the rigid part of the end fitting. According to the invention, the jaws are substantially conical and have the shape of a wedge so that the wire exhibits no singular point in the end fitting to avoid straining the armours at the anchoring point thereof. A singular point is understood to be a point of the armour where the shape (three-dimensional path) of the armour varies abruptly, i.e. a point for which the shape (path) derivative is not continuous. At a singular point, the armour undergoes high stresses (stress concentration), which generates a reduction in static resistance and fatigue strength. Singular points can be due to the shape of the armour (a discontinuity for example, or a turn-up as described in patent application FR-2,816,389 Al), or to the manufacturing process. A large angle formed by two line segments is an example of a singular point.

Indeed, one advantage of the invention is the anchoring progressivity, which is made possible by the wedging system and a geometry without singular points. This is possible with a geometry with the following characteristics: -the (three-dimensional) geometry of the wire is continuous, the derivative of the mean fiber of the armour wire being continuous, -the wire laying surface has no inflection point, the second derivative of the equation of the wire laying curve f(x) is always of the same sign, f"(x) 0 or f"(x) s 0.

Figure 11 gives an example of geometry G of the armour wire in the anchor as a function of the anchoring depth. This profile consists of two successive radii of curvature.

When the wire laying envelope consists of an assembly of tangentially connected surfaces, the connections will induce normal curvature shifts. However, these curvature shifts generate an additional bending stress that needs to be limited. This stress adds to the tensile stress due to the normal operating load undergone by the flexible pipe.

According to the invention, the overstress Aa generated by curvature shift AC,, should not be high and this stress preferably does not exceed 10 % of the maximum stress allowable by the armour wire in random length (amax = 0.55 ae, with ce the elastic limit of the armour wire). The following relation can be written: Au = . AC n, with E the 2 n Young's modulus and e the armour thickness. In order to avoid too great overstresses, the curvature shifts are minimal at the anchor inlet where the stress in the wire is maximal. It is possible to modify the path of the wire of random length with a minor change in the local curvature of the armour wire. Furthermore, in the anchor, greater curvature shifts are allowable provided that the overstress does not exceed the maximum stress of the random length.

According to the invention, in order to undergo no overstress, the normal curvature of the wire in the anchor undergoes no abrupt curvature variation. Advantageously, curvature variation AC of the armour wire in the anchor can be limited, preferably in such a way that Ac < 7 0with C,, expressed in mm-1. The random-length normal curvature for a flexible pipe of diameter D wound (armoured) at an angle a is expressed as follows: C,, - Sit/2a This curvature for flexible pipes of between 2" 1) (about 5.08 cm) and 20" (about 50.8 cm) armoured at an angle between 20° and 55° ranges between: 4,6.10 3 < Cf.? < 26.10 I nam.

For example, for a 4" (about 10.16 cm) flexible pipe armoured at 35°, the random-length curvature is a = 6.5.10-3 mm-1. Therefore, according to the above criterion, the curvature variation should not exceed: SC; 9.10 Gunn 2.

Advantageously, the jaws have the shape of a cone of revolution whose bases are substantially circular and whose generatrix can be a straight line, an arc of a circle, a portion of an ellipse, of a parabola or of a hyperbola, or it can be made up of two consecutive radii of curvature. Thus, the path of the armour wire in the end fitting can be a straight line, but it is preferably a curve between the geodesic (zero transverse curvature in the armour) and the loxodrome (constant armour angle) allowing to have an additional holding force through capstan effect. Thus, the radius of curvature of the tip length of the armour is substantially continuous, which enables good distribution of the wire stresses within the anchor and avoids singular points in the end fitting (limitation of stress concentrations at a point of the tip length). Indeed, this jaw geometry allows to have: -progressive clamping pressure from the jaw inlet to the final termination, - progressive armour immobilization, and - good fatigue strength.

The tensile stress level in the armour wire is progressively reduced by the load transfer resulting from the friction between the wire and the jaws.

Figure 10 shows the winding angle of an armour wire (4) around a conical frustum.

Armour wire (4) is thus wound around a conical frustum (jaw). Angle [3 between tangent (t) to the wire and axis (A) of the conical frustum preferably ranges between 10° and 60°. This winding allows the wire to be pressed against the surface of the conical frustum (thus creating a normal wire/jaw stress). The intensity of the normal stress depends on the tensile stress exerted on the wire. Considering a friction coefficient at the wire/jaw interface, a stress can be transmitted at the interface by friction (capstan effect).

It can be noted that the jaw grip length can be quite limited (between 100 mm and 500 mm).

According to a variant embodiment of the invention, the cone angle (vertex half angle) of the jaws preferably ranges between 2° and 30°, and it preferably is substantially 5° in order to limit the radius of curvature of the armours.

Anchoring of the armours can be common (see first embodiment of Figure 2) or not (see second embodiment of Figure 3) to the two plies between two jaws (entirely independent system). The rest of the description and the figures are given for a flexible pipe comprising a carcass, an internal sheath, a pressure vault and two armour plies; the invention is however suited for all types of flexible pipes comprising at least one internal pressure sheath and at least one ply of tensile armours wound around the pressure sheath. In particular, the invention is suited for all numbers of armour plies, notably four armour plies. Advantageously, the armour plies are arranged in pairs to provide torsion equilibrium since two tensile armour plies are wired in opposite directions.

For the first embodiment of the invention illustrated in Figure 2, the flexible pipe consists, from the inside to the outside, of a carcass (1), an internal sheath (2), a pressure vault (3) and two tensile armour plies (4), and armour plies (4) are anchored in end fitting (6) by wedging by means of two jaws (7, 8). Jaws (7, 8) are displaceable towards one another in the axial direction of the pipe so as to generate a clamping force for anchoring armours (4). For this first embodiment of the invention, armour plies (4) are arranged one above the other between jaws (7, 8). Thus, anchoring of the two armour plies (4) is achieved simultaneously.

One (8) of the jaws is in contact with the cover of end fitting (6) and the other jaw (7) is in contact with the inner layers (vault or sheath) of the flexible pipe. Jaws (7, 8) can slide on the inner parts (layers beneath the armours) or the outer parts (cover). Alternatively, one of the jaws is mechanically secured to the part supporting it by screwing, threading, welding or from the manufacturing stage. Clamping of jaws (7, 8) can be achieved using a threaded rod or a threaded ring, or any other similar means. Hydraulic provisional preclamping can be used.

For the second embodiment of the invention illustrated from Figure 3, the flexible pipe consists, from the inside to the outside, of a carcass (1), an internal sheath (2), a pressure vault (3) and two tensile armour plies (4), and armour plies (4) are anchored in end fitting (6) by wedging by means of three jaws (7, 9, 10). Jaws (7, 9, 10) are displaceable in the axial direction of the pipe so as to generate a clamping force for anchoring armours (4). For this second embodiment of the invention, armour plies (4) are arranged individually between two jaws: a first armour is wedged between a jaw (7) arranged on the flexible pipe and an intermediate jaw (9), and second armour (4) is wedged between intermediate jaw (9) and a jaw (8) arranged in the cover of end fitting (6). Jaws (7, 10) can slide on the inner parts (vault or sheath of the flexible pipe) or on the external parts (cover), or they can be secured to the part supporting it by screwing, threading, welding or from the manufacturing stage. This second embodiment thus consists in dissociating the anchoring of each ply so as to optimize the anchoring forces (two friction surfaces) and in pinching each armour ply in a jaw that allows the armour wire to have a continuous radius of curvature from the main portion to the anchor end thereof.

Figure 4 is a three-dimensional view of this embodiment. It notably shows the embodiment of end fitting (6) in two parts: cover (6a) provides sealing and connecting flange (6b) allows connection of the flexible pipe to an end fitting of another flexible pipe or to terminal equipments.

Clamping of jaws (7, 9, 10) can be achieved by means of a threaded rod or a threaded ring, or any other similar means. Hydraulic provisional preclamping can be used. Figure 5 shows a variant of this embodiment of the invention where common clamping of jaws (7, 9, 10) is achieved by means of a threaded rod (11) running through the three jaws. Alternatively, clamping of jaws (7, 9, 10) can be independent so as to achieve separate anchoring of armours (4).

The three jaws of the second embodiment are shown as single-piece parts. However, for ease of mounting and to avoid remachining, jaws made up of several parts (cut lengthwise) can be used in order to adjust armour positioning by clamping.

The second embodiment of the invention can be suited for flexible pipes with even numbers of armours: for each pair of armour plies, anchoring is achieved with three jaws.

The jaws can be made from mild steel so as to obtain a plastic deformation at the surface of contact in order to improve crimping. The assembly can thus be dismantled but the mild steel parts need to be replaced.

Figure 9 illustrates a variant embodiment of the jaws according to the invention. In some cases, steel/steel contacts can be avoided so as to limit corrosion and/or fretting problems. A polymer layer (13) can be provided between armour wire (4) and jaw (7, 8, 9, 10). Using jaws with a polymer layer (13) allows to limit slippage at the interface with armour wires (4) because these jaws (7, 8, 9, 10) deform under stress. The thickness of this non-steel element (13) can range between 1 and 50 mm. The polymer can be selected from elastomers.

In order to guarantee armour anchoring, the armours can be preformed prior to being mounted.

Hydraulic clamping of the jaws can be provided prior to starting the assembly work.

To improve the anchoring performances, the friction level at the armour wire/jaw interface can be increased. Structural bonding and/or surface texturing can be used therefore.

A surface of the jaws can be grooved to preposition the armour wire. The non-grooved jaw is then mobile and allows crimping.

An armour wire prepositioning system can be used when mounting the end fitting.

The clamping pressure exerted by the jaws on said tip length of the armour wires ranges between 3 and 100 MPa, and it is preferably substantially 50 MPa in order to provide sufficient clamping without creating a stress concentration in the armours.

According to an example embodiment of the invention, the approximate dimensions of the invention are: - the overall length (total length) of the end fitting is of the order of 1400 mm, - the diameter of cover (6a) is 300 mm, - the anchor part dimension is about 400 mm in length (per ply) and 250 mm in 10 diameter.

Predimensioning example Figure 6 shows different stresses involved upon clamping. The elements considered for the predimensioning calculation are: - a cone/cone geometry (vertex half angle) at 5°, -the armours are pinched between two plane jaws, - a friction coefficient at the wire/jaw interface of 0.3, i.e. a friction angle of 17°, - the jaw system is self-wedging but this effect is not taken into account, - the stress take-up by capstan effect is not considered, - an anchoring length of 300 mm, -the wire width considered in contact is 10 mm to take account of the rounded corners, - a tension stress Ftm, of 1000 kN.

The normal tension stress FN to be exerted on each armour ply face is 1666 kN (= 1000/0.3/2) to frictionally retain the armours. The axial clamping force has to be 145 kN (= 1666 x sin (17°+5°)). This clamping can be achieved by threaded rods, two M12 screws for example.

The elongation at the connection outlet can be estimated by considering a lock at the end thereof if the maximum stress is reached, 1200 MPa, then the maximum L 1200.300 elongation is about 2 mm ( - ). The elongation at the end fitting E 210 000 outlet will depend on the free length of armour present in the end fitting (between the jaws outlet and the end fitting outlet). This distance is of the order of 400 mm, it thus increases the elongation at the end fitting outlet to about 4 mm.

This jaw system allows to embed the armour wire at the end thereof and to release it progressively. The friction force will allow to hold the wire over the length of engagement of the jaws and to limit the displacements/elongations thereof.

Furthermore, the invention relates to a flexible pipe comprising at least one pressure sheath, at least one armour ply and at least one end fitting as described above at one end thereof. By means of the end fitting, the flexible pipe according to the invention can be connected to another flexible pipe portion or to a terminal equipment. For example, the make-up of the flexible pipe can be that of the flexible pipe of Figure 1.

The flexible pipe according to the invention can be used notably for offshore exploitation of an oil and/or gas reservoir. The flexible pipe according to the invention can meet, among other things, the recommendations of normative documents API 1 7J "Specification for Unbonded Flexible Pipe" and API RP 17B "Recommended Practice for Flexible Pipe" established by the American Petroleum Institute.

The invention thus affords many advantages: - the specific geometry of the jaws (circular, elliptic, parabolic) allows progressive locking of the armours and prevents any singular point (advantage in relation to the current concept), -anchoring is suited to provide good resistance under fatigue stress, - the armours require no specific shaping (no folding/unfolding, hook). Furthermore, preforming of the wires is not necessarily required (assembly simplification). However, preforming can be a way of improving the invention to reduce the maximum stresses or to facilitate mounting, -for the second embodiment of the invention, immobilization of the armours is achieved ply by ply with a series arrangement allowing the assembly to be flanged with the same system, - Figure 7 illustrates a stage prior to the assembly of end fitting (6). Setting of cones (7, 9, 10) requires cutting armours (4) to the suitable length, the outer layers are the shortest, which facilitates the preparation operation. A collar (12) intended for temporary immobilization of the armours allows to keep the arrangement of plies (4) for mounting. Preferably, it is removed thereafter. The assembly of connection end fitting (6) according to the invention is thus facilitated, - the system is removable. If jaws made from mild steel or if structural bonding of the armours is used, removal requires specific tools and changing some of the parts when reassembling, - mechanical stress take-up according to the invention is enhanced by the self-wedging effect of the cones and by the capstan effect, - whether by tightening with a torque wrench or clamping with a hydraulic system, the invention provides perfect control of the flanging compressions, independently of the operator, -access to the sealed zones does not depend on the anchoring technology. Indeed, Figure 8 shows the sealed zones (Ze) that do not depend on the anchoring means.

Claims

CLAIMS1) A connection end fitting of a flexible pipe, said flexible pipe being of unbonded type and comprising notably an internal pressure sheath (2) and at least one ply of tensile armours (4) wound around said pressure sheath (2), each of said tensile armour plies (4) comprising a tip length anchored in said end fitting (6), characterized in that anchoring of each of said tip is achieved by wedging said tip between two jaws (7, 8, 9, 10) so that said tip length has no singular point, said jaws being arranged in said end fitting (6) and being substantially conical.
2) An end fitting as claimed in claim 1, wherein said tip length has a substantially continuous radius of curvature.
3) An end fitting as claimed in any one of claims 1 or 2, wherein said jaws (7, 8, 9, 10) have the shape of a cone of revolution whose generatrix is substantially a straight line forming an angle with the axis of revolution of said flexible pipe smaller than 20°, preferably smaller than 10° and more preferably substantially equal to 5°, an arc of a circle or a portion of an ellipse, of a parabola or of a hyperbola, or made up of two consecutive radii of curvature.
4) An end fitting as claimed in any one of the previous claims, wherein said flexible pipe comprises at least two tensile armour plies (4) wound around said pressure sheath (2), said tips of said tensile armour plies (4) being arranged one above the other and 20 wedged between two jaws (7, 8).
5) An end fitting as claimed in any one of claims 1 to 3, wherein said flexible pipe comprises at least two tensile armour plies (4) wound around said pressure sheath (2), each tip of said tensile armour plies (4) being wedged individually between two jaws (7, 9, 10).
6) An end fitting as claimed in claim 5, wherein said flexible pipe comprises two tensile armour plies (4) wound around said pressure sheath (2) and said end fitting comprises three jaws (7, 9, 10), among which an intermediate jaw (9) in contact with each one of said tips of said tensile armour plies (4).
7) An end fitting as claimed in any one of the previous claims, wherein at least one of said jaws (7, 8, 9, 10) is moved by means of at least one threaded rod (11).
8) An end fitting as claimed in any one of the previous claims, wherein at least one of said jaws (7, 8, 9, 10) is made from mild steel.
9) An end fitting as claimed in any one of the previous claims, wherein at least one of said jaws (7, 8, 9, 10) can have a polymer layer (13) at the contact point with said tip length of one of said tensile armour plies (4).
10) An end fitting as claimed in claim 9, wherein said polymer layer (13) is made from an elastomer material.
11) An end fitting as claimed in any one of the previous claims, wherein one of said jaws (7, 8, 9, 10) is fastened to said end fitting (6) or to one of the layers of said flexible pipe.
12) An end fitting as claimed in any one of the previous claims, wherein at least one of said jaws (7, 8, 9, 10) is grooved for prepositioning said tip length of a tensile armour ply (4).
13) An end fitting as claimed in any one of the previous claims, wherein the clamping pressure exerted by said jaws (7, 8, 9, 10) on said tip length ranges between 3 and 100 MPa, and it is preferably substantially equal to 50 MPa.
14) An unbonded type flexible pipe comprising notably an internal pressure sheath (2) and at least one ply of tensile armours (4) wound around said pressure sheath (2), characterized in that said flexible pipe comprises at least at one of its ends a connection end fitting (6) as claimed in any one of the previous claims.