Abstract:
The invention relates to a pipe structure ( 10 ) comprising a length of a flexible pipe connected to an end fitting, the flexible pipe comprising an armour layer ( 11; 19 ) and an underlying pipe layer ( 12; 11 ) to said armour layer, said underlying pipe layer having an outer surface around which armouring wires ( 111; 191 ) of an armouring layer are helically wound. The object of the present invention is to provide a coupling between a flexible pipe comprising armouring wires and an end fitting, the coupling exerting a relatively low bending or flexure strain on the wires during normal operation of the flexible pipe. The problem is solved in that the transition path of an armouring wire between the flexible pipe and the end fitting comprises an straight-line-section ( 194 ) between a wire-pipe-exit-point ( 195 ) where the wire extends away from its underlying pipe layer and a straight-line-end-point ( 196 ) on a support unit ( 15 ) of the end fitting where the armouring wire in question has its first tangential point of contact. This ahs the advantage that in a loaded situation where the armouring wires will elongate elastically leading to a change in the helical angle of the armouring wires, a pipe structure according to the invention will experience a slight twist and a controlled bending of the armouring wires on the surface of the support unit (due to a possible change in the base point of contact of the armouring wire with the support unit induced by the change of helical angle), thereby avoiding substantial bending of the individual armouring wires, which is of particular importance when the armouring wires are formed of a composite material. The invention may be used in flexible pipes for the off shore transport of fluids (e.g. oil).

Description:
TECHNICAL FIELD OF THE INVENTION  
       [0001]     The present invention relates to a flexible pipe for transporting a fluid substance (e.g. oil or gas or a mixture thereof) and especially to the connection of a flexible pipe to an end fitting for connecting the flexible pipe to an installation (at land or on a vessel at sea or on the seabed) or for connecting to another pipe, e.g. another flexible pipe or a rigid pipe. The invention deals with the subject of adapting a relatively flexible pipe to a relatively stiff end fitting. The invention relates specifically to a pipe structure comprising a length of a flexible pipe connected to an end fitting, the flexible pipe comprising an armour layer and an underlying pipe layer to said armour layer, said underlying pipe layer having an outer surface around which armouring wires of an armouring layer are wound.  
       DESCRIPTION OF RELATED ART  
       [0002]     Flexible pipes are used in a variety of applications, including water supply lines, sewage lines for transporting chemicals such as liquid ammonia and phosphoric acid in high-pressure off-shore applications in the oil and gas industry.  
         [0003]     The tensile armour layer or layers of the flexible pipe and the joint between this or these layers and the end fitting provides the majority of the resistance to axial tensile loads acting on the assembly of the end fitting and the pipe. The joint between the flexible pipe and the end fitting performs the function of adapting a relatively flexible pipe to a relatively stiff fitting.  
         [0004]     Un-bonded flexible pipes are conventionally reinforced with metallic wires, wound at an angle around the pipe to give the pipe its increased flexibility. A conventional metallic armoured pipe is very stiff both radially and axially, thus limiting the problem of the transition in flexibility of the structure from the running length of pipe to the connector unit. Further, a conventional steel armouring element, wire, may yield to a local intensity of stress, caused by an abrupt change in stiffness, without reducing the load bearing capacity of the element. Solutions for the anchoring of metallic armouring elements of conventional un-bonded flexible pipes are available.  
         [0005]     Conventional composite pipes are bonded and rigid, thus barrier- and reinforcing layers are fixed to each other at their interfaces. Further, the reinforcing fibres are embedded in resin, forming a continuous layer. Rigid composite reinforced pipes are generally less stiff than their metallic counterparts and the anisotropy of the material—giving it different properties in different directions—calls for a carefully engineered transition to the connector unit. Many solutions can be found for the anchoring of the fibre reinforced layers in conventional composite pipes, cf. e.g. U.S. Pat. Nos. 4,701,231 and 4,530,379.  
         [0006]     Composite reinforced un-bonded flexible pipes differ from the conventional structures described above in that the pipe is axially and radially less stiff than the metallic reinforced flexible pipe and the layers containing the composite reinforcement are not continuous, but consist of a number of individual wires, each made of a composite material, which will not yield to a local stress intensity but rather initiate failure.  
         [0007]     In the following, a novel solution to the efficient anchoring of a wire based armouring in an end connector for a flexible pipe is presented. The solution may be used for pipes reinforced with metallic or composite armouring wires and for bonded as well as un-bonded pipes.  
       SUMMARY  
       [0008]     The object of the invention is to provide a coupling between a flexible pipe comprising armouring wires and an end fitting, the coupling exerting a relatively low bending or flexure strain on the wires during normal operation of the flexible pipe (i.e. in a situation—within the design specifications of the pipe—of internal and/or external radial pressure and external tension in the longitudinal direction of the pipe).  
         [0009]     The object of the invention is achieved by the invention described in the accompanying claims and as described in the following.  
         [0010]     A pipe structure according to the invention comprising a flexible pipe connected to an end fitting is provided, the flexible pipe comprising an armour layer and an underlying pipe layer to said armour layer, said underlying pipe layer having an outer surface around which armouring wires of an armouring layer are wound, the flexible pipe having a longitudinal axis wherein  
         [0011]     said end fitting comprises 
        one or more anchoring elements adapted for anchoring at least one of said armouring wires, and     a support unit arranged coaxially around said underlying pipe layer     at least one of said armouring wires comprising 
            a conforming-wire-pipe-section forming a helical path and conforming to the outer surface of said underlying pipe layer of said flexible pipe at least over a part of its length, and     a wire-end-fitting-section,     said two wire sections extending in opposite directions from a wire-pipe-exit-point where said armouring wire separates tangentially away from said underlying pipe layer, and    
            said wire follows an essentially straight line of a length L free  between said wire-pipe-exit-point and a straight-line-end-point on said support unit, said essentially straight line part of the wire being defined as the straight-line-section.        
 
         [0019]     In the present context, the term ‘armouring wires’ is taken to mean elongate elements having e.g. a circular, rectangular (tape formed) cross sectional form or any other form appropriate for serving the purpose of stabilizing the pipe in its longitudinal and/or radial direction.  
         [0020]     The ‘longitudinal axis’ of the flexible pipe is taken to mean the axis of symmetry in a direction of fluid flow defined by the flexible pipe in operation when it is held in a straight line (uncurved) configuration.  
         [0021]     A flexible pipe for transporting a fluid substance, egg. oil, has an inside which is in contact with the fluid substance during operation and an outside which is in contact with the environment, e.g. a marine environment. In the present context, the term ‘an outer surface’ of an element in a flexible pipe is taken to mean a surface that faces towards the outside (as opposed towards the inside) of the flexible pipe (not necessarily having a direct contact to the environment, though). Similarly, the terms a ‘convex’ or ‘an outward’ curvature and a ‘concave’ or an ‘inward’ curvature, respectively, are taken to be seen relative to the longitudinal axis of the flexible pipe.  
         [0022]     In the present context, the term ‘an unloaded condition’ of a flexible pipe or pipe structure is taken to mean a condition where the flexible pipe is in a relaxed, unstressed situation, i.e. without being pressurised from inside or outside and without being subject to external twist or longitudinal stress.  
         [0023]     In the present context, the terms ‘wire-pipe-exit-point’ and ‘a straight-line-end-point’ are taken to mean the end points of contact between an armouring wire and, respectively, the underlying pipe layer and the support unit of the end fitting, between which the armouring wire follows an essentially straight line. Instead of points of contact ‘wire-pipe-exit-point’ and ‘a straight-line-end-point’ are to be interpreted as lines or curves of contact, if said wire has a cross section that adapts to the surface of said underlying pipe layer and/or said support unit, e.g. a tape form. The same applies to a ‘support-unit-exit-point’ (see later) where the armouring wire leaves the surface of the support unit for being locked in one of the anchoring elements.  
         [0024]     In a preferred embodiment the ratio of the ‘free length’ or ‘straight-line-section’ L free  (in an unloaded condition of the pipe) of an armouring wire to its maximum cross sectional dimension D wire  is larger than 2, preferably in a range from 2-20, more preferred in a range from 5-10, the ‘free length’ being defined as the length of an armouring wire between its exit point from the underlying pipe layer (the ‘wire-pipe-exit-point’) and its point of contact with the support unit of the end fitting (‘straight-line-end-point’).  
         [0025]     An advantage of the invention is that in a loaded situation comprising a combination of internal pressure and external tension and where the armouring wires will elongate elastically leading to a change in the helical angle of the armouring wires, a pipe structure according to the invention will experience a slight twist and a controlled bending of the armouring wires on the surface of the support unit (due to a possible change in the base point of contact of the armouring wire with the support unit induced by the change of helical angle), thereby avoiding substantial bending of the individual armouring wires. This is for example of particular importance when the armouring wires are formed of a composite material. A complete and simple anchoring can then be incorporated in the end fitting design at any point after the ‘straight-line-end-point’ on the support unit (in the direction of the end fitting, i.e. when viewed from the pipe towards the end fitting), as the wire after this point is only stressed in its own direction.  
         [0026]     The various parts of an end fitting may preferably be made of structural materials e.g. metals such as steel, titanium, aluminium, reinforced polymers such as fibre glass/polyester, carbon-fibre/epoxy, etc. The parts may e.g. be manufactured by a numerically controlled machine or by moulding.  
         [0027]     In an embodiment of the invention, the wire-end-fitting-section is arranged to follow a predefined termination path between said wire-pipe-exit-point and one of said anchoring elements when said pipe structure is in an unloaded condition. The dynamic range of locations of the wire-pipe-exit-point and the straight-line-end-point may be predetermined according to the normal operating conditions of the pipe structure. The part of the wire-end-fitting-section of the armouring wire that is located after the dynamic range of locations of the straight-line-end-point (when viewed in a direction of the end fitting) may be fixed to a predetermined path on the support unit (e.g. using guiding channels or the like) to simplify the mounting of the flexible pipe to the end fitting.  
         [0028]     In an embodiment of the invention, the straight-line-section is essentially unsupported between said wire-pipe-exit-point and said straight-line-end-point on said support unit. The term ‘essentially unsupported’ is in the present context taken to mean having a negligible effect on the deformation behaviour of the wire.  
         [0029]     In an embodiment of the invention, the straight-line-section extends away from said longitudinal axis when viewed from said wire-pipe-exit-point.  
         [0030]     In an embodiment of the invention, the straight-line-section of said armouring wire has a tangential point of contact with said support unit in said straight-line-end-point. In this embodiment, the armouring wire has a free (i.e. mechanically unrestricted) linear path between the points of contact with the underlying pipe layer and the support unit. Alternatively, the armouring wire may be strained in contact with (but without locking it to) the support unit e.g. by a surrounding body (e.g. in the form of an assisting element, see later), in which case the slope of the straight-line-section of the armouring wire may deviate from the tangent to the support unit at the point of contact.  
         [0031]     The underlying surface to the armour may have significant stiffness established through an insert. This will reduce the angular change of the helix of the armouring wires during loading.  
         [0032]     In an embodiment of the invention, said underlying pipe layer of said flexible pipe comprises an armouring reinforcement on a section of the pipe structure including said wire-pipe-exit-point and extending in a direction of the end fitting as defined by a direction from the flexible pipe towards the end fitting.  
         [0033]     An armouring reinforcement may be present (if necessary for the operating conditions of the pipe in question) and comprise an annual armouring body forming part of the underlying pipe layer and is intended for supporting the flexible pipe over the part of the end fitting where some of the armouring wires are leaving the flexible pipe for being supported by the support unit, thereby weakening the armouring effect. Alternatively an armouring reinforcement may form part of the support unit and annularly enclose the underlying pipe layer so that the wire-pipe-exit-point is located on the armouring reinforcement-part of the support unit. In an alternative embodiment, this substitute armouring layer may be inserted on the inner side of the armouring layer or layers in question, in which case the wire-pipe-exit-point will be located on the so-called underlying pipe layer. The purpose of the armouring reinforcement is to give a mainly radial stiffness over its length and represents a transition between the flexible pipe and the stiff end fitting.  
         [0034]     In an embodiment of the invention, said predefined termination path further comprises a supported-wire-section running on the outer surface of said support unit from said straight-line-end-point to a support-unit-exit-point where the armouring wire leaves the surface of said support unit for being locked in one of said anchoring elements, said supported-wire-section essentially constituting a geodetic curve between said straight-line-end-point and said support-unit-exit-point on said outer surface of said support unit.  
         [0035]     In the present context the term ‘a geodetic curve’ is taken to mean a curve on a surface for which the curve has a primary normal vector which in all points is identical to the normal vector of the surface. A geodetic curve on a surface represents the shortest distance along the surface between two points on the surface. A geodetic curve on a surface has a geodetic curvature ρ g =0, the geodetic curvature of a curve at a point P on a surface being defined as the length of the projection (calculated with sign) of the vector of curvature on the tangent plane of the surface at the point P. The vector of curvature ρn of curve r(s) at a point P (given as r 1 (s)) is defined as d 2 r 1 /ds 2 =ρn, ρ being the curvature of the curve at the point P and n a unit vector.  
         [0036]     The term ‘essentially constitutes a geodetic curve’ is in the present context taken to mean that the path in question follows a geodetic curve on the surface of the support unit in question within the mechanical processing tolerances, e.g. so that the relative length difference between the actual path and the geodetic curve is less than 5%, preferably less than 1%.  
         [0037]     The advantage hereof is that the armouring wires are located in stable positions when the flexible pipe is in an unloaded state because all wires are positioned to follow a shortest possible path on the support unit of the end fitting. This minimizes the ‘repositioning’ of the armouring wires when the flexible pipe is loaded.  
         [0038]     A geodetic curve between two points on a surface may in practice be found by means of a string with no bending resistance, which under tension will find the shortest path between to points.  
         [0039]     In an embodiment of the invention, said support unit has an outer surface that describes a surface of revolution with an axis of revolution that coincides with the longitudinal axis of the flexible pipe. This has the advantage of providing a symmetric element which is relatively easily manufactured. Alternatively, the support unit may take many other forms, e.g. more complex forms where elements are arranged to receive individual armouring wires. In an embodiment of the invention, the supporting surface of the support unit in the area where the straight-line-end-point is located is individually formed for different wires having their straight-line-end-point located on the support unit. An advantage of hereof is that assembly of the wires to the end fitting is eased and reliability improved. In an embodiment of the invention, the supporting surface of a wire is a single curved surface oriented such that every normal to this surface lies in a plane that is parallel to any plane containing the longitudinal axis of the pipe. In the present context, “a single curved surface” is taken to mean a surface that curves in only one dimension (a simple example is a cylinder generated by a circle, but any other curve may be used). The use of a single curved surface in the present construction has the advantage that the construction of the individual surface parts are well-suited for implementation with standard manufacturing tools (e.g. numerically controlled tools).  
         [0040]     Typically, the support unit is arranged around and ‘resting on’ the underlying pipe layer. It might, however, alternatively be arranged around the underlying pipe layer without touching it or resting thereon. In an embodiment of the invention, the support unit comprises an annular body with an opening that fully encloses the armouring layer in question around which the support unit is mounted coaxially, the opening being of a form and size that allows the support unit to be positioned relative to the underlying pipe layer in such a way that a straight line path (‘the straight-line-section) is defined between a wire-pipe-exit-point on the underlying pipe layer to a point of contact (‘the straight-line-end-point’) on the inner outline of said opening of the support unit. In an embodiment of the invention, the surface around the location of the predicted points of contact during normal operation is formed so that its surface is concave when seen relative to the longitudinal axis of the flexible pipe in a cross section including said axis. In an embodiment of the invention, the support unit is arranged annularly around the underlying pipe layer, e.g. in the form of an annular ring (e.g. a torus) with an inner diameter that is larger than the diameter of the underlying pipe layer so that an armouring wire may have its straight-line-end-point on the annular ring surface and a supported-wire-section that extends through the inner opening of the annular ring for being locked in an anchoring element.  
         [0041]     In an embodiment of the invention, the anchoring elements form part of the support unit.  
         [0042]     In an embodiment of the invention, said support unit has an outer surface which includes a part of a torus on which the ‘straight-line-end-point’ is located.  
         [0043]     The term ‘an outer surface which includes a part of a torus’ is in the present context taken to mean that said surface has a part that has the shape of a part a torus, e.g. corresponding to a 15 or 45 or 90 degree cut of a fully revolved torus (the quoted angles being centre angles of the local circle that generates the torus by a 360° rotation about its axis of revolution).  
         [0044]     In a preferred embodiment, the pipe structure is adapted so that the SAME geodetic  5  curve is used by an armouring wire when the flexible pipe is in an unloaded situation as when the flexible pipe is loaded, the only difference being that the point of contact changes along the length of the geodetic curve in question (whereby the angle of the free path of the armouring wire varies). The decisive parameters determining the course of the armouring wire on the torus surface are, respectively, a) the diameter of the layer on which the armouring is wound (e.g. the underlying pipe layer), b) the helix angle (the winding angle e.g. relative to the longitudinal axis of the flexible pipe, e.g. 54°), c) the diameter of the circle of the torus body in a cross section perpendicular to a direction of revolution (the local diameter), and d) the diameter of the circle of revolution generating the torus (the global diameter).  
         [0045]     In practice it may be necessary to deviate from this optimum geometry for other considerations, but with the knowledge acquired through this solution, the additional stresses may be predicted and an acceptable compromise can be achieved.  
         [0046]     In an embodiment of the invention, said support unit has a convex part with an outer surface with an outward curvature and said ‘straight-line-end-point’ is located on said convex part of the support unit.  
         [0047]     This has the advantage of providing a relatively easily manufacturable part that may be positioned annularly around and resting on said underlying pipe layer and with an outer surface that extends away from the longitudinal axis at least over the convex (e.g. torus-formed) part of the surface of the support unit where the armouring wire in question ‘lands’ (.i.e. around the predicted location of the straight-line-end-point when the flexible pipe is operated within its specifications).  
         [0048]     In an embodiment of the invention, said support unit comprises at least a first and a second body, the outer surfaces of each body having a different geometrical form, and said straight-line-end-point is located on said first body. In an embodiment of the invention, the outer surfaces of said first and second bodies of the support unit are separated by a gap. In an embodiment of the invention, said first and second bodies of the support unit are adjoined. In an embodiment of the invention, said second body of the support unit comprises dedicated elements for receiving and/or guiding one or more armouring wires.  
         [0049]     In an embodiment of the invention, said support unit comprises at least a first and a second body, said first body of the support unit has an outer surface which includes a part of a torus, and said second body has an outer surface that describes a surface of revolution, both surfaces having the same axis of revolution, said axis coinciding with the longitudinal axis of the flexible pipe, and both surfaces having coinciding tangents in a joining point in a cross sectional plane including the axis of revolution.  
         [0050]     In a preferred embodiment, said second body is a cylinder. Alternatively the second body may include a conoidous part, whose surface extends away from or verge on its axis of revolution when viewed from the torus formed part of the support unit in the direction of the end fitting. In another preferred embodiment, the support unit comprises a concave part extending from the convex part of the support unit hosting the straight-line-end-point in a direction towards the wire-pipe-exit-point, the concave part having an outer surface with an inward curvature (or a linear surface, when viewed in a cross section including the longitudinal axis of the flexible pipe).  
         [0051]     In an embodiment of the invention, said second body comprises guiding elements for guiding armouring wires received from said first body.  
         [0052]     In a preferred embodiment the second body comprises guiding channels for guiding armouring wires received from the first body. The purpose of the guiding channels is to lead the armouring wires from the first body in the direction of the anchoring elements. The channels may extend fully or partially over the length of the second part of the support unit. The channels may be fully or partially embedded in the support unit, i.e. may constitute buried channels over a part of their longitudinal extension. The inclusion of guiding channels is an advantage for the mounting of the end fitting with the flexible pipe and feasible because the armouring wire will only be stressed in its own longitudinal direction after leaving the first body of the support unit.  
         [0053]     In an embodiment of the invention, said anchoring elements for locking said armouring wires to said end-fitting are distributed on one or more terminating parts.  
         [0054]     It may be an advantage to separate the anchoring elements from the support unit by providing the anchoring elements in one or more terminating parts, to be able to customize the support unit and the terminating part(s) individually.  
         [0055]     In an embodiment of the invention, the flexible pipe comprises more than one armouring layer and separate support units and terminating parts are allocated to each layer.  
         [0056]     In an embodiment of the invention, separate support units and terminating parts are arranged sequentially after each other along the longitudinal axis of the flexible pipe, e.g. first the support unit(s) and terminating part(s) corresponding to the outermost armouring layer followed by the support unit(s) and terminating part(s) corresponding to the second outermost armouring layer, etc.  
         [0057]     In another embodiment of the invention, corresponding of said separate support units and terminating parts, respectively, are arranged concentrically around each other, the element corresponding to the innermost armouring layer being arranged closest to the axis of the flexible pipe (i.e. support units are arranged concentrically around each other followed in a longitudinal direction by terminating parts being arranged concentrically around each other).  
         [0058]     In yet another embodiment of the invention, a combination of sequentially and concentrically arranged support units and terminating parts are used.  
         [0059]     In an embodiment of the invention, the straight-line-section of an armouring wire is surrounded by a material which does not substantially alter the deformation behaviour of the flexible pipe and the wire.  
         [0060]     To avoid the intrusion of impurities, it may be advantageous to fill the space around the free path part (or straight-line-section) of the armouring wire path with a filler that does not substantially effect the free movement of the armouring wire. Such material could e.g. be a suspension or emulsion of a polymer, e.g. polyethylene or polyurethane. A further advantage hereof is that such a material may be used for cooling or flushing purposes, if the end fitting is cooled with a coolant, e.g. water to remove heat from the transported fluid of the flexible pipe, e.g. an oil of an elevated temperature compared to room temperature.  
         [0061]     In an embodiment of the invention, said pipe structure further comprises an assisting element arranged coaxially around said armour layer and adapted for maintaining at least one of said armouring wires in contact with the outer surface of said underlying pipe layer, and said armouring wire conforms to said underlying pipe layer between said assisting element and said wire-pipe-exit-point in which the armouring wire separates tangentially away from said underlying pipe layer.  
         [0062]     In an embodiment of the invention, the pipe structure comprises an assisting element arranged coaxially around said underlying pipe layer and adapted for guiding at least one of said armouring wires.  
         [0063]     In an embodiment of the invention, an assisting element is adapted for supporting armouring wires from a particular one of the one or more armouring layers of the flexible pipe.  
         [0064]     In an embodiment of the invention, an annular assisting element is arranged around an armouring layer to maintain at least one armouring wire in contact with the support unit at the straight-line-end-point, in which case the slope of the straight-line-section of the armouring wire may differ from the tangent to the surface of the support unit in the straight-line-end-point.  
         [0065]     In an embodiment of the invention, an assisting element forms part of the end fitting.  
         [0066]     In another embodiment of the invention, an assisting element forms part of the flexible pipe, e.g. in the form of an armour holding layer around an armouring layer, the armour holding layer being terminated at a point of the flexible pipe structure located before the support unit of the end fitting, when viewed in a direction of the end fitting. Alternatively, an assisting element may take the form of a discrete annular ring positioned around an armouring layer at certain intervals over a length of the flexible pipe, one of these rings being used for guiding an armouring wire towards its corresponding support unit.  
         [0067]     In an embodiment of the invention, the flexible pipe is an un-bonded flexible pipe, preferably comprising a tube formed by an inner armouring layer (carcass) surrounded by a liquid tight inner liner and one, two or more outer armouring layers.  
         [0068]     An un-bonded flexible pipe has the advantage over a corresponding bonded type that it is more flexible.  
         [0069]     In an embodiment of the invention, said flexible pipe comprises two layers of helically wound armouring wires, the winding angles with respect to the longitudinal direction of the flexible pipe being between 50 and 60°, such as between 53 and 56°, e.g. 55° said armour layers preferably comprising helically wound wires which are wound in opposite directions in neighbouring layers. This has the advantage of providing a balanced pipe whose length has a relatively small dependence on its operating conditions such as pressure and temperature.  
         [0070]     For a composite reinforced un-bonded flexible pipe, no solutions are available to facilitate the transition in stiffness of the pipe and connector structure without drastically reducing the load bearing capacity of the composite armour. This is a result of the opposing desires to control the stiffness on one hand and make a complete, secure, and thus very stiff anchoring on the other hand.  
         [0071]     In an embodiment of the invention, said armouring wire or wires are made of a composite material, said composite material preferably comprise one or more polymers, such as epoxy, thermoplastic and polyurethane, optionally comprising reinforcing fillers such as fibres and/or whiskers. An advantage thereof is that the pipe is stronger (tensile strength) and lighter (which is a special advantage during layout and use in deep see environments), more corrosion resistant in certain media than a corresponding pipe comprising metallic armouring wires.  
         [0072]     A composite material is in the present context taken to mean a material comprising several parts, e.g. of different atomic structure, different chemical composition, e.g. a matrix of a given material comprising enclosed elements of another material or micro-structural constitution (e.g. micro-crystalline grains in an otherwise amorphous matrix) or a layered material comprising distinct layers of different materials or identical materials in a sandwich structure.  
         [0073]     In an embodiment of the invention, said armouring wire or wires are in the form of a layered wire comprising 2 or more layers of materials which may be identical or different from each other. A layered wire is a wire made up of thin strips, assembled longitudinally on each other. This has the advantage of being able to combine properties of different materials, the tapes/strips may be pre-fabricated, provide ease of handling, and/or be readily deformable in the pipe manufacturing process.  
         [0074]     In an embodiment of the invention, said armour layers of the wire or wires are made from one or more of the materials selected from the group consisting of metals, such as steel, thermoplastic polymers such as polyurethane and thermosetting polymers such as epoxy, said polymeric materials optionally comprise reinforcing fillers such as fibres and/or whiskers.  
         [0075]     In an embodiment of the invention, said armouring wire or wires is/are in the form of a layered wire comprising 2 or more layers of materials which layers being held together by a wrapping material and/or by adhesive forces. An advantage of using a wrapping material is that it may save the use of adhesives. An advantage of using an adhesive is that it maintains positions of the layers and the assembly structure in production and provides means/possibility to splice.  
         [0076]     In an embodiment of the invention, the or each armour layer comprises one or two armouring wires. In another embodiment of the invention, each armouring layer comprises a multitude of armouring wires.  
         [0077]     In an embodiment of the invention, said armouring wire(s) is/are flat, said wire or wires having a square formed cross section, optionally a square formed shape with rounded corners. This has the advantage of providing a compact solution that minimizes the volume around the wires taken up by air (when compared e.g. to a solution with circular wires).  
         [0078]     In an embodiment of the invention, each of the layers of the flexible pipe is fixed to the end-fitting.  
         [0079]     In an embodiment of the invention, said end-fitting comprises an axially extending through opening, said armouring wire or wires being supported by the outer surface of said support unit, wherein the outer surface means the surface turning away from the axially extending through opening.  
         [0080]     In an embodiment of the invention, the armouring wire or wires is/are anchored by being embedded in a casting material, preferably in the form of a polymer such as an epoxy or a cementidious material. The term ‘a cementidious material’ is in the present context taken to mean a material bound together by cement (which is a product comprising among other things calcium, carbon, silicon, characterized in that it cures to a hard, stony compound in a reaction with water). Cementidious materials may be concrete, mortar, Portland White™, all characterised by a binder (cement) and a filler, usually rocks, stones, sand, etc. (i.e. silica based particles). This has the advantage of providing means for anchoring, by adhesion, mechanical locking, etc.  
         [0081]     In an embodiment of the invention, the end-fitting comprises one or more locking cavities said armouring wire or wires is/are anchored in said locking cavity or cavities.  
         [0082]     In an embodiment of the invention, the armouring wire or wires being anchored by use of a spreader element driven into the wire or wires in said locking cavity or cavities.  
         [0083]     In an embodiment of the invention, at least one locking cavity has a length dimension defined as the length dimension of a wire mounted in the locking cavity. The cross sectional area perpendicular to the length of the locking cavity differs along its length in one or more steps or continuously, wherein a first cross section area perpendicular to the length of the locking cavity is smaller, such as at least 5% smaller, such as at least 30% smaller than a second cross section area perpendicular to the length of the locking cavity, wherein the first cross section is closer to the support unit than the second cross section.  
         [0084]     In an embodiment of the invention, the armouring wire or wires is/are anchored by use of a spreader element driven into the wire or wires in the part of said locking cavity or cavities where a first cross sectional area perpendicular to the length of the respective locking cavity is larger than a second cross sectional area perpendicular to the length of the respective locking cavity, the second cross section being taken closer to the support unit than the first.  
         [0085]     In an embodiment of the invention, the armouring wire or wires is/are anchored to the end-fitting by use of a spreader element driven into the wire to thereby spread the wire into two or more laminates whereby the laminated wire or wires is fixed against the wall or walls of a locking cavity formed in the end-fitting. In a preferred embodiment, the armouring wire or wires is/are embedded in a casting material in the locking cavity, preferably additionally using a wedge element driven into the wire.  
         [0086]     In an embodiment of the invention, the flexible pipe comprises two armour layers and the end fitting comprise two annular support units, the wire or wires of a first armour layer being supported by a first annular support unit, and the wire or wires of a second armour layer being supported by a second annular support unit.  
         [0087]     In an embodiment of the invention, the pipe structure comprises a reinforcement sleeve layer placed below the one or more armouring layer or layers, said reinforcement sleeve layer extend along the pipe structure in a length which include the section of the pipe structure between the wire-pipe-exit-point and the straight-line-end-point, said reinforcement sleeve preferably extend along the pipe structure in a length which includes the anchoring point or points on the end-fitting.  
         [0088]     It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other stated features, integers, steps, components or groups thereof 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0089]     The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:  
         [0090]      FIG. 1  shows a pipe structure according to the invention comprising a simplified flexible pipe connected to an end fitting,  
         [0091]      FIG. 2  shows a path of an armouring wire from the underlying pipe layer of the flexible pipe to the support unit of the end fitting,  
         [0092]      FIGS. 3 . a  and  3 . b  show different perspectives of a pipe structure according to the invention with two armouring layers with opposite winding angles,  
         [0093]      FIGS. 4 . a ,  4 . b ,  4 . c  show an embodiment of an anchoring element for locking an armouring wire to an end fitting by means of a spreader element, the locking cavity having a stepwise changing cross sectional area,  
         [0094]      FIG. 5 . a ,  5 . b ,  5 . c  show an embodiment of an anchoring element for locking an armouring wire to an end fitting by means of a spreader element, the locking cavity having a continuously changing cross sectional area,  
         [0095]      FIG. 6  shows an example of a flexible pipe suitable for being connected to an end fitting in a pipe structure according to the invention, and  
         [0096]      FIG. 7  shows partial view of an embodiment of a pipe structure according to the invention,  FIG. 7 . a  being a side view,  FIG. 7 . b  a cross sectional view and  FIG. 7 . c  a perspective view. 
     
    
       [0097]     The figures are schematic and simplified for clarity, and they just show details which are essential to the understanding of the invention, while other details are left out.  
       DETAILED DESCRIPTION OF EMBODIMENTS  
       [0098]      FIG. 1  shows a pipe structure according to the invention wherein an open end of a flexible pipe is connected to an end fitting, the flexible pipe comprising armouring wires that are locked to the end fitting in anchoring elements thereby fixing the flexible pipe to the end fitting.  
         [0099]     The pipe structure  10  (comprising a flexible pipe and an end fitting) comprises two armouring layers, a lower armouring layer  11  and an upper armouring layer  19 , each comprising a helically wound armouring wire ( 111  and  191 , respectively). For clarity, only one armouring wire of each layer is shown in the drawing. It should be noted that the armouring wires  111  and  191  may represent examples of a multitude of armouring wires constituting the lower and upper armouring layer, respectively. It should further be noted that the parts  193 ,  113  (see later) of the armouring wires of the upper and lower armouring layer, respectively, may not originate from (be part of) the same physical wire as is indicated by the reference numerals  191 ,  111 , respectively. The armouring wires of the two armouring layers are wound with opposite winding angles (as seen relatively to the longitudinal direction  121  of the flexible pipe). The winding angles {acute over (α)} upper , {acute over (α)} lower  of the upper and lower armouring layer, respectively, are preferably in the range between 50 and 60°, e.g. {acute over (α)} upper =−{acute over (α)} lower =55°.  
         [0100]     The lower armouring layer  11  surrounds an underlying pipe layer  12  in the form of a cylindrical liner (optionally surrounding an inner carcass, not shown in  FIG. 1  but shown as  2  in  FIG. 6 ) around which the armouring wire  111  is helically wound. The upper armouring layer  19  surrounds the lower armouring layer  11  (which thus represents ‘the underlying pipe layer’ for the upper armouring layer) around which the armouring wire  191  is helically wound. An intermediate layer (not shown) between the two armouring layers  11 ,  19  may be inserted (in which case the intermediate layer represents the underlying pipe layer for the upper armouring layer). The armouring wires  1   1 ,  191  of the lower and upper armouring layers have a tape formed cross section when viewed perpendicular to a longitudinal direction of a wire (i.e. the wire is wider in a dimension that is tangential to the underlying pipe layer than in a dimension perpendicular to that). An advantage of the tape form, is that it conforms to the curvature of the underlying pipe layer and that it is relatively easy to avoid the introduction of twist to the wire during assembly.  
         [0101]     The underlying pipe layer  12  for the lower armouring layer  11  comprises an armouring reinforcement section  122  that is designed to compensate the decreasing armouring effect of the armouring wires in the end fitting part of the pipe structure. The armouring reinforcement section  122  comprises a cylindrical part  124  extending through the end fitting to the terminating flange  181  (for connecting the pipe structure to installations or to another pipe at land or at sea) and a conical part  123  which adapts the dimension of the cylindrical part  124  to that of the underlying pipe layer  12  (or alternatively to that of the underlying pipe layer of the upper armouring layer), thereby providing a smooth transition section for the armouring wires  111 ,  191  of the lower and upper armouring layers  11 ,  19 . In an embodiment of the invention, the cylindrical part  124  is terminated in the first support unit  15  (i.e. does not extend through the end fitting in its fall length to the terminating flange). In an embodiment of the invention, the lower armouring layer  11  runs beneath armouring reinforcement section  122  to be terminated in the support unit  17  and/or terminating part  16 . In another embodiment of the invention, the cylindrical part  124  is terminated in the “second” support unit  17  (i.e. does not extend through the end fitting in its full length to the terminating flange). In an embodiment of the invention, the lower armouring layer  11  runs beneath the support unit  15  to be terminated in the support unit  17  and/or terminating part  16 .  
         [0102]     The armouring wire  191  of the upper armouring layer  19  has a conforming-wire-pipe-section  192  which conforms to the underlying pipe layer  11  (including a part of the armouring reinforcement section  122 ) until a wire-pipe-exit-point  195  where the armouring wire tangentially extends away from the underlying pipe layer  11  (in the form of the armouring reinforcement section  122 ). The part of the armouring wire  191  from the wire-pipe-exit-point to its termination in an anchoring element  141  in a terminating part  14  is termed ‘the wire end fitting section’  193 . The terminating part  14  may preferably be an integral part of the support unit  15  or alternatively be an independent part adjoined the support unit. Extending from the wire-pipe-exit-point  195  the armouring wire has an unsupported ‘free path’ or straight-line-section  194  that is terminated by the tangential point of contact  196  (‘the straight-line-end-point’) with the support unit  15 . The support unit which is adapted to receive the armouring wire after its separation from the underlying pipe layer has a rotational symmetry around the longitudinal axis  121  of the flexible pipe and is arranged to surround the underlying pipe layer (i.e. including the armour reinforcement  122 ). The outer surface of the ‘landing part’  152  of the support unit  15  on which the straight-line-end-point is located during normal operating conditions of the flexible pipe takes the form of a part of a torus (the outer surface  152  may alternatively be any convex surface of revolution relative to the longitudinal axis of the flexible pipe). The adapting part  151  of the support unit  15  serves as an intermediate body between the cylindrical part  124  of the armouring reinforcement section  122  and the landing part  152  of the support unit  15 . The outer surface of the adapting part  151  has an inward curvature relative to the longitudinal direction of the flexible pipe. It might, however, take on other forms e.g. conical or even have an outward curvature, e.g. continue the torus form of the landing part  152 .  
         [0103]     The armouring wire  191  is supported by the support unit  15  from the straight-line-end-point  196  to an exit point  197  where the wire is received and fixed by an anchoring element  141 . Embodiments of the anchoring element are discussed in relation to  FIGS. 4 and 5 . Guiding channels  153  are arranged on or in connection with the transition part  154  of the support unit that supports the armouring wire between the landing part  152  and the terminating part  14  which hosts the anchoring elements  141 . The anchoring of the wire may alternatively be located on the transition part  154 . The transition part of the support unit has a conical outer surface that verge on the longitudinal axis  121  of the flexible pipe when viewed in a direction of the terminating flange  181 . This yields a preferred, relatively compact solution. It may alternatively extend outwards, and possibly have an outward curvature. It is preferred that the wire end fitting section  193  of the path of the armouring wire is adapted to be free from ‘points of discontinuity’, i.e. that the outer surface transitions between the various parts of the support unit  15  are ‘smooth’.  
         [0104]      FIG. 1  further shows a support unit  17  and terminating part  16  for the lower armouring layer  11 . The upper armouring layer  19  is arranged on the lower armouring layer  11  and the lower layer comprises a tape formed wire  111 . The wire  111  of the lower layer is for descriptive purposes divided in a conforming-wire-pipe-section  112  and an end fitting section  113 . The armouring layer  11  extends beneath the support unit  15  and terminating part  14  for the upper armouring layer  19 . The armouring wire  111  of the lower armouring layer  11  is terminated on the support unit  17  and/or the terminating part  16 .  
         [0105]     In  FIG. 2 , the path of an armouring wire at the transition between the flexible pipe and the end fitting is shown. In a preferred embodiment as illustrated in  FIG. 1 , each armouring layer has its own support unit ( 15  and  17  in  FIG. 1 ).  FIG. 2  and the following description may apply to the lower armouring layer  11  as well as to the upper armouring layer  19  of  FIG. 1 . The armouring wire  211 —preferably of a composite nature—initially conforming to the underlying surface  22  at a prescribed helical angle with the longitudinal axis  221  of the flexible pipe, is formed away from the underlying pipe surface  22 , in such a way that the tangent direction at the point of separation  215  from the underlying surface is followed by the wire until this direction becomes tangent with the outer surface of a torus  252  at a straight-line-end-point  216 , this torus being a part of the support unit  25 . In a preferred embodiment, the wire  211  then follows a geodetic curve from the point of tangency  216  on the torus, until another surface  254  supports the wire. The geodetic curve is found by winding under tension. On this second surface the wire again follows a geodetic curve and may be securely and completely anchored by various means in an anchoring element (not shown, but corresponding to  141  in  FIG. 1 ). Between the pipe tangent point  215  (the wire-pipe-exit-point) and the torus tangent point  216  (the straight-line-end-point), the wire follows a straight line path  214 . The wire, having a rectangular cross section, is twisted to conform to both surfaces at the tangent points. In a preferred embodiment of the invention, the wire is surrounded by a soft filler material (e.g. an emulsion of a polymer) at least over the free path, unsupported section between the tangent points. The soft material is chosen to have a negligible effect on the deformation behaviour of the pipe and composite wire. This soft material may provide cooling or flushing of the environment surrounding the composite wire. The filler may be introduced in the volume of the end fitting limited by the support unit and the underlying pipe layer (e.g. the reinforcement section) and an outer layer surrounding the armouring layers or by the casing  18  of the end fitting (cf.  FIG. 1 ) extended in the opposite direction of the end fitting.  
         [0106]      FIGS. 3 . a  and  3 . b  show an embodiment of a part of a pipe structure according to the invention. The figures show the part of the pipe-to-end fitting transition, where the armouring wires of an armouring layer extend away from their underlying pipe layer for being received by a support unit of an end fitting.  FIGS. 3 . a  and  3 . b  show the same section of the pipe structure exhibiting the same features but from different perspectives. A cut-out is made, so that the central opening of the pipe structure in the longitudinal direction  321  of the flexible pipe is exposed. An armouring reinforcement section  322  comprising a cylindrical section  324  and a conical section  323  surrounds an underlying pipe layer  32 . Two armouring layers  31  and  39  each comprising helically wound, tape-formed armouring wires are shown. The lower armouring layer  31  is wound on the underlying pipe layer  32  and on the armouring reinforcement section  322  which it leaves for landing on a lower support unit  35 , each armouring wire of the lower armouring layer  31  having an unsupported section between the armouring reinforcement section  322  and the lower support unit  35 . The upper armouring layer  39  is wound on the lower armouring layer  31  which it leaves for landing on an upper support unit  37 , each armouring wire having an unsupported section there between. The lower and upper support units  35 ,  37  supporting the lower and upper armouring layers  31 ,  39 , respectively, are arranged concentrically around the underlying pipe layer  32  (with the armouring reinforcement section  322 ) and the upper support unit  37  is arranged around the lower support unit  35 .  
         [0107]     The layers  301  and  302  indicate other pipe layers, e.g. inner armouring layers, cf. e.g.  FIG. 6  where various layers of an exemplary flexible pipe are shown. The support units  35 ,  37  and the anchoring elements (not shown) for fixing the armouring wires to the end fitting are surrounded by an outer casing  38 .  
         [0108]      FIG. 4 . a  shows an anchoring element  42  for locking an armouring wire  41  to an end fitting by means of a wedge formed spreader element  44  having a narrow end  441  and a broad end  442 , the locking cavity  45  for holding the wire end and the spreader element having a stepwise changing cross sectional area, so that a first cross sectional area A 1  is larger than a second cross sectional area A 2 , both taken perpendicular to the longitudinal direction of the wire in the locking cavity, the first cross section  421  (corresponding to A 1 ) being taken closer to the broad end  442  of the spreader element  44  than the second cross section  422  (corresponding to A 2 ) when the spreader element  44  is placed in the locking cavity  45 , and at least one stepwise change  423  of the cross section of the locking cavity is present between the first and second cross sections  421  and  422 . The anchoring element  42  for fixing an armouring wire  41  to an end fitting comprises a locking cavity  45  formed in a solid material (which may be part of a terminating element hosting a number of anchoring elements, cf.  14  or  16  in  FIG. 1 ) and a wedge-formed element  44  adapted to be driven into the end of an armouring wire  41  thereby separating the wire in two parts  411 ,  412  over a certain length (when viewed in a cross section including a longitudinal axis of the wire) and fixing the wire to the solid material of the walls of the locking cavity  45 . An adhesive  432  may optionally be introduced between the wedge and the split parts of the wire (represented by  411  and  412  in the cross sectional view of  FIG. 4 . a ). An adhesive  431  may preferably be introduced between the wire  41  and the walls of the locking cavity  45 . The wedge  44  may preferably be made of similar materials as the wire  41 , e.g. composite, metallic (e.g. steel, aluminium, titanium), or another composite (than the wire). The wire may preferably be made of a composite material or a metallic material in any combination. The adhesive may e.g. comprise epoxy, polyurethane, a thermoplastic adhesive, a cementidious material, all possibly comprising particles/fibres/whiskers.  
         [0109]      FIG. 4 . b  shows a cross sectional view of the armouring wire  41  in the locking cavity  45  in the cross section indicated by  421  in  FIG. 4 . a  whereas  FIG. 4 . c  shows a cross sectional view of the armouring wire  41  in the locking cavity  45  in the cross section indicated by  422  in  FIG. 4 . a . In  FIG. 4 . b  the cross sectional area Al comprises the wedge  44  and the two separated parts  411 ,  412  of the wire embedded in an adhesive  431  fully of partially filling the empty volume between the wire and the surrounding solid material of the anchoring element  42 . In  FIG. 4 . c  the cross sectional area A 2  comprises essentially only the wire  41  surrounded by the solid material of the anchoring element  42 .  
         [0110]     Various methods of securing an armouring wire to an end termination are disclosed in our co-pending international patent application entitled “A method of securing reinforcement wires to an end termination of a pipeline or a cable, an end termination, and uses of the method and the end termination” published as WO-A-01/07818 and which is incorporated herein by reference.  
         [0111]      FIG. 5 . a  shows an anchoring element  52  for locking an armouring wire  51  to an end fitting by means of a wedge formed spreader element  54  having a narrow end  541  and a broad end  542 , the locking cavity  55  for holding the wire end and the spreader element having a continuously changing cross sectional area (at least over a part of its length along the wire), so that a first cross sectional area A 1  is larger than a second cross sectional area A 2 , both taken perpendicular to the longitudinal direction of the wire in the locking cavity, the first cross section  521  (corresponding to A 1 ) being taken closer to the broad end  542  of the spreader element  54  than the second cross section  522  (corresponding to A 2 ) when the spreader element  54  is placed in the locking cavity  55 . The anchoring element  52  for fixing an armouring wire  51  to an end fitting comprises a locking cavity  55  formed in a solid material (which may be part of a terminating element hosting a number of anchoring elements, cf.  14  or  16  in  FIG. 1 ) and a wedge-formed element  54  adapted to be driven into the end of an armouring wire  51  thereby separating the wire in two parts  511 ,  512  over a certain length (when viewed in a cross section including a longitudinal axis of the wire) and fixing the wire to the solid material A moulding  53  may preferably be introduced between the wire  51  and the walls of the locking cavity  55 .  
         [0112]      FIG. 5 . b  shows a cross sectional view of the armouring wire  51  in the locking cavity  55  in the cross section indicated by  521  in  FIG. 5 . a  whereas  FIG. 5 . c  shows a cross sectional view of the armouring wire  51  in the locking cavity  55  in the cross section indicated by  522  in  FIG. 5 . a . In  FIG. 5 . b  the cross sectional area A 1  comprises the laminated wire  51 , which comprises alternating layers  513 ,  514  of a wire material (e.g. composite material, metallic tape, or other) and an adhesive material, respectively, the laminated wire being embedded in a ‘grout’ or moulding  53  (e.g. a particle filled casting material, cementidious material, a polymer, epoxy) which again is surrounded by the solid material of the anchoring element  52 . In  FIG. 5 . c  the cross sectional area A 2  comprises essentially only the armouring wire  51  (with layers  513 ,  514 ) surrounded by the solid material of the anchoring element  52 .  
         [0113]     A possible way of constructing laminated armouring wires is e.g. disclosed in our co-pending international patent application no. PCT/DK02/00355 entitled “A method of manufacturing a reinforcement element for a flexible pipe” which is incorporated herein by reference.  
         [0114]      FIG. 6  shows an ordinary structure of a flexible reinforced pipe  1  with its different layers. The flexible pipe in  FIG. 6  consists of an inner liner  3  surrounding a carcass which is formed by a helically wound metal tape  2  that forms an inner pipe. The metal tape  2  is formed with flaps in the manufacture which engage each other so as to lock the individual turns of the metal tape  2  to each other in such a manner that the carcass can be bent in its longitudinal direction. Since the inner carcass per se is not tight, the surrounding inner liner  3  serves the purpose of preventing flow of fluids to or from the interior of the pipe.  
         [0115]     One or more layers of profiles  5 ,  6  are helically wound externally on the inner liner  3 , said profiles forming turns of a great angle (e.g. 80-90°) relative to the longitudinal direction of the pipe. Because of the great angle, the profiles will primarily be capable of absorbing radial forces that occur because of internal or external pressures. The internal pressures occur in the operation of the pipe. The external pressures are caused partly by the hydrostatic pressure of the surroundings and partly by mechanical impacts during the laying of the pipe.  
         [0116]     The turns thus form a compressive reinforcement which prevents’ the inner liner  3  from bursting because of a high pressure on the inner side of the pipeline, or from collapsing because of a high pressure on the outer side of the pipeline.  
         [0117]     It is additionally shown in  FIG. 6  that the compressive reinforcement has externally applied thereto a tensile reinforcement, which consists of one or more layers  7 ,  8  comprising helically wound armouring wires.  
         [0118]     An intermediate jacket may be interposed between the compressive reinforcement and the tensile reinforcement, serving the purpose of preventing fluids from migrating between the compressive reinforcement and the tensile reinforcement.  
         [0119]     These layers may finally be surrounded by an outer sheath  9 .  
         [0120]     The tensile reinforcement  7 ,  8  is usually composed of two helically wound layers of steel profiles with opposite winding direction. The armouring wires may alternatively be made of other materials, e.g. composite materials.  
         [0121]     In conventional pipe systems, the tensile reinforcement is secured to the end termination by welding. It may, however, as discussed above with relation to  FIGS. 4 and 5  preferably be secured by means of a spreader element driven into the end of an armouring wire, the wire end with the spreader element being secured in a wedge-formed cavity a method (cf. also WO-A-01/07818).  
         [0122]      FIG. 7  shows an embodiment of a pipe structure according to the invention.  FIG. 7 . a  shows a side view of the pipe structure,  FIG. 7 . b  a view along a longitudinal axis of the pipe structure, and  FIG. 7 . c  a perspective view. An armour wire with a wedged end and two principal end fitting components, the support unit and an armouring reinforcement section unit, are shown.  
         [0123]     For illustrative purposes only one wire of one layer is shown in  FIG. 7 . Other wires of the armouring layer  7  of which the wire  71  forms part may be locked in the ‘empty’ anchoring elements (here termination slots  73 ) of the support unit  72 . It is understood that these components are a part of an assembly and as such do not show the complete end fitting. Wires of possible other layers may likewise be terminated in the locking grooves or alternatively in a separate set of grooves (as conceptionally illustrated in  FIGS. 1 and 3 ).  
         [0124]     The  FIGS. 7 . a  to  7 . c  show a wire  71  representing the armour layer  7  which is to be terminated in part by the components shown and in part by additional components that make up the complete end fitting structure, comprising a conforming-wire-pipe-section  711  resting by surface contact on the armouring reinforcement section  74  that is designed to compensate the decreasing armouring effect of the armouring wires in the end fitting part of the pipe structure. The armouring reinforcement section is placed under the armour layer  7  and comprises a cylindrical section  741  shown here and other sections not shown that facilitate a transition to the underlying layer (cf. e.g.  FIG. 1 ).  
         [0125]     In an embodiment of the invention, the support unit  72  contains individual wire-support-and termination-slots  73  for receiving and terminating each wire  71 . In an embodiment of the invention, each slot is made in the plane of tangency  75  ( FIG. 7 . b ) of the wire to be terminated by that particular slot. This ensures that pipe deformation and resulting change of armouring wire angle with respect to the longitudinal axis  77  of the pipe is transformed into pure bending about the thinnest dimension of the armouring wire, thereby minimising stresses. Each supporting surface  731  of the support unit  72  is a single curved surface (i.e. a surface that curves in only one dimension), oriented perpendicular to the tangent plane  75  wherein the corresponding armouring wire has its wire-pipe-exit-point, straight-line-section and straight-line-end-point. Therefore, the change in angle of the armour layer associated with applying tension and pressure to the pipe occurs in this tangent plane, moving the straight-line-end-point on the same curve on the supporting surface, namely the curve created by the intersection of the single curved supporting surface and the tangent plane.  
         [0126]     In the embodiment of the invention shown in  FIG. 7 , the anchoring elements (here termination-slots  73 ) form part of the support unit  72 . The anchoring elements are created by the individual-wire-support-and termination-slots  73  which create locking cavities  735  by the surfaces  733  and  734 . The locking cavities  735  provided by the support unit are further enclosed by components not shown, such as an end flange to the support unit  72  and outer casing, represented schematically on  FIG. 7 . b  by the circle  76 .  
         [0127]     The armouring wire  71  of the armour layer  7  has a conforming-wire-pipe-section  711  which conforms to the underlying pipe layer that includes the armouring reinforcement section  74  until a wire-pipe-exit-point  712  where the armouring wire tangentially extends away from the underlying pipe layer and thereby the armouring reinforcement section  74 . The wire extends over a straight-line-section  713  to the tangential point of contact  714  (the straight-line-end-point), where a curved surface  731  of the individual-wire-support-slot  73  provides a smooth and controlled transition to the wire anchoring. The straight wire section  715  of the transition to the anchoring section  735  ensures that the anchoring is loaded only by a pure unidirectional tension, which maximise the effectiveness of the anchoring principle. The wire is lead into the locking cavity  735  by the straight-slot-section  732 , wherein the wire is anchored. The anchoring is provided by driving a wedge formed spreader element  718  into the end of the wire  71 , and secure the split armour wire parts  716  and  717  to the spreader element by gluing. Furthermore, anchoring is provided by the principle described in  FIG. 5 , since the angled surfaces  733  and the locking-cavity-side  734  provides an expanding cross sectional area of the locking cavity  735 , and the wedged end  719  of the wire  71  also provides an increasing cross section, both in the direction towards the broad end of the wedged wire. An angled surface  733  and its adjacent straight-slot section surface  732  may preferably form an angle between 25° and 50°. A locking-cavity-side surface  734  and its adjacent straight-slot section surface  732  may preferably form an angle between 0° and 30°. The offset of the wedged wire end  719  relative to the locking cavity  735 , in the direction of and away from the straight-slot-section  732 , creates room for a moulding material, as described with respect to  FIG. 5 .  
         [0128]     In an embodiment of the invention the angled surfaces  733  and locking-cavity-side  734  and even the surface of the straight-slot-section  732  may be a continuous surface, providing a smooth transition from the straight-slot-section  732 , conforming to the wire thickness dimension and to the expanding cross sections in the locking cavity  735 .  
         [0129]     It is clear that the  FIG. 7 . a - 7   c  shows only the principle for terminating a single wire layer, however it can applied to two or more layers in the manner given by  FIG. 1  or  FIG. 3 .  
         [0130]     An advantage of the embodiment of  FIG. 7  is that because every wire is oriented on its own individually part-support-surface  731 , assembly of the wires to the end fitting is eased because the anchoring elements are securely separated and shaped to ensure that wires do not slip on the surface and are not located in a wrong position thereby improving reliability. Further each anchoring element has its own separate cavity for fastening a wire with a corresponding wedge.  
         [0131]     Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject-matter defined in the following claims.