GB2433566A

GB2433566A - Connector for threaded multi-layer pipes

Info

Publication number: GB2433566A
Application number: GB0625534A
Authority: GB
Inventors: John Peter Booth
Original assignee: ITI Scotland Ltd; Helical Pipelines Ltd
Current assignee: ITI Scotland Ltd; Helical Pipelines Ltd
Priority date: 2005-12-23
Filing date: 2006-12-22
Publication date: 2007-06-27
Anticipated expiration: 2026-12-22
Also published as: GB0526411D0; GB2433566C; GB2433566B; GB2433564A; GB0625534D0

Abstract

A tubular body or pipe 100 comprises an inner hollow core 106 and an outer casing 104 having a helically extending rib portion 102. A tubular member 110, 112 has helical grooves 114 on its inner surface that may engage with rib 102. The tubular member 110,112 may be used for securing ends of two pipes 100 together or may be used to facilitate repair of a defective portion of pipe 100, or to secure a flange to the pipe 100. There is a structural member between the pipe and the tubular member, which may be an adhesive, or a solid or segmented ring 120. The ring 120 is inserted into any gap between the pipe and the core to fill the void that would otherwise exist.

Description

TUBULAR BODIES AND METHODS OF JOINING OR

REPAIRING THE SAME

This invention relates to a tubular bodies and methods of joining the same and more particularly but not exclusively to the production of pipes for use in pipework systems such as pipelines for carrying natural gas or petroleum products under pressure and to methods and apparatus for joining or repairing such pipes. Other forms of tubular bodies such as pylons, towers, support arms and the like may also be manufactured, jointed or repaired according to the invention described herein.

It is known that natural gas and petroleum products produced in recent years or held in reserve for future extraction contain carbon dioxide and hydrogen sulphide. It is also known that under normal operating conditions of pressure, pipelines formed of conventional materials carrying such products are particularly likely to be subject to failure due to stress corrosion cracking.

Such failures often result in catastrophic longitudinally extending fractures of the pipes of the pipelines.

Previous attempts to reduce the risk of such failures have involved the use of corrosion inhibitors, added to the products being carried by the pipelines. Unfortunately, this results in unacceptable costs including not only the cost of the inhibitors and adding them to the products but also the cost of removing and recovering the corrosion inhibitors in due course from the products carried by the pipelines. The use of corrosion inhibitors is also not advisable, particularly in offshore pipelines, due to the environmental problems created if there is any escape of the corrosion inhibitors from the pipelines.

Alternative ways of reducing the risk of stress corrosion cracking in pipes by reducing the tensile stress on the part of the pipes in contact with the products being carried have been proposed.

These include the use of pipes formed of, for example, two tubes inserted one inside the other and to then during production mechanically forcing the inner pipe into contact with the outer pipe so that the inner pipe has a compressive stress and the outer pipe has a tensile stress. This process is known as auto-frettage" and one way of carrying out this operation mechanically is described in U.S. Patent No. 4,823,847. It will be appreciated that the two pipes must be made to very tight tolerances if one is to be able to insert one into the other and perform an auto-frettage step without adversely damaging the inner pipe. It will also be appreciated that this particular auto-frettage operation is only suitable for use in small lengths of pipe and suffers from the disadvantage of being a time consuming and therefore expensive operation to carry out. A further disadvantage of the production of a pipeline from such small lengths of pipe, typically 8 to 10 metre lengths, is that it will involve numerous joints being made which in themselves are points of weakness in a pipeline.

Tubular bodies of a different kind are also known from US Patent No. 4,657,049 in which metal strips are helically wound in overlapping fashion and embedded in an adhesive matrix to produce a rigid tubular structure. US Patent No. 3,530,567 describes a method of forming a tube by helically winding a metal strip in self-overlapping fashion so that the thickness of the wall of the tube at any point is formed from a plurality of laps. In order to remove the helical ridges on the internal bore of the tube formed by the edges of the strip, the laps of the strip material are flattened one against the other after winding by expanding the tubular structure beyond the yield point of the metal strips. Such a procedure presents significant manufacturing difficulties.

Additionally, the repair of such structures in the field is difficult to achieve due to the difficulty of cutting out sections of self overlapping bonded steel windings and joining in new sections which must be seam welded around a circumferentially extending and accurately produced join.

GB2280889 discloses a method of forming a hollow elongated or tubular body and comprises helically winding at least one strip of material in self-overlapping fashion to provide a multi-layer tubular structure. In this arrangement the strip is pre-formed to provide a transverse cross-section having at least one step which, in each convolution of the strip accommodates the overlapping portion of the next convolution. A tubular body having a wall thickness formed of a plurality of laps may thus be continuously made from a single strip of material, the wall thickness generally being one strip thickness greater than the number of steps formed in the cross-section of the strip.

The above arrangement may be provided with internal or external liners, the form of which will depend upon the application for which the tubular structure is intended but may comprise a filament wound fibre-reinforced matrix. In the fabrication of such a tubular structure, the inner liner may be pre-formed so as to provide a mandrel upon which the helically wound reinforcing core is wound. Alternatively an inner liner may be formed by winding resin impregnated reinforcement fibres or fabrics for the inner liner onto a suitable mandrel, and then winding over the liner a stepped steel strip to produce the reinforcement core, followed by winding the required resin impregnated reinforcement fibres or fabrics for an outer liner. Unfortunately, such a process is only able to produce discrete lengths of pipe section and does not lend itself to the use of the auto-freftage" process. Additionally, the repair of such a pipe system is difficult due to the combination of materials being used and the difficulty of gaining access to the various layers without damaging the otherwise undamaged portions of pipe.

Presently, the pressure capacity of such pipes is limited by the economics of the materials being used and the weight of the final product which must be transported and moved into position, often in vary difficult circumstances. The most common pipe used in gas transportation has an X65 steel grading (65,000 psi minimum yield strength) but even this standard of pipe cannot meet the newer requirements, which demand up to 120,000 psi yield strength. Whilst one can clearly increase the thickness and specification of the pipe wall, this will only add to the cost, weight, and complexity of installation. Additionally, such arrangements must be girth welded which is difficult to achieve and costly.

In addition to the above, such pipes are difficult to repair successfully by welding as cutting out defective sections and welding in new ones is problematic and expensive. There is, therefore, a need for a high performance pipe which is both strong and light whilst being economical to produce and relatively easy to transport as well as a method of repairing and/or jointing the same.

Still further, there exists a need for a system that allows for the repair of a pipe or the joining of an end thereof which ensures any pressure load from within the pipe itself is adequately transmitted to any outer load carrying member so as to reduce and possibly eliminate undue distortion and possible failure of any jointed or repaired section.

The object of the present invention is to provide a tubular body and a method of repairing or joining the same in which the risk of stress corrosion cracking is reduced and in which one or more of the other above-mentioned disadvantages of the known pipes and methods of forming, repairing or joining the same are alleviated.

Accordingly, the present invention provides a pipe system having a pipe section having a helically extending thread portion on a first surface thereof, a first tubular member having a first surface thereon and a thread portion on said first surface, in which said thread portion is a spiral groove having a profile corresponding to the helically extending thread portion on a pipe to which it is to be joined and the system includes a load transmitting structural insert between the pipe section and the tubular member for transmitting load between said pipe and said tubular member.

Preferably, said structural insert comprises an adhesive or a metal ring which may comprise comprises a segmented ring.

Preferably, the jointing system comprises a tubular system having a circular cross-section and in which an inner diameter of the first surface is greater than the diameter of any pipe onto which it is to be placed by an amount not greater than the depth of an externally formed thread on a pipe around which the system is to be placed.

Advantageously, the first tubular member comprises two or more circumferentially extending segments.

Preferably, the segments include securing means for securing the segments to each other. Such segments may further include mutually confronting flanges having bolting holes therein and in which the securing means comprises a plurality of nut and bolt assemblies for bolting through said bolting holes.

Preferably, the first tubular member includes a second surface on a side opposite to said first surface and said second surface has a diameter which tapers from a greater diameter at a proximal end thereof to lesser diameter at a distal end thereof.

Advantageously, the member includes a second tubular member having an inner diameter which tapers from a greater diameter at a proximal end to a lesser diameter at a distal end thereof and in which the inner diameter of the second tubular member is a tight or interference fit with the outer diameter of the tapered portion of the first tubular member when said second tubular member is placed around said first tubular member.

A pipe system as claimed in claim 10 in which the second tubular member is a single section tube for axially translation over said first tubular member so as to cause inter engagement of said tapered surfaces.

The segments may further include mutually confronting flanges having bolting holes therein and in which the securing means (Q comprises a plurality of nut and bolt assemblies for bolting through said bolting holes.

The second tubular member may comprise two segments and one of said segments includes an opening formed therein and having a tubular extension portion extending therefrom and a flange assembly formed around the tubular extension portion.

Preferably, the flange portion includes a circumferentially extending groove on an outer side of said flange for receiving a flange insert. The system may include a flange insert for insertion into said groove.

Advantageously, the pipe system may including an end coupling having a flange having a central hole for communication with the interior of the pipe and being fixedly connected to said first portion and may further including bolts for securing said flange to said tubular member.

The present invention also provides a method of joining two portions of a pipe of the type having a helically extending rib provided on a surface thereof comprising the steps of: i) providing a first tubular member having a first surface thereon and a rib portion on said first surface corresponding to the mirror of the thread on said pipe; ii) positioning a second portion of pipe in spiral thread alignment with the first portion of pipe; iii) securing said first tubular member around said pipe at a position bridging confronting ends thereof such that the thread l portions on the tubular member engage with the thread portions on each section of pipe; and iv) inserting a load carrying member between said tubular member and the pipe.

The method may include the further step of inserting the load carrying member by injecting an adhesive into any gap formed between the tubular member and the pipe.

Advantageously, the method may also include the step of inserting the load carrying member by inserting a metal ring into any gap formed between the tubular member and the pipe.

The method may also include the step of: i) providing a section of pipe of a length equal to a gap between pipe portions to be joined together; ii) providing a second tubular member having a first surface thereon and a thread portion on said first surface corresponding to the mirror of the thread portion on said pipe; and iii) securing said first and second tubular members around said pipe at respective positions bridging confronting ends thereof such that the thread portions on each tubular member engage with the thread portions on each section of pipe adjacent thereto.

The or each tubular member may be secured around the pipe by: i) engaging the thread portion of the tubular member with the thread portion of a portion of pipe to be joined; ii) translating said tubular portion along the thread on the pipe portion with which it is engaged so as to clear the end thereof; iii) translating said tubular portion back along the thread on the pipe portion and over a portion of said second portion of pipe, thereby to secure said first and second portions of said pipe to each other by said tubular member or members.

The present invention also provides a method of securing a flange to an end of a pipe of the type having an inner liner and an outer casing having a helically extending thread formed thereon, the method including the steps of: i) providing a tubular member having a first surface thereon and a thread portion on said first surface corresponding to the mirror of the thread portion on said pipe; ii) providing a flange portion having an inner hole corresponding to the diameter of the pipe; iii) securing said tubular member to said pipe by engaging the thread formed thereon with the corresponding thread on said pipe; iv) securing said flange to said tubular member; and v) inserting a load carrying member between said pipe and said tubular member..

Still further, the present invention provides a method of forming a junction on a pipe of the type having an inner liner and an outer casing having a helically extending thread portion provided thereon, the method having the steps of: a. cuthng a hole through the outer casing and inner liner at a position at which it is desired to form a junction; b. removing a further portion of the outer casing around the position at which it is desired to form a junction, thereby to expose a portion of the inner liner; c. inserting a junction liner portion into the hole and engaging it with the inner liner; d. joining said junction liner portion to said inner liner; e. securing a first tubular member having a junction portion therein corresponding to said hole over said hole; and f. securing said tubular member to said pipe, thereby to form said junction.

The above method may also include the steps of: iv) providing a flange around a free end of said junction portion of said first tubular member; v) providing a recess in said flange for receiving a flange insert; vi) providing a flange insert and inserting said flange insert in said recess; and vii) joining said flange insert to the otherwise free end of the junction liner portion, thereby to provide a sealed junction.

Advantageously, the method includes the step of adhesively bonding the tubular member to the pipe.

Prefereably, the method includes the step of injecting adhesive into a gap between the pipe and the tubular member, thereby to adhesively bond said pipe and tubular member together.

According to another aspect of the present invention the re is provided a method of repairing a pipe of the type having a helically extending thread portion on an outer surface thereof and an inner core of material, the method including the steps of: i) removing a portion of outer casing surrounding a defect in said inner casing, ii) repairing said defect, iii) space filling any hole created by the removal of any portion of outer casing; iv) securing an outer circumferentially extending segmented ring around said repaired portion; v) securing said segmented ring in position by application of an external segmented securing ring; and vi) securing the portions of the segmented securing ring to each other.

The invention also provides a pipe substantially as described herein with reference to or as illustrated in the accompanying drawings as well as a method substantially as described herein with reference to or as illustrated in the accompanying drawings.

The steel strip laminate (SSL) technology described and claimed herein offers the energy industry potential new methods of low cost pipeline construction suitable for onshore gas and oil transmission lines and offshore flow lines working in a corrosive environment. Pressure burst tests demonstrated that a 160mm diameter HelipipeTM comprising a 1mm thick 316L stainless steel liner and an outer reinforcing layer of two layers of 0.5mm Martinsite wrapped in a self overlapping arrangement burst at 235Barg which is sufficient to meet and exceed the X200 pipe specification. Detailed Finite Element Analysis on the composite pipe, which was undertaken by the AEA Technology at Harwell, verified that the burst test results were within 2% of the theoretical burst pressure and predicted that Helipipe would be a third of the weight and three times more flexible than the equivalent X65 steel pipe. Economic studies undertaken by II, Halliburton Subsea 7 and Advanced Engineering Solutions, which predicted that Helipipe was on average 40% cheaper than the conventional X65 steel pipeline.

Additionally, the method and apparatus for joining such pipes as disclosed herein provides the energy industry with an efficient and simple method of joining or repairing defective pipes, such as those described above and discussed in detail herein.

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings of which: Figure 1 is a schematic longitudinal view, partially cut-away and partially in section, of a tubular member; Figure 2 is a schematic longitudinal view, partially cut-away and partially in section, of an alternative outer casing of the tubular member: Figure 3 is a stress strain graph of the tubular member; Figure 4 is a stress strain graph of the tubular member during a pressure treatment cycle; Figure 5 is a stress strain graph of a number of other alternative materials which may lend themselves to inclusion as materials in a tubular body according to one aspect of the present invention; Figures 6 to 9 illustrate a first jointing/repair system suitable for the above-mentioned pipe system and which forms as second aspect of the present invention; Figures 10 to 13 illustrate a second repair system suitable for the above-mentioned pipe system; Figures 14 to 17 illustrate a flanging branch connection system suitable for the above-mentioned pipe system; Figures 18 and 19 illustrate a third repair system suitable for the above-mentioned pipe system; and Figure 20 illustrates an end connector suitable for use with the above-mentioned pipe system.

Referring now to Figure 1 of the drawings, a tubular body indicated generally at 10 forming a pipe for use in a pipework system such as a pipeline carrying natural gas or petroleum products under pressure comprises an inner core in the form of an inner pipe 12 which may be formed by any one of a number of forming processes. In the preferred process the tube 10 comprises a metal tube which is roll formed and welded along confronting surfaces to form the tube. Alternatively, the tube may be drawn as a fully formed tube in either metal or plastics material. When provided as a metal it may be desirable to provide it in the form of a corrosion-resistant material such as stainless steels, alloys or titanium, to name but two suitable materials. An outer casing indicated generally at 14 is formed on the inner metal pipe 12 by helically winding a strip 16 of material onto the outer surface 12a of the pipe 12 in self-overlapping fashion in the manner which is described in detail for the formation of a pipe on a mandrel in the specific descriptions of the applicants U.K. Patent No. 2,280,889 and U.S. Patent No. 5,837,083. In the present arrangement the tubular body 10 can, if necessary, be continuously constructed by the above-described techniques or by any suitable alternative. The strip 16 has one or more transverse cross-sectional steps 18 and 20 each of which is preferably of a depth corresponding to the thickness of the strip 16. The steps 18, 20 are preferably preformed within the strip 16, each extending from one end of the strip 16 to the other to facilitate an over-lapping centreless winding operation in which each convolution of the strip accommodates the overlapping portion of the next convolution. Whilst the strip may comprise any one of a number of materials such as a plastic, a composite material or indeed metal, it has been found that metal is particularly suitable in view of its generally high strength capability and ease of forming and joining as will be described later herein. Examples of suitable metals include steel, stainless steel, titanium and aluminium, some of which are particularly suitable due to their anti-corrosion capabilities. Particular materials are discussed in the examples tested later herein. The internal surface 16i of the strip 16 and the outer surface of the pipe 120 may be secured together by a structural adhesive, as may the overlapping portions 16a of the strip. The use of an adhesive helps ensure that all individual components of the tubular member 10 strain at a similar rate.

Further advantage may be gained from the application of a protective primer to the metal strip. Martinsite, for example, although high strength and low carbon, it is still mild steel and subject to corrosion. One suitable primer is BR127, available from Cyrec Engineering materials of 1300 revolution St, Hrvre de Grace, MD 21078 USA from whom a full data sheet may be obtained. This primer is compatible with a wide variety of adhesives, has established corrosion resistance properties and is also a bonding adhesion promoter. Incorporation of this primer, in conjunction with an outer protective wrap of BP's CURVE TM material (CyCURV), as described later herein provides a feasible, high performance protection system that may easily be applied to the present invention. Application of the CURVE TM may be by adhesive bonding if so desired but as this material can be pre formed having a desired radius of curvature adhesive may not be necessary.

Conventional pipeline protection systems (especially 3 layer Fusion Bonded Epoxy) could not be used with the present pipe because of temperature restrictions or process incompatibility.

An important enabling feature of the Cytec primer is that it can be applied to flat Martinsite strip and is resistant to the rib forming process without cracking or reduction in properties.

Referring now to Figure 2 of the drawings, a tubular body indicated generally at 22 has an alternative outer casing 24 formed as previously described from a steel strip 26 having only a single step 28 but which is preformed with a projection or rib 30 forming on one side a detent 30a and on another an indent 30b extending longitudinally of the strip 26 to, in effect, form a helical thread on the external surface of this alternative outer casing 24.

It will be appreciated that this alternative form of casing may be would onto the core 12 in the same manner as described above, save for the fact that the strip is wound in overlapping relationship such that the indent 30b on any second layer co-operates with the detent 30b of rib 30 on a previously deposited portion of said strip 26, thereby to locate the layers relative to each other and form said external helical thread which may be used as a location feature for a flange fitted to said tubular structure 12 in the manner described later herein, It will be appreciated that multiple ribs 30 may be provided on each strip, each rib 30 being longitudinally extending and parallel with its neighbour.

In either of the above arrangements the strip 16 or 26 may advantageously be provided with one edge I 6a, 26a longer than the other I 6b, 26b, thereby to provide a curve to said strip which upon winding onto the core 12 helps secure the strip to the core with a degree of clamping and I or facilitate correct overlapping.

Additionally, the adhesives referred to above may take the form of a strip of adhesive applied to the core 12 or the strip 16, 26 prior to or during winding of said strip 16, 26 onto said core 12.

The adhesive may, for example comprise a curable polymer and conveniently comprises a single part film based epoxy having a textile liner, such as to facilitate the easy application of the adhesive and the easy curing thereof once it has been depostted. If desired the adhesive may be provided with an anti-bacterial capability or with radiation resistant properties to name but two examples of properties that may be provided. The examples listed below employs Crytec FM 8210-1 as the adhesive. This adhesive may be cured in just two minutes at 180 C which is in stark contrast with some other adhesives which, in order to be cured in 2 minutes require a temperature of 250 C which can have a detrimental effect on the adhesive properties. In order to eliminate quality control problems during any manufacturing stage it may be desirable that the Martinsite strip be cleaned! shot blasted! mechanically or chemically etched, degreased, primed and pre-coated with the adhesive in factory conditions and supplied as a roll of production prepared product. It will be appreciated that other forms of adhesive may be used and their selection and suitability will depend on the use to which the final product it to be put. For example, it may be desirable to provide a highly flexible adhesive if the pipe is to be rolled onto a drum for transportation or a very high strength and rigid adhesive when the pipe is used in high strain applications such as high pressure pipelines and support arms.

If desired a further protective coating in the form of a layer of CURVE TM may be provided as a layer of wrapped material around the outside of the pipe. Curve is a low weight, high strength polypropylene material invented by Professor Ian Ward of Leeds University, England, developed by BP and now available from PROPEX of Groneau, Germany. The product comprises a plurality of high tensile fibres of polypropylene woven into a mat and then heated under pressure such that the outer portions of each fibre melts and bonds with its adjacent neighbour whilst maintaining a core of high tensile material.

Other forms of protective coating may be used and the present invention should not be considered as being limited to the use of CURVE TM When CURVETM is employed it may be provided as a long strip and wound onto the outer portion of the tubular body in overlapping or abutting relationship. It may, if desired be adhesively bonded to the tubular body by means of any suitable adhesive such as the Cytec adhesive mentioned above.

The technique known as "auto-frettage" and how it may be applied to one aspect of the present invention will now be described with reference to Figures 3 and 4, where the inner core 12 is formed of a stainless steel having a lower yield strength and better elongation properties than the "Martinsite" TM from which the strips 16, 26 forming the outer casing 14, 24 are formed. The typical stress/strain graph of the selected materials is shown in Figure 3.

Figure 4 shows the stress/strain graphs of the two materials during the auto-frettage" process. Both materials start with the same zero loading (pointi) and when the composite tubular body described above is subjected to an internal pressure loading to a predetermined "shakedown" pressure limit which is above the yield strain (point 2) of the inner pipe 12 butbelow the yield strain of the outer casing 16, 26 the inner pipe 12 undergoes yielding and plastic deformation (points 3 and 4) whilst the outer casing 16, 26 remains within its elastic limits as it reaches the stress loadings at its corresponding points 3* and 4* On unloading the tubular body, the inner core 12 returns to a state of compressive stress under zero load (point 5) whilst the outer casing 16, 26 remains in a state of tensile stress (point 5*) well below its yield stress. On subsequent reloading of the tubular body to a working pressure (up to point 6 and 6*) both the outer casing 16, 26 and the inner core 12 behave in a linear manner and any further load cycling will be within elastic limits and the inner pipe 12 will be operating at a reduced tensile stress level. This reduction in the operating tensile stress of the inner pipe 12 is termed uauto frettage" and will result in a reduction in the risk of stress corrosion cracking occurring. It will be appreciated that as the inner pipe is effectively compressively "pre-loaded" it may be subjected to internal pressures in normal operation, which, under normal conditions, would result in plastic deformation, whilst remaining below the yield point of that material. It will also be appreciated that not all uses of the invention as described herein will need to be subjected to an "auto-frettage" step. For example, if one simply needs to produce very long lengths of pipe which is not subjected to excessive internal pressures one may simply form the pipe by means of a continuous process of forming the inner core 12 and wrapping the outer casing 16, 26 therearound.

In order to manufacture a pipe 10 one must first form an inner liner 12 and then wrap the outer casing onto the liner 12. In practice, the inner liner may be formed by any one of a number of techniques such as metal or plastic extrusion or continuous winding but it has been found that forming a liner by rolling a long strip of metal about its longitudinal axis and then seam welding the confronting surfaces in a continuous manner is particularly suitable. Once the inner liner 12 has been formed one may form the outer casing by wrapping a strip 14 of material around the liner 12 such that each revolution of the strip 14 mechanically engages with the previous revolution. Mechanical engagement may take any one of a number of different forms, some of which are illustrated in the drawings attached hereto.

Referring briefly to Figurel, one will appreciate that one preferred form of mechanical engagement could comprise a self over- lapping arrangement achieved by deforming the strip 14 along its longitudinal axis before being laid down onto the core 12 such as to provide a step 20 in the strip 14 which acts to locate the overlapping portion of the next revolution of the strip.

The strength of this arrangement may be enhanced by applying an adhesive between the layers of the self over-lapping portion and, if desired, between the inner liner 12 and the outer portion 14. Alternatives to adhesives may be used, such as mechanical inter-engagement or nano-technology surface modification, which is aimed at attracting confronting surfaces to each other and maintaining them in position once they are suitably engaged. As an alternative or addition to the above-mentioned mechanical engagement one may form the longitudinally extending projection 30 forming on one side the detent 30a and on the other side the indent 30b mentioned above with reference to Figure 2. This projection may be formed by passing the strip 14 between a pair of suitably shaped pinch rollers (not shown) before the strip is rolled onto the outer surface of inner core 12, such as to cause the indent 30b to fit over the preceding portion of detent 30a. This mechanical engagement may be used on its own or in combination with one or more of the mechanical engagements discussed herein. Each of the above arrangements may be enhanced by the step of applying an adhesive in the form discussed above to the contacting surfaces of the overlapping outer layer 14 and! or between the inner liner 12 and the outer strip 14.The original build specimen is detailed in the first column of Table 1 below and the liner's yield strength was selected to be as high as possible to match that of the Martinsite (1350 MPa). Therefore heavily cold worked 316L stainless steel with a 862 Mpa ultimate tensile stress (UTS) was selected. Whilst this specimen did not burst until the test pressure reached 11 OBarg, this pressure was considered to be somewhat lower than might be expected. After investigation it was realised a disadvantage of this material is that the weld heat affected zone (HAZ) has limited strain capacity and could not strain follow the Martinsite and it was concluded that this problem could be addressed by lowering the yield stress of the inner liner such that, even when welded, it is able to accommodate the strain under which it is placed.

The pipe was then redesigned employing fully annealed stainless steel with a high strain capacity but with a much lower yield strength at 306/308 MPa. and this didn't burst until a pressure of 235 Barg was achieved. Such a mismatch in yield strengths between the liner and the reinforcing windings allows the pipe to fully incorporate the principles of auto-frettage to gain the maximum working pressure from the composite assembly. The original and modified build specifications are shown in the following table where the 0.2 % proof stress is substantially equal to the yield stress. to

Test Specimen Build details

TABLE I

Properties original Modified Reinl'orcrng vlarlinsite 220 Martinsite 220 Windings Material Winding Strip 0.5mm 0.5mm Thickness Yield Stress 1350 MPa 1350 MPa UTS I55OMPa I55OMPa % Elongation 4.50% 4.50% Liner Material Semi Hard cold Fully annealed 31 6L Stainless Steel 31 6L Stainless Steel Liner I hickness 0.77mm 1.00mm 0.2 Prool'Stress 747 / 771 MPa 306 / 308 MPa UTS 862 / 872 MPa 604 / 605 MPa % Elongation 1 7% /1 0/ 45% Parent material Vickers Hardness 295 160 Number VHN Adhesive primer Solvent based Cytec Solvent based (ytec BR 127 BR 127 Adhesive Single Part Film Single Part Film Based Epoxy with Based Epoxy ith lextile Carner Textile Carrier Cytec FM 82 10-1 Cytec FM 82 10-1

Build Specification Liner wall Liner wall -1.00mm

0.75mm 2 layers 2 layers Martinsite =1.0mm Martmsite -1.0mm 2 layers 2 layers adhesive =0.34mm adhesive -0.34mm Wall thickness = Wall thickness -2.34mm 2.09mm In each of the above specimens the bore of the pipe was 160mm.

Whilst it will be appreciated that one may use a number of different materials for the core and the outer casing we have conducted tests on the above and found the combination of a core fully annealed 36L Stainless Steel having a yield stress of 28OMPa and a high strength Martinsite TM reinforcing outer casing 16, 26 having a yield stress of I35OMPa provides excellent results. The table below provides details of the auto-frettage pressures used on this preferred sample.

design calculations for helipipe pressure test incorporating auto-frettage Working S Line Line M Pressure hakedown r Yield r Stress range artinsite Pressure Pressure after after Stress range B shakedown shakedown after Bar ar MP shakedown a MPa 9 1 141 -1.485507246 186/586 4 40 It has been calculated that operating with a working pressure of 94 bar and subject to a shakedown pressure of 140 bar, the stress range in the 316L liner would vary from 205 MPa compressive stress to 138 MPa tensile stress. This has dramatically decreased the tensile stress in the liner, which is ideal for fatigue and stress corrosion cracking. The Martinsite reinforcing windings would operate at a maximum stress of 586 MPa and have a residual stress of I86MPa. With a yield of 1350 MPa the winding will have a factor of safety (FOS) of 2.3 The above test sample was pressure tested at 20 C and failed at a pressure of 235.5 Barg. At this pressure the end connector showed no sign of failure or distortion.

The table below gives the results of further cases for which the liner is 6mm of X42 (yield stress of 290 MPa) and the pipe has a diameter of 900mm. Parameters have been adjusted to give a SF in the martinsite of about 2.

Table 3 Helipipe Design Cases (No Axial Load) Case Fl F2 Gi Gla G2 WPBar 104 101 201 205 203 Martinsite M220 M130 M220 M220 M130 grade ______ ______ ______ ______ ______ Martinsite 1350 923 1350 1350 923 yield stress MPa Martinsite 6.5 8.5 13 10 20 thickness Mm FOS 2.2 2.1 2.2 1.8 2.2 (after shakedown) ______ Liner -270 -180 -290 -290 -236 hoop stressrange 103 133 186 288 115 (ZP to WP after shakedown) MPa ______ ______ ______ ______ _____ Martinsite 249 127 134 174 71 hoop stress range 622 440 610 752 422 (ZP to WP after shakedown) MPa ______ ______ ______ ______ In the above, ZP is zero pressure and WP is working pressure.

Cases Fl and F2 are for a nominal WP of 100 Bar and show the effect of changing the Martinsite grade from the strongest (M220) to the weakest (M130). In both cases the liner yields at the SP (1.5*WP) and goes into compression at WP: but does not go into reverse yield.

Cases GI and G2 are for a nominal WP of 200 Bar, again with changes in Martinsite grade explored. In case Gi the liner yield in tension at SP and also in compression at ZP (i.e. reverse yield), but on reloading the liner stress is below yield and so plastic cycling does not occur.

Table 4

Case Fl Gi Gla WPBar 104 201 205 Martinsite grade M220 M220 M220 Martinsite 1350 1350 1350 yield stress MPa Martinsite thickness 6.5 13 10 mm FOS 22 2.2 1.8 (after shakedown) ______ ______ Liner hoop stress range -270 -290 -290 (ZP to WP after 103 186 288 shakedown) MPa ______ ______ Martinsite hoop stress 249 134 174 range (ZP to WP after 622 610 752 shakedown) MPa ______ _______ ______ In the above FSO is factor of safety.

Table 5 (No Axial Load) Case H OD(mm) 160 WPBar 105 Martinsite grade M220 Martinsite yield stress MPa 1350 Martinsite thickness I mm Liner Material 316L Liner PS MPa 300 Liner Thickness mm I FOS (after 1.8 shakedown) Liner hoop stress -299 range (ZP to WP after 100 shakedown) MPa ____________ Martinsitc hoop 299 stress range (ZP to WP after 740 shakedo n) MPa It will be appreciated that many other materials may be selected for use in the manufacture of a tubular body according to the present invention. By way of example only, we draw the reader's attention to Figure 5 which illustrates the stress strain curves for a number of different materials. From this Figure it can be seen that the stress strain curve for 6061-T651 Aluminium (MI) would lend itself to use as a liner material due to its relatively low yield stress. Additional materials such as Copper (M2), annealed 1018 Steel (M3) and possibly half rolled C2600 brass (M4) may also be suitable, when matched with a casing material having a suitably high yield stress. Cold rolled 1018 Steel (M5) is also an option but its relatively high yield should be taken into consideration. When selecting the combination of materials one should remember that the outer casing needs to be stronger than the inner core so as to allow the core to experience plastic deformation during the uautofrettageJ step whilst the outer casing remains under elastic strain conditions so that upon returning to zero pressure the inner core is subjected to compressive stresses and the outer casing remains under tensional stress and provides the inner core with its compressive stress. The property to observe is the ultimate tensile stress (UTS) of the materials concerned as the UTS of the inner core must be lower than that of the outer casing (as shown in the graphs) in order to allow plastic deformation of the inner to occur whilst the outer casing is still within its elastic limit.

Although the production of a new tubular body 10 is described above, it will be appreciated that this procedure with the inner pipe 12 being constituted by an existing pipe can be utilised to refurbish and up-grade an existing pipe of a pipeline or the like and also to produce pylons, towers, support arms, drive shafts and sub-sea dynamic risers, to name but a few examples.

A particular advantage of one form of the present invention resides in the fact that the "auto-frettage" process can be performed once the length of pipe has been installed in its final location. Under such circumstances one simply needs to subject the pipe to the auto-frettage" process by raising the pressure of the fluid within the core 12 in order to follow the profile shown in Figure 4. The core 12 essentially expands beyond its elastic limit and upon relaxation of the internal pressure is subjected to a compressive force from the outer casing 16, 26 such that, upon subsequent raising of the internal pressure to the desired working pressure the inner core 12 remains well below its elastic limit and is, therefore, less prone to stress corrosion cracking.

It will be appreciated that the present forming process may be employed to produce a tapered product by simply winding the convolutions in a manner which results in the product diameter increasing or decreasing as the product is formed. This arrangement may be very beneficial in the production of towers or other such products where a load spreading effect is required or where one simply needs to alter the diameter for other performance or aesthetic requirements.

The design of the preferred pipe is based around a corrosion resistant pressure containing liner supported by fully elastic high strength Martinsite windings. Under high internal pressures the 2J Matinsite wind ings remain elastic and carry the majority of the hoop stress. The role of the liner is to strain follow the Martinsite wind ings to order to provide a leak free passage for the product.

The second aspect of the present invention will now be more particularly described with reference to figures 6 onwards which illustrate systems for joining or repairing pipes such as the pipe described above, it will be appreciated that the system may be used on other forms of pipe so long as those pipes have a helically extending feature that can be used as a location feature for locating with a corresponding feature provided on the jointing system to be described in more detail below.

Figure 6 illustrates the first step of a repair of a defective portion lOOa of pipe 100 which is simply cut out and removed as directed by arrows A1 and A2. The pipe section itself includes a helically extending rib portion 102 which as shown stands proud of an outer casing portion 104 of the pipe 100. It will, however, be appreciated for reasons that will become clear later herein that the helically extending feature could be a groove (not shown) formed in the outer casing 104. Figure 7 illustrates the second of a series of repair steps in which a portion of the outer casing 104 is removed from the free end of the sound pipe portions 1 OOb and lOOc so as to expose the inner liner 106. A repair section shown generally at 108 comprises a sound section of pipe 100 cut to a suitable length and having a portion of the outer casing 104 cut away so as to expose the inner liner 106, in the manner described above with reference to the sound portions of the pipe 100. Added to the replacement portion are a pair of tubular members 110 and 112 which surround the pipe casing 104 and eLl\ each of which is provided with a helically extending groove I 14a or grooves 1 14a, 114b, I 14c corresponding to the helically extending rib 102. Also provided are and a plurality of optional holes 116, each of which extend from an outer surface llOa, I 12a of the tubular member to the internal thread portion or groove 114 so as to facilitate the injection of an adhesive bonding agent thereinto as will be described later herein. The tubular members 110, 112 are each provided with an inner surface 118 which is of a diameter greater than that of the pipe 104 such that each member 110, 112 is free to move along the helical rib upon rotation in the direction of arrows B1 and B2 of figure 8. In order to effect a repair, the replacement section 108 is inserted between the sound old sections of pipe I 00b, I OOc by moving it in the direction of arrows C1 and C2 in figure 7. Once the repair section 108 is in position and the helical rib 102 is aligned with that on the sound portion (as shown in figure 7) the inner liners 106 are welded or otherwise joined to each other as shown diagrammatically by weld 120 before tubular members and 112 are each wound along the helically extending portion 102 such as to bridge the joint 120 and mechanically connect inserted portion 108 to the existing portions I OOb, lOOc of pipe 100 and thereby secure the sections together. If a greater degree of location and strength of joint is required the gap G between the inner surface of the tubular members may be space filled by injecting an adhesive into holes 116 and allowing it to flow along the helical rib portion 102 and into any space S created by the removal of portions of the outer casing 104 and/or between the tubular members 110,112 and the pipe 100. Such an adhesive should, preferably, be of such a compressive strength as to transmit any internal pressure to the outer casing without adverse distortion of the liner 106. The adhesive may be a reinforced polymer such as an epoxy or polyester resin filled with, say, glass fibre, composite or steel strengthening strands or flakes to reinforce the adhesive and improve its compressive strength. Should a greater degree of load transmission be required it would be advantageous to space fill any gap G with a split or segmented ring shown generally at 122 in figure 8. The final, assembled, arrangement is shown in figure 9, part of which is in cross section so as to illustrate the injection point 116 and how it leads to the space S formed by removing some of the outer casing 104.

An alternative repair system is illustrated in figures 10 to 13 from which it can be seen that a small inclusion 130 may be repaired by removing a portion of the outer casing 100 surrounding the defect to expose the defective portion of the inner casinglo6 before repairing the defect by, for example welding, as shown at 131. Once the defect is repaired one should space fill the removed outer casing portion and this can best be done by space filling with a suitably shaped portion of metal 132 let in to replace the removed portion and bonded in position by any suitable load bearing adhesive. Alternatively, one could space fill with a load bearing adhesive such as an epoxy or polyester resin filler, as discussed in detail in other portions of this specification.

Once the repair has been done one may complete the task by placing a circumferentially extending segmented encapsulation ring 1 34a, I 34b over the patch such that it is in close proximity thereto. A helical groove or grooves I 36a, I 36b engages with the helical rib portion 102 as discussed above with reference to figures 6 to 9. An outer segmented securing ring 137 is then placed over the encapsulation ring 134 and bolted in position by means of a nut and bolt assembly (not shown). These bolts are secured through holes in mutually confronting flanges 140 provided on each portion of the securing ring 137. The outer surface of the encapsulation ring 134 may be provided with a tapered profile 142 tapering from one end of the ring to the other and the securing ring may be provided with a corresponding taper 144 on its inner surface so as to match therewith and allow the outer securing ring to be bolted together before sliding over the encapsulation ring until the confronting sloping surfaces 142, 144 engage with each other and clamp the encapsulation ring in position. Clearly, if one has access to the end of the pipe to be repaired one may provide one or other or both of the encapsulation ring 134 and/or the securing ring 136 as complete circular forms which can be slid along the helical feature 102 or simply slid along the pipe in the case of the larger diameter securing ring 137. An adhesive may be injected into any gap between the encapsulation ring 134 and the pipe 100 should it prove desirable to do so. Such an adhesive should, preferably, be of such a compressive strength as to transmit any internal pressure to the outer casing 100 without adverse distortion of the liner 106. The adhesive may be a reinforced polymer such as an epoxy or polyester resin filled with, say, glass fibre, composite or steel strengthening strands or flakes to reinforce the adhesive and improve its compressive strength. It will be appreciated that such an adhesive may replace It will be appreciated that either of the above two arrangements may be used as single units to connect the ends of two serviceable pipe sections. In such an arrangement the tubular member 110, 112 or 134 is simply positioned over the confronting ends of the two pipe portions by winding it along the helical thread formed by 102 before securing it to said pipe sections 100 by a clamping means as described above or by the use of an adhesive injected as described above.

It will also be appreciated that engagement of the rib 102 and the groove 136 is by inter-engagement along the helically extending surfaces thereof and that any load experienced by said junction is spread along that contact surface, which is considerable. By adopting this approach one can provide a strong and robust joint in what can be a complex product that

must perform to a high specification.

Referring now to figures 14 to 17 which illustrate a flange connection for the above-mentioned pipe arrangement, it will be appreciated that in order to gain access to the inner liner 106 one must first remove a portion of the outer casing 104. This casing is most easily removed by simply drilling or cutting a large diameter hole 150 through both the inner liner 106 and outer casing 104 by any conventional means. Once the hole has been cut one must then remove a further portion of the outer casing 102 so as to gain access to the inner liner 106 and allow the insertion of a junction liner portion 152 into the created hole so as to allow it to be joined to the liner 106 by, for example, welding along the joint 154 therebetween. Once the junction liner 152 is secured to the inner liner 106 one may encapsulate the newly formed junction by securing a first tubular member 156 having a junction portion 156 formed therein such as to surround the junction liner portion 152 and encase it. Should a greater degree of load transmission be required it would be advantageous to space fill any gap G1 with a split or segmented ring shown generally at 153 in figure 17. As shown, the tubular member 156 comprises a two part arrangement with an upper portion 156a and a lower portion 1 56b joined thereto by bolts 160 passing through holes 162 in flanges 164 provided on both sides thereof. The upper portion is provided with an extension 166 having a flange 168 provided thereon which surrounds the junction liner 152 and which is provided with a recess 170 for receiving a flange insert 172 which is preferably of a similar material to that of the junction liner portion 152 so as to allow a welded joint to be formed therebetween as referenced by 174. The flange may be further provided with bolt holes 176 for allowing the flange to be joined by means of bolts to a further pipe portion (not shown). Again, an adhesive may be injected into any gap formed between the components of the connector. Such an adhesive should, preferably, be of such a compressive strength as to transmit any internal pressure to the outer casing 100 without adverse distortion of the liner 106. The adhesive may be a reinforced polymer such as an epoxy or polyester resin filled with, say, glass fibre, composite or steel strengthening strands or flakes to reinforce the adhesive and improve its compressive strength. It will be appreciated that this adhesive may replace and/or supplement the ring 153 described above.

A modification to the above jointing or repair systems is shown in figures 18 and 19 in which provides a segmented tubular member 180 having the features as discussed with reference to figures 16 and 17 such as inner grooves 114 and tapered outer portion 142 which are, therefore, not discussed further here. The additional feature provided in this arrangement is the radially and circumferentially extending portion 182 which, in operation, acts to space fill a void caused by the removal of a segment or convolution of the outer casing 104 cut away to allow access to and repair of an inner core 106. Such an arrangement may lend itself for use in arrangements where the inner liner is of a material that does not easily lend itself to repair and/or needs the additional support of a mechanically strong backing once the repair has been completed. In the example shown, a further outer clamping ring 184 with an inner tapered surface 186 is positioned over the outer tapered surface 142 of the segmented tubular member 180, although this portion may be omitted in some arrangements. Whilst not shown in this drawing, holes may be provided for the injection of an adhesive as described with reference to figures 16 and 17 above. Such adhesive assists to further secure the components to each other and make a stronger repair. Figure 19 illustrates the assembly of figure 18 in an assembled position.

A still further arrangement is illustrated in figure 20, in which the coupling concept as described above has been applied to an end fitting or coupling shown generally at 200. In detail, a segmented or non segmented tubular member 210 is similar to that described above in as much as it is provided with an internal groove or grooves 214a, 214b, 214c corresponding to the helically extending rib 102 provided on the pipe 100 itself and an outer tapered or non-tapered surface 216. When provided with a tapered surface the outer tapered surface 216 may engage with an encapsulation ring 218 which is similarly profiled in as much as it has an inner surface 218a which is tapered to correspond with that provided on the tubular member itself. In operation, the segments of the tubular member are placed around the helical groove or the complete annular tubular member is wound over the threads of the pipe such that it engages therewith along the outer surfaces thereof and, once in position, the encapsulation ring 218 may be slid over the tubular member such as to engage with the tapered surface 216. Further axial movement of encapsulation ring will lock the arrangement in position by mechanically biasing the tubular member inwardly such as to allow the grooves 214 to mechanically engage with the helical rib portion 102. It will be appreciated that to achieve the desired degree of clamping the segments should be formed such as to maintain a gap G between each other as they are placed around the pipe 100. Whilst this inter-engagement will provide a secure coupling it may be supplemented by injection of an adhesive similar or the same as that described above into any gap formed between the pipe 100 and the tubular member, as described above. An access hole 220 may be provided for this purpose. A flange 222 may be added to the tubular member 210 by means of a botted assembly shown generally at 224. Other forms of flange securing will present themselves to those skilled in the art and include integral flanges and welded assemblies. Additional bolt holes 226 may be provided on flange 222 so as to allow jointing of said flange to further flanged articles such as a further pipe or a valve (not shown). A further feature of figure 20 is the provision of a recess 226 in flange 222 for receiving a sealing ring 228 of material similar to that of the inner core 106 and weld joint 230 for joining said ring 228 to said inner core 106.

It will be appreciated that the above-described invention will work with a single or multiple start rib 102 provided on the strip which forms the spiral wound outer casing 100. In practice, it has been found that two or three ribs formed on each strip before it is formed into the pipeprovides a good degree of rigidity whilst also providing an excellent amount of contact surface area for the grooves of the tubular members to engage with.

Claims

CLAIMS

1. A pipe system having a pipe section having a helically extending thread portion on a first surface thereof, a first tubular member having a first surface thereon and a thread portion on said first surface, in which said thread portion is a spiral groove having a profile corresponding to the helically extending thread portion on a pipe to which it is to be joined and the system includes a load transmitting structural insert between the pipe section, the tubular member for transmitting load between said pipe and said tubular member.

2. A pipe system as claimed in claim I wherein said structural insert comprises an adhesive.

3. A pipe system as claimed in claim I wherein said structural insert comprises a metal ring.

4. A pipe as claimed in claim 3 wherein said ring comprises a segmented ring.

5. A pipe jointing system as claimed in any one of claims I to 4 in which the jointing system comprises a tubular system having a circular cross-section and in which an inner diameter of the first surface is greater than the diameter of any pipe onto which it is to be placed by an amount not greater than the depth of an externally formed thread on a pipe around which the system is to be placed. 2)ç,

6. A pipe jointing system as claimed in any one of claims I to in which the first tubular member comprises two or more circumferentially extending segments.

7. A pipe jointing system as claimed in claim 6 in which the segments include securing means for securing the segments to each other.

8. A pipe system as claimed in claim 7 in which the segments further include mutually confronting flanges having bolting holes therein and in which the securing means comprises a plurality of nut and bolt assemblies for bolting through said bolting holes.

9. A pipe system as claimed in any one of claims I to 8 in which the first tubular member includes a second surface on a side opposite to said first surface and said second surface has a diameter which tapers from a greater diameter at a proximal end thereof to lesser diameter at a distal end thereof.

10. A pipe system as claimed in claim 9 and further including a second tubular member having an inner diameter which tapers from a greater diameter at a proximal end to a lesser diameter at a distal end thereof and in which the inner diameter of the second tubular member is a tight or interference fit with the outer diameter of the tapered portion of the first tubular member when said second tubular member is placed around said first tubular member.

11. A pipe system as claimed in claim 10 in which the second tubular member is a single section tube for axially translation over said first tubular member so as to cause inter engagement of said tapered surfaces.

12. A pipe system as claimed in any one of claims I to 11 in which the segments further include mutually confronting flanges having bolting holes therein and in which the securing means comprises a plurality of nut and bolt assemblies for bolting through said bolting holes.

13. A pipe system as claimed in any one of claims I to 12 in which the second tubular member comprises two segments and one of said segments includes an opening formed therein and having a tubular extension portion extending therefrom and a flange assembly formed around the tubular extension portion.

14. A pipe system as claimed in claim 13 in which the flange portion includes a circumferentially extending groove on an outer side of said flange for receiving a flange insert.

15. A pipe system as claimed in claim 14 including a flange insert for insertion into said groove.

16. A pipe system as claimed in any one of the previous claims including an end coupling having a flange having a central hole for communication with the interior of the pipe and being fixedly connected to said first portion.

17. A pipe system as claimed in claim 16 and further including bolts for securing said flange to said tubular member.

18. A method of joining two portions of a pipe of the type having a helically extending rib provided on a surface thereof comprising the steps of: i) providing a first tubular member having a first surface thereon and a rib portion on said first surface corresponding to the mirror of the thread on said pipe; ii) positioning a second portion of pipe in spiral thread alignment with the first portion of pipe; iii) securing said first tubular member around said pipe at a position bridging confronting ends thereof such that the thread portions on the tubular member engage with the thread portions on each section of pipe; and iv) inserting a load carrying member between said tubular member and the pipe.

19. A method as claimed in claim 18 further including the step of inserting the load carrying member by injecting an adhesive into any gap formed between the tubular member and the pipe.

20. A method as claimed in claim 18 further including the sep of inserting the load carrying member by inserting a metal ring into any gap formed between the tubular member and the pipe.

21. A method as claimed in claim 19 or 20 including the step of: i) providing a section of pipe of a length equal to a gap between pipe portions to be joined together; ii) providing a second tubular member having a first surface thereon and a thread portion on said first surface corresponding to the mirror of the thread portion on said pipe; and iii) securing said first and second tubular members around said pipe at respective positions bridging confronting ends thereof such that the thread portions on each tubular member engage with the thread portions on each section of pipe adjacent thereto.

22. A method as claimed in claim 19 or 20 in which the or each tubular member is secured around the pipe by: i) engaging the thread portion of the tubular member with the thread portion of a portion of pipe to be joined; ii) translating said tubular portion along the thread on the pipe portion with which it is engaged so as to clear the end thereof; iii) translating said tubular portion back along the thread on the pipe portion and over a portion of said second portion of pipe, thereby to secure said first and second portions of said pipe to each other by said tubular member or members.

23. A method of securing a flange to an end of a pipe of the type having an inner liner and an outer casing having a helically extending thread formed thereon, the method including the steps of: i) providing a tubular member having a first surface thereon and a thread portion on said first surface corresponding to the mirror of the thread portion on said pipe; ii) providing a flange portion having an inner hole corresponding to the diameter of the pipe; iii) securing said tubular member to said pipe by engaging the thread formed thereon with the corresponding thread on said pipe; iv) securing said flange to said tubular member; and v) inserting a load carrying member between said pipe and said tubular member..

24.A method of forming a junction on a pipe of the type having an inner liner and an outer casing having a helically extending thread portion provided thereon, the method having the steps of: a. cutting a hole through the outer casing and inner liner at a position at which it is desired to form a junction; b. removing a further portion of the outer casing around the position at which it is desired to form a junction, thereby to expose a portion of the inner liner; c. inserting a junction liner portion into the hole and engaging it with the inner liner; d. joining said junction liner portion to said inner liner; e. securing a first tubular member having a junction portion therein corresponding to said hole over said hole; and f. securing said tubular member to said pipe, thereby to form said junction.

25. A method as claimed in claim 24 including the steps of: i) providing a flange around a free end of said junction portion of said first tubular member; ii) providing a recess in said flange for receiving a flange insert; iii) providing a flange insert and inserting said flange insert in said recess; and iv) joining said flange insert to the otherwise free end of the junction liner portion, thereby to provide a sealed junction.

26. A method as claimed in any one of claims 20 to 25 including the step of adhesively bonding the tubular member to the pipe.

27. A method as claimed in claim 26 including the step of injecting adhesive into a gap between the pipe and the tubular member, thereby to adhesively bond said pipe and tubular member together.

28. A method of repairing a pipe of the type having a helically extending thread portion on an outer surface thereof and an inner core of material, the method including the steps of: i) removing a portion of outer casing surrounding a defect in said inner casing, ii) repairing said defect, iii) space filling any hole created by the removal of any portion of outer casing; iv) securing an outer circumferentially extending segmented ring around said repaired portion; v) securing said segmented ring in position by application of an external segmented securing ring; and vi) securing the portions of the segmented securing ring to each other.

29. A pipe substantially as described herein with reference to or as illustrated in the accompanying drawings.

30. A method substantially as described herein with reference to or as illustrated in the accompanying drawings.