AU2009201495B2

AU2009201495B2 - Conduits Manufactured by Tubular Lamination and Methods of Joining Them

Info

Publication number: AU2009201495B2
Application number: AU2009201495A
Authority: AU
Inventors: Anthony Martin
Original assignee: Stainless Tube Mills Australia Ltd; Stainless Tube Mills Pty Ltd
Current assignee: Stainless Tube Mills Australia Ltd
Priority date: 2008-04-18
Filing date: 2009-04-16
Publication date: 2012-03-15
Anticipated expiration: 2029-04-16
Also published as: AU2009201495A1

Abstract

A composite pipe or tubing is fabricated by drawing a liner of suitable material and thickness into a conduit of suitable material and thickness and reducing the diameter of the conduit by rolling down, the reduction 5 being sufficient to create a high contact force between layers and, thereby, a good mechanical (frictional) bond between the conduit and liner. The method of rolling down employs a plurality of closely-spaced, skewed rollers in a cylindrical arrangement, the central zones of the rollers being urged into contact with and passing in overlapping spiral paths over the 10 surface of the conduit. Where the liner material is a fusible polymer, lengths of pipe or tubing are joined end-to-end by first butt welding the liners and then joining the conduits using joining sleeves or flanges. Where conduit and liner are both of metal, liners are joined by hand or machine-welding.

Description

ORIGINAL Australia Patents Act 1990 Complete Specification for the Invention Entitled CONDUITS MANUFACTURED BY TUBULAR LAMINATION AND METHODS OF JOINING THEM The invention is described in the following statement: 2 CONDUITS MANUFACTURED BY TUBULAR LAMINATION AND METHODS OF JOINING THEM This invention relates to methods and apparatus for the making of conduits by the lamination of tubular pre-forms of different materials and 5 the joining of such conduits, including the joining of primary and secondary members. In industries in which it is necessary to pump corrosive fluids, abrasive slurries or the like, conduits lined with durable materials are commonly employed. Conduit lining materials have included, glass, 10 polymer materials, stainless steel, cement, bitumen and epoxy resin. In such lined conduits, it is normal for a strong, tubular outer member to support an inner lining which is resistant to the deleterious effects of a fluid conveyed through the conduit, but has little intrinsic strength or flexibility. Methods of installing liners in conduits include spraying 15 and/or trowelling, curing in place of a liner preform impregnated with a settable resin, collapsing of a polymer liner which is drawn into place and its circular shape reinstated, reduction in diameter of a polymer liner which is drawn into place and its diameter reinstated, reduction in diameter of a conduit to capture a drawn-in liner, expansion of a drawn-in 20 liner to capture it within a conduit, extrusion of a polymer liner into a conduit, welding of a metal liner into a metal conduit by heating to melt a fusible metal powder between the two or by diffusion welding, elongation of a lined conduit to lock together the component parts, explosive bonding of a conduit and liner, or rolling and seam welding of a skelp of duplex 3 metal. The principal objective in bonding the layers of composite pipe or tubing is to render it stronger and more rigid than one in which the layers are not bonded. A secondary objective is to prevent relative movement between layers of composite pipe or tubing and thereby to eliminate 5 adverse effects resulting therefrom. Where the diameter of a conduit is reduced to capture a drawn-in liner, this is normally effected by drawing through a die, as taught by Imasaki et al in US 6,659,137. Similarly, Imasaki et al teach the expansion of a liner into intimate contact with a conduit by a drawing a die 10 through it. In a method taught by Hardwick in US 5,259,547, a bi-metallic tube is expanded by passing it over a profiled mandrel while simultaneously rolling externally to form a bonded composite. An examination of the literature shows that almost all methods disclosed for the fabrication of multi-layered metallic pipe or tubing involve the use of 15 high cost techniques, many of which cannot be operated on a continuous basis. Where a conduit is fabricated from a material having a coefficient of thermal expansion substantially different from that of liner of a polymer material and the conduit and liner are not bonded together, excessive 20 heating or cooling may cause problems. In the case of excessive heat, expansion of a liner may cause internal buckling or rupture of a joint. In the case of excessive cooling, shrinkage may cause breakage of a liner at a joint flange. For example, PCT patent application No. PCT/AU98/00917 taught a method of installing a polymer liner in a conduit by drawing-in, 4 the length of the liner being adjusted to suit a specified operating temperature range. The liner was not bonded to the conduit and, as a result, failures caused by excessive temperature variation were experienced. 5 PCT patent application No. PCT/AU2004/000726 teaches a method of reducing the diameter of pipe or tubing by rolling it with a plurality of closely-spaced, skewed rollers. The method is capable of effecting a substantial reduction in diameter of a metal pipe or conduit in a single pass, even in thick-walled conduits. The reduction is sufficient to 10 create a good mechanical fictionala) bond between a conduit and liner such that the resultant composite does not suffer from the effects of excessive temperature change previously alluded to. The method may also be employed to reduce the diameter of a polymer liner prior to its installation in a conduit by drawing-in. 15 The principal object of the present invention is to provide a method of fabricating composite pipe and tubing in combinations of metal and polymer materials which minimises the cost of production. A second object is to provide a fabrication method which may be operated more or less on a continuous basis. A third object is to provide means of joining 20 sections of the composite pipe or tubing. According to the present invention, composite pipe or tubing is fabricated by drawing a liner of suitable material and thickness into a conduit of suitable material and thickness and reducing the diameter of the conduit by rolling down. The method of rolling down is that described in 5 PCT patent application No. PCT/AU2004/000726 which employs a plurality of closely-spaced, skewed rollers in a cylindrical arrangement, the central contact zones of the rollers passing spirally over the surface of the conduit. The method is capable of effecting a substantial reduction in 5 diameter of a metal pipe or conduit in a single pass, even in thick-walled conduits, the reduction being sufficient to create a high contact force between layers and, thereby, a good mechanical fictionala) bond between a conduit and liner. Where a liner is made from a fusible polymer material, lengths of the pipe or tubing are joined end-to-end by using a 10 heated plate to simultaneously heat the exposed ends of the liner above the melting point of the material and then by urging the heated ends of the liner together to effect a butt weld. Any flash created is trimmed flush with the surfaces of the liner and the conduit is joined by installation of a joining sleeve. Where a junction of a secondary conduit with a primary 15 conduit is to be created, the primary conduit is cut away in the appropriate position to expose a suitable area of the polymer liner, allowing a suitable aperture to be cut out. A suitable four-axis router is then employed to cut suitable mating surfaces on the end surface of the polymer liner of the secondary conduit and the edges of the aperture in the primary conduit 20 liner. Using a suitable heated die, the shaped surface of the aperture and end surface of the liner of the secondary conduit are simultaneously heated above the melting point of the material and the heated surfaces then urged together to effect a butt weld. Two halves of a suitable jacket encompassing the full circumferences of the end zone of the secondary 6 conduit and the connection zone of the primary conduit are then fixed together with suitable fastenings to effect a mechanical join. Where a connection flange is to be fitted to the end of a conduit, the end surfaces of the polymer conduit liner and edge surfaces of an aperture in a polymer 5 flange are provided with complementary shapes. Using a suitable heated die, the end surfaces of the conduit liner and edge surfaces of the aperture are simultaneously heated above the melting point of the material and the heated surfaces urged together to effect a butt weld. A supporting sleeve with a supporting flange fixed to its end is then slipped over the conduit 10 bringing the supporting flange into abutment with the polymer flange and is fixed to the conduit, thereby supporting the polymer flange. Obviously, hand welding of liner-to-liner and liner-to-flange joints may be effected. Where the layers of composite pipe or tubing are both metal, similar joining methods are employed, excepting that liners are joined by hand or 15 machine welding. The various aspects of the present invention will be more readily understood by reference to the following description of preferred embodiments given in relation to the accompanying drawings in which: Figure 1 is a longitudinal cross-sectional view of the 20 process of heating the ends of polymer conduit liners; Figure 2 is a longitudinal cross-sectional view of conduits following the butt welding of their polymer liners; Figure 3 is a longitudinal cross-sectional view of the situation depicted in Figure 2, but with flash trimmed flush with 7 the surfaces of the polymer liner; Figure 4 is a longitudinal cross-sectional view of the situation depicted at Figure 3, but with the conduit joined by installation of ajoining sleeve; 5 Figure 5 is an enlarged longitudinal cross-sectional view of the situation depicted at Figure 4, showing filling of the void between conduit ends; Figure 6 is a transverse cross-sectional view on A-A of the situation depicted at Figure 5; 10 Figure 7 is a view of a conduit with ghosted in detail showing a method of installing a joining sleeve using tapered lugs; Figure 8 is a transverse cross-sectional view on B-B of the situation depicted at Figure 7; Figure 9 is a longitudinal cross-sectional view of the right 15 angled joint of a secondary conduit with a primary conduit; Figure 10 is a transverse cross-sectional view on C-C of the situation depicted at Figure 9; Figure 11 is a longitudinal cross-sectional view of the oblique joint of a secondary conduit with a primary conduit; 20 Figure 12 is a transverse cross-sectional view on D-D of the situation depicted at Figure 11; Figure 13 is a partially cut-away side view of the supporting arrangements of a conduit and four-axis router; Figure 14 is a partially cut away end view of the situation 8 depicted at Figure 13; Figure 15 is a transverse cross-sectional view of a primary conduit and longitudinal cross-sectional view of a secondary conduit showing use of a heated die to heat complementary 5 surfaces of polymer liners; Figure 16 is a side view of the joint zone of a secondary conduit with a primary conduit showing jacketing; Figure 17 is a side view of the end-to-end joint of conduit showing common jacketing; 10 Figure 18 is a side view of the end-to-end joint of conduit showing a combination joining sleeve and jacketing; Figure 19 is a side view of a jacketed conduit bend; Figure 20 is a longitudinal cross-sectional view of a polymer flange butt welded to the end of a polymer conduit liner; 15 Figure 21 is a longitudinal cross-sectional view of a polymer flange hand welded to the end of a polymer conduit liner and supported by a supporting sleeve with a supporting flange fixed to its end; Figure 22 is an enlarged longitudinal cross-sectional view 20 of an alternative to the joining arrangement depicted in Figure 5. With reference to Figure 1, composite pipe or tubing is fabricated by drawing a liner 2 of suitable material and thickness into a conduit 1 of suitable material and thickness and reducing the diameter of the conduit by rolling down. The method of rolling down is that described in PCT patent 9 application No. PCT/AU2004/000726 which employs a plurality of closely-spaced, skewed rollers in a cylindrical arrangement, the central contact zones of the rollers passing spirally over the surface of the conduit. The method is capable of effecting a substantial reduction in diameter of a 5 metal pipe or conduit in a single pass, even in thick-walled conduits, the reduction being sufficient to create a high contact force between layers and, thereby, a good mechanical (frictional) bond between a conduit and liner. With additional reference to Figure 2, where a liner 2 of said composite pipe or tubing is made from a fusible polymer material, lengths 10 of said pipe or tubing are joined end-to-end by using a heated plate 3 to simultaneously heat the exposed ends of said liner above the melting point of the material and then by urging the heated ends of the liner together to effect a butt weld. In the preferred embodiment, to facilitate their manipulation, said lengths of said pipe or conduit are slidingly supported 15 in supports 4 during said heating process. With reference to Figure 3, flash created during the making of said butt weld is trimmed flush with the surfaces of said liner, leaving a gap 7 between the adjacent ends of conduit lengths 1. With reference to Figure 4, conduits I are joined by installation of a joining sleeve 6 over them, in the preferred embodiment, said joining 20 sleeve being fixed to said conduit by tack welding 8. Annular void 9 formed beneath said joining sleeve and between the adjacent ends of said conduit is optionally filled with a suitable settable resin or cementitious material 10 to support said liner against the effect of internal pressure. In an alternative embodiment, a supporting band (not shown) of suitable 10 thickness and material is installed in gap 7 prior to installation of said joining sleeve. With additional reference to Figures 5 and 6, void 9 is depicted filled with a suitable settable resin or cementitious material 10, suitable apertures 11 being provided in joining sleeve 6 to permit ingress 5 of said resin or cementitious material and egress of air and overflow. With reference to Figures 7 and 8, in an alternative embodiment, said adjacent ends of lengths of conduit I are joined by joining sleeve 6 having tapered lugs (location depicted in broken line) 13 provided on its inner surface, said lugs being adapted to engage complementary tapered 10 lugs 2 provided in the exterior surface of said conduit. Also provided on the inner surface of said joining sleeve are supporting pads 14 which act in the installed position of said joining sleeve to support supporting band 15 of suitable thickness and material, said supporting band being installed in the gap (depicted as 7 in Figure 3) between the adjacent ends of said 15 conduit prior to the installation of said joining sleeve. Small gaps 16 are provided between the ends of said supporting sleeve to prevent their abutment during installation of said joining sleeve. Rotation of said joining sleeve in its installed position causes complementary tapered lugs 12, 13 to wedgingly engage and thereby connect the ends of said conduit 20 lengths. The circumferential lengths of tapered lugs 13 and supporting pads 14 are such as to permit them to pass axially between tapered lugs 12 during installation of said joining sleeve. Obviously, in an alternative embodiment, said void occupied by said supporting band may be filled with said settable resin or cementitious material, providing support of said 11 liner against internal pressure and acting to retain said joining sleeve in place. With reference to Figures 9 and 10, where a junction of a secondary conduit with a primary conduit is to be created, primary conduit 5 1 is cut away in the appropriate position to produce opening 17 exposing a suitable area of the polymer liner 2 and allowing a suitable aperture to be cut out. A suitable four-axis router (depicted in Figures 13, 14) is then employed to cut suitable mating surfaces on the end surface of the polymer liner 18 of said secondary conduit and the edges of the aperture in primary 10 conduit liner 2. Using a suitable heated die (depicted as 22 in Figure 15), the shaped surface of said aperture and said end surface of said liner of said secondary conduit are simultaneously heated above the melting point of the material and the heated surfaces then urged together to effect a butt weld 19. The term, butt weld, is used loosely herein and, in the preferred 15 embodiment, the joined faces of said butt weld are inclined at more or less equal angles 20, 21. In alternative embodiments (not shown), said joined faces meet at faces more or less normal to the longitudinal axis of said secondary conduit. With additional reference to Figures 11 and 12, where said secondary conduit is inclined to the longitudinal axis of said primary 20 conduit at an angle of less than 90*, the joined faces of said butt weld are inclined at substantially unequal angles 23, 24. With reference to Figures 13 and 14, router cutter 51 is driven in rotation by suitable motor 46 and displaced in Z axis by suitable motor 47 driving ball screw arrangement 45. Said ball screw arrangement is fixed 12 to horizontal carriage 48 which is slidingly supported in suitable rails and linear bearings (not shown) fixed to transverse supporting members 53, 54. Said horizontal carriage is displaced in X axis by a suitable motor and ball screw arrangement (not shown) supported from vertical carriages 40. 5 Vertical carriages 40 are slidingly supported in suitable rails and linear bearings (not shown) fixed to inner vertical supporting members 38a. Said vertical carriages are displaced in Y axis by a suitable motor and ball screw arrangement (not shown) supported from inner horizontal supporting members 38b. Inner supporting members 38a, 38b are 10 yawingly supported in gimbals 44 pivotally fixed to intermediate supporting members 43b. Intermediate supporting members 43a, 43b are tiltingly supported in gimbals 39 pivotally fixed to outer supporting members 34a. Yawing displacement of inner supporting members 38a, 38b on gimbals 44 is effected by ball screw 42 pivotally supported from 15 strut 41 fixed to intermediate supporting member 43a and pivotally connected to either said inner supporting member. Tilting displacement of intermediate supporting members 43a, 43b on gimbals 39 is effected by ball screw 50 pivotally supported from strut 49 fixed to outer supporting member 43a and pivotally connected to either said intermediate supporting 20 member. In the preferred embodiment, all said ball screw arrangements are driven by suitable stepper motors and the operation of said stepper motors are simultaneously controlled by a suitable microprocessor-based control unit to provide X, Y and Z axis displacement combined with tilt and yaw of said supporting members to permit router cutter 51 to generate 13 complex shaping of the end surface of polymer conduit liner 2. Said liner is supported in clamp 25 closed by suitable quick-release fastenings (positions indicated as 27), said clamp being pivotally supported on trunnions 26 working in suitable bearings in support plates 28. Pivotal 5 displacement of said conduit liner may facilitate the shaping of the end surfaces of said secondary conduit liners for oblique joints. Where said side edges of an aperture in a said conduit liner are to be shaped, said liner is supported transversely in suitable clamping means (not shown), the position of said liner being indicated in broken line as 52. Other conduit 10 liner support means (not shown) and said outer supporting members are, in turn, supported by vertical, longitudinal and transverse supporting members 33, 36, 35, 29, 30, 31, vertical members being supported on suitable feet 32, 37. With reference to Figures 11, 12, 15 and 16, using a suitable 15 heated die 22, the shaped surface 55 of aperture 63 and said shaped end surface 56 of liner 18 of said secondary conduit are simultaneously heated above the melting point of the material by contact, respectively, with heated die surfaces 86, 87 and then urged together to effect a butt weld. Upon cooling of said butt weld, the joint zone is encased in the two parts 20 of jacket 58, 59, the flanges 60, 61 of said jacket parts being strongly drawn together by suitable fastenings (positions depicted as 62) to capture primary conduit I and secondary conduit 57. In the preferred embodiment, the inner surfaces of said jacket parts are suitably treated to enhance their frictional attachment to said conduits.

14 With reference to Figure 17, two conduit lengths are joined end-to end by a suitable two-part jacket 64, the flanges 65 of which are strongly drawn together by suitable fastenings (positions depicted as 66) to capture conduit 1. In the preferred embodiment, the inner surfaces of said jacket 5 parts are suitably treated to enhance their fictional attachment to said conduits. With reference to Figure 18, two conduit lengths are joined end-to end by a combination two-part jacket 67 and joining sleeve 72. The flanges 68 of said jacket are strongly drawn together by suitable fastenings 10 (positions depicted as 69) to capture one end of conduit 1, in the preferred embodiment, the inner surfaces of said jacket parts being suitably treated to enhance their fictional attachment to said conduit. Said joining sleeve is made with an extension 71 which neatly overlaps the end of said jacket, the two being joined by suitable fastenings (positions indicated as 70), said 15 joining sleeve being fixed to the other end of conduit I by tack welding 73. In an alternative embodiment, said joining sleeve is fixed to said conduit by complementary tapered lugs as depicted in Figure 7. With reference to Figure 19, a polymer conduit liner bend is encased in a two-part jacket 74, the flanges 75 of said jacket being 20 strongly drawn together by suitable fastenings (positions depicted as 76) to capture said bend. Said jacket is joggled at its ends (not shown) to permit the capture of the ends of conduits 1. In the preferred embodiment, the inner surfaces of said jacket parts are suitably treated to enhance their fictional attachment to said liner and said conduit. To create said liner 15 bend, a straight length of said liner is heated to a suitable temperature and bent in suitable die means (not shown). With reference to Figure 20, a polymer flange is fixed to the end of polymer conduit liner 2. The end surfaces of said conduit liner and edge 5 surfaces of an aperture in said polymer flange are provided with complementary shapes and a suitable heated die (as depicted in Figure 15) is employed to simultaneously heat the end surfaces of said conduit liner and edge surfaces of said aperture above the melting point of the material and the heated surfaces urged together to effect a butt weld. With further 10 reference to Figure 21, said polymer flange is hand or machine welded to the end surface of said liner at recessed point 80. Supporting sleeve 83 of a suitable material with supporting flange 81 fixed to its end is then slipped over conduit 1 bringing said supporting flange into abutment with said polymer flange with their attachment holes 78, 82 coincident. Said 15 supporting sleeve is then fixed to said conduit by tack welding 85, thereby supporting said polymer flange against mechanical loads. In the preferred embodiment, said supporting sleeve is welded to said supporting flange at point 84. With reference to Figure 22, in a joining arrangement somewhat 20 similar to that depicted in Figure 5, joining sleeve 6 is pressed over conduits I creating annular void 9 over said welding zone (depicted in broken line as 86). Said annular void is optionally filled with a suitable settable resin or cementitious material (as depicted in Figures 5 and 6) or a supporting band (as depicted in Figures 7 and 8), to support liner 2 against 16 the effect of internal pressure. Said joining sleeve is not tack welded to conduits I and said join is strengthened by split clamps 79 clampingly fixed to said conduits outside of said joining sleeve and retained in position one to another by two or more longitudinally arranged suitable 5 fastenings 80 equally spaced in a circumferential sense and passing through both said split clamps. In the preferred embodiment, the inner surface of said split clamps contacting the outer surfaces of said conduits is provided with suitable serrations 81 to improve the efficiency of attachment of said split clamps. The position of one said split clamp is 10 depicted in broken line, the two parts being secured in clamping arrangement by suitable fastenings 82. Obviously, in alternative embodiments of the present invention, said conduits may be rolled down in diameter to engage said liner; said liner may be rolled down in diameter, installed in said conduit and 15 expanded with the use of internal pressure to engage said conduit; or a combination of both methods employed. In an alternative embodiment to that depicted in Figures 20 and 21 (not shown), a flange is formed on the end of said liner by heating the end of said liner above the melting point of the material with a suitable heated 20 die. Said heated die is progressively advanced inwardly towards a fixed die, said flange being formed between the two. A suitable cooled sleeve fixed to said heated die passes inwardly into the bore of said liner, thereby preventing and flow of melted material into said bore. In the preferred embodiment, said conduit and liner are supported in suitable jig means 17 during the forming of said flange and said heated die is advanced by suitable moveable supporting means supported from said jig means. Suitable holes to accommodate fasteners are formed in said flange by pins provided on said heated die or are optionally drilled in said flange after its 5 forming. To facilitate its removal after forming of said flange, said fixed die is made in split form. Obviously, hand or machine welding of liner-to-liner and liner-to flange joints may be effected. Where the layers of composite pipe or tubing are both metal, 10 joining methods similar to those described are employed, excepting that liners are joined by hand or machine welding. In an alternative embodiment (not shown), a composite metal pipe comprising two parts is formed by the product of a first tube mill of suitable diameter being fed into the bore of the product of a second tube 15 mill of suitable diameter during its forming. The welded seam of said first tube mill product is rolled and cleaned in the usual way. During rolling of the welded seam of said second tube mill product, it is supported internally by suitable supporting means provided within the bore of said first tube mill product. Following its completion of forming, said second tube mill 20 product is rolled down in diameter using the said method of PCT/AU2004/000726 to bring the two said products into intimate contact and thereby create said composite pipe. In the preferred embodiment, said welded seams of said two tube mill products are disposed in a diametrically opposed arrangement. In a first alternative embodiment, the 18 skelp from which said products are formed is suitably cleaned and the outer surface of said first tube mill product is coated with a suitable welding medium, said composite pipe being heated after said rolling down process to weld both said tube mill products together. In a second 5 alternative embodiment, the outer surface of said first tube mill product is coated with a suitable adhesive which bonds both said tube mill products together following said rolling down process. In a third alternative embodiment, the contacting surfaces of both said tube mill products are coated with a soft metal, such as aluminium or tin, which forms a pressure 10 weld during said rolling down process. In an alternative application of the present invention (not shown), armoured electrical cabling is created by rolling down in diameter a polymer sheath into intimate contact with a plurality of insulated conductors using the method of PCT/AU2004/000726 and then rolling 15 down in diameter a metal sheath into intimate contact with said polymer sheath.

Claims

1. A composite conduit system comprising an outer conduit of suitable material and thickness and a liner of suitable material and 5 thickness, said liner having an outside diameter such as to just permit it to be drawn into said outer conduit; said outer conduit, following installation of said liner, being reduced in diameter by rolling down to create a high contact force of said outer conduit against said liner and, consequently, a good mechanical bond 10 between the two said components; said rolling down being performed by a plurality of closely-spaced rollers in cylindrical array, said rollers being skewed to urge their central contact zones strongly into contact with the exterior surface of said outer conduit, said outer conduit passing axially through said roller array which is 15 rotationally displaced such that said roller contact zones pass over said exterior surface in a series of overlapping, helical paths and thereby locally work the material of said outer conduit beyond its yield strength. 1A The composite conduit system of Claim 1 in which discrete lengths 20 of said composite conduit are joined by fusion of abutting ends of said liner previously trimmed to extend for a suitable distance beyond the ends of said outer conduit and by the installation of a joining sleeve over adjacent end zones of said lengths of outer conduit, fixing of the ends of said joining sleeve to said outer 20 conduit and filling the annular void beneath said joining sleeve and between adjacent ends of said outer conduit. lB The composite conduit system of Claim 1 in which discrete lengths of said composite conduit are joined in a second 5 embodiment by the fusing or welding of polymer flanges to adjacent ends of said liner, said ends being previously trimmed to extend for a suitable distance beyond the ends of said outer conduit, fixing to the ends of said outer conduit supporting sleeves such that supporting flanges fixed to the ends of said supporting 10 sleeves abut and support said polymer flanges, and securing together said adjacent polymer and supporting flange combinations using fastenings passed through coincident apertures in them such that the outer faces of said polymer flanges are urged into sealing abutment. 15

2. The composite conduit system of Claim I in which said annular void is filled with a settable resin or cementitious material to support said liner against the effects of internal pressure.

3. The composite conduit system of Claim 2 in which suitable apertures are provided in said joining sleeve to permit ingress of 20 said settable resin or cementitious material and egress of air and overflow.

4. The composite conduit system of Claim 1 in which said annular void is filled with a circumferential supporting band of suitable thickness to support said liner against the effects of internal 21 pressure.

5. The composite conduit system of Claim 4 in which suitable gaps are provided between adjacent ends of said supporting sleeve to prevent abutment of said ends during installation of said joining 5 sleeve.

6. The composite conduit system of Claim I in which said liner is made sufficiently thick to accommodate without collapse the compressive force generated by said reduction in diameter of said outer conduit. 10

7. The composite conduit system of Claim 1 in which said liner is made from a fusible, thermoplastic polymer providing suitable characteristics of resistance to chemical or mechanical erosion.

8. The composite conduit system of Claim 1 in which butt-joining by fusion of abutting ends of said liner is effected by simultaneously 15 applying said ends to the opposing faces of a heated plate and, when the material of said ends has been raised above its melting point, removing said heated plate and urging said ends together to achieve a fusion joint.

9. The composite conduit system of Claim 8 in which flash generated 20 by said butt-joining process is trimmed flush with the surface of said liner.

10. The composite conduit system of Claim 8 in which discrete lengths of said composite conduit are slidingly supported in suitable supports during said butt-joining process. 22

11. The composite conduit system of Claim 1 in which short or long tack welding is used to fix said ends of said joining sleeve to said outer conduit.

12. The composite conduit system of Claim 1 in which said joining 5 sleeve is fixed to said adjacent end zones of said lengths of said outer conduit by the wedging engagement of a plurality of circumferentially arranged, tapered lugs provided on its interior surface with a plurality of complementary, circumferentially arranged, tapered lugs provided on said end zone exterior surfaces, 10 said complementary lugs being brought into wedging engagement by rotation of said joining sleeve on said outer conduits.

13. The composite conduit system of Claims 4 and 12 in which supporting pads are provided on the inner surface of said joining sleeve to support and retain said supporting band in place. 15

14. The composite conduit system of Claim 12 in which the circumferential separation of said tapered lugs of said joining sleeve and said outer conduit end zones is such as to permit said sets of tapered lugs to be axially displaced across each other.

15. The composite conduit system of Claim 12 in which said 20 supporting band is supported and retained in place by the filling of the annular void between said sets of tapered lugs with a settable resin or cementitious material.

16. The composite conduit system of Claim 15 in which said settable resin or cementitious material, when set, acts to retain said joining 23 sleeve in place against any movement.

17. The composite conduit system of Claim 1 in which the conduit of a secondary circuit is joined to the conduit of a primary circuit by cutting away a suitable area of said outer conduit of said primary 5 circuit to expose said liner and cutting a suitably shaped aperture in said primary circuit liner conforming to the projected internal shape of said secondary circuit liner at the angle of joining; cutting away a suitable area of said outer conduit of said secondary circuit and cutting the exposed end of said secondary circuit liner to 10 conform to the exterior shape of said primary circuit liner at the angle of joining; simultaneously applying a heated, suitably shaped die to the attachment zone of said primary circuit liner and applying said shaped end of said secondary liner to the suitably shaped opposing face of said heated die and, when the material of 15 said attachment zone and said end has been raised above its melting point, removing said die and urging said end against said attachment zone to achieve a fusion joint; trimming away flash generated by said butt-joining process; and, upon cooling of said fusion joint, enclosing the whole of the joint zone and adjacent 20 areas with a more or less T-shaped jacket clamped tightly to said outer conduits.

18. The composite conduit system of Claim 17 in which said jacket is made in two mirror-image parts fastened together with a plurality of fasteners. 24

19. The composite conduit system of Claim 17 in which the inner surfaces of said jacket abutting said conduit exterior surfaces are suitably treated to enhance their frictional attachment to said outer conduit surfaces. 5

20. The composite conduit system of Claim 17 in which said exposed end of said secondary circuit liner and the edges of said aperture cut in said primary circuit liner are shaped to provide an approximate mitering with, at any particular point, more or less equal angles between the two shaped surfaces and the axes of the 10 conduits to which they relate.

21. The composite conduit system of Claim 17 in which said exposed end of said secondary circuit liner is simply shaped to conform to said exposed exterior surface of said primary circuit liner.

22. The composite conduit system of Claim 17 in which said 15 secondary circuit conduit is slidingly supported in suitable supports during said joining process.

23. The composite conduit system of Claim 17 in which a router-type cutter with four-axis support is employed to generate complex shapes on the edges of said suitably shaped aperture in said 20 primary circuit liner to make it conform to the projected internal shape of said secondary circuit liner at the angle of joining and to generate complementary shapes on the exposed end of said secondary circuit liner conforming to the exterior shape of said primary circuit liner at the angle of joining; said four axis support 25 having freedom of movement in x, y and z-axes, with additional fourth-axis freedom of movement conferred by pivoting said cutter in vertical and horizontal planes and by pivoting a workpiece in vertical and horizontal planes. 5

24. The composite conduit system of Claim 23 in which displacement of said router-type cutter in x, y and z axes and said fourth-axis modes of displacement is effected by stepper motors under the control of a microprocessor-based control unit.

25. The composite conduit system of Claim 1 in which said joining 10 sleeve installed over adjacent end zones of said lengths of outer conduit takes the form of a jacket made in two mirror-image parts fastened together with a plurality of fasteners and clamped tightly to said outer conduit end zones.

26. The composite conduit system of Claim 25 in which the inner 15 surfaces of said jacket abutting said outer conduit exterior surfaces are suitably treated to enhance their frictional attachment to said outer conduit surfaces.

27, The composite conduit system of Claim 1 in which said joining sleeve installed over adjacent end zones of said lengths of outer 20 conduit has two different ends, one said end taking the form of a complete cylindrical sleeve installed over one said outer conduit end zone and fixed to it by long or short tack welding and the other a jacket made in two more or less mirror-image parts fastened together with a plurality of fasteners and clamped tightly to the 26 other said outer conduit end zone.

28. The composite conduit system of Claim 27 in which the inner surfaces of said jacket abutting said outer conduit exterior surface are suitably treated to enhance their frictional attachment to said 5 outer conduit surface.

29. The composite conduit system of Claim 27 in which said jacket is replaced by a cylindrical sleeve which is fixed to said conduit end part by the wedging engagement of a plurality of circumferentially arranged, tapered lugs provided on its interior surface wedgingly 10 engaging a plurality of complementary, circumferentially arranged, tapered lugs provided on the exterior surface of said end zone.

30. The composite conduit system of Claim 1 in which a liner bend is encased in an outer conduit made in two mirror-image parts fastened together with a plurality of fasteners and clamped tightly 15 to said liner bend.

31. The composite conduit system of Claim 30 in which the inner surfaces of said outer conduit abutting said liner bend exterior surface are suitably treated to enhance their frictional attachment to said liner bend surface. 20

32. The composite conduit system of Claim 1 in which the end surface of a length of said liner and the surfaces of the opening in a said polymer flange are chamfered to complementary angles, said chamfered surfaces are simultaneously applied to a heated, suitably shaped die and, when the material of said chamfered surfaces has 27 been raised above its melting point, said die is removed and said surfaces urged together to achieve a fusion joint.

33. The composite conduit system of Claim 1 in which a said polymer flange is welded to the end of a said liner by conventional hand or 5 machine welding.

34. The composite conduit system of Claim 1 in which a said supporting sleeve is retained in position on said outer conduit with its said supporting flange abutting said polymer flange by its free end being fixed to said outer conduit by short or long tack welding. 10

35. The composite conduit system of Claim 1 in which adjacent said liner ends are joined by fusion, said joining sleeve is installed over adjacent end zones of said lengths of outer conduit, said annular void beneath said joining sleeve and between adjacent ends of said outer conduit is filled with a settable resin or cementitious material 15 or by a said supporting band to support said liner against the effects of internal pressure; split clamps being clamped to said outer conduit to either side of said joining sleeve and a plurality of axially arranged tie bolts passing through said split clamps are tensioned to maintain said joint. 20

36. The composite conduit system of Claim 35 in which the inner surfaces of said split clamps are provided with suitable serrations to improve the efficiency of attachment of said clamps to said outer conduit exterior surfaces.

37. The composite conduit system of Claim 1 in which a said liner of 28 suitable diameter is reduced in diameter by rolling down in the manner described, installed in said outer conduit and expanded by internal pressure to bring its exterior surface into intimate contact with the interior surface of said outer conduit. 5

38. The composite conduit system of Claim 1 in which a said liner of suitable diameter is reduced in diameter by rolling down in the manner described, installed in said outer conduit and expanded by internal pressure to bring its exterior surface into close contact with the interior surface of said outer conduit, following which 10 said outer conduit is reduced in diameter by rolling down in the manner described to generate a full interference fit between the two said components.

39. The composite conduit system of Claim 1 in which a flange is formed on the end of said polymer liner by applying a suitable 15 heated flange-type die to the end surface of said liner, said die being progressively advanced inwardly as the material of said liner melts, a cooled, cylindrical die being positioned in the lumen of said liner to prevent any inward displacement of melted material and a cooled, flange-type die with a circumferential collar of 20 suitable width projecting axially towards said heated die being positioned inwardly from the end of said liner, said melted liner material being urged against said cooled, flange-type die to form the inner surface of said flange, the circumferential surface of said flange being formed against the inner surface of said 29 circumferential collar.

40. The composite conduit system of Claim 39 in which said liner, said heated flange-type die, said cooled, cylindrical die and said cooled, flange-type die are supported in suitable jigs, said 5 supporting jig for said heated flange-type die permitting its progressive advancement inwardly towards the end of said liner.

41. The composite conduit system of Claim 39 in which suitable pins and complementary apertures are provided in said heated flange type die and said cooled flange-type die to form fastening access 10 holes in said flange.

42. The composite conduit system of Claim I in which said liner is made from a suitable metal material, liners of successive lengths of said composite conduit being joined by hand or machine welding.

43. The composite conduit system of Claim 1 in which said outer 15 conduit is made from a suitable metal material.

44. The composite conduit system of Claim 1 in which a first seam welded tube is formed on a first tube mill and its weld seam rolled and finished; said first seam-welded tube then passing to a second tube mill where a second seam-welded tube is formed around it, 20 said second seam-welded tube being supported by support means positioned inside said first seam-welded tube during rolling and finishing of its weld seam; the resultant composite tube being rolled down in diameter to create a strong interference fit between said first and second seam-welded tubes. 30

45. The composite conduit system of Claim 44 in which the weld seams of said first and second seam-welded tubes are substantially displaced from each other in a circumferential sense.

46. The composite conduit system of Claim 44 in which the exterior 5 surface of said first seam-welded tube is coated with suitable welding media and, after completion of said rolling down process, said composite tube is heated to weld both said seam-welded tubes together

47. The composite conduit system of Claim 44 in which the exterior 10 surface of said first seam-welded tube is coated with a suitable adhesive which acts to bond both said seam-welded tubes together during said rolling down process.

48. The composite conduit system of Claim 44 in which the exterior surface of said first seam-welded tube is coated with a suitable soft 15 metal such as aluminium or tin which forms a pressure weld to bond both said seam-welded tubes together during said rolling down process.

49. The composite conduit system of Claim 1 in which electrical cabling is led through a polymer sheath which is rolled down in 20 diameter to bring it into intimate contact with said cabling, said polymer sheath and cabling then being led through an outer metal sheath which is rolled down in diameter to bring it into intimate contact with said polymer sheath.

50. A composite conduit system as hereinbefore described with 31 reference to the drawings.