Flexible pipe and coupling therefor

Abstract

Embodiments of the invention relate to the construction of a sealed connection between an elastomeric or synthetic polymer flexible pipe or hose and a metallic coupling member. The coupling member surrounds an armor layer at a free end of the flexible pipe or hose. A sealing area is defined by a recessed portion of the pipe coupling into which a sealing material is introduced. An inner layer of the flexible pipe or hose may extend into the sealing area where it is bonded to the sealing material. The sealing material and the inner liner layer may each be comprised of a semi-crystalline thermoplastic material. Furthermore, a reinforcement material is provided in the inner layer.

Claims

1. An elastomeric flexible hose for transportation of hydrocarbon liquids or gases, the elastomeric flexible hose comprising: (i) a semi-crystalline thermoplastic inner liner layer; (ii) an armour layer surrounding the inner liner layer at an end of the flexible hose; (iii) a metallic hose coupling disposed at the end of the hose and surrounding the armour layer; (iv) a sealing area defined by a recessed portion of the metallic hose coupling; (v) a semi-crystalline thermoplastic sealing material, or a cross-linked elastomeric sealing material, disposed in the sealing area; wherein a portion of the inner liner layer at said hose end extends into the sealing area and is bonded to the sealing material; and wherein a helically wound reinforcement material is provided wholly within the inner liner layer and further in that the inner liner layer is bonded to the semi-crystalline thermoplastic sealing material, the semi-crystalline thermoplastic sealing material being bonded to an inner surface of the metallic hose coupling within the sealing area by a tie layer that is coated to the inner surface of the metallic hose coupling.

2. The flexible hose according to claim 1, wherein the reinforcement material is not bonded to the semi-crystalline thermoplastic material.

3. The flexible hose according to claim 1, wherein the reinforcement material comprises helically at least one of wound steel cord and steel wires, or at least one of one or more fiber strands and rovings selected from the group consisting of glass fibers, carbon fibers, ultra high molecular weight polyethylene (UHmwPE) fibers, and aramid fibers.

4. The flexible hose according to claim 3, wherein at least one of separate helically wound steel cord and steel wires are arranged in an interlocking fashion.

5. The flexible hose according to claim 1, wherein the reinforcement material is arranged within the inner liner layer in a wound fashion at an angle of between 25 degrees and 85 degrees relative to a longitudinal axis of the flexible hose.

6. The flexible hose according to claim 1, wherein an electrical heating element is provided within the inner liner layer.

7. The flexible hose according to claim 1, wherein a cylindrical sleeve member is disposed beneath the inner liner at the end of the flexible hose and cooperates with the hose coupling proximate the sealing area to support a portion of the inner liner layer which extends into the sealing area.

8. The flexible hose according to claim 1, wherein the sealing material is provided as an injectable fluid or molten synthetic polymer.

9. The flexible hose according to claim 1, wherein the sealing material is provided as a solid meltable seal.

10. The flexible hose according to claim 9, wherein the solid meltable seal comprises metallic particles selected from the group consisting of fibres, coarse grains, chips, and fine powder.

11. The flexible hose according to claim 10, wherein different sizes of metallic particles are distributed throughout the solid meltable seal.

12. The flexible hose according to claim 1, wherein the inner liner layer is coupled to the hose coupling by a crimped or swaged connection.

13. The flexible hose according to claim 1, wherein all adjacent layers of the flexible hose are partially or fully bonded in a permanent connection.

14. The flexible hose according to claim 1, wherein an outer cover layer surrounds the armour layer and comprises a semi-crystalline thermoplastic material.

15. The flexible hose according to claim 14, wherein a reinforcement material is provided within the outer cover layer.

16. The flexible hose according to claim 15, wherein the reinforcement material comprises one or more materials selected from the group consisting of steel cord, steel strands, fiber strands, and fiber rovings.

17. The flexible hose according to claim 16, wherein the fiber strands or rovings comprise one or more fibers selected from the group consisting of glass fibers fibres, carbon fibers, UHmwPE (ultra high molecular weight polyethylene) fibers, and aramid fibers.

18. The flexible hose according to claim 15, wherein the reinforcement material within the outer cover is aligned in a uni-directional, bi-directional, or multi-directional manner.

19. The flexible hose according to claim 15, wherein the reinforcement material within the outer cover layer is provided within a fabric or a plied tape.

20. The flexible hose according to claim 1, wherein a stainless steel interlock cover layer surrounds an exterior of the flexible hose.

21. A method of manufacturing an elastomeric flexible hose for transportation of hydrocarbon liquids or gases, the method comprising: (i) providing a hose coupling comprising a recessed portion defining a sealing area; (ii) providing a hose comprising a semi-crystalline thermoplastic inner liner layer, and an armour layer surrounding the inner liner layer at an end of the flexible hose; (iii) providing a semi-crystalline thermoplastic sealing material, or a cross-linked elastomeric sealing material, for introduction into the sealing area; (iv) providing a helically wound reinforcement material wholly within the inner liner layer; (v) providing a tie layer that is coated on an inner surface of the hose coupling to bond the hose coupling to the semi-crystalline thermoplastic sealing material within the sealing area, the semi-crystalline thermoplastic sealing material being bonded to the inner liner layer; (vi) fitting the hose coupling to the end of the hose; and (vii) establishing a permanent chemical bond within the sealing area between the hose end and the sealing material; and the hose coupling and the sealing material respectively.

22. The method according to claim 21, wherein the step of establishing a permanent chemical bond within the sealing area involves introducing the sealing material into the sealing area by mounting a solid meltable seal proximate the hose end before fitting the hose coupling to the hose end.

23. The method according to claim 22, wherein the step of fitting the hose coupling to the hose end is followed by the step of introducing a supporting member beneath an inner surface of said hose end, the supporting member incorporating a heater which melts the solid meltable seal within the sealing area.

24. The method according to claim 23, wherein the step of introducing the supporting member involves employing an inflatable supporting member which is temporarily inflated against the inner surface of said hose end whilst the permanent chemical bond is established.

25. The method according to claim 23, wherein the step of introducing a supporting member is followed by permanently swaging it against the inner surface of said hose end.

26. The method according to claim 23, wherein the step of melting the solid meltable seal within the sealing area is accompanied by the step of applying a vacuum to remove substantially all air from the sealing area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a cross-sectional schematic view showing a pipe or hose coupling fitted over the end of a flexible pipe or hose;

(3) FIG. 2a is a cross-sectional schematic view showing the sealing area of FIG. 1 in more detail;

(4) FIG. 2b is a cross-sectional schematic view showing the sealing area of FIG. 2a filled with a non-elastomeric sealing material;

(5) FIG. 3a is a cross-sectional schematic view showing an alternative sealing area allowing for more mechanical grip;

(6) FIG. 3b is a cross-sectional schematic view showing the alternative sealing area of FIG. 3a filled with a non-elastomeric sealing material;

(7) FIG. 4a is a cross-sectional schematic view showing the lay angle of reinforcement within the inner liner;

(8) FIG. 4b is a cross-sectional schematic view showing an alternative lay angle and a heating means within the inner liner;

(9) FIG. 5 is a cross-sectional schematic view showing a hose coupling fitted over the end of a flexible pipe or hose having an alternative outer reinforcement structure;

(10) FIG. 6 is a cross-sectional schematic view showing a pipe or hose build-up whereby the constituent layers have been progressively stripped back towards the pipe/hose end in preparation for fitting a pipe/hose coupling thereto;

(11) FIG. 7 is a cross-sectional schematic view showing a pipe or hose build-up of FIG. 6 with a meltable sealing ring mounted to its free end;

(12) FIG. 8a is a cross-sectional schematic view showing a pipe or hose coupling fitted over the end of the meltable sealing ring of FIG. 7;

(13) FIG. 8b is a cross-sectional schematic view showing a pipe or hose coupling fitted over the end of an alternative L-shaped meltable sealing ring;

(14) FIG. 9 is a cross-sectional schematic view corresponding to FIG. 8a showing a supporting member incorporating an induction heater;

(15) FIG. 10 is a cross-sectional schematic view corresponding to FIG. 8a showing the establishment of chemical bond in the sealing area after removal of the supporting member shown in FIG. 9;

(16) FIG. 11a is a cross-sectional schematic view showing the sealing area of FIG. 8a in more detail;

(17) FIG. 11b is a cross-sectional schematic view showing the sealing area of FIG. 10 in more detail.

(18) FIG. 12a is a cross-sectional schematic view showing the sealing area of FIG. 8b in more detail prior to activation of an induction heater; and

(19) FIG. 12b is a cross-sectional schematic view showing the sealing area of FIG. 8b in more detail after activation of an induction heater.

DETAILED DESCRIPTION

(20) FIG. 1 shows a schematic cross-sectional view of an end of a flexible hose surrounded by an annular hose coupling 13. The innermost layer of the flexible hose is a semi-crystalline polymer inner liner 1 within which is embedded a reinforcement material 2. In some embodiments (not shown) a flexible stainless steel interlock or carcass may be disposed radially within (i.e. beneath) the inner liner 1 and chemically bonded or crimped thereto to form the innermost layer.

(21) The inner liner 1 may be formed from any suitable type of semi crystalline thermoplastic, e.g. polymers derived from polyolefins. Possible options include, but are not necessarily limited to: polypropylene; fully or partially cross-linked polyethylene; polyamides such as polyamide-polyimide; polyimide (PI) (PA6, PA11 or PA12); polyurethanes (PU); polyureas; polyesters; polyacetals; polyethers such as polyethersulphone (PES); polyoxides; polysulfides such as polyphenylene sulphide (PPS); polysulphones such as polyarylsulphone (PAS); polyacrylates; polyethylene terephthalate (PET); polyether-ether-ketones (PEEK); polyvinyls; polyacrylonitriles; polyeterketoneketone (PEKK). Further options include co-polymers of the foregoing such as fluorous polymers; homo-polymers or copolymers of, for example, trifluoroethylene (VF3) or tetrafluoroethylene; copolymers or terpolymers comprising two or more different members selected from VF2, VF3, chlorotrifluorethylene, tetrafluoroethylene, hexafluoropropene or hexafluoroethylene; polymer blends comprising one or more of the above mentioned polymers and composite materials, such as an abovementioned polymer compounded with reinforcement fibres such as glassfibers and/or carbon fibers and/or aramid fibers. The choice of semi crystalline thermoplastic for a given application will depend on the specific expected service conditions of the flexible pipe and perhaps other considerations such as ease of manufacture and cost.

(22) The inner liner 1 is surrounded by a consolidating fabric layer 8. The fabric layer 8which may include rubberis surrounded by a steel sleeve 7 which increases in thickness towards the end of the flexible hose. The steel sleeve 7 is surrounded by one or more armour layers 9 comprising of, for example, one or more helically wound layers of steel cord, steel wires or glass/carbon/aramid fibre strands or rovings embedded within a rubber cushioning layer 10. The armour layers 9 and cushioning layers 10 may be provided in the form of tape which is wound around the inner liner 1 in one or more plies. Different plies may be wound at different winding angles.

(23) If present, the reinforcement material 2 within the inner liner 1 may take the form of helically wound steel cord, steel wires or fibre strands or rovings with a winding angle of between 25 degrees and 85 degrees relative to the longitudinal axis 100 of the flexible hose (see FIG. 4a). Preferably, the winding angle will be as close as possible to the neutral angle of 54-55 degrees. The winding angle may be adjusted depending on particular requirements. However, the winding angle will normally not be less than 25 degrees or more than 85 degrees to ensure controlled bending behaviour. Exceptionally, the winding angle may be less than 25 degrees if the application requires the inner liner 1 to be collapsible (see FIG. 4b). In that specific case the embedded reinforcement layers act as a stiffener for the inner liner 1 limiting the elongation to a value of less than the elongation threshold of the inner liner's thermoplastic material. In one embodiment, one or more additional layers of the same reinforcement material 2 may be wound at different angles with compatible thermoplastic materials over-extruded to fully embed the respective additional reinforcement layers.

(24) The steel cord and/or steel wires may be wound such that adjacent windings are interlocked. The reinforcement material 2 may also comprise fibre strands and/or rovings selected from the list comprising: glass fibres, carbon fibres, UHmwPE (ultra high molecular weight polyethylene) fibres (Dyneema) and aramid fibres. It will be understood that this list is non-exclusive. The reinforcement material may be a textile weave or fabric made up of one or more of the aforementioned materials. The reinforcement material 2 may be provided in the form of a tape containing one or more of the abovementioned materials. The reinforcement material 2 may be over-extruded with the same semi-crystalline thermoplastic material from which the inner liner 1 is made. It is preferable that the reinforcement material 2 may accommodate shear deformation caused by the application of loads, e.g. during bending. Accordingly, the reinforcement material 2 is optionally not bonded to the thermoplastic material of the inner liner 1 within which it is embedded.

(25) A source of heat may be incorporated into the inner liner 1, for example by adding an electric heat tracing layer above and/or below and/or amongst the reinforcement material 2 (also shown in FIG. 4b). It is essential that the generated heat is maintained well below the melting point of the thermoplastic material of the inner liner 1. The heat tracing elements may comprise separate conductive wires or utilise the steel cables or steel based fabrics or composite materials of the reinforcement material 2 itself.

(26) The internal diameter of the annular hose coupling 13 increases in a generally stepwise fashion from left to right as viewed in FIG. 1. A recessed portion 3 is provided at one end of the body of the hose coupling 13 nearest its narrowest internal diameter. The term recessed portion is to be understood in this context as defining the inner enlarged diameter space bounded by the hose coupling body, the cylindrical sleeve 6, and the innermost layers 1, 8 of the flexible hose, i.e. as indicated with the closely spaced diagonal shading in FIGS. 1 and 5.

(27) The end portion of the flexible hose is prepared to receive the hose coupling in a conventional manner, for example by curing and stripping back to progressively expose its underlying layers. A cylindrical inner sleeve 6 is disposed within the end portion of the flexible hose. The internal diameter defined by the inner sleeve 6 is selected so as to be substantially equal to the internal diameter of the flexible hose defined by its inner liner 1. The outer surface of the inner sleeve 6 tapers towards the longitudinal axis 100. As the inner sleeve 6 is inserted into the end of the flexible hose its tapered portion(s) engage the innermost surface of the inner liner 1. Progressive insertion of the inner sleeve 6 into the flexible hose causes the internal diameter of the inner liner 1 to expand as it is forced up the tapered surface(s) of the inner sleeve 6.

(28) The recessed portion 3 of the hose coupling 13 is partially closed by the inner sleeve 6 when the hose coupling is fitted over the expanded end of the flexible hose. Once positioned over its end, the hose coupling may optionally be crimped onto the flexible hose from the outside. An epoxy resin 11 is introducedvia end caps 12into the area between the inner surface of the hose coupling body 13 and the stripped back layers of the flexible hose.

(29) Once the hose coupling is in place, the inner sleeve 6 therefore supports the expanded end portion of the inner liner 1 within the recessed portion 3 of the hose coupling body 13 together with an end of the surrounding fabric layer 8 and steel sleeve 7. All three layers are compressedfor example by crimping or swaging from the insidebetween the outer surface of the inner sleeve 6 and an opposing surface of the hose coupling body 13 in a manner which closes off the path between the recessed portion 3 and the internal cylindrical volumes of the flexible hose and the coupling body 13.

(30) The internal volume of the recessed portion 3hereinafter the sealing areais bounded by the inner wall of the coupling body 13 andin a preferred embodimentthe radial outer surface of the inner sleeve 6. One surface portion of the inner wall of the coupling body 13 is inclined at an acute angle relative to the longitudinal axis 100 of the flexible hose. The acute angle may be approximately 45 degrees. An end portion of the flexible hosei.e. its inner liner 1 and fabric layer 8extends into the sealing area 3 as shown in greater detail in FIG. 2a.

(31) FIGS. 3a and 3b show an alternative sealing area 3 whereby the inner wall of the coupling body 13 and the radial outer surface of the inner sleeve 6 are provided with a serrated surface profile 16. The serrations 16 provide an enhanced mechanical connection between the surfaces within the sealing area 3 and the sealing material 15. As shown in FIG. 3b, the presence of the serrations 16 may mean that the tie layer 14 need only be applied to any non-serrated surfaces within the sealing area 3. One surface portion of the inner wall of the coupling body 13 within the sealing area 3 is inclined at an obtuse angle relative to the longitudinal axis 100 of the flexible hose. The obtuse angle may be approximately 135 degrees. This serves to increase the surface area of the sealing bond between the sealing material 15 and the coupling body 13 and hence further strengthens the bond.

(32) A passage is provided through an exterior surface of the hose coupling body 13 to provide access to the sealing area 3 via a removable end cap 5. In one embodiment, a non-elastomeric sealing material can be introduced into the sealing area 3 through the passage using a built-in nipple connector 4. As shown in FIG. 2b, the sealing material 15 completely fills the sealing area 3 and may be cured to establish a permanent polymer-to-polymer and polymer-to-metal chemical bond between the end portion of the inner liner 1 and the sealing material 15; and the surfaces of the hose coupling body 13 and the sealing material 15 respectively. As best shown in FIGS. 2a and 3a, a steel or synthetic polymer ring 25 carrying an elastomeric sealing surface 22 is provided between an inner surface of the hose coupling body 13 and the inner layer 1 of the flexible hose. This performs the dual functions of: (i) preventing epoxy resin, introduced via the end caps 12, from entering the sealing area; and (ii) providing a compressive force to the layers between it and the inner sleeve 6 (i.e. via the inner liner 1 and the reinforcement material 2, if present).

(33) For some types of sealing material 15, complete bonding between the respective surfaces within the sealing area 3 necessitates coating them with a tie layer 14 before introducing the sealing material 15. The tie layer may be applied using conventional electrostatic coating techniques. Application of a tie layer may also add thermal insulation and mechanical strength to the connection within the sealing area 3.

(34) In one embodiment, the sealing material 15 comprises a non-elastomeric semi-crystalline thermoplastic material such as an injection grade polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA) or a cross-linked polyethylene (PEX). In one embodiment, the sealing material 15, the inner liner 1 and the tie layer 14 each comprise a non-elastomeric semi-crystalline thermoplastic material. Ideally, the inner liner 1, the tie layer 14, and the sealing material 15 are formed from the same non-elastomeric semi-crystalline thermoplastic material so as to create a single homogeneous polymer structure providing the best possible chemical bond between the hose coupling body 13 and the inner liner 1 within the sealing area 15.

(35) The homogeneous polymer structure, e.g. based on the PVDF, PFA or PEX materials discussed above, will be substantially liquid impervious at a pressure difference of the order of 5-10 bar. Consequently, any reinforcement material 2 embedded within the inner liner 1 is protected from corrosion. If the selected polymer structure is formed from a more liquid permeable thermoplastic material then a fibre-based reinforcement material 2 (as described above) may be utilised as an alternative to steel. Where fibre-based material is undesirable, galvanised steel wire or cable may be employed as a means of protecting against corrosion.

(36) All adjacent layers of the flexible hose are permanently chemically bonded to each other in a manner known in the art. However, in a preferred embodiment it is important that the bonding process employed does not affect the non-bonded character of the reinforcement material 2 within the flexible hose's inner liner 1. For example, the thermoplastic material, e.g. PEX, may become cross-linked upon adding the reinforcement material 2.

(37) The thermoplastic material of the inner liner 1 is permanently and fully chemically bonded to the surrounding rubber encased armour layers 9, 10. Consequently, shear deformation of the thermoplastic material of the inner liner 1 during bending and the application of combined loads may be minimised. The PVDF, PFA or PEX materials discussed above have sufficient bonding and mechanical properties for high pressure applications. If more inert and temperature resistant materials like partially or fully fluorinated thermoplastics are employed, additional production steps may be required to obtain full bonding. The term full bonding is to be understood as meaning that either the mechanical strength limit of the elastomer rubber or that of the thermoplastic layer is exceeded before the bond is broken. Since deformation and compound loadings on a fully bonded pipe are taken up by both the inner liner 1 and the surrounding rubber encased armour layers 9, 10, this helps to avoid known failure mechanisms and provides a significant performance improvement in flexible hoses.

(38) The external layers of the flexible hose surrounding the rubber encased armour layers 9, 10 comprise an anti-wear layer 17 and an outer cover 18. These layers may be applied in the form of tapes and may comprise uni-directional, bi-directional or multi-directional reinforcement material selected from one or more of the types already described above. The external layers may be over-extruded with a final thermoplastic layer. For example, an impact resistant layer 19 in the form of a UHmwPE (ultra high molecular weight polyethylene) tape may be applied to provide extra impact resistance and anti-wear characteristics. An alternative arrangement (shown in FIG. 8b) may employ fibre reinforced or hybrid steel/fibre fabric layers 26 in addition to, or instead of, tapes as an impact resistant layer. The external layers extend over the coupling body 13 of the attached hose coupling.

(39) An alternative arrangement for the external layer of the flexible hose is shown in FIG. 5 whereby stainless steel interlock 21 is employed over an intermediate rubber cushion layer 20. This arrangement may be more susceptible to damage within the moon pool area of a drillship or platform than the alternative arrangement shown in FIG. 1.

(40) An alternative manner of effecting a sealed connection between a hose and a metallic coupling member will now be described with reference to FIGS. 6 to 12b. FIG. 6 is a cross-sectional schematic view showing the constituent layers of a hose which is substantially similar to that illustrated in FIGS. 1 and 5. The constituent layers have been progressively stripped back towards the free end of the hose (i.e. at the left hand side of FIG. 6) in preparation for fitting a hose coupling thereto in the manner described below.

(41) The innermost layer of the flexible hose is a semi-crystalline polymer inner liner 1 within which is embedded a reinforcement material 2. The inner liner 1 is exposed at the free end of the hose and formed with an angled chamfer at its distal end which is complementary in shape to an annular seat formed in the hose coupling 13 (see the left hand side of the recess in FIGS. 11a to 12b). The inner liner 1 may be formed from any suitable type of semi crystalline thermoplastic, e.g. polymers derived from polyolefins as already described above with reference to the embodiment of FIG. 1. The various layers which surround the inner liner 1 are also described above with reference to the embodiment of FIG. 1 and so need not be replicated here. However, as shown in FIG. 6 to 12b, it is possible to remove the fabric layer 8 (shown in the embodiment of FIGS. 1 to 5) because the inner reinforcement 2 can be designed to take up its structural function.

(42) FIG. 7 shows a meltable sealing ring 23 which is slidably mounted on the exposed portion of the inner liner 1 at the free end of the hose. The meltable sealing ring 23 is a hybrid of semi-crystalline thermoplastic material (preferably the same type as the inner liner) and metallic particles selected from one or more of the group comprising: fibres, coarse grains, chips, or fine powder. The particles may be provided as a mixture of different sizes to ensure an even distribution throughout the solid meltable seal.

(43) FIG. 8a shows an annular hose coupling 13 which has been push-fitted over the free end of the hose and properly aligned with the central longitudinal axis 100. The hose coupling 13 may be bonded to the stripped back layers of the flexible hose. This is achieved in a known manner by first heating the hose coupling 13 (e.g. by means of an induction coil) and introducing an epoxy resin through the end caps 12. In order to prevent epoxy resin from entering into the sealing area, a metal or polymer ring 25 carrying an elastomer sealing surface 22 is mounted above the inner liner 1 adjacent to the steel sleeve 7. The internal diameter of the annular hose coupling 13 increases in a generally stepwise fashion from left to right as viewed in FIG. 8a. A recessed portion 3 is provided at one end of the body of the hose coupling 13 nearest its narrowest internal diameter and defines a sealing area.

(44) The term recessed portion is to be understood in this context as defining the inner enlarged diameter space bounded by the hose coupling body and the inner liner 1 of the flexible hose, i.e. including the volume within which the solid meltable sealing ring 23 is seated. The radial passage closed by the end cap 5 is initially empty as shown more clearly in FIG. 1a. A nipple connector 4 is provided inside this passage to allow connection of a vacuum hose. The recessed portion may be provided with an annular seat within which an end portion of the solid meltable sealing ring 23 may be received (see the left hand side of the recessed portion 23 in FIGS. 8 to 12b). This ensures a secure mechanical lock between the annular hose coupling 13 and the meltable sealing ring 23 prior to it being heated as described below.

(45) FIG. 8b is similar to FIG. 8a but shows an alternative arrangement whereby the meltable sealing ring 23 is L-shaped in cross-section so as to extend over both the outer surface and the distal end of the inner liner 1 at the free end of the hose. This arrangement is shown in more detail in FIGS. 12a and 12b prior to, and after, activation of the induction heater respectively.

(46) FIG. 9 shows the same arrangement as FIG. 8a whereby a supporting memberin the form of a sealed silicone rubber hose incorporating a heatable induction coilhas been introduced beneath the inner liner 1. In use, the sealed silicone rubber hose is inflated using an air supply line 29 so as to apply a radial supporting pressure against the cylindrical inner wall of the inner liner 1. Before and/or during activation of the heatable induction coil via electrical connections 28, substantially all air is removed from the recessed portion 3. By maintaining vacuum conditions through the nipple connector 4 within the recessed portion 3 when the heatable induction coil is activated, all air bubbles are removed. The heating process continues until the solid meltable sealing ring 23 becomes molten and increases in volume to fill the recessed portion 3 to a predetermined level as shown more clearly in FIG. 11b. This can be visually verified by checking the level of the sealing material through the end cap 5. The duration and temperature of heating will vary depending upon hose design and material choices. During this process, the inflated rubber hose ensures that the cured seal is correctly aligned.

(47) A tie layer 14 may be applied to the inner surface of the hose coupling 13 to provide a more reliable cohesive bond between the sealing material and the metallic (e.g. steel) hose coupling. The choice of tie layer 14 will vary depending upon the chemical make-up of the thermoplastic material used in the sealing material. The cohesive bond, between the sealing material and the surface of the hose coupling 13 within the sealing area, must be able to withstand the tendency for the inner liner 1 to creep under high temperatures and/or pressures.

(48) FIG. 10 is a cross-sectional schematic view corresponding to FIG. 8b now showing the establishment of chemical bond in the sealing area after removal of the sealed silicone rubber hose incorporating a heatable induction coil as shown in FIG. 9.

(49) It will be appreciated that the various embodiments of the present invention provide a number of advantages over existing arrangements for connecting a flexible hose to a hose coupling. Most significantly, by providing a non-elastomeric semi crystalline sealing material within the sealing area which is the same (or chemically similar) as that of the inner liner of the flexible hose, a homogeneous polymer structure extends from the flexible hose all the way into the hose coupling, i.e. the liner becomes the seal and the seal is the liner. This structure provides a moisture-proof and gas-tight barrier more capable of withstanding harsh production environments than known prior art products.

(50) Also, by embedding reinforcement material within the inner liner layer of the flexible hose, its connection with a hose coupling can be further strengthened and improved. The integration of a reinforcement material into the inner liner layer closer to the core of the flexible hose makes the bonded hose stronger and thus enables downscaling, if desired, of the outer armour layers. For example, the number of rubber outer reinforcement plies or the size thereof may be reduced. Consequently, it becomes possible to achieve a more lightweight and/or flexible hose system. A properly designed reinforced inner layer can also replace the need for an inner carcass because the supporting function is now incorporated within the inner liner layer itself.

(51) The embodiment of FIGS. 6 to 11b provides the further advantage of eliminating all air pockets from the sealing area. This arrangement also obviates the need for inserting the inner cylindrical supporting sleeve 6 shown in FIGS. 1 to 3 and 5. The process of expanding the sleeve to swage the overlying sealing area is also eliminated. Instead, the inner liner 1 of the flexible hose becomes part of the seal and so the process steps are significantly simplified and shortened.

(52) The various embodiments of the present invention provide a sealing arrangement that overcomes, or at least ameliorates, one or more of the following problems associated with elastomeric seals. Firstly, high temperatures cause softening of elastomers which results in an increased rate of liquid/gas diffusion, thus accelerating chemical degradation. This temperature-related issue can arise independently of high pressure considerations, although of course high pressures will further exacerbate the problem.

(53) Modifications and improvements may be made to the foregoing without departing from the scope of the invention as defined by the accompanying claims. For example, a possible alternative to the aforementioned meltable seal is a susceptor tape which could be wound around the outer surface of the flexible hose and its liner prior to fitting of the hose coupling.