GB2540422A

GB2540422A - Fluid conduit liner

Info

Publication number: GB2540422A
Application number: GB1512583.4A
Authority: GB
Inventors: Broughton Paul
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2015-07-17
Filing date: 2015-07-17
Publication date: 2017-01-18
Also published as: GB201512583D0

Abstract

A fluid conduit 130 is lined with a heat-shrinkable, fluid-tight lining tube 110. This lining tube 110 may be heated then stretched to increase its length and reduce its cross-section, prior to inserting the lining tube 110 into the conduit 130. The lining tube 110 is then heated, for example by passing a heated fluid through the tube heating it to above 100 degree Celsius, so that its cross-section expands to contact, and thus line, the fluid conduit 130. The lining tube 110 may be formed on a mandrel and be formed from a cross-linked polymer, such as polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE) or fluoroelastomer. The fluid conduit 130 may comprise an organic matrix compound. The lining tube 110 may be bonded to the fluid conduit 130 by melting the inner surface of the conduit, using the same heat source that heats and expands the lining tube 110. The lined fluid conduit 100 may be formed in a panel for use in a gas turbine engine dressing or raft.

Description

Fluid Conduit Liner

The present disclosure relates to a lined fluid conduit and/or a method of lining a fluid conduit and/or a component, such as a panel and/or a gas turbine engine, comprising a lined fluid conduit and/or a method of making such a component.

Fluid conduits are used in a very wide range of applications to transfer fluid from one place to another place. Some applications use metallic conduits (which may be referred to as pipes), which are generally fluid-tight and robust but may be heavy. Some applications use plastic conduits (which may be referred to as pipes) which may be lighter than metallic pipes but may not be so robust and/or strong. Furthermore, some plastic conduits may have inherent porosity. For example, composite pipes are generally unpopular because of the inherent porosity of the composite material.

Pipes/conduits manufactured using any material may have inherently poor internal surface quality, which may in turn lead to excessive pressure loss as the fluid passes through the conduit. Expensive and/or time-consuming manufacturing processes may be required in order to smooth the inner, fluidcontacting, surface to a level suitable for carrying fluid without excessive losses.

It would be advantageous to be able to provide an improved fluid conduit that has improved properties compared with conventional fluid conduits.

According to an aspect, there is provided a method of lining the internal surface of a fluid conduit. The method comprises providing a heat shrinkable tube (which may optionally be a flexible cross-linked polymer tube) having a length along a longitudinal axis and a cross-section normal to the longitudinal axis. The method comprises inserting the tube into the conduit. The method comprises heating the tube inside the conduit so as to reduce its length and increase its cross-section such that the tube contacts and thereby lines the internal surface of the conduit. The cross-section may be considered to be the cross-sectional area that is encircled by (or defined by) the walls of the tube.

Such a heat-shrink material may change its shape when heat is applied.

According to an aspect, there is provided a rigid fluid conduit lined with a heat shrinkable material. The heat shrinkable material may be a tube, which may be a polymer tube and/or may have a cross-linked polymer structure.

According to an aspect, there is provided a rigid panel having a fluid conduit lined with a heat shrinkable material, which may be a tube, which may be a polymer tube optionally having a cross-linked polymer structure.

Any liner or lining (for example tube and/or polymer tube) as described and/or claimed herein may be fluid-tight, for example fluid-impermeable.

Providing a lined fluid conduit as described and/or claimed herein may allow the conduit to have various advantages over conventional fluid conduits. For example, the conduit may be fluid tight and/or have a smooth internal surface by virtue of the liner. This may allow a wider choice of material for the fluid conduit/panel, which may be cheaper and/or stronger and/or lighter and/or more robust than would otherwise be possible, for example.

The tube may be stretched along its longitudinal axis so as to reduce its cross-section and increase its length before inserting it into the conduit. The reduced cross-section may thus be small enough to enable the tube to be inserted into at least a part of the conduit. In some arrangements, the cross-section of the tube may be too large to fit into the conduit prior to stretching.

The tube and/or conduit may have any desired cross-section, for example a circular cross-section.

The method may comprise heating the tube before stretching it, for example to a temperature that is above its operating temperature and/or the temperature at which it was formed. Such a temperature may be referred to as the material’s transition temperature.

The step of heating the tube after inserting it into the conduit in order to reduce its length and increase its cross-section may comprise passing fluid through the tube. Any type of fluid may be used, for example a liquid or a gas, such as air.

The step of heating the tube after inserting it into the conduit may comprise heating the tube to any suitable temperature. For example, the tube may be heated above its operating temperature and/or above the temperature at which it was formed and/or above room temperature, which may be referred to as its transition temperature. Purely by way of example, the tube may be heated to above 80 degrees Celsius, for example above 100 degrees Celsius, for example above 120 degrees Celsius. The temperature to which the tube is heated may depend, for example, on the material and/or structure of the tube.

The flexible cross-linked polymer tube may be formed in any suitable manner. For example, the flexible cross-linked polymer tube may be formed by extrusion. Additionally or alternatively, the flexible cross-linked polymer tube may be formed on a mandrel. The mandrel may then be removed in order to provide the flexible cross-linked polymer tube. Such a mandrel may, for example, be collapsible.

The tube may be bonded to the internal surface of the conduit. Such bonding may be achieved using an adhesive applied to the inner surface of the fluid conduit and/or the outer surface of the polymer tube (for example a one-part adhesive or a two-part adhesive). Additionally or alternatively, such bonding may comprise heating the internal surface of the conduit to a sufficient temperature to cause melting of the internal surface. Where heat is used to cause melting of the internal surface, the heat required to heat the stretched tube and the heat required to melt the internal surface of the conduit may be from the same heat source (or, indeed, from a different source).

The tube may comprise polyetheretherketone and/or polytetrafluoroethylene and/or fluoroelastomer. The cross-linked polymer may comprise polyetheretherketone and/or polytetrafluoroethylene and/or fluoroelastomer.

The fluid conduit may be formed in an organic matrix composite. For example, the fluid conduit may be formed in a rigid panel made from an organic matrix composite. The polymer tube may be said to line a rigid material that comprises an organic matrix composite. Such an organic matrix composite may comprise, for example, carbon fibres, glass fibres, aramid fibres, and/or para-aramid fibres. The fibres may be of any type, such as woven and/or chopped. Any suitable resin may be used, for example epoxy, BMI (bismaleimide), PEEK (polyetheretherketone), PTFE (polytetraflouroethylene), PAEK (polyaryletherketone), polyurethane, and/or polyamides (such as nylon).

The fluid conduit may be formed in a panel. Such a panel may be for use with a vehicle and/or may be attached for a vehicle (such as an automobile, water-based vehicle, or aircraft), for example as part of a fluid system of the vehicle. Such a panel may, for example, be for use with a gas turbine engine and/or may be attached to a gas turbine engine. A panel attached to a vehicle and/or gas turbine engine may form part of the engine/vehicle dressing, and may be referred to as a dressing panel. Such a panel may be referred to as a raft, a rigid raft, a rigid panel, a rigid dressing raft or a rigid dressing panel, for example.

Such a panel may further comprise at least a part of an electrical system of a gas turbine engine and/or vehicle. For example, such a panel may have at least one electrical conductor embedded therein. Such an electrical conductor may be, for example, in the form of a flexible printed circuit board or an electrical wire, which may be sheathed.

In arrangements in which the rigid panel is a dressing panel for a gas turbine engine/vehicle, the fluid conduit may be part of a fluid system of a gas turbine engine/vehicle. Such a fluid system may be any type of fluid system of the gas turbine engine/vehicle, for example a liquid system such as a fuel, oil or water system, or a gas system, such as an air system (which may, for example, be used for cooling and/or sealing).

According to an aspect, there is provided a gas turbine engine comprising a fluid conduit as described and/or claimed herein. Such a fluid conduit may be provided in a rigid panel such as those described and/or claimed herein. For example, the rigid panel may also comprise at least a part of an electrical system for a gas turbine engine, for example at least one electrical conductor embedded in the rigid panel.

Using dressing panels for gas turbine engines may provide various advantages over conventional engine dressing arrangements. For example, fluid conduits and/or electrical conductors embedded in the rigid panel may be provided with greater protection by the rigid material of the panel, for example due to being resistant to breaking and/or snapping and/or piercing and/or puncturing. The dressing panels may provide improved protection to the conduits and/or conductors during manufacture/assembly of the panel/gas turbine installation, and/or during service/operation/maintenance of the gas turbine engine. This may result in lower maintenance costs, for example due to fewer damaged components requiring replacement/repair and/or due to the possibility of extending time intervals (or service intervals) between inspecting the electrical and/or fluid system, for example compared with a system using only conventional engine dressings.

Use of one or more dressing panels may significantly reduce build time of an engine. For example, use of one or more dressing panels may significantly reduce the part count involved in engine assembly compared with a conventional dressing arrangement. The number and/or complexity of the operations required to assemble an engine (for example to assemble/install the fluid and/or electrical system (or network) and/or other peripheral components) may be reduced. For example, rather than having to install/assemble a great number of fluid pipes and connectors, and optionally wires and/or wiring looms together on the engine installation, it may only be necessary to attach a relatively small number of dressing panels, which themselves may be straightforward to handle, position, secure and connect. Connection between the panels and other fluid/electrical components may be particularly convenient and straightforward. Thus, use of dressing panels in a gas turbine installation may reduce assembly time and/or reduce the possibility of errors occurring during assembly.

Use of dressing panels may provide significant advantages during maintenance, such as repair and overhaul. As discussed above, the dressing panels may be particularly quick and straightforward to assemble. The same advantages discussed above in relation to assembly apply to disassembly/removal from the gas turbine engine. Thus, any repair/overhaul that requires removal of at least a part of the fluid system or electrical harness (for arrangements in which electrical conductors are also provided in the dressing panel) may be simplified and/or speeded up through use of dressing panels, for example compared with conventional dressings. Use of dressing panels may allow maintenance procedures to be advantageously adapted. For example, some maintenance procedures may only require access to a certain portion of the gas turbine engine that only requires a part of the fluid system and/or electrical system to be removed. It may be difficult and/or time consuming, or not even possible, to only remove the required part of a conventional harness or fluid system from a gas turbine engine. However, it may be relatively straightforward to only remove the relevant dressing panel, for example by simply disconnecting it from the engine and any other dressing panel/components to which it is connected. Decreasing maintenance times has the advantage of, for example, reducing out-of service times (for example off-wing times for engines that are used on aircraft).

The build/assembly times may be additionally or alternatively reduced by preassembling and/or pre-testing individual and/or combinations of dressing panels prior to engine assembly. This may allow the fluid and optionally the electrical and/or mechanical operation of the dressing panels to be proven before installation, thereby reducing/eliminating the testing required during engine installation.

The dressing panels may be a particularly lightweight solution for transferring fluid and optionally electrical signals around an engine. The use of the liner for the fluid conduit as described and/or claimed herein may be particularly advantageous in this regard, allowing a wider choice of materials to be used for the material of the panel, for example materials that are less dense and/or have a greater strength to weight ratio. A plurality of fluid conduits and/or electrical conductors may be embedded in a dressing panel, whereas in a conventional arrangement a large number of heavy, bulky fluid pipes, connectors and attachment brackets, and optionally a large number of electrical wires and/or insulating sleeves would be required. The reduced weight may be particularly advantageous, for example, when used on gas turbine engines on aircraft.

Dressing panels may be more easily packaged and/or more compact, for example than conventional engine dressings. Indeed, the dressing panels can be made into a very wide range of shapes as desired. This may be achieved, for example, by manufacturing the dressing panel using a mould conforming to the desired shape. As such, each dressing panel may be shaped, for example, to turn through a tighter corner (or smaller bend radius) than a conventional fluid pipe or electrical harness. The dressing panels may thus provide a particularly compact solution for transferring fluid and optionally electrical signals around a gas turbine engine. The dressing panels may be readily shaped to conform to neighbouring components/regions of a gas turbine engine, for example components/regions to which the particular dressing panel is attached.

At least some of the advantages and optional features discussed herein in relation to a dressing panel having a fluid conduit with liner embedded therein also apply to arrangements in which the fluid conduit with liner is not embedded in a dressing panel. Purely by way of non-limitative example, the advantages of the use of the liner as described and/or claimed herein allowing a wider choice of materials to be used for the material of the rest of the conduit, for example materials that are less dense and/or have a greater strength to weight ratio, may apply regardless of whether the fluid conduit is part of a dressing panel.

Except where mutually exclusive, any feature described and/or claimed in relation to any one or more of the above aspects may be applied to any other aspect. Furthermore except where mutually exclusive any feature described and/or claimed herein may be applied to any aspect and/or combined with any other feature described and/or claimed herein.

It will be appreciated that aspects of the disclosure cover structures that are manufactured according to the methods described and/or claimed herein.

Embodiments will now be described by way of example only, with reference to the Figures, in which:

Figure 1 is a sectional side view of a gas turbine engine having a fluid conduit in accordance with an example of the disclosure;

Figure 2 is a schematic view of a liner for a fluid conduit prior to insertion into a fluid conduit;

Figure 3 is a schematic representation of a liner for a fluid conduit being inserted into a fluid conduit;

Figure 4 is a schematic of a stretched liner after insertion into a fluid conduit;

Figure 5 shows a schematic of a lined fluid conduit; and

Figure 6 shows a schematic of a rigid panel have a lined fluid conduit embedded therein.

With reference to Figure 1, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, an intermediate pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, an intermediate pressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20. A nacelle 21 generally surrounds the engine 10 and defines both the intake 12 and the exhaust nozzle 20.

The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the intermediate pressure compressor 14 and a second air flow which passes through a bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 14 compresses the air flow directed into it before delivering that air to the high pressure compressor 15 where further compression takes place.

The compressed air exhausted from the high-pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.

Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

The gas turbine engine 10 comprises fluid systems. For example, the gas turbine engine 10 may comprise liquid systems, such as fuel, water and oil systems, and gas systems, such as cooling air and sealing air systems, such gas systems sometimes being referred to as secondary air systems (or SAS). The various fluid systems comprise fluid conduits that are used to transport the respective fluid around the engine.

The gas turbine engine 10 comprises various fluid conduits 101, 102, 103 in accordance with the present disclosure. Each of these fluid conduits 101, 102, 103 may each be an example of a general fluid conduit 100 described in more detail in relation to Figures 2 to 6. A gas turbine engine 10 in accordance with the present disclosure may comprise any one or more fluid conduit 100, which may, for example, be in the form of any one or more of the fluid conduits 101, 102, 103. A fluid conduit 100 according to the present disclosure may be provided to and/or mounted directly to a structure, such as a vehicle or part thereof, for example to the gas turbine engine 10 shown in Figure 1. In the Figure 1 example, the fluid conduit (or pipe) 101 is mounted directly to a fan casing 30. In other examples, fluid conduits 100 may be mounted to other parts of a gas turbine engine, for example other rigid structures, such as other casings. A fluid conduit 100 according to the present disclosure may be provided, for example, in a panel. For example, the fluid conduit 102 is embedded in a rigid panel 200 in the Figure 1 example. The rigid panel 200 is attached to the fan casing 30 of the gas turbine engine 10. A rigid panel 200 may (or may not) also comprise electrical conductors, for example by having electrical conductors embedded therein. In the Figure 1, for example, the rigid panel 200 also has a printed circuit board 300 comprising electrical conductors embedded therein.

By way of further example, a fluid conduit 100 according to the present disclosure may be mounted on top of a rigid panel 200 instead of or in addition to having a fluid conduit 100 embedded in the panel 200. For example, the rigid panel 200 shown in Figure 1 has a fluid conduit 102 mounted to the rigid panel 200.

Each fluid conduit 100 comprises a liner 110. Figure 2 shows an example of a liner 110 in the form of a tube, prior to being fitted inside the outer part of the fluid conduit 100. The tube 110 shown in Figure 2 is cylindrical, but the tube (or liner 110) may take any suitable form, for example it may have any suitable cross section depending on, for example, the shape of the fluid conduit 100. Purely by way of example, the liner 110 may be manufactured by forming it (for example by braiding) on a mandrel, which may be a collapsible mandrel.

The liner 110 is shown in a first state in Figure 2, which may be (or may be referred to as) an unstretched or original (or natural) shape. The liner 110 is manufactured from a shrinkable material, for example a heat-shrinkable material. Such a material may be manipulate when heat is applied, for example from one shape or configuration to another shape or configuration. This may be achieved by manufacturing the liner 110 using a cross-linked polymer, as illustrated schematically by the lines 112 in Figure 2 (only some of which are labelled for the sake of clarity). Such a cross-linked polymer may comprise, for example, polyetheretherketone and/or polytetrafluoroethylene and/or fluoroelastomer.

In order to line the fluid conduit 100, heat may be applied to the liner to take it above an transition temperature at which the shape of the liner 110 can be changed. The liner 110 is then stretched along its longitudinal axis, in the direction of arrows A shown in Figure 2, i.e. in a direction that would create tension in the absence of deformation.

After stretching, the liner 110 becomes longer and thinner, as shown on the right hand side of Figure 3. The liner (or tube) 110 may be said to have its axial (or longitudinal) direction increased, and its cross-sectional area (or internal area, or enclosed area, that is the area through which flow may pass) decreased. In the case of a cylindrical tube 110, such as that shown in Figures 2 and 3, the length of the tube increases, and the diameter of the tube decreases.

In some arrangements, it may not be necessary to heat the liner 110 in order to stretch it. Alternatively, still, the liner 110 may be formed in the stretched state in some arrangements.

As shown purely schematically in Figure 3, it may be the change in alignment and/or direction of the cross-linked polymers 112 under the application of the force A that generates the change in shape. Once the heat has been removed and/or the temperature of the liner 110 falls back under the transition temperature, it may remain in the deformed (or stretched) condition even if the deforming force A is removed.

The deformed liner 110 may then be inserted into the outer body 130 of the fluid conduit, as illustrated by way of example by the arrow B in the Figure 3 example. Without deforming the liner 110, it may not have been possible to insert it into the outer body 130, for example because the diameter of the undeformed liner 110 shown in Figure 2 may not have been small enough to fit within the outer body 130.

Figure 4 shows the deformed liner 110 placed inside the outer body 130. In order to line the outer body (or outer pipe/conduit) 130 so as to form the fluid conduit 100, heat may be provided to the deformed liner 110, for example to take it back above its transition temperature. Such heat may be provided in any suitable form. For example heat may be provided in the form of a fluid (for example a heated gas, such as air, or a heated liquid) passed along, over, around and/or through the liner 110. In the illustrative example of Figure 4, fluid is passed through the stretched liner tube 110 as indicated by arrow C.

Providing heat to the stretched liner 110 results in it returning (or at least trying to return) to its original, undeformed shape. This may be due to the cross-linked polymers 112 returning (or at least trying to return) to their original form. In the case of the tubular example shown in the Figures, this results in a reduction in the axial length and an increase in the cross-sectional shape, back towards the original shape illustrated by way of example in Figure 3.

The application of heat may therefore result in the liner 110 expanding (radially) to meet the inner surface of the outer body 130, thereby lining the outer body 130 to produce the lined fluid conduit 100, an example of which is shown in Figure 5. The liner 110 may be an interference fit in the outer body 130. The liner 110 may be expanded (radially, or more generally cross-sectionally) back to its original shape. Alternatively, the liner 110 may only be partially expanded back to its original shape before contacting, and thus being restrained by, the outer body 130. This may assist in holding the liner 110 in position, for example as an interference fit.

In some arrangements, the liner 110 may be held in the fluid conduit 100 (for example inside the outer body 130) using an adhesive. The adhesive may be a separate adhesive that is applied to the liner 110 and/or the outer body 130. Such an adhesive (which may be a two-part adhesive, for example) may be activated by heat. In such an arrangement, the heat may be provided in any suitable manner, for example the heat provided to the liner /tube 110 in order to return it to its original shape may also activate the adhesive. Alternatively, a separate heat source may be used. In some arrangements, the liner 110 may be held in position by virtue of a softening or melting of the liner 110 and/or the outer body through application of heat. When the heat is removed, the material may re-harden, thereby holding the liner 110 in position. In such an arrangement the liner 10 may be considered to be held in position by adhesive although no separate adhesive may be required.

Once the liner/tube 110 is located and/or fixed in position in the fluid conduit 100, the fluid conduit may be said to be lined. As described elsewhere herein, such a liner 110 may be advantageous in providing a smooth inner surface of the conduit through which the fluid may flow, resulting in minimal pressure losses in the flow (for example, reduced pressure losses compared with an unlined fluid conduit). Additionally or alternatively, the liner 110 may provide a fluid-tight lining. This, in turn, may allow a wider choice of materials for the outer body 130 of the pipe, for example materials that are lighter and/or stronger than would otherwise be necessary to ensure a fluid-tight conduit. Of course, any liner and/or tube 110 as described and/or claimed herein may be fluid-tight, and thus prevent fluid passing through the conduit 100 from escaping or leaking.

Figure 6 shows a further example of a fluid conduit 100, but in this example the fluid conduit 100 is formed in a rigid panel 200. Such a rigid panel 200 may be as described and/or claimed elsewhere, for example in relation to the gas turbine engine 10 shown in Figure 1. In the Figure 6 example, each fluid conduit 100 (of which there may be one, two, three, four, five or more than five, for example) is provided with a lining tube 110. The lining tubes 110 may be as described and/or claimed elsewhere herein, and may be inserted into position using the methods described and/or claimed elsewhere herein, for example in relation to Figures 2 to 5. Once again, providing the lining tubes 110 for the fluid conduits 100 may allow a wider choice of materials for the surrounding body 210 (which may be referred to as the rigid material of the panel 200). Purely by way of example, the surrounding body 210 may be an organic matrix composite, such as carbon fibre. Flowever, it will be appreciated that the material of the surrounding body 210 may be any material suitable for the particular application.

The rigid panel 200 in the example of Figure 6 is also provided with electrical conductors 310, although these may not be present in some examples. In the Figure 6 example, the electrical conductors 310 are provided in the form of a flexible printed circuit board, although they may be provided in any other desired form, such as sheathed or unsheathed wires.

Providing electrical conductors 310 means that the rigid panel 200 can provide at least a part of an electrical system, as well as at least a part of a fluid system (which may be provided by the fluid conduit(s) 100). This may be particularly beneficial if the rigid panel 200 is a rigid dressing panel arranged to provide dressings to a vehicle and/or component thereof, such as a gas turbine engine 10. A tube/liner 110 such as that described and/or claimed herein may be provided, for example, to a panel 200 or fluid conduit 100 of any shape. For example, the panel 200 or fluid conduit 100 may comprise a bend. Such a bend may be present before or after insertion of the liner 110. Where the bend is present before insertion of the liner 110, the liner 110 may be bendable upon insertion, for example by being held above its transition temperature.

The tube/liner 110 may be used as required for a fluid conduit. For example, a liner 110 may be provided during initial manufacture of a component including a fluid conduit 100. Additionally or alternatively, a tube/liner 110 such as that described and/or claimed herein may be provided to repair a fluid conduit 100, for example one in which a leak has developed. Furthermore, some examples of liner 110 may be removable from a fluid conduit 100, for example by reheating above the transition temperature, stretching along its longitudinal axis so as to reduce its diameter, and then withdrawing from the conduit 100. This may be considered to be the reverse of the operation described above for inserting a tube 110 into the fluid conduit 100.

It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. For example, the liner and/or tubes 110 may take any suitable shape, as may the fluid conduits 100. By way of further example, the rigid panels 200 and fluid conduits 100 may be used in any structure as desired, including but not limited to vehicles and/or gas turbine engines. By way of further example, the principle of using a heat shrink tubing to line a fluid conduit as described and/or claimed herein may be used to line (or cover) the outside of a component, such as conduit, for example in order to provide a fire-proof layer. This may involve sliding a heat-shrinkable tube over the component/fluid conduit, and then heating it so that its length increases and diameter decreases, thereby forming a barrier layer over the component. In such an arrangement, the heat-shrinkable tube may be compressed, thereby shortening its axial length and increasing its cross-section, prior to inserting it over the component/conduit. Of course, a fluid conduit may be provided both with a heat-shrinkable lining and a heat-shrinkable covering.

Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

Claims

1. A method of lining the internal surface of a fluid conduit (100) comprising: providing a heat-shrinkable tube (110) having a length along a longitudinal axis and defining a cross-section normal to the longitudinal axis; inserting (B) the tube into the conduit; and heating the tube inside the conduit so as to reduce its length and increase its cross-section such that the tube contacts and thereby lines the internal surface of the conduit.

2. A method of lining the internal surface of a fluid conduit according to claim 1, wherein the tube is a cross-linked polymer tube (112).

3. A method of lining the internal surface of a fluid conduit according to claim 1 or claim 2, further comprising stretching (A) the tube along its longitudinal axis so as to reduce its cross-section and increase its length before inserting the tube into the conduit, the reduced cross-section being small enough to enable the tube to be inserted into at least a part of the conduit.

4. A method of lining the internal surface of a fluid conduit according to claim 3, wherein the step of stretching the tube along its longitudinal axis comprises applying heat before and/or during stretching.

5. A method of lining the internal surface of a fluid conduit according to any one of the preceding claims, wherein the step of heating the tube inside the conduit so as to reduce its length and increase its cross-section comprises passing fluid (C) through the tube.

6. A method of lining the internal surface of a fluid conduit according to any one of the preceding claims, wherein the step of heating the tube inside the conduit so as to reduce its length and increase its cross-section comprises heating to above 100 degrees Celsius.

7. A method of lining the internal surface of a fluid conduit according to any one of the preceding claims, wherein the step of providing the heat-shrinkable tube comprises forming the tube on a mandrel and then removing the mandrel.

8. A method of lining the internal surface of a fluid conduit according to any one of the preceding claims, further comprising bonding the tube to the internal surface of the conduit.

9. A method of lining the internal surface of a fluid conduit according to claim 8, wherein the step of bonding the tube to the internal surface of the conduit comprises heating the internal surface of the conduit to a sufficient temperature to cause melting of the internal surface.

10. A method of lining the internal surface of a fluid conduit according to claim 9, wherein the heat required to heat the tube inside the conduit and the heat required to melt the internal surface of the conduit is from the same heat source.

11. A method of lining the internal surface of a fluid conduit according to any one of the preceding claims, wherein an outer portion (130) of the fluid conduit is formed using an organic matrix composite.

12. A method of lining the internal surface of a fluid conduit according to any one of the preceding claims, wherein the fluid conduit is formed in a panel (200) for use as a gas turbine engine dressing.

13. A method of lining the internal surface of a fluid conduit according to claim 12, wherein the panel further comprises at least a part of an electrical system (300) of a gas turbine engine, the electrical system optionally including at least one electrical conductor (310) embedded in the panel.

14. A fluid conduit (100) lined with a tube (110), the tube comprising a heat-shrinkable material, the heat shrinkable material optionally comprising cross-linked polymer structure (112).

15. A rigid panel (200) having a fluid conduit according to claim 14 formed therein.

16. A rigid panel according to claim 15, wherein: the rigid panel is a dressing panel for a gas turbine engine (10); and the fluid conduit is part of a fluid system of a gas turbine engine.

17. A rigid panel according to claim 15 or claim 16, further comprising at least one electrical conductor (310) embedded in the rigid material of the rigid panel.

18. A rigid fluid conduit according to claim 14 or a rigid panel according to any one of claims 15 to 17, wherein the heat-shrinkable material is a cross-linked polymer comprising polyetheretherketone and/or polytetrafluoroethylene and/or fluoroelastomer.

19. A fluid conduit according to claim 14 or a rigid panel according to any one of claims 15 to 18, wherein the tube lines a rigid material that comprises an organic matrix composite.

20. A gas turbine engine (10) comprising a rigid panel according to any one of claims 15 to 19, wherein the fluid conduit is part of a fluid system of the gas turbine engine, the fluid system optionally being one of a fuel system, an oil system, an air system or a water system.