GB2639558A

GB2639558A - Pipe fitting for bonded pipe joint

Info

Publication number: GB2639558A
Application number: GB2403286.4A
Authority: GB
Inventors: James Deacon Jonathan; John Peachey Daniel; James Cooper William; bryant Anthony
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2024-03-07
Filing date: 2024-03-07
Publication date: 2025-10-01
Also published as: GB202403286D0

Abstract

A pipe fitting 10 comprising: a body with an outer face 22, and an inner face 21 forming a socket 23 defining an axial direction; a pair of features 30, 31 which are located in the socket and spaced apart in the axial direction; an adhesive injection port 33 which passes through the body and opens into a space between the features 30, 31; and an exhaust port 34 which passes through the body and opens into the space between the features. Embodiments include: A pipe joint comprising an inner face 21 forming a socket with a stop feature 35; a first ring of adhesive bonding an end face of the pipe to the stop feature; a sleeve of adhesive bonding an outer face of the pipe to an inner face of the pipe fitting and a method of bonding a pipe to a pipe fitting comprising: applying a pair of rings of adhesive which cure to bond the pipe to the pipe fitting; and after the rings of adhesive have at least partially cured, injecting further adhesive into the socket between the rings of adhesive, wherein the further adhesive cures to further bond the pipe to the pipe fitting.

Description

PIPE FITTING FOR BONDED PIPE JOINT FIELD OF THE INVENTION

[0001] The present invention relates to a pipe fitting, a pipe joint, a method of manufacturing a pipe joint, and a method of bonding a pipe to a pipe fitting.

BACKGROUND OF THE INVENTION

[0002] In US 2012/0057267 Al, a pipe connector is disclosed, comprising two connector elements, arranged for interconnection of two pipes. One or both of the connector elements is formed from electrically resistive material so as to provide electrical resistance between the connected pipes.

[0003] Conductive fixing agent in the form of a conductive adhesive is used for bonding each connector element to a respective pipe. Concentricity between the connector element and its respective pipe is reliant on the connector element being assembled and held concentric with the pipe until the adhesive has cured.

SUMMARY OF THE INVENTION

[0004] A first aspect of the invention provides a pipe fitting comprising: a body with an outer face, and an inner face forming a socket defining an axial direction; a pair of features which are located in the socket and spaced apart in the axial direction; an adhesive injection port which passes through the body and opens into a space between the features; and an exhaust port which passes through the body and opens into the space between the features.

[0005] Optionally each feature comprises a protrusion or step.

[0006] Optionally each feature comprises a protrusion with a pair of sides which meet at an apex.

[0007] Optionally the body and the apex of each feature are formed from the same material.

[0008] Optionally a width of the protrusion, between the pair of sides, tapers inwardly towards the apex.

Optionally each protrusion comprises a ridge which runs around at least a major part of a circumference of the socket.

[0010] Optionally each protrusion has a triangular shape, when viewed in cross-section.

[0011] Optionally each feature comprises a frustoconical wall which faces a mouth of the socket.

[0012] Optionally each feature runs around a full circumference of the socket.

[0013] Optionally the body comprises a stop feature which is positioned behind the features and forms a boundary of the socket.

[0014] Optionally the body of the pipe fitting comprises a polymeric material [0015] Optionally the polymeric material is a thermoplastic polymeric material. [0016] Optionally the body and each feature are formed from the same material.

[0017] Optionally the body and each feature are formed as a single piece from the same material.

[0018] Optionally the adhesive injection port and the exhaust port are positioned on directly opposite sides of the socket [0019] Optionally an electrical resistance from end to end of the pipe fitting is greater than 50 kilo-ohms.

[0020] Optionally an electrical resistance from end to end of the pipe fitting is less than 5 mega-ohms.

[0021] Optionally the body comprises electrically conductive filler particles.

[0022] A further aspect of the invention provides pipe joint comprising: a pipe fitting according to the first aspect; a pipe received in the socket, wherein the pipe contacts the pipe fitting at each end of the space; and an adhesive in the space which bonds an outer face of the pipe to the inner face of the pipe fitting.

[0023] Optionally the pipe contacts each feature to form an interference fit at each end of the space.

Optionally the pipe comprises a pipe material; the body of the pipe fitting comprises a fitting material; and the fitting material has a higher electrical resistivity than the pipe material.

[0025] Optionally the pipe material comprises a metallic material.

100261 Optionally the pipe joint further comprises pipework coupled to the pipe fitting; and an electrically conductive member electrically connecting the pipe fitting to the pipework.

[0027] Optionally the adhesive in the space is electrically conductive.

100281 Optionally the adhesive in the space comprises electrically conductive filler particles.

100291 Optionally the pipe has an end face which is bonded to a stop feature of the pipe fitting by a ring of adhesive which is located outside the space.

[0030] Optionally the pipe joint further comprises a ring of adhesive bonding an end face of the pipe fitting to the outer face of the pipe, wherein the ring of adhesive is located outside the space.

[0031] Optionally the pipe joint is configured to carry fuel.

100321 Optionally the pipe is cylindrical with a substantially constant cross-section along its length.

100331 A further aspect of the invention provides an aircraft comprising a pipe joint according to the preceding aspect 1003,11 A further aspect of the invention provides a method of manufacturing the pipe joint, the method comprising: inserting the pipe into the socket; and injecting adhesive into the space via the adhesive injection port, wherein air escapes the space via the exhaust port as the adhesive is injected.

100351 Optionally adhesive escapes the space via the exhaust port after the space has filled with adhesive.

100361 Optionally the pipe contacts the pipe fitting to form an interference fit with the pipe fitting as the pipe is inserted.

Optionally the pipe contacts the features to form an interference fit with the features as the pipe is inserted.

[0038] Optionally the pipe and/or the pipe fitting deforms as the interference fit is formed.

[0039] Optionally the features deform as the interference fit is formed.

[0040] A further aspect of the invention provides a pipe joint comprising: a pipe fitting comprising: a body with an end face, and outer face, and an inner face forming a socket with a stop feature; a pipe received in the socket; a first ring of adhesive bonding an end face of the pipe to the stop feature; a sleeve of adhesive bonding an outer face of the pipe to an inner face of the pipe fitting; an adhesive injection port which passes through the body and is positioned in line with the sleeve of adhesive; an exhaust port which passes through the body and is positioned in line with the sleeve of adhesive; and a second ring of adhesive bonding an end face of the pipe fitting to the outer face of the OW.

10041 1 A further aspect of the invention provides a method of bonding a pipe to a pipe fitting, wherein the pipe is received in a socket of the pipe fitting, the method comprising: applying a pair of rings of adhesive which cure to bond the pipe to the pipe fitting; and after the rings of adhesive have at least partially cured, injecting further adhesive into the socket between the rings of adhesive, wherein the further adhesive cures to further bond the pipe to the pipe fitting.

[0042] Optionally the further adhesive has a higher electrical conductivity than the rings of adhesive.

[0043] Optionally the further adhesive has a different composition to the rings of adhesive.

[0044] Optionally the further adhesive cures more slowly than the rings of adhesive. BRIEF DESCRIPTION OF THE DRAWINGS [0045] Embodiments of the invention will now be described with reference to the accompanying drawings, in which: [0046] Figure 1 is a schematic view of an aircraft fuel system; Figure 2 is a cross-sectional view of a pipe connector; [0048] Figure 3 is an isometric view of a pipe assembly; [0049] Figure 4 is an isometric view-showing components of the pipe assembly of Figure 3; [0050] Figure 5 is an isometric view-of a pipe end fitting; [0051] Figure 6 is a cross-sectional view of the pipe end fitting of Figure 5; [0052] Figure 7 is an enlarged cross-sectional view showing a first ridge at a mouth of a socket; [0053] Figure 8 is an enlarged cross-sectional view showing a second ridge at the back of the socket; [0054] Figure 9 shows the cross-sectional profile of a step feature; [0055] Figure 10 is a cross-sectional view of the pipe fitting of Figure 5 with a first ring of adhesive applied before insertion of a pipe; [0056] Figure 11 is a cross-sectional view of the pipe fitting of Figure 5 with a pipe inserted, and two at least partially cured rings of adhesive; and [0057] Figure 12 is a cross-sectional view of a pipe joint showing the cured adhesive. DETAILED DESCRIPTION OF EMBODIMENT(S) [0058] An aircraft 1 shown in Figure 1 comprises a pair of wings faked into a fuselage. Each wing carries an engine and an internally located fuel tank 2. The fuel tanks are connected to the engines by a set of metallic fuel lines or pipes. The metallic fuel pipes are constructed from a series of lengths of pipe jointed using pipe connectors 4.

[0059] Figure 2 shows an exemplary pipe connector 4 which comprises a pipe end fitting 10 and a split part adapter 11. The pipe fitting 10 is bonded to a pipe 12 by a hybrid single-lap joint. The split part adapter has a large socket 13 which receives the pipe fitting 10, and a flange 14 which is fastened to a mating connector (not shown) with an 0-ring between them. The mating connector is connected to a second pipe (not shown). A conductive 0-ring 15 provides a fluid-tight seal between the cylindrical wall of the large socket 13 and the pipe fitting 10.

Figure 3 shows a pipe assembly 16 comprising the pipe 12 with a pipe fitting 10 bonded to the pipe 12 at each end; and Figure 4 shows the two pipe fittings 10 before they have been bonded to the pipe 12. The two pipe fittings 10 are identical.

[0061] As shown in Figure 4, the pipe 12 is cylindrical with a substantially constant cross-section along its length, and is typically formed by extrusion.

[0062] Referring to Figure 6, the pipe fitting 10 comprises a generally cylindrical body with an inner face 21 and an outer face 22. The inner face 21 forms a socket 23 defining an axial direction 26. The socket 23 has a mouth 24 surrounded by an end face 25 of the pipe fitting 10 as shown in Figure 7.

[0063] A pair of annular ridges 30, 31 are located in the socket 23 and spaced apart in the axial direction 26. These ridges 30, 31 provide a pair of opposed walls which are spaced apart in the axial direction 26, with an open space 32 between them.

[0064] An adhesive injection port 33 passes through the body 20 (from the inner face 21 to the outer face 22) and opens into the space 32 between the ridges 30, 31. An exhaust port 34 passes through the body 20 (from the inner face 21 to the outer face 22) and also opens into the space 32 between the ridges 30, 31. The adhesive injection port 33 and the exhaust port 34 are positioned on directly opposite sides of the socket 23.

[0065] The inner face 21 is formed with a stop feature 35 (in this case a planar annular step) which is positioned behind the ridges 30, 31 in the axial direction 26 and forms a rear boundary of the socket 23.

[0066] At the other end of the pipe fitting 10, a pair of flanges are provided with a recess which receives the 0-ring 15.

[0067] In a first manufacturing step, the mating surfaces of the pipe fitting 10 and pipe 12 are cleaned and abraided.

[0068] Next, a first ring 40 of adhesive is applied to the stop feature 35 outside the space 32 as shown in Figure 10.

[0069] While the first ring 40 of adhesive is still wet, the cylindrical end of the pipe 12 is inserted into the socket 23 in the axial direction 26 until the planar end face of the pipe 12 contacts the first ring 40 of adhesive as shown in Figure 11. Insertion of the pipe 12 into the socket 23 may he performed by moving the pipe 12 and/or by moving ] ] ] fitting 10 (Le. pushing the pipe fitting 10 onto the pipe 12). Most typically the pipe 12 is inserted by pushing the pipe fitting 10 onto the pipe 12, with the pipe 12 remaining stationary.

[0070] The stop feature 35 and first ring 40 of adhesive provide a stop for the planar end face of the pipe 12 to butt up against during insertion of the pipe 12. Any internal spew from the first ring 40 of adhesive which has been squeezed out by the end of the pipe 12 is then wiped away, and a second ring 41 of adhesive is applied as shown in Figure 11. The second ring 41 of adhesive has a fillet cross-section with one side of the fillet contacting the planar end face 25 of the pipe fitting 10 and another side of the fillet contacting the cylindrical outer surface of the pipe 12. The second ring 41 of adhesive provides corrosion protection by preventing ingress of contaminants into the socket 23.

[00711 The same adhesive may be used for both rings 40, 41 of adhesive, and preferably the adhesive has a quick cure time -for instance about 20 minutes. By way of example the adhesive may be a two-part epoxy.

[0072] After curing, the first ring 40 of adhesive bonds the planar end face of the pipe 12 to the planar stop feature 35, and the second ring 41 of adhesive bonds the planar end face 25 of the pipe fitting 10 to the cylindrical outer face of the pipe 12.

[0073] Once the first and second rings 40, 41 of adhesive have at least partially cured, a further adhesive (typically a conductive adhesive) is injected via the adhesive injection port 33 into the space 32 between the first and second rings 40, 41 of adhesive. The conductive adhesive flows in both directions and displaces air which escapes the space 32 via the exhaust port 34. After the space 32 has filled with conductive adhesive, excess conductive adhesive escapes the space 32 via the exhaust port 34. When this excess conductive adhesive is witnessed at the exhaust port 34, signalling a full adhesive bond, the injection process is stopped.

[00741 Positioning the adhesive injection port 33 and the exhaust port 34 on directly opposite sides of the socket 23 ensures that the space 32 fills completely with adhesive and avoids air bubbles.

[0075] The conductive adhesive then cures to form a cylindrical sleeve 42 of adhesive shown in Figure 12. The sleeve 42 bonds the outer face of the pipe 12 to the inner face 21 of the pipe fitting 10. The adhesive injection port 33 is positioned in line with the cal sleeve 42 of adhesive and may contain a first stub 43 of adhesive protruding from the cylindrical sleeve 42. Similarly the exhaust port 34 is positioned in line with the cylindrical sleeve 42 of adhesive and may contain a second stub 44 of adhesive protruding from the cylindrical sleeve 42.

[0076] Each ring 40, 41 of adhesive is located outside the space 32. In this example there is no contact between the cylindrical sleeve 42 of adhesive and the rings 40, 41 of adhesive.

[0077] Note that the adhesive 40, 41, 42 is shown in Figure 12, but omitted in Figure 2 for purposes of clarity.

[0078] The conductive adhesive forming the sleeve 42 may cure more slowly than the quick-cure adhesive which is used to form the rings 40, 41 of adhesive, due to its different composition. For instance the conductive adhesive may have a cure time of at least 24 hours. By way of example the conductive adhesive may be a two-part epoxy mixed with electrically conductive filler particles such as nickel particles, aluminium beads or carbon particles. Alternatively the same adhesive may be used throughout the joint [0079[ As shown in Figures 7 and 8, each ridge 30, 31 has a pair of sides 30a,h; 31a,b which meet at an apex 30c, 31c, one of the sides 30b, 31a forming a wall which bounds the space 32 between the ridges 30, 31. Before the pipe 12 is inserted, the outer diameter of the end of the pipe 12 is slightly greater than the inner diameter of the socket 23 (at the apex of each ridge).

[0080[ Figure 7 shows the interference distance D between the outer diameter of the pipe 12 and the inner diameter of the socket 23 (defined by the apexes 30c, 31c). This interference distance D is typically less than 0.3mm.

[00811 Hence the pipe 12 contacts the ridges 30, 31 to form an interference fit with the pipe fitting 10 at each end of the space 32 as the pipe 12 is inserted. The end of the pipe 12 contacts a left-facing side 30a, 31a of the ridge, then the ridge 30, 31 deforms as the pipe 12 is inserted further and the interference fit is formed with the cylindrical outer face of the pipe 12 as shown in Figure 11.

] This contact between the pipe 12 and the ridges 30, 31 ensures concentricity between the pipe 12 and the pipe fitting 10 as the pipe 12 is inserted.

[0083] The width of each ridge 30, 31, between the pair of sides, tapers inwardly towards the apex 30e, 31e, so that the apex is relatively narrow relative to the base of the ridge. This minimises the contact area, and enables each ridge 30, 31 to deform easily to accommodate the pipe 12.

[0084] The left-facing side 30a, 31a of each ridge provides a frustoconical wall which faces the mouth 24 of the socket 23 and is contacted by the end of the pipe 12 during insertion. The oblique angle of this frustoconical wall 30a, 31 a provides a lead-in which enables the pipe 12 to he inserted relatively easily.

[0085] In this example each ridge 30, 31 has a triangular shape, when viewed in cross-section as in Figures 7 and 8, the pair of sides of the triangle having the same length. Alternatively each ridge may have another cross-sectional shape such as a semi-circle, or a trapezoid with a pair of sides which meet at an apex which is flat when viewed in cross-section.

[0086] In this example, each side 30a,b; 31a,b of each ridge is frustoconical (and hence appears as an oblique straight line in the cross-sectional views of Figures 7 and 8).

[0087] The pipe assembly 16 of Figure 3 has an electrical resistance from end to end which is tailored to be sufficiently low to permit electrostatic discharge (that is, dissipating or conducting static electrical charges) whilst also being sufficiently high to prevent high currents from flowing during a lightning strike.

[0088] Hence preferably the electrical resistance between the two ends of the pipe assembly 16 is less than 10 mega-ohms or less than 1 mega-ohms; and greater than 100 kilo-ohms or greater than 200 kilo-ohms or greater than 500 kilo-ohms.

[0089] In a preferred embodiment the electrical resistance between the two ends of the pipe assembly 16 is within the range of 500 kilo-ohms to 1 mega-ohms.

[0090] An electrically conductive member is also required at each end of the pipe assembly 16 to electrically connect the pipe fitting 10 to the adjacent pipework.

[0091] In this example, the electrically conductive member is provided by making the 0-ring 15 electrically conductive, but in other embodiments the electrically conductive r may he a bonding lead which electrically connects the pipe fitting 10 to the split part adapter 11, or to another part of the adjacent pipework such as the second pipe (not shown).

[0092] The 0-ring 15 is electrically conductive and resiliently flexible, and formed from a single homogenous seal material. The seal material comprises an elastomeric material mixed with a fill material. The fill material has a higher electrical conductivity than the elastomeric material. The elastomeric material may be, for example a fluorosilicone, nitrile or VitonTM. A variety of fill materials may be used, including carbon (for instance carbon black or carbon nanotuhes) or metallic fill materials such as silver or nickel. The elastomeric material makes the seal resiliently flexible, and the fill material makes it electrically conductive. Preferably, the fill material is a particulate fill material. In another embodiment the seal material comprises a thermoplastic material.

[0093] Further details of the 0-ring 15 can be found in US2021/388924 Al, the contents of which are incorporated herein by reference.

[0094] Electrical continuity between the pipe 12 and the pipe fitting 10 is achieved by the use of conductive adhesive for the cylindrical sleeve 42 of adhesive, which bonds the outer face of the pipe 12 to the inner face 21 of the pipe fitting 10. This conductive adhesive has a higher electrical conductivity than the adhesive used for the rings 40, 41.

[0095] The electrical resistance between the two ends of the pipe assembly 16 may be introduced by fabricating the pipe 12 from an electrically resistant pipe material. However such materials can be expensive and/or difficult to extrude so more preferably the pipe 12 comprises a metallic pipe material such as Aluminium. Hence the electrical resistance between the two ends of the pipe assembly 16 is instead introduced by fabricating the pipe fitting 10 from an electrically resistant fitting material. So the body 20 of the pipe fitting 10 comprises a fitting material; and the fitting material has a higher electrical resistivity than the pipe material. In this case the fitting material is a resistive material arranged to provide the pipe fitting 10 with a predetermined degree of electrical resistance.

[0096] In one embodiment, the fitting material is a polymeric material mixed with electrically conductive filler particles such as carbon black, graphite, short carbon Jarbon nanotubes, or a metallic powder such as silver or nickel. The type and proportion of the conductive filler determines the resistivity of the fitting material.

[0097] By way of example, the polymeric material may comprise a thermoplastic polymer such as polyether ether ketone (PEEK), Nylon or polyphenylene sulfide (PPS).

[0098] The pipe fitting 10 may he formed by injection moulding, or by machining from a billet. In either case, all parts of the pipe fitting 10 (including the body 20 and each ridge 30, 31 all the way to its apex) arc formed as a single piece from the same material.

[0099] To achieve the total end to end resistance values mentioned above for the pipe assembly 16, the individual resistance of each pipe fitting 10 should be halved. Hence preferably the electrical resistance from end to end of the pipe fitting 10 is less than 5 mega-ohms or less than 500 kilo-ohms; and greater than 50 kilo-ohms or greater than 100 kilo-ohms or greater than 250 kilo-ohms [0100] In a preferred embodiment the electrical resistance from end to end of the pipe fitting 10 is within the range of 250 kilo-ohms to 500 kilo-ohms.

[0101] In the embodiments above, each ridge 30, 31 is a closed ring which runs around a full circumference of the socket 23. Hence each ridge forms a seal around the full circumference of the pipe 12 and completely seals off a respective end of the space 32, providing a barrier which impedes the conductive adhesive from escaping at either end of the space 32 during injection.

[0102] Even if this seal fails, the at least partially cured first or second ring 40, 41 of adhesive provides a second barrier which impedes any further escape of the conductive adhesive.

[0103] The conductive adhesive is injected after the rings 40, 41 of adhesive have at least partially cured. Before the conductive adhesive is injected, the rings 40, 41 of adhesive need to be sufficiently cured to enable them to provide an effective barrier without substantial mixing with the conductive adhesive.

[0104] Optionally a second 0-ring may be fitted in a space 36, shown in Figure 8, between the ridge 31 and the stop feature 35 to provide yet a further barrier.

[0105] In other embodiments, one or both ridges 30, 31 may have a gap so that the ridge only runs around a major part of the circumference of the socket 23. In such cases the Live adhesive will he able to escape through the gap but prevented from escaping any further by the first or second ring 40, 41 of adhesive.

[0106] In summary, the pipe fitting 10 has a pair of surface features, formed in the inner surface 21 of the body, which can engage with the pipe 12 in the socket to ensure concentricity. In the embodiments above, the surface features are a pair of ridges 30, 31 located in the socket 23 and spaced apart in the axial direction 26, and the space 32 is located between the ridges 30, 31. These ridges 30, 31 solve the "concentricity" problem by contacting the cylindrical outer surface of the pipe 12. In other embodiments, the ridges 30, 31 may be replaced with other surface features in the socket which solve the "concentricity" problem in a similar way.

[0107] For instance one or each ridge 30, 31 may be replaced by another type of protrusion, such as three or more semi-spherical domed pins which are distributed around the circumference of the socket 23. In this case the gaps between the pins will permit the conductive adhesive to escape the space 32, but any further escape will be prevented by the first or second ring 40, 41 of adhesive.

101081 Alternatively one or each ridge 30, 31 may he replaced by a step 50 as shown in Figure 9. In this case the interference fit is formed with a cylindrical face 51 of the step 50, rather than an apex of a ridge, pin or other type of protrusion. Like the ridge 31 it replaces, the step 50 has a frustoconical wall 52 which faces the mouth 24 of the socket 23 and provides a lead-in which enables the pipe 12 to be inserted relatively easily. A protrusion (such as a ridge or pin) is generally more preferred than the step 50 because a protrusion will deform more easily during insertion of the pipe 12. However, the step 50 of Figure 9 is easier to injection-mould due to the omission of the space 36.

[0109] In the embodiments above the electrical resistance between the two ends of the pipe assembly 16 is introduced by fabricating each pipe fitting 10 from an electrically resistant fitting material. In an alternative embodiment, the electrical resistance between the two ends of the pipe assembly 16 may instead be introduced by fabricating the pipe 12 from an electrically resistant pipe material, such as a composite material. In this case each pipe fitting 10 may be made from an electrically conductive material such as steel.

Where the word 'or' appears this is to he construed to mean 'and/or' such that items referred to are not necessarily mutually exclusive and may be used in any appropriate combination.

[0111] Although the invention has been described above with reference to one or more preferred embodiments, it will he appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1 A pipe fitting comprising: a body with an outer face, and an inner face forming a socket defining an axial direction; a pair of features which are located in the socket and spaced apart in the axial direction; an adhesive injection port which passes through the body and opens into a space between the features; and an exhaust port which passes through the body and opens into the space between the features.
2. A pipe fitting according to claim 1, wherein each feature comprises a protrusion or step.
3. A pipe fitting according to any preceding claim, wherein each feature comprises a protrusion- 4. A pipe fitting according to claim 3, wherein each protrusion has a pair of sides which meet at an apex 5. A pipe fitting according to claim 3 or 4, wherein a width of each protrusion, between the pair of sides, tapers inwardly towards the apex.6. A pipe fitting according to any of claims 3 to 5, wherein each protrusion comprises a ridge which runs around at least a major part of a circumference of the socket.7. A pipe fitting according to any preceding claim, wherein each feature comprises a frustoconical wall which faces a mouth of the socket.8. A pipe fitting according to any preceding claim, wherein each feature runs around a full circumference of the socket.9. A pipe fitting according to any preceding claim, wherein the body comprises a stop feature which is positioned behind the features and forms a boundary of the socket.10. A pipe fitting according to any preceding claim, wherein the body and each feature are formed as a single piece from the same material.11. A pipe fitting according to any preceding claim, wherein an electrical resistance from end to end of the pipe fitting is greater than 50 kilo-ohms.12. A pipe fitting according to any preceding claim, wherein an electrical resistance from end to end of the pipe fitting is less than 5 mega-ohms.13. A pipe joint comprising: a pipe fitting according to any preceding claim; a pipe received in the socket, wherein the pipe contacts the pipe fitting at each end of the space; and an adhesive in the space which bonds an outer face of the pipe to the inner face of the pipe fitting.14. A pipe joint according to claim 13, wherein the pipe contacts each feature to form an interference fit at each end of the space.15. A pipe joint according to claim 13 or 14, wherein the pipe is cylindrical with a substantially constant cross-section along its length.16. A pipe joint according to any of claims 13 to 15, further comprising pipework coupled to the pipe fitting; and an electrically conductive member electrically connecting the pipe fitting to the pipework.17. A pipe joint according to any of claims 13 to 16, wherein the pipe has an end face which is bonded to a stop feature of the pipe fitting by a ring of adhesive which is located outside the space.18. A pipe joint according to any of claims 13 to 17, further comprising a ring of adhesive bonding an end face of the pipe fitting to an outer face of the pipe, wherein the ring of adhesive is located outside the space.19. An aircraft comprising a pipe joint according to any of claims 13 to 18.20. A method of manufacturing the pipe joint of any of claims 13 to 18, the method comprising: inserting the pipe into the socket; and injecting adhesive into the space via the adhesive injection port, wherein air escapes the space via the exhaust port as the adhesive is injected.21. A method according to claim 20, wherein the features deform as the interference fit is formed.21 A pipe joint comprising: a pipe fitting comprising: a body with an end face, and outer face, and an inner face forming a socket with a stop feature; a pipe received in the socket; a first ring of adhesive bonding an end face of the pipe to the stop feature; a sleeve of adhesive bonding an outer face of the pipe to an inner face of the pipe fitting; an adhesive injection port which passes through the body and is positioned in line with the sleeve of adhesive; an exhaust port which passes through the body and is positioned in line with the sleeve of adhesive; and a second ring of adhesive bonding an end face of the pipe fitting to the outer face of the pipe.21 A method of bonding a pipe to a pipe fitting, wherein the pipe is received in a socket of the pipe fitting, the method comprising: applying a pair of rings of adhesive which cure to bond the pipe to the pipe fitting; and after the rings of adhesive have at least partially cured, injecting further adhesive into the socket between the rings of adhesive, wherein the further adhesive cures to further bond the pipe to the pipe fitting.24. A method according to claim 23, wherein the further adhesive has a higher electrical conductivity than the rings of adhesive.25. A method according to claim 23 or 24, wherein the further adhesive cures more slowly than the rings of adhesive.