WO2013108036A2

WO2013108036A2 - Apparatus and method for surface treating a pipe

Info

Publication number: WO2013108036A2
Application number: PCT/GB2013/050108
Authority: WO
Inventors: Ian Guthrie
Original assignee: Gemini Corrosion Services Limited
Priority date: 2012-01-18
Filing date: 2013-01-18
Publication date: 2013-07-25
Also published as: EP2805095A2; GB201200806D0; WO2013108036A3

Abstract

A surface treatment apparatus and method are disclosed for treating the inside surface of a pipe (44), for example by applying a metal coating, the apparatus comprising a treatment head (10) mounted on a boom (32) for insertion into the pipe. The apparatus is suitable for insertion into a riser pipe for an oil or gas well, and preferably comprises an arc wire spraying gun.

Description

APPARATUS AND METHOD FOR SURFACE TREATING A PIPE

[001] The present invention relates to a surface treatment apparatus and method for treating the inside surface of a pipe, for example a surface treatment apparatus and method for coating the inside surface of a pipe for protection against sour gas damage.

[002] Crude oil and natural gas are considered "sour" if they contain significant amounts of hydrogen sulphide (H₂S) . For example, natural gas is usually considered "sour" if it contains more than 4ppm by volume of H₂S per cubic metre.

[003] Hydrogen sulphide in the presence of water damages piping by sulphide stress cracking. Certain alloys, in particular steels, react with H₂S to form metal sulphides and atomic hydrogen as corrosion byproducts. The atomic hydrogen can recombine on the metal surface to form H₂, or diffuse into the metal matrix.

[004] At high temperatures and high partial pressures hydrogen can diffuse into carbon steel alloys. The hydrogen combines with carbon within the alloy to form methane. The methane creates a pressure build-up within the metal matrix, which can lead to embrittlement and cracking of the pipe.

[005] A widely employed method for providing protection against sour gas damage is to insert either one or a series of liner pipes, normally stainless steel, inside the carbon steel pipe. However, this is an extremely expensive method. For example, the normal construction method for a riser pipe is to weld together pipe sections having machined ends and then pressure test the completed pipe. However, this process must be interrupted if a protective liner pipe is to be inserted, to allow for the insertion, vacuum evacuation, welding and sealing of the liner pipe before final assembly can take place.

[006] The present invention seeks to provide an apparatus and method for treating the inside surface of a pipe, for example for applying a coating to the inside surface of a pipe for protection against sour gas damage without the need for protective liner pipes. [007] Thus, according to the present invention in a first aspect there is provided surface treatment apparatus for treating the inside surface of a pipe, the apparatus comprising a treatment head mounted on a boom for insertion into the pipe.

[008] The apparatus of the present invention can preferably be inserted into a pipe, for example a riser pipe for an oil or gas well, having a diameter as small as 150mm. A typical section of riser pipe is approximately 12.2m long.

[009] The apparatus of the present invention comprises a treatment head. The treatment head preferably comprises an arc wire spraying gun, for applying a coating to the inside surface of a pipe. Arc wire spraying is a known form of thermal spraying in which two consumable metal wires which form the coating are fed independently into a spray gun. The wires are electrically oppositely charged and an arc is generated between them. The heat from the arc melts the wire, and compressed air is used to project the molten particles onto the substrate to coat the substrate.

[0010] The arc wire spraying gun is thus preferably used to apply a metal coating to the inside of the pipe, for example a metal alloy coating, such as a nickel chromium coating. [0011] The arc wire spraying gun is preferably removable, and replaceable with a different treatment head, for example a flame spraying gun. In preferred embodiments, the apparatus of the present invention may thus comprise an arc wire spraying gun for coating the inside of a pipe with a first coating by arc wire spraying, which may be interchanged with a flame spraying gun, for example for applying a second coating to the inside of the pipe by flame spraying. However, the apparatus of the present invention may comprise other interchangable treatment heads, such as blast equipment for pipe preparation, other thermal spray guns, sealant guns, and so forth.

[0012] The apparatus of the present invention may thus preferably further comprise a flame spraying gun. Flame spraying is another known form of thermal spraying in which a wire forming the coating is continuously fed through the centre of an oxy-fuel torch, where molten particles from the tip of the gun are projected onto the substrate by the flame gasses.

[0013] The flame spraying gun may be used to apply a polymer layer to the inside surface of the pipe, for example a polymer sealing layer applied over a first coating, such as a nickel chromium coating. For example, the polymer sealing layer may comprise a polyaryletherketone .

[0014] Polyaryletherketones are a family of semi-crystalline thermoplastic polymers having high heat, chemical and wear resistance. They are characterised in having phenylene rings (-C₆H₄-) linked via oxygen bridges in the form of ether and carbonyl (ketone) groups. Different ratios of ether to ketone groups affect the physical properties of the polymer, such as glass transition temperature and melting point. Polymers in this family include polyetherketone (PEK), polyetheretherketone (PEEK), and polyetherketoneketone (PEKK) .

[0015] The apparatus of the present invention is for use in an enclosed environment (i.e. inside a pipe) in which the temperature (for example, from molten metal particles) can reach 400 to 500°C. Accordingly, the treatment head is preferably thermally and/or electrically insulated, for example by comprising a thermally and/or electrically insulating casing.

[0016] As discussed above, the apparatus of the present invention preferably comprises a removable arc wire spraying gun. As is understood by persons skilled in the art, an arc wire spraying gun typically comprises wire feeds for feeding metal wires, which will form the coating, to a melting zone; electrode members for electrically oppositely charging the wires to thus generate an arc between the wires, the heat from which melts the wires in the melting zone; and a compressed air supply for supplying compressed air into melting zone to thus project the molten metal particles onto the substrate to coat the substrate.

[0017] In the preferred apparatus of the present invention, the arc wire spraying gun preferably comprises a wire feeder for each wire, for feeding the wires to the melting zone, the wire feeders being independent of each other. Thus, the wire feeders may for example work from independent springs so they can be individually altered. In this way the pressure applied to the wires by the feeders can be independently regulated to help ensure equal feeding of each wire. If a single feeder is used to feed more than one wire to the melting zone, then mis-feeds can occur, for example due to minor wear and misalignment with drive feed wheels or minor wire imperfections, such as kinks, which might eventually cause the arc wire spraying gun to stall due to wire feed not being equal from each side.

[0018] In a conventional arc wire spraying gun, the wires are typically fed into the gun along substantially parallel tracks and are then gradually angled together by guide means within the gun so as to contact in the melting zone for an arc to form between the wires. [0019] The apparatus of the present invention preferably comprises an arc wire spraying gun for applying a metal coating to the inside surface of a pipe having a longitudinal axis. The metal wires, electrical supply cables, and means for supplying compressed air must thus pass along the pipe, i.e. substantially along its longitudinal axis (as described in more detail below), into the arc wire spraying gun. A preferred embodiment of the apparatus of the present invention is adapted so that the molten metal is sprayed from the gun radially from the longitudinal axis of the pipe onto the inside surface (circumference) of the pipe. Preferably, the arc wire spraying gun head is angled from 30 to 60° to the longitudinal axis, more preferably approximately 45°. In these embodiments, the wires are preferably fed within the gun both towards each other so as to make contact and actuate in the melting zone, and away from the longitudinal axis of the pipe, preferably through an angle of 30 to 60° to the longitudinal axis, more preferably approximately 45° as described, towards the arc wire spraying gun head. This multi-angled wire feed is preferably achieved using independent wire feeders, as described above.

[0020] The apparatus of the present invention is for treating the inside surface of a pipe, and comprises a treatment head mounted on boom for insertion into the pipe. To cater for various pipe diameters, the boom height can preferably be automatically adjusted, for example by motors attached to boom supports. The boom position may be communicated to an operator by means of a digital readout that ensures accuracy when repeating non-continuous work.

[0021] The boom is preferably telescopic allowing for treatment of the inside surface of a pipe along the length of the pipe, and for the treatment of different pipes of various lengths. The boom preferably comprises multiple lengths of reducing diameter sections that slide into one another. The section having the smallest diameter should preferably have a diameter which is sufficiently large to house the required supply systems (for example, metal wires, electrical supply cables, means for supplying compressed air) . This section of the boom preferably has a smaller cross sectional area than treatment head so that the boom does not extend beyond the treatment head.

[0022] An advantage of a telescopic boom is that the external surface of a pipe can be treated, for example if the pipe is capped at each end maintaining internal surface integrity, by simply retracting the boom so that it does not interfere with the operation. This means that separate apparatuses for external and internal surface treatments are not required.

[0023] Each telescopic boom section preferably incorporates a support roller ball assembly at the end of each section. If the boom is to enter into a pipe then the weight of the boom is distributed across the boom supports. As the boom extends into the pipe the bending moment experienced at the end of the boom increases, which can result in the treatment head at the end of the boom beginning to sag/bend downwards, which alters the angle between the treatment head and the inner surface of the pipe. This can result in the optimum treatment angle not being achieved. The roller ball assemblies effectively transfer the weight of the boom from the boom supports to the roller ball assemblies within the pipe. When the boom is withdrawn, the opposite occurs and the roller balls transfer the weight distribution from inside of the pipe back to the boom supports.

[0024] The apparatus of the present invention preferably further comprises moving means, for moving a pipe around the treatment head. For example, the pipe may be track and/or roller driven. Thus, preferred embodiments allow for the pipe to be rotated about and/or moved along the treatment head, and for the treatment head to move longitudinally inside the pipe along the length of the pipe to treat the inside surfaces. Rotating the pipe around the treatment head helps to ensure process repeatability, as gravity then has no effect on the surface treatment, for example the projection of energised particles. [0025] The apparatus of the present invention is preferably controlled by a programmable logic controller (PLC) . For example, in preferred embodiments a PLC may control the speed of movement of the movement means, and the speed of operation of the treatment head, such as the rate at which molten metal particles are deposited on the inside surface of the pipe from an arc wire spraying gun. As all of these variables can be adjusted prior to processing and then kept constant, and surface treatment can be kept uniform across the length of the pipe, and may be repeatable across multiple lengths with identical levels of accuracy.

[0026] Thus, in preferred embodiments of the apparatus of the present invention, the movement means and treatment head are preferably integrated into a fully automated unit that has a single point of control. Thus, for the repetitive treatment of multiple identical pipes, preferred apparatus can be set up and then left to run/monitored, only requiring a change of pipe and re-start at the end of each operation. [0027] The apparatus of the present invention may further comprise extraction means, for extracting unwanted particles and from inside of the pipe. A preferred extraction means uses a "push-pull" system. Thus, in those preferred embodiments which comprise an arc wire spraying gun, compressed air is used to project molten metal particles onto the inside surface of the pipe. Once passed the application point, the excess air effectively pushes the unwanted particles down the pipe. To compliment this extraction, an extraction tube fed by an extraction unit may be connected to the opposite end of the pipe to which the boom enters the pipe. In this way, the tube can create an air-tight seal at that end of the pipe such that there is substantially no pressure loss as would be experienced with an open system, and an enhanced extraction rate is achieved. The extraction means may comprise an integrated valve, which allows the extraction rate to be altered, which is dependent on factors such as the inner diameter of the pipe.

[0028] Whilst the apparatus of the present invention has particular utility for applying a protective coating to a pipe for protection against sour gas damage, and is preferably used for coating a riser pipe for an oil or gas well, for example a nickel chromium coating, it is not so limited and may be used to treat the surfaces of pipes for other applications.

[0029] The present invention also provides in a second aspect a method of treating the inside surface of a pipe by inserting a treatment head on a boom into the pipe. [0030] The method of the second aspect of the present invention preferably employs the apparatus of the first aspect of the present invention. Thus, the apparatus of the present invention can preferably be inserted into the pipe, for example a riser pipe for an oil or gas well, and for example coating the inside of the pipe by arc wire spraying. As noted above, the apparatus of the present invention may be used to coat pipes having a diameter as small as 150mm. [0031] A preferred surface treatment applied by the method of the present invention is the application of a metal coating, such as a metal alloy coating, and more preferably a nickel chromium coating. [0032] The coating may be applied to the inside surface of the pipe to any suitable thickness. Thus, the coating may be between 50 and ΙΟΟΟμιη, for example between 100 and 500μηι, preferably from between 150 and 250μηι thick. [0033] In the method of the present invention, the pipe is preferably moved about the treatment head. Thus, in preferred embodiments the pipe is rotated about and/or moved along the treatment head. The treatment head may move longitudinally inside the pipe along the length of the pipe to treat the inside surfaces. Rotating the pipe around the treatment head helps to ensure process repeatability, as gravity then has no effect on the surface treatment, for example the projection of energised particles. The pipe may be placed onto rollers and/or a track, which may be controlled by a PLC.

[0034] The molten particles are preferably sprayed onto the inside of the pipe using compressed air or nitrogen. [0035] The method of the present invention preferably provides an inner surface corrosion barrier to the pipe. The method of the present invention may further comprise applying a sealing layer over the coating, to provide additional protection. For example, in particularly hostile subsea sour environments, a sealing layer may be advisable to reduce increases in the porosity of the coating.

[0036] A preferred sealing layer material is a polyaryletherketone, for high heat, chemical and wear resistance.

[0037] The sealing layer is preferably be applied by flame spraying. For example, in a preferred method of the present invention using the apparatus of the first aspect of the present invention, an arc wire spaying gun is changed for a flame spraying gun to apply the sealing layer.

[0038] The method of the present invention may further comprise extracting unwanted particles from inside of the pipe. A preferred extraction process uses a "push-pull" system. In these preferred embodiments, compressed air is used to project molten metal particles onto the inside surface of the pipe. Once passed the application point, the excess air effectively pushes the unwanted particles down the pipe. To compliment this extraction, an extraction tube fed by an extraction unit may be connected to the opposite end of the pipe to which the boom enters the pipe. In this way, the tube can create an air-tight seal at that end of the pipe such that there is substantially no pressure loss as would be experienced with an open system, and an enhanced extraction rate is achieved. The extraction means may comprise an integrated valve, which allows the extraction rate to be altered, which is dependent on factors such as the inner diameter of the pipe. [0039] The present invention further provides in a third aspect a coating composition for coating a pipe, the coating composition comprising a nickel chromium alloy. [0040] The coating composition may further comprise a sealing layer comprising a polyaryletherketone .

[0041] The present invention still further provides in a fourth aspect a pipe which has either been treated using the apparatus of the first aspect of the present invention, or by the method of the second aspect of the present invention, or with the coating composition of the third aspect of the present invention. [0042] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 shows a view of an arc wire spraying gun for use in preferred apparatus of the present invention;

Figures 2 and 3 show reverse angle views of the gun of Figure 1 with the casing removed; Figure 4 shows preferred apparatus of the present invention incorporating a gun shown in Figures 1 to 3; and

Figure 5 shows a simplified view of apparatus of the present invention being positioned into a pipe.

[0043] Thus, Figure 1 shows an arc wire spraying gun 10 for use in the apparatus of the present invention. The gun comprises a casing 12 which is thermally and electrically insulating, and impact-proof. Also shown in Figure 1 are wire feeder clamps 14 for clamping wire feeders onto the wires (not shown in Figure 1), first wire inlet 16 through which the wire (not shown in Figure 1) enters the gun, positive power feed 18, and spraying gun application guide 20 from which the molten metal particles are projected onto the inner surface of a pipe (not shown in Figure 1) .

[0044] In preferred embodiments of the present invention, the molten metal particles are sprayed from the gun 10 radially from the longitudinal axis of the pipe onto the inside surface (circumference) of the pipe. Preferably, the arc wire spraying gun head is angled from 30 to 60° to the longitudinal axis, more preferably approximately 45°, as shown in Figure 1 by the angle Θ (the "application angle") . The longitudinal axis of the pipe is shown by the general direction A, and the molten metal particles are sprayed from the gun 10 in the general direction B, i.e. radially away from direction A towards the inner surface of the pipe, with the application angle Θ being the approximate angle between these two axes.

[0045] Further details of the arc wire spraying gun 10 can be seen in Figure 2, which shows a reverse angle view of the gun shown in Figure 1 with the casing 12 removed. With the casing removed, it can be seen that the arc wire spraying gun 10 comprises three main parts: a central structure 11 which comprises attachment mechanisms (not shown in Figure 2), and two wire guide modules 13 and 15 which are attached to the central structure 11. [0046] In addition to the wire feeder clamps 14, wire inlet 16, positive power feed 18, and spraying gun application guide 20, Figure 2 shows the wire feed wheel assembly drive input 22, negative power feed 24, quick-change attachment arm 26 by which the gun 10 is interchangeably attached to a boom (not shown in Figure 2), wire feed slave wheel 28 and wire feed drive wheel 30. The wire feed slave wheel 28 provides resistance against the wire feed drive wheel 30 when clamping the wire. Two metal wires are fed to the spraying gun head 20 in the arc wire spraying gun 10, but only the wire feeder clamps 14 and the lower and upper wire feeder wheels 28 and 30 for one wire, i.e. of the side of the gun nearest the viewer, are shown in Figure 2.

[0047] The wire enters the gun through wire inlet 16, and passes between wire feed slave and drive wheels 28 and 30 respectively. Wire feeder clamp 14 clamps the wire feeder wheels 28 and 30 onto the wire, to ensure correct feeding of the wire to the spraying gun head 20. Preferred embodiments of the arc wire spraying gun 10 comprise a wire feeder clamp 14 for each wire, being independent of each other. In this way the pressure applied to the wires by the feeder clamps 14 can be independently regulated to help ensure egual feeding of each wire. Feeding of the wires to the spraying gun application guide 20 is shown in more detail in Figure 3.

[0048] Thus, Figure 3 shows a cutaway view of the arc wire spraying gun 10 shown in Figure 2. A wire 32 is shown entering the gun 10 and passing between the lower and upper wire feeder wheels 28 and 30 to the spraying gun head casing 21. In this embodiment, the wire 32 and the second wire (not shown) are fed both towards each other so as to make contact with each other and actuate in the spraying gun head casing 21, and also through the application angle Θ. This multi- angled wire feed is preferably achieved using independent wire feeder clamps 14, as described above.

[0049] Figure 4 shows preferred apparatus of the present invention incorporating an arc wire spraying gun 10 and a boom 32. The gun 10 is attached to the boom 32 by attachment arm 26.

[0050] The boom 32 is telescopic allowing for treatment of the inside surface of a pipe along the length of the pipe, and for the treatment of different pipes of various lengths. The boom 32 comprises multiple lengths of reducing diameter sections 32a (the largest diameter) , 32b, 32c and 32d (the smallest diameter), that slide into one another. The section having the smallest diameter 32d has a diameter which is sufficiently large to house the required supply systems (for example, metal wires, electrical supply cables, means for supplying compressed air, not shown in Figure 4) . The boom 32 has a smaller cross sectional area than the gun 10 so that the boom 32 does not extend beyond the gun 10.

[0051] The boom sections 32a to 32d are attached to and supported by boom supports 34a to 34d respectively. Each of the boom supports 34a to 34d sits on a track 36a to 36d respectively. Boom support 34a, which supports the largest diameter section of the boom 32a, remained fixed in position relative to the track 36a. Boom supports 34b to 34d however can move along tracks 36b to 36d to extend the sections of the boom 32b to 32d respectively, and thus telescopically extend the boom 32 as indicated by arrow A.

[0052] To cater for various pipe diameters, the height of the boom 32 can be adjusted. In this regard, each boom section 32a to 32d is connected to its respective boom support 34a to 34d by a support member 38a to 38d respectively which may be raised and lowered by motors 40a to 40d respectively. The position of the boom 32 may be communicated to an operator by means of a digital readout that ensures accuracy when repeating non-continuous work. [0053] Each telescopic boom section 32a to 32d incorporates a support roller ball assembly 42a to 42d at the end of each section 32a to 32d respectively. If the boom 32 is to enter into a pipe then the weight of the boom is distributed across the boom supports 34a to 34d. As the boom 32 extends into the pipe the bending moment experienced at the end of the boom increases, which can result in the arc wire spraying gun 10 at the end of the boom 32 beginning to sag/bend downwards, which alters the application Θ. This can result in the optimum treatment angle not being achieved. The roller ball assemblies 42a to 42d effectively transfer the weight of the boom 32 from the boom supports 34a to 34d to the roller ball assemblies 42a to 42d within the pipe. When the boom 32 is withdrawn, the opposite occurs and the roller ball assemblies 42a to 42d transfer the weight distribution from inside of the pipe back to the boom supports 34a to 34d.

[0054] The extension and retraction and raising and lowering of the boom sections 32a to 32d are preferably controlled by a programmable logic controller (PLC) (not shown in Figure 4).

[0055] The embodiment of the apparatus of the present invention shown in Figure 4 has four telescopic boom sections 32a to 32d, but the boom 32 may be formed of a different number of sections as appropriate.

[0056] Figure 5 shows a simplified view of apparatus of the present invention being positioned into a pipe 44, one end of which is shown in cross section in Figure 5. An arc wire spraying gun 10 is attached to a boom 32 by attachment arm 26. The boom sections 32a to 32d are shown in a partially extended state, extending in direction A within the pipe 44, i.e. along the longitudinal axis of the pipe 44. The boom sections 32a to 32d are supported by boom supports 34a to 34d respectively (boom section 34a not shown in Figure 5), and travel along tracks 36a to 36d (only tracks 36a and 36b shown in Figure 5) . The pipe 44 rests on rollers 46 (one of which is shown in Figure 5) for rotating the pipe 44 about the arc wire spraying gun 10, i.e. about the longitudinal axis of the pipe approximately indicated by arrow A. Thus, if the roller 46 is rotated in direction X the pipe will rotate about the arc wire spraying gun 10 in opposite direction Y. The rollers 46 are preferably controlled by a programmable logic controller (PLC) (not shown in Figure 5), together with extension and retraction and height adjustment of the boom sections 32a to 32d, and operation of the arc wire spraying gun 10, to form an integrated system.

[0057] As discussed above, the method of the present invention preferably includes extracting unwanted particles from inside of the pipe, using an extraction tube fed by an extraction unit may be connected to the opposite end of the pipe to which the boom enters the pipe. In the arrangement shown in Figure 5, the extraction tube would thus be attached to the end of the pipe in the direction of arrow A (but is not shown in Figure 5) . In this way, the tube can create an air-tight seal at that end of the pipe such that there is substantially no pressure loss as would be experienced with an open system, and an enhanced extraction rate is achieved. The extraction means may comprise an integrated valve, which allows the extraction rate to be altered, which is dependent on factors such as the inner diameter of the pipe.

Claims

1. A surface treatment apparatus for treating the inside surface of a pipe, the apparatus comprising a treatment head mounted on a boom for insertion into the pipe.

2. Apparatus according to claim 1 for insertion into a a riser pipe for an oil or gas well.

3. Apparatus according to claim 1 or 2 for insertion into a pipe having a diameter as small as 150mm.

4. Apparatus according to claim 1, 2 or 3 wherein the treatment head comprises an arc wire spraying gun.

5. Apparatus according to any preceding claim for applying a metal coating to the inside of the pipe.

6. Apparatus according to claim 5 wherein the metal coating is a nickel-chromium coating.

7. Apparatus according to any preceding claim which comprises interchangeable treatment heads.

8. Apparatus according to claim 7 comprising interchangeable arc wire spraying and flame spraying guns.

9. Apparatus according to any preceding claim which comprises a flame spraying gun for applying a polymer layer to the inside surface of the pipe.

10. Apparatus according to claim 9 wherein the polymer layer is a polymer sealing layer.

11. Apparatus according to claim 10 wherein the polymer sealing layer comprises a polyaryletherketone .

12. Apparatus according to claim 11 wherein the polyaryletherketone is seleted from polyetherketone (PEK), polyetheretherketone (PEEK), and polyetherketoneketone (PEKK) .

13. Apparatus according to any preceding claim wherein the treatment head is thermally and/or electrically insulated .

14. Apparatus according to any preceding claim which comprises an arc wire spraying gun, the arc wire spraying gun comprising separate independent wire feeders.

15. Apparatus according to any preceding claim which comprises an arc wire spraying gun wherein the arc wire spraying gun head is angled from 30 to 60° to the longitudinal axis of the pipe to be treated.

16. Apparatus according to claim 15 wherein the arc wire spraying gun comprises a multi-angled wire feed for feeding the wires within the gun both towards each other so as to make contact and actuate in the melting zone, and away from the longitudinal axis of the pipe towards the arc wire spraying gun head.

17. Apparatus according to any preceding claim wherein the boom height can adjusted.

18. Apparatus according to any preceding claim wherein the boom is telescopic.

19. Apparatus according to claim 18 wherein the boom comprises multiple lengths of reducing diameter sections that slide into one another.

20. Apparatus according to claim 19 wherein the boom section having the smallest diameter has a diameter which is sufficiently large to house the required supply systems for the treatment head.

21. Apparatus according to claim 19 or 20 wherein each telescopic boom section incorporates a support roller ball assembly at the end of each section for transferring the weight of the boom to the support roller ball assemblies when the boom extends.

22. Apparatus according to any preceding claim which comprises moving means for moving a pipe around the treatment head .

23. Apparatus according to claim 22 wherein the moving means is track and/or roller driven allowing for the pipe to be rotated about and/or moved along the treatment head, and/or for the treatment head to move longitudinally inside the pipe along the length of the pipe.

24. Apparatus according to any preceding claim which is controlled by a programmable logic controller (PLC) .

25. Apparatus according to claim 24 which comprises movement means and a treatment head which are integrated into an automated unit that has a single point of control.

26. Apparatus according to any preceding claim which comprises extraction means, for extracting unwanted particles and from inside of the pipe.

27. Apparatus according to claim 26 wherein the extraction means comprises an extraction tube fed by an extraction unit for connection to an end of the pipe to be treated .

28. Apparatus according to claim 27 wherein the extraction means comprises an integrated valve which allows the extraction rate to be altered.

29. A method of treating the inside surface of a pipe by inserting a treatment head on a boom into the pipe.

30. A method according to claim 29 which employs apparatus according to any one of claims 1 to 28.

31. A method according to claim 29 or 30 for treating the inside surface of a riser pipe for an oil or gas well.

32. A method according to claim 29, 30 or 31 which comprises coating the inside of the pipe by arc wire spraying .

33. A method according to any one of claims 29 to 32 which comprises applying a metal coating to the inside surface of a pipe.

34. A method according to claim 33 wherein the coating is a nickel-chromium coating.

35. A method according to any one of claims 29 to 34 which comprises applying a coating of a thickness from 50 to ΙΟΟΟμπι to the inside of the pipe.

36. A method according to any one of claims 29 to 35 wherein the pipe is rotated about and/or moved along the treatment head.

37. A method according to any one of claims 29 to 36 wherein the treatment head is moved longitudinally inside the pipe .

38. A method according to any one of claims 29 to 37 which provides an inner surface corrosion barrier to the inside surface of the pipe.

39. A method according to any one of claims 29 to 38 which provides a sealing layer to the inside surface of the pipe .

40. A method according to claim 39 wherein the sealing layer material is a polyaryletherketone .

41. A method according to claim 39 or 40 wherein the sealing layer is applied by flame spraying.

42. A method according to any one of claims 29 to 41 which comprises extracting unwanted particles from inside of the pipe.

43. A method according to claim 42 which comprises attaching an extraction tube fed by an extraction unit to the opposite end of the pipe to which the boom enters the pipe.

44. A coating composition for coating a pipe, the coating composition comprising a nickel-chromium alloy.

45. A coating formed from the coating composition of claim 44 which further comprise a sealing layer comprising a polyaryletherketone.

46. A pipe the inside surface of which has either been treated using apparatus according to any one of claims 1 to 28, or by a method according to any one of claims 29 to 43, or with a coating composition or coating according to claims 44 or 45.

47. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.

48. A method of coating the inside surface of a pipe substantially as hereinbefore described with reference to the accompanying drawings.