GB2487546A

GB2487546A - Magnetic flux guide with variable geometry.

Info

Publication number: GB2487546A
Application number: GB1101289.5A
Authority: GB
Inventors: Shahriar Abtahi
Original assignee: Tubefuse Applications BV
Current assignee: Tubefuse Applications BV
Priority date: 2011-01-26
Filing date: 2011-01-26
Publication date: 2012-08-01
Also published as: GB201101289D0

Abstract

There is provided an apparatus for use in inductively heating an object, such as a pipe, the apparatus comprising a magnetic flux guide 10. The magnetic flux guide is positioned in proximity to the object to guide magnetic flux during inductive heating of the object and is configured to define a variable geometry so as to be positioned to conform with the surface of the object to be heated. The flux guide comprises a series of rings forming flux layers 14a having ferritic flux elements 16a separated by elastic filler 18a which allows the flux guide to be expanded for positioning about a pipe, its unexpanded state configuring the guide in the heating position. Alternatively the guide may be inserted within a pipe and expanded to it heating position. A further embodiment show the guide in use for heating a tubular structure with a step variation in diameter where the unexpanded guide engages the smaller diameter part in a heating position and expand to accommodate the larger diameter portion in a heating position as the tube moves axially though the heating zone.

Description

HEATING APPARATUS AND METHOD

TECHNICAL FIELD

The invention relates to apparatus and associated methods for use in the inductive heating of an object, and in particular, but not exclusively, for use in inductively heating a pipe.

BACKGROUND

Pipes are used in many industries, for example to transport fluids such as oil or water. Long pipelines may be formed by connecting tubular sections together, typically with joins which are fluid tight. For example, in the oil and gas industry lengths of pipe called casing are secured together to form a casing string which is run into a bore to provide a reliable fluid conduit. Typically, individual casing tubulars are attached to each other end to end using threaded connectors. However threaded connectors have associated disadvantages. For example, threaded connectors require machining of the pipe ends to high tolerances, which increases the production costs. Furthermore, threaded connectors require careful handling and can require additional sealing components, further increasing costs. The threaded connections often define mechanical weak points and/or sources of loss of integrity of fluid tight pipelines.

It has been proposed in the art to secure tubular sections together by welding, for example by forge welding. Material is typically heated during the welding process by inductive or resistive heating. Aside from welding, tubular sections are often heated for other objectives: for example, for heat treatment to alter material characteristics such as strength. However, localised variations in heating can result in compromised weld integrity and/or variations in material characteristics.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an apparatus for use in inductively heating an object, the apparatus comprising a magnetic flux guide configured to be positioned in proximity to an object to guide magnetic flux during inductive heating of the object, wherein the magnetic flux guide is configured to define a variable geometry.

The magnetic flux guide may be configured for use with an induction coil. In use, the magnetic flux guide may be configured to define a variable geometry such that the magnetic flux guide may better conform to the object being heated, maximising the heating effect established by the induction coil. The magnetic flux guide may improve efficiency and/or quality and/or speed of an inductive heating process. An activated induction coil in proximity to an object to be heated generates eddy currents in said object. A resistance of the object to the eddy currents results in the heating of the object. In addition, in objects with magnetic properties, such as ferrous objects, magnetic hysteresis losses may contribute to the inductive heating process. The presence of the magnetic flux guide proximal to an object during inductive heating reduces eddy current losses by directing the flow of eddy currents to encounter resistance within the object. The apparatus may comprise an induction coil.

An object may be heated as part of a forming process, such as a welding or a forging process. For example, an end portion of a first pipe and/or an end portion of a second pipe may be heated during a forge-welding process to join the first pipe to the second pipe at a seam region. Additionally or alternatively, an object may be heated as part of a heat treatment process. For example, it may be desired to alter material characteristics according to a heating regime. The heating may be by induction and/or resistive heating.

The magnetic flux guide may be configured to reduce energy loss from a heating process.

The magnetic flux guide may be configured to concentrate magnetic flux on an object to be heated or on a portion of an object to be heated.

The magnetic flux guide may be ferritic.

The magnetic flux guide may be configurable to more accurately conform to a surface of an object to be heated. More accurately conforming to the surface of an object to be heated may allow the magnetic flux guide to be placed in closer proximity to the object and/or may allow the magnetic flux guide to more uniformly guide flux in the object.

The variable geometry may comprise a shape or profile of a surface. For example, the magnetic flux guide may be configured to vary the curvature of a surface, such as the ovality. Additionally, or alternatively, the variable geometry may comprise a dimension. For example, the magnetic flux guide may comprise a scaleable shape.

Variable geometry may assist to prevent damage to and/or damage caused by the flux guide. For example, the variable geometry may provide for a transit configuration of the flux guide, the transit configuration having a reduced profile thus reducing the likelihood, during movement of the flux guide, of contact between the flux guide and another object, such as an inner surface of a pipe.

The magnetic flux guide may be configurable to define a predetermined dimension. The predetermined dimension may be related to a target heating object dimension.

The magnetic flux guide may be configurable to reduce a separation between the magnetic flux guide and a heatable object. The separation may be an annular separation.

The magnetic flux guide may be configured to vary a diameter.

The magnetic flux guide may be configured to be mechanically expandable.

The magnetic flux guide may be radially expandable.

The magnetic flux guide may be configured to expand outwardly. Additionally, or alternatively, the magnetic flux guide may be configured to expand inwardly.

The magnetic flux guide may be configured for use with a pipe. The magnetic flux guide may be configured for use within a pipe. Additionally, or alternatively, the magnetic flux guide may be configured for use externally of a pipe, for example with an external pipe surface.

The magnetic flux guide may be variable to define a first geometry in a first configuration and a second geometry in a second configuration. The magnetic flux guide may be configured to expand from the first configuration to the second configuration. Alternatively, the magnetic flux guide may be configured to contract from the first configuration to the second configuration. In use, the magnetic flux guide in one configuration may provide for improved heating of an object, relative to the magnetic flux guide in the other configuration.

The magnetic flux guide may comprise multiple components. The multiple components may be configured to be assembled together. For example, the magnetic flux guide may comprise a plurality of flux elements.

The plurality of flux elements may be configured to be displaced relative to each other to permit variation of the variable geometry. The flux elements may be configured to be displaced radially outwardly. The magnetic flux guide may be configured for radial movement of the flux elements. For example, the magnetic flux guide may comprise flux elements circumferentially arranged; such as segments, or portions of segments, arranged around an axis. The flux elements may be configured to be displaced by a predetermined amount.

The flux elements may be arranged to define a flux layer, such as a disc or a cylinder, or a portion of a disc or a cylinder (e.g. a ring). The flux elements may be arranged to define gaps between adjacent flux elements. The flux layer may comprise gaps separating the flux elements. The flux elements may be arranged to permit the flux elements to be displaced relative to each other. For example, the flux elements may be circumferentially arranged whereby circumferential gaps separate adjacent flux elements of the flux layer. The flux elements may be arranged to increase the gaps by expansion of the magnetic flux guide. Alternatively, the flux elements may be arranged to decrease the gaps by expansion of the magnetic flux guide.

The gaps may comprise a substance, such as an elastic filler. The gaps may comprise a magnetic substance, such as ferritic particles. Additionally, or alternatively, the gaps may comprise a magnetically inert material such as a rubber.

The flux elements may be arranged to define multiple layers. The magnetic flux guide may comprise a plurality of flux layers. The flux layers may be axially arranged, for example the flux layers may be stacked.

The magnetic flux guide may be configured to substantially homogeneously guide flux.

The flux layers may be arranged to stagger gaps in adjacent flux layers. The flux layers may be arranged such that gaps in a first flux layer are offset from gaps in at least a second flux layer. For example, a gap between two flux elements of a first flux layer may be adjacent a flux element of a second flux layer. A gap between two flux elements of a first flux layer may be aligned with a flux element of a second flux layer such that the gap between two flux elements of the first flux layer is offset form a gap between two flux elements of the second flux layer. The gaps in a first flux layer may be offset from the gaps in a second flux layer. The gaps may be angularly offset. The gaps may be axially offset. The flux elements in a first flux layer may overlap the gaps between flux elements in a second flux layer. The first flux layer may be adjacent the second flux layer.

The apparatus may be configured for use with an actuator. The actuator may form part of the apparatus. Activation of the actuator may vary the geometry of the magnetic flux guide. Activation of the actuator may progress the magnetic flux guide from a first configuration to a second configuration. The magnetic flux guide may be biased towards one configuration when the actuator is deactivated.

The apparatus may be configured for positioning relative to an object.

The apparatus may be configured for use with a tool for locating the magnetic flux guide (e.g. a toolstring for locating the magnetic flux guide axially and/or radially in a pipe). The tool may form part of the apparatus.

The apparatus may be configured to accommodate an object to be heated. For example, the apparatus may comprise a surface adapted to receive a corresponding surface of an object to be heated.

The apparatus may comprise a thermal insulation. For example, the apparatus may be adapted to reduce heat loss from an object during and/or after heating.

Additionally, or alternatively, the apparatus may comprise a thermal conductor. For example, the apparatus may comprise a thermally conductive material configured to channel heat away from and/or towards target regions. Heat may be channelled to provide substantially homogeneous heating of an object.

According to a second aspect of the invention there is provided a method of guiding magnetic flux, the method comprising: positioning a magnetic flux guide proximal to an object to be heated, the magnetic flux guide adapted to guide magnetic flux during inductive heating; and configuring the magnetic flux guide to define a variable geometry.

The method may further comprise: configuring the magnetic flux guide to define a first geometry; moving the magnetic flux guide to a target location; reconfiguring the magnetic flux guide to define a second geometry.

Configuring and/or reconfiguring the magnetic flux guide may comprise defining a shape and/or a dimension. For example, the method may comprise expanding the magnetic flux guide to more accurately conform to a surface of a pipe, such as an inner surface.

The magnetic flux guide may comprise a brittle material such that moving the magnetic flux guide in an unexpanded configuration may reduce damage and/or the likelihood of damage to the magnetic flux guide compared to moving the magnetic flux guide in an expanded configuration. The target location may be a portion or a surface of an object to be heated, such as a region of a pipe to be inductively heat treated.

According to a third aspect of the invention, there is provided a magnetic flux guide for use in inductive heating of an object, comprising a plurality of components configured to be moved relative to each other to define a variable geometry.

According to a fourth aspect of the invention, there is provided an induction heater comprising an apparatus according to the first aspect.

According to a fifth aspect of the invention, there is provided a method of inductively heating an object, the method comprising: positioning a magnetic flux guide proximal to an object to be heated, the magnetic flux guide adapted to guide magnetic flux during inductive heating; configuring the magnetic flux guide to define a variable dimension; and inductively heating the object.

The above summary is intended to be merely exemplary and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1(a) is a schematic representation of a magnetic flux guide for use in inductively heating an object in accordance with a first embodiment of the present invention in an unexpanded configuration; Figure 1(b) is a schematic representation of the magnetic flux guide of Figure 1(a) in an expanded configuration; Figure 2(a) is a cross-section of an apparatus comprising the magnetic flux guide of Figure 1(a) further comprising a tool string, inserted within a pipe arrangement; Figure 2(b) is a cross-section of the apparatus of Figure 2(a) wherein the magnetic flux guide in an unexpanded configuration is moved adjacent a section of the pipe arrangement to be heated; Figure 2(c) is a cross-section of the apparatus of Figure 2(a) wherein the magnetic flux guide is expanded adjacent a section of the pipe arrangement to be heated; Figure 2(d) is a cross-section of the apparatus of Figure 2(a) wherein the magnetic flux guide is in an expanded configuration adjacent a section of the pipe arrangement after heating; Figure 3(a) shows an apparatus comprising the magnetic flux guide of Figure 1(a) in an unexpanded configuration further comprising an actuator; Figure 3(b) shows the apparatus of Figure 3(a) in an expanded configuration; Figure 4(a) shows a magnetic flux guide for use in inductively heating an object in accordance with a second embodiment of the present invention in an unexpanded configuration in use; Figure 4(b) shows the magnetic flux guide of Figure 4(a) in an expanded configuration in use.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to Figures 1(a) and 1(b) in which there is shown a magnetic flux guide 10 in accordance with a first embodiment of the present invention for use in inductively heating an object. In the embodiment shown the magnetic flux guide 10 has a substantially cylindrical outer surface 12 for accommodating a substantially cylindrical surface of an object to be heated, such as an interior surface of a pipe. Figure 1(a) shows the magnetic flux guide 10 in an unexpanded configuration; whilst Figure 1(b) shows the magnetic flux guide 10 in an expanded configuration.

In the example shown, the magnetic flux guide 1 0 comprises a plurality of flux layers 14a arranged axially along a common central axis. Each flux layer 14a comprises a plurality of flux elements iGa. The flux elements 16a in the embodiment shown are circumferentially arranged, separated by circumferential gaps 18a between adjacent flux elements 1 6a. The flux elements 1 6a are ferritic segments and the circumferential gaps 1 8a comprise an elastic filler. The flux elements 1 6a are of similar dimensions and are arranged around a central axis of the flux layer 14a at regular intervals. The circumferential gaps 18a between the flux elements 16a are also of similar dimensions and arranged around the central axis at regular intervals. The circumferential gaps 18a between the flux elements 16a provide localised variations in magnetic flux guidance, such as variations in flux intensity. Evenly distributing the circumferential gaps 1 8a around the flux layer 1 4a provides a substantially even distribution of localised variations in magnetic flux guidance such that the magnitude of the localised variations within a flux layer 1 4a is reduced.

In the embodiment shown in Figures 1(a) and 1(b) the flux layers 14a are arranged with respect to each other such that the circumferential gaps 1 8a of each flux layer 14a are angularly offset from each adjacent flux layer 14a. Aligning the circumferential gaps 18a axially with a flux element 16a, rather than with a circumferential gap 1 8a, of an adjacent flux layer 1 4a provides for a substantially even distribution of gaps 18a in an axial direction such that the magnitude of localised variations in magnetic flux guidance properties is reduced. In the embodiment shown, each circumferential gap 18a is surrounded by flux elements 16a at the exterior of the magnetic flux guide 10, longitudinally and circumferentially.

Figures 2(a) to 2(d) show diagrammatic cross-sectional views of an apparatus comprising the magnetic flux guide 10 of Figures 1(a) and 1(b) in an exemplary use during heating and welding of first and second pipes 26, 28. The apparatus 20 is mounted on a tool string 24 (partially shown). The two pipes 26, 28 are separated by an offset 30 at a seam region 32. In an alternative embodiment (not shown) the two pipes may already have been joined or may be abutting, and the pipes may be heated to alter material characteristics. In the embodiment shown, the seam region 32 is to undergo heating during joining of the two pipes 26, 28. In Figure 2(a) the magnetic flux guide 10 is in an unexpanded configuration and is run into the first pipe 26 towards the seam region 32. Figure 2(b) shows the magnetic flux guide 10 aligned with the seam region 32 and still in an unexpanded configuration. Setting the magnetic flux guide 10 in an unexpanded configuration during deployment as shown in Figures 2(a) and 2(b) reduces the likelihood of the magnetic flux guide 10 contacting an internal surface of the pipe 26. The magnetic flux guide 10 shown is a brittle ferrite such that contact between the magnetic flux guide 10 and the pipe 26 could damage the magnetic flux guide 10 in particular, and/or the pipe 26. Reducing the likelihood of contact reduces the likelihood of damage. Moving the magnetic flux guide 10 in the unexpanded configuration may also enable the magnetic flux guide 10 to be moved past objects which may otherwise obstruct the path of the magnetic flux guide 10, such as annular restrictions (e.g. flanges or narrowings) in the pipe 26. The unexpanded configuration of the magnetic flux guide 10 permits the magnetic flux guide 10 to be accurately positioned, for example so that the offset 30 is located at the middle of the magnetic flux guide 10. Once at a desired location proximal to the seam region 32, the magnetic flux guide 10 is expanded to an expanded configuration as shown in Figure 2(c). The annular separation between the magnetic flux guide 10 and the pipes 26, 28 is reduced with the magnetic flux guide 10 expanded.

Figure 2(c) further shows an induction coil 34. The induction coil 34 is positioned proximal to the seam region 32. In the embodiment shown, the induction coil 34 is positioned on an opposite side of the pipe 26, 28 from the magnetic flux guide 10.

However, in other embodiments (not shown) the induction coil 34 may be placed on the same side of an object as the magnetic flux guide 10. The magnetic flux guide 10 concentrates magnetic flux in the seam region 32 to be heated. The induction coil 34 generates eddy currents within the seam region 32. The resistance of the seam region 32 to the eddy currents results in the heating of the seam region 32. In addition, the pipes 26, 28 shown are ferrous such that magnetic hysteresis losses add to the heating process. The presence of the magnetic flux guide 10 proximal to the seam region 32 reduces eddy current losses, by directing the flow of eddy currents to encounter resistance within the seam region 32. The magnetic flux guide 10 in the expanded configuration reduces eddy current losses compared to the unexpanded configuration, by reducing the separation between the magnetic flux guide 10 and the seam region 32. A reduced separation between the magnetic flux guide 10 and the seam region 32 reduces the potential for eddy current losses in a gap 36 between the magnetic flux guide 10 and the seam region 32. The seam region 32 is heated according to a heating regime in order to permit joining of the pipes 26, 28 as shown in Figure 2(d), such as by forge welding. Upon completion of heating, the magnetic flux guide 10 is contracted to the unexpanded configuration of Figure 2(b), aiding subsequent movement of the magnetic flux guide 10 such as axial removal or movement to another region to be heated. In some embodiments, the ferrite core may be used subsequent to welding, for example to achieve a desired temperature/cooling/heating profile.

Figure 3(a) shows an apparatus 40 comprising the magnetic flux guide 10 of Figures 1(a) and 1(b) mounted on an actuator 41, with the magnetic flux guide 10 in the unexpanded configuration. The actuator 41 shown is a tube 42 comprising a transition 44 from a first diameter 46 to a larger second diameter 48. The first diameter 46 of the tube 42 corresponds to the magnetic flux guide 10 in an unexpanded configuration.

Figure 3(b) shows the apparatus 40 of Figure 3(a) with the magnetic flux guide 10 in the expanded configuration located at the second diameter 48 of the tube 42. Axial movement of the tube 42 relative to the magnetic flux guide 10 progresses the magnetic flux guide 10 from the first tube diameter 46 through the transition 44 to the second tube diameter 48. The relative axial movement of the tube 42 therefore results in a radial expansion of the magnetic flux guide 10. In the embodiment shown, relative movement of the tube 42 from the position of Figure 3(b) to the position of Figure 3(a) results in the contraction of the magnetic flux guide 10 from the expanded configuration of Figure 3(b) to the unexpanded configuration of Figure 3(a).

Figures 4(a) and 4(b) show an alternative embodiment of a magnetic flux guide 50 according to the present invention. The magnetic flux guide 50 for use in inductively heating an object comprises flux layers 54a comprising flux elements 56a and circumferential gaps 58a. In the embodiment shown the magnetic flux guide 50 has a substantially cylindrical inner surface 60 for accommodating a substantially cylindrical surface of an object to be heated, shown as an outer surface 62 of a pipe 64. Figure 4(a) shows the magnetic flux guide 50 in an unexpanded configuration; whilst Figure 4(b) shows the magnetic flux guide 50 in an expanded configuration. The magnetic flux guide 50 in the unexpanded configuration of Figure 4(a) has a reduced separation 66a from the pipe 64 compared to the separation 66b from the pipe 64 in the expanded configuration of Figure 4(b) such that losses during inductive heating, such as by an induction coil located inside the pipe 64 (not shown), are reduced. The magnetic flux guide 50 in the expanded configuration of Figure 4(b) aids in movement, such as axial movement, of the magnetic flux guide 52 relative to the pipe 64.

It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention. For example, although shown here with ferritic flux elements, other magnetic flux guide materials may be used, such as rare earth Cobalt or Aluminium/Nickel/Cobalt alloys; or combinations of magnetic flux guide materials. In alternative embodiments, the apparatus may comprise a magnetic flux guide wherein the magnetic flux guide is a continuous magnetic flux guide, such as without discernible circumferential gaps. Alternatively an expandable magnetic flux guide may comprise a substantially increased number of circumferential and/or axial and/or annular gaps, such as with a three-dimensional distribution of discrete magnetic flux guide particles within an elastic support, such as a bellows.

Claims

CLAIMS1. An apparatus for use in inductively heating an object, the apparatus comprising a magnetic flux guide configured to be positioned in proximity to the object to guide magnetic flux during inductive heating of the object, wherein the magnetic flux guide is configured to define a variable geometry.
2. The apparatus of claim 1, wherein the magnetic flux guide is configured for use with an induction coil.
3. The apparatus of claim 1 or 2, wherein the magnetic flux guide is configured to define the variable geometry such that the magnetic flux guide better conforms to the object being heated.
4. The apparatus of claim 2 or 3, wherein the apparatus comprises the induction coil.
5. The apparatus of any preceding claim, wherein the magnetic flux guide is configured to concentrate magnetic flux on a portion of the object to be heated.
6. The apparatus of any preceding claim, wherein the magnetic flux guide is ferritic.
7. The apparatus of any preceding claim, wherein the magnetic flux guide is configured to vary the curvature of a surface.
8. The apparatus of any preceding claim, wherein the variable geometry comprises a dimension.
9. The apparatus of any preceding claim, wherein the magnetic flux guide comprises a scaleable shape.
10. The apparatus of any preceding claim, wherein the magnetic flux guide is configurable to define a predetermined dimension.
11. The apparatus of claim 10, wherein the predetermined dimension is related to a target heating object dimension.
12. The apparatus of any preceding claim, wherein the magnetic flux guide is configurable to reduce a separation between the magnetic flux guide andthe heatable object.
13. The apparatus of claim 12, wherein the separation is an annular separation.
14. The apparatus of any preceding claim, wherein the magnetic flux guide is configured to vary a diameter.
15. The apparatus of any preceding claim, wherein the magnetic flux guide is configured to be mechanically expandable.
16. The apparatus of any preceding claim, wherein the magnetic flux guide is radially expandable.
17. The apparatus of any preceding claim, wherein the magnetic flux guide is configured to expand outwardly.
18. The apparatus of any preceding claim, wherein the magnetic flux guide is configured to expand inwardly.
19. The apparatus of any preceding claim, wherein the magnetic flux guide is configured for use with a pipe.
20. The apparatus of any preceding claim, wherein the magnetic flux guide is variable to define a first geometry in a first configuration and a second geometry in a second configuration, wherein, in use, the magnetic flux guide in one configuration provides for improved heating of the object, relative to the magnetic flux guide in the other configuration.
21. The apparatus of any preceding claim, wherein the magnetic flux guide comprises multiple components.
22. The apparatus of claim 21, wherein the multiple components are a plurality of flux elements configured to be assembled together.
23. The apparatus of claim 22, wherein the plurality of flux elements are configured to be displaced relative to each other to permit variation of the variable geometry.
24. The apparatus of claim 22 or 23, wherein the flux elements are configured to be displaced radially outwardly.
25. The apparatus of any of claims 22 to 24, wherein the magnetic flux guide is configured for radial movement of the flux elements.
26. The apparatus of any of claims 22 to 25, wherein the flux elements are configured to be displaced by a predetermined amount.
27. The apparatus of any of claims 22 to 26, wherein the flux elements are arranged to define a flux layer comprising gaps separating the flux elements.
28. The apparatus of claim 27, wherein the magnetic flux guide comprises a plurality of flux layers.
29. The apparatus of claim 28, wherein the flux layers are arranged to stagger the gaps in adjacent flux layers.
30. The apparatus of any preceding claim, wherein the magnetic flux guide is configured to substantially homogeneously guide flux.
31. The apparatus of any preceding claim, wherein the apparatus is configured for use with an actuator, wherein, in use, activation of the actuator varies the geometry of the magnetic flux guide.
32. The apparatus of any preceding claim, wherein the apparatus is configured for use with a tool for locating the magnetic flux guide.
33. A method of guiding magnetic flux, the method comprising: positioning a magnetic flux guide proximal to an object to be heated, the magnetic flux guide adapted to guide magnetic flux during inductive heating; and configuring the magnetic flux guide to define a variable geometry.
34. The method of claim 33, further comprising: configuring the magnetic flux guide to define a first geometry; moving the magnetic flux guide to a target location; and reconfiguring the magnetic flux guide to define a second geometry.
35. The method of claim 33 or 34, wherein configuring the magnetic flux guide comprises defining a dimension.
36. The method of any of claims 33 to 35, wherein the method comprises expanding the magnetic flux guide to more accurately conform to a surface of a pipe.
37. A magnetic flux guide for use in inductive heating of an object, comprising a plurality of components configured to be moved relative to each other to define a variable geometry.
38. An induction heater comprising the apparatus according to any of claims 1 to 32.
39. A method of inductively heating an object, the method comprising: positioning a magnetic flux guide proximal to an object to be heated, the magnetic flux guide adapted to guide magnetic flux during inductive heating; configuring the magnetic flux guide to define a variable dimension; and inductively heating the object.
40. Apparatus substantially as described herein with reference to Figures 1 to 4(b).
41. Methods substantially as described herein with reference to Figures 1 to 4(b).