WO2011012846A1

WO2011012846A1 - Welding method and system

Info

Publication number: WO2011012846A1
Application number: PCT/GB2010/001417
Authority: WO
Inventors: Neil Starsmore; Richard Parkes
Original assignee: Tubefuse Applications V.O.F.
Priority date: 2009-07-30
Filing date: 2010-07-27
Publication date: 2011-02-03
Also published as: GB0913217D0

Abstract

A method for welding a first component to a second component, such as a first pipe (4) to a second pipe (6), comprises heating at least one of the first and second components, and establishing a predetermined interference between the first and second components before a temperature of at least one of the first and second components falls below a predetermined temperature.

Description

WELDING METHOD AND SYSTEM

FIELD OF THE INVENTION

The present invention relates to a method and system for welding components and, in particular, but not exclusively, for welding steel pipes.

BACKGROUND OF THE INVENTION

Existing methods for welding components typically involve bringing the components to be welded together into intimate contact and compressing the components together. For many applications, the quality of a welded joint obtained using such methods may be important. For example, the weld shear strength, axial strength, durability, permeability, physical size and/or shape may be important weld quality parameters. The quality of the weld may be affected by many variables, such as, for example, ambient conditions, weld temperature, weld force and the like. It is desirable to ensure that the weld quality is maximised by controlling the welding conditions. However, in some environments this may be difficult.

In the oil and gas industries there is a requirement to join together multiple lengths of pipe for lining boreholes formed by drilling to provide a supported and/or sealed conduit between a wellhead at ground level and an underground reservoir of oil or gas. Existing methods for joining pipes typically include threaded connections.

However, such methods can be time-consuming and costly due to the requirements to form the screw threads and to subsequently screw couple the pipes together. It has been proposed to utilise welding techniques to join pipes together in place of threaded connections. Known welding methods can, however, be time-consuming, hazardous and costly. Furthermore, these disadvantages may be exacerbated if the welded joints between the pipes are not consistently of a sufficient quality. This is especially true in an offshore environment where operating conditions may be difficult and operational time constraints may be paramount. SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method of welding a first component to a second component, comprising:

heating at least one of the first and second components; and

establishing a predetermined interference between the first and second components before a temperature of at least one of the first and second components falls below a predetermined temperature. The inventor has discovered that establishing the predetermined interference in this way allows the predetermined interference to be established during a period when plastic deformation of at least one of the first and second components is still possible. This may, for example, serve to reduce the number of welded joint failures and/or to enhance weld quality and weld quality consistency.

The predetermined interference may be established between the first and second components by compressing the first and second components together over a predetermined relative distance. A force may, for example, be applied to at least one of the first and second components so as to compress the first and second components together. The predetermined interference may be established by arranging one of the first and second components to be positioned above the other component. In such an arrangement the weight of the upper component may act or assist to force the upper component towards the lower component.

The step of establishing the predetermined interference may at least partially overlap the step of heating at least one of the first and second components.

Alternatively, the step of establishing the predetermined interference may follow the step of heating at least one of the first and second components.

The method may comprise controlling the movement of at least one of the first and second components over a predetermined relative distance.

The predetermined interference may be established substantially simultaneously with the instant when the temperature of at least one of the first and second components falls to the predetermined temperature. This may serve to maximise the time taken to establish the predetermined interference while the temperature of at least one of the first and second components is above or equal to the predetermined temperature. Maximising the time taken to establish the predetermined interference in this manner may be advantageous in that weld quality may be improved when the time taken for fusion and plastic deformation of at least one of the first and second components is increased.

The method may comprise predicting the instant when the temperature of at least one of the first and second components will fall to the predetermined temperature.

The method may comprise controlling the velocity of at least one of the first and second components so as to establish the interference before a temperature of at least one of the first and second components falls below the predetermined temperature. The velocity of at least one of the first and second components may, for example, be controlled in response to the time remaining until the predicted instant. The method may comprise monitoring, for example sensing the temperature of at least one of the first and second components. The method may, for example, comprise sensing temperature at multiple points of at least one of the first and second components.

The method may comprise sensing temperature at multiple points around at least a portion of an interface between the first and second components. The method may, for example, comprise sensing the temperature at multiple points around an entire interface between the first and second components.

The temperature of at least one of the first and second components according to the first aspect of the present invention may be a function of the temperature measured at each of the multiple points. The temperature of at least one of the first and second components according to the first aspect of the present invention may, for example, be the minimum temperature measured across all the multiple points. Sensing the temperature at multiple points in this way may provide an advantage in that a more uniform weld chemistry and/or weld metallurgy may be obtained.

Furthermore, in the event that a distribution of the temperatures across the multiple points is not sufficiently uniform, the method may be interrupted to allow, for example, the replacement, re-working, re-alignment or re-heating of one or both of the components. This may provide an advantage that weld chemistry uniformity and/or weld metallurgy uniformity and/or other weld quality parameters may be improved.

The method may comprise monitoring the relative positions of the first and second components.

The method may comprise controlling an alignment system so as to move at least one of the first and second components.

The method may comprise sensing data representative of the forces applied to at least one of the first and second components. This may be advantageous when trying to establish when the first and second components first come into contact or when controlling the velocity of at least one of the first and second components.

The step of heating at least one of the first and second components may comprise heating at least one of the first and second components to a predetermined initial temperature. The predetermined initial temperature may, for example, be selected to be less than a limit temperature. The limit temperature may be determined in accordance with, for example, the material of at least one of the first and second components, ambient conditions or the like. In a specific application of welding steel components, for example, the limit temperature may be in the region of 1000⁰C. Exceeding such a limit temperature may require post-forging heat treatment of the components to ensure a satisfactory weld quality. Such post-forging heat treatment may, however, be undesirable since, among other things, it will prolong the overall welding process time.

The method may comprise establishing the predetermined interference between the first and second components before a temperature of at least one of the components falls below a first predetermined temperature and then holding the first and second components together by a predetermined force to maintain the predetermined interference at least until the temperature of at least one of the first and second component falls to a second predetermined temperature. This may assist to improve weld quality. For example, this may further increase the weld shear strength or the weld axial strength.

Heating at least one of the first and second components may comprise raising the temperature of at least one of the first and second components by generating heat in or supplying heat to at least one of the first and second components. At least one of the first and second components may, for example, be heated electrically, by magnetic induction, by the action of friction or by supplying heat from an external heat source such as a combustion heat source or a chemical reaction.

The method may comprise welding the first component to the second component in a controlled environment. The first and second components may, for example, be welded together in an environment substantially devoid of oxygen. For example, the first and second components may be welded together in an environment that has less than 100 ppm of oxygen.

The method may comprise sealing at least a portion of the first and second components in a chamber and extracting air from the chamber and/or purging the chamber with a gas such as nitrogen or an inert gas such as a noble gas or the like prior to welding of the first and second components so as to remove oxygen from the chamber. The method may comprise repeatedly evacuating the chamber and purging the chamber with a gas such as nitrogen or an inert gas such as a noble gas or the like prior to the step of heating at least one of the first and second components. The method may comprise applying heat to at least one of the portions of the first and second components in the chamber.

The first and second components may be welded together in an environment comprising a pre-selected or preferred gas. The gas may, for example, comprise nitrogen or an inert gas such as a noble gas or the like.

The gas may comprise a mixture of gases. For example, the gas may comprise a mixture of nitrogen and hydrogen, for example, 95% nitrogen and 5% hydrogen. The method may comprise sealing at least a portion of the first and second components in a chamber, injecting the pre-selected or preferred gas into the chamber and heating at least one of the first and second components in the preselected or preferred gas. The method may comprise applying heat to at least one of the portions of the first and second components in the chamber.

The method may comprise recording data associated with the welding process. The method may, for example, comprise recording data representative of position, movement, temperature force and the like. This has the advantage that the data recorded may be reviewed at a later date for audit or quality control purposes.

In some embodiments the method may comprise heat treating the components subsequent to welding together. For example, the method may comprise heat treating a weld region defined between the joined components. Heat treatment may be achieved electrically. Heat treatment may be achieved inductively.

The method may be configured to weld first and second tubular bodies together. The tubular bodies may define individual pipes configured to be joined together to define a pipeline or tubing string.

The tubular bodies may define weilbore tubular bodies, such as casing tubulars, liner tubulars, production tubulars or the like.

The tubular bodies may be formed of steel.

The method may be configured to weld first and second tubular bodies together prior to or while being run into a weilbore.

According to a second aspect of the present invention there is provided a system for welding a first component to a second component comprising:

a heating arrangement for heating at least one of the first and second components; and

a controller arranged to establish a predetermined interference between the first and second components before a temperature of at least one of the first and second components falls below a predetermined temperature.

The system may further comprise a temperature sensor arranged to measure the temperature of at least one of the first and second components. The system may, for example, comprise a temperature sensor configured to measure a temperature distribution around at least a portion of an interface between the first and second components. The temperature sensor may be configured to measure the temperature distribution around an entire interface between the first and second components.

The temperature sensor may, for example, be capable of measuring the temperature around at least a portion of the interface in real-time during welding thus allowing for the real-time control of the movement of at least one of the first and second components. An added advantage of real-time temperature measurement is that time-resolved quality of weld data around at least the portion of the interface may be stored for audit or quality control purposes.

The system may further comprise an alignment system which is controlled by the controller so as to move at least one of the first and second components in response to the temperature of at least one of the first and second components.

The alignment system may comprise an actuator. The actuator may be arranged to be mechanically connected to at least one of the first and second components. The actuator may comprise a hydraulic, electric, mechanical or pneumatic device, or the like, or any combination thereof. The actuator may, for example, comprise a hydraulic pump, an electric motor or solenoid, an internal combustion engine, a compressor, or any combination thereof. 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 is a schematic front elevation of a system for welding a first component to a second component, specifically a first pipe to a second pipe, in accordance with an embodiment of the present invention;

Figure 2 is a schematic cross-section on XX of the welding system of Figure

1;

Figure 3 shows a temperature profile and a corresponding component separation as a function of time in accordance with a first example of a method of welding a first component to a second component;

Figure 4(a) schematically illustrates the relative positions of first and second components at a time before instant t, of Figure 3;

Figure 4(b) schematically illustrates the relative positions of the first and second components at a time between instants U and t₂ of Figure 3;

Figure 4(c) schematically illustrates the relative positions of the first and second components at a time between instants t₂ and t₃ of Figure 3;

Figure 4(d) schematically illustrates the relative positions of the first and second components at a time between instants t₃ and t₄ of Figure 3;

Figure 4(e) schematically illustrates the relative positions of the first and second components at a time after instant t₄ of Figure 3; and

Figure 5 is a flow chart illustrating a first example of a method of establishing an interference between the first component and the second component. DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a system generally designated 2 for welding a first component 4 to a second component 6. In the present embodiment the first and second components 4 and 6 are pipes, specifically oilfield pipes and are formed from an electrically conductive material such as steel. The system of Figure 1 is designed to weld a first end face 8 of the first pipe 4 to a first end face 10 of the second pipe 6. The pipes 4 and 6 are arranged so as to be co-axial with their respective longitudinal axes aligned in the z direction. Figure 1 shows the positions of the pipes 4 and 6 prior to welding, in which the end face 8 of the first pipe 4 is disposed towards the end face 10 of the second pipe 6, and the pipe end faces 8 and 10 are separated by a gap 12. The pipes 4 and 6 are co-axially aligned by fitting the end faces 8 and 10 over a cylindrical rod 14. The external diameter of the cylindrical rod 14 is substantially matched to the internal diameters of the pipes 4 and 6 so that the annular end face 8 of the first pipe 4 is substantially aligned with the annular end face

10 of the second pipe 6. Although the cylindrical rod 14 is shown in Figures 1 and 2 as being solid, it should be understood that the cylindrical rod 14 may, alternatively, be hollow and comprise a pipe.

Each pipe 4 and 6 is held by a respective clamp 16 and 18. The first clamp 16 is mechanically connected to a first actuator 20 and the second clamp 18 is mechanically connected to a second actuator 22. The mechanical connection 24 between the second clamp 18 and the second actuator 22 is diagrammatically shown in Figure 2, for example, and serves to transfer a linear actuation force generated by the actuator 22 to the clamp 18 and, consequently, to the second pipe 6. Each actuator 20, 22 may comprise a hydraulic, electrical, mechanical or pneumatic device, or the like, or any combination thereof. For example, each actuator 20, 22 may comprise a hydraulic pump, a solenoid, an internal combustion engine or a compressor, or the like, or any combination thereof.

The welding system 2 further comprises a first electrode 26 having a first contact 28 and a second contact 30, and a second electrode 32 having a first contact

34 and a second contact 36. When it is required to raise the temperature of the first pipe 4 in the vicinity of the end face 8, the contact 28 of the first electrode 26 and the contact 34 of the second electrode 32 are arranged in contact with the first pipe 4 at diametrically opposed positions adjacent the end face 8 of the first pipe 4. Similarly, when it is required to raise the temperature of the second pipe 6 in the vicinity of the end face 10, the contact 30 of the first electrode 26 and the contact 36 of the second electrode 32 are arranged in contact with the second pipe 6 at diametrically opposed positions adjacent the end face 10 of the second pipe 6.

The welding system 2 also comprises temperature sensors 38, 40, 42 and 44 which are distributed so as to collectively sense the circumferential temperature profiles of the first pipe 4 and the second pipe 6 in the vicinity of the end faces 8 and

10 respectively. As shown in Figure 2, for example, the temperature sensors 38, 40, 42 and 44 are aligned with the xy plane in the middle of the gap 12 and have a uniform angular distribution about the longitudinal z axis of the pipes 4 and 6. Each temperature sensor 38, 40, 42 and 44 is capable of measuring the temperature in a field of view that extends at least across the gap 12. In addition, each temperature sensor 38, 40, 42 or 44 has a field of view, which extends across a 90° angular range about the z axis.

The welding system 2 further comprises a controller 46. As indicated by the dotted lines in Figures 1 and 2, the controller 46 is capable of communicating with the actuators 20 and 22, the electrodes 26 and 32, and the temperature sensors 38, 40,

42 and 44. At least one of the actuators 20, 22 further comprises a position sensor and, optionally, a force sensor. Furthermore, in use, the controller 46 controls the operation of each actuator 20, 22 in response to data received from one or more position sensors and one or more temperature sensors 38, 40, 42, 44. Optionally, the controller 46 may control the operation of each actuator 20, 22 in response to data received from the one or more force sensors. In addition, in use, the controller 46 controls the electric current driven through each pipe 4 and 6 between the electrodes 26 and 32 in response to temperature data received from one or more temperature sensors 38, 40, 42, 44.

The detailed operation of the welding system of Figures 1 and 2 is now described with reference to Figures 3, 4(a) -4(e) and 5. The upper graph in Figure 3 shows a temperature profile of the first and/or second components during a first example of a method of welding. The temperature T may, for example, comprise an average of the temperatures sensed by the temperature sensors 38, 40, 42 and 44. The lower graph in Figure 3 shows a corresponding separation s of the first and second components along the z axis as a function of time t, where it should be understood that the separation s of the first and second components may be calculated from relative position data provided by the position sensor of one or both of the actuators 20, 22.

The welding process begins at a time prior to instant U with the temperature T of the first and/or second components at or around an ambient temperature T_amb and the first and second components separated by a gap d_gap as shown in Figure 4(a). Between instants ti and t₂, the temperature T of the first and/or second components is raised towards an initial target temperature T_1n, by appropriate activation of the first and second electrodes 26, 32, as shown in Figure 4(b). As the temperature T approaches the initial target temperature T,_nl, the current driven through the electrodes 26 and 32 may be controlled by the controller 46, so as to stabilise the temperature T to within a predetermined degree of accuracy of the initial target temperature Tm, before the current is switched off at a time t₂. Alternatively, a constant current may be driven through the electrodes 26 and 32 and simply switched off at time t₂, once the temperature T approaches the initial target Temperature T,_nι to within a predetermined degree of accuracy. For the present example in which the first and second components 4 and 6 are steel pipes having an outer diameter of approximately 219 mm, the initial target temperature T_ιnl may be 98O⁰C. Using such a target temperature is particularly desirable in this case, because if the temperature of one of the steel pipes 4 or 6 is raised above approximately 1000⁰C, then this can necessitate a post-welding heat treatment step to ensure a satisfactory weld quality. In some cases such a post-welding heat treatment step may, however, be undesirable, since it can prolong the overall welding process time.

After instant t_2l the first and second components 4 and 6 begin to cool towards the temperature T_amb- Simultaneously, the first and second components 4 and 6 are brought rapidly together between instants t₂ and t₃ as shown in Figure 3 and Figure 4(c). To bring the components 4 and 6 together in this way, requires that either the separation d_gap is known from a measurement during alignment of the first and second components prior to raising the temperature of the first and/or second components or that the forces applied by one or both of the actuators 20, 22 are monitored. In the latter case, an increase in the force required to achieve a given relative movement between the first and second components 4 and 6 may increase significantly once the components are in contact.

Once the components 4 and 6 are in contact at instant t_3l further relative movement between the components is controlled according to the method diagrammatically represented in Figure 5, so as to establish a predetermined compression or interference having a magnitude of df_Orge by the time the temperature T falls to a first predetermined threshold temperature T_m1.

The method of establishing an interference begins at step 50 in Figure 5 corresponding to the instant t₃ in Figure 3 when the first and second components are first brought into contact. A counter i is initialised at step 51 and sampling of the temperature T of the first and/or second components begins at step 52 together with sampling of the separation s of the first and second components. The counter i is incremented at step 53 and the temperature T and the separation s are re-sampled at step 54.

The rate of cooling dT/dt and the rate of change of the separation of the components ds/dt are calculated at step 56. The rate of cooling dT/dt may, for example, be calculated from any combination of two or more samples T, (j = i, i-1 , ...) of the temperature T. Similarly, the rate of change of the separation of the components ds/dt may be calculated from any combination of two or more samples S₁ (j = i, i-1, ...) of the separation s. At step 58, a mathematical model of the cooling of the first and/or second components is used together with the rate of cooling dT/dt and the rate of change of the separation ds/dt to predict the expected temperature T_exp of the first and/or second components at which the predetermined interference - d_fo_rge will be achieved. As indicated at step 60, in the event that the expected temperature T_exp is in excess of the first predetermined threshold temperature T_w, then the rate of interference is increased at step 62, otherwise the rate of interference is decreased at step 64. One skilled in the art will, of course, appreciate that for the separation s defined as shown in Figure 3, ds/dt will be negative in the period between instants t₃ and t₄ and increasing the rate of interference comprises increasing the magnitude of ds/dt without changing the sign of ds/dt. Similarly, decreasing the rate of interference comprises decreasing the magnitude of ds/dt without changing the sign of ds/dt.

At step 66, a check is performed to determine whether the predetermined interference -d_fo_rge has been achieved. If the predetermined interference -d_fOr_ge has been achieved, then the movement of the first and/or second components ceases at step 68. Alternatively, if the predetermined interference -d_fOrge has not been achieved, then control returns to step 53 where the counter i is incremented and further sampling takes place at step 54.

Establishing the predetermined interference before the temperature of at least one of the first and second components falls below T_th1 allows the predetermined interference to be established before the first and/or second components 4 and/or 6 become unduly stiff at their respective end faces 8 and/or 10. Establishing the predetermined interference substantially simultaneously with the instant when the temperature of at least one of the first and second components falls to T_th1 as described above with reference to Figure 5, maximises the time to establish the predetermined interference. This is advantageous because the time taken for plastic deformation and fusion of the components to take place is, therefore, maximised which, in turn, maximises the weld quality. Alternatively, however, the predetermined interference -d_forg_e may be established before the temperature falls to the first predetermined threshold temperature T_th1 if it is preferable to do so.

In the example where the components 4 and 6 are steel pipes having an outer diameter of approximately 219 mm, and the initial target temperature T_ini is 980^°C, the rate of cooling of the pipes is relatively rapid. This requires that a forge movement of approximately 4.5 mm be completed within a time scale of less than approximately 500 ms in order that the end faces of the pipe components do not become so stiff so as to prevent completion of the forge movement altogether or so as to produce a weld of insufficient quality. Thus, the sampling rate used in such an example may be of the order of 30 Hz.

Following the cessation of all component movements at instant t₄ in Figure 3, the forces holding the components together are maintained constant during the period extending between instants t₄ and t₅ until the temperature T falls to a second threshold temperature T_th2. Maintaining these forces has the additional benefit of further improving the weld quality. In the case of steel pipes, a suitable second threshold temperature T,_h2 is approximately 600⁰C.

It should be understood that to further improve weld chemistry, the welding process outlined with reference to Figures 3, 4(a) to 4(e) and 5 may be performed in a controlled gaseous environment. Such a gaseous environment may, for example, be controlled by the controller 46. When welding steel pipes together, for example, the weld process may be performed in a gaseous mixture comprising 95% nitrogen and 5% hydrogen in which the concentration, pressure, flow rate and temperature of the gaseous mixture may be controlled for improved weld metallurgy.

In addition, all temperature, separation, force and welding environment data may be recorded for audit or quality control purposes.

Such a system and method for welding components is particularly suitable for welding steel pipe components in an offshore environment for applications in the oil or gas industries where weld time and weld quality are often critical.

It should be understood that the embodiments described herein are merely exemplary and that modifications may be made thereto without departing from the scope of the present invention. For example, although the first and second pipes 4 and 6 are described as being co-axially aligned with the aid of the cylindrical rod 14, the first and second pipes may, alternatively be aligned without the aid of the cylindrical rod 14.

Furthermore, although the welding system 2 and the associated method of welding have been described for the particular example of first and second pipes 4 and 6 which are welded together at an interface between their respective annular end faces 8 and 10, it should be understood that the first and second components 4 and 6 may not be pipes but may have corresponding features by which the first and second components are to be welded together, in such a generalised case, an alternative or modified alignment system to that of the actuators 20 and 22 shown in Figure 1 may be required. It may be, for example, that alignment of the corresponding features of the first and second components is required in up to three linear axes and/or up to three rotational axes requiring a more sophisticated alignment system than that depicted in Figures 1 and 2.

Although the orientation of the longitudinal axes of the pipes 4 and 6 in Figures 1 and 2 is shown as being in the vertical z direction, the longitudinal axes of the pipes 4 and 6 may instead be oriented horizontally or oriented in any other direction.

Although a system and method for welding first and second components 4 and 6 has been described, the method is not limited to welding together two components and may be used to weld together three or more components.

Although the first and second components 4 and 6 may be formed of an electrically conductive material such as steel, the first and second components 4 and 6 may, alternatively, be formed of any material which may be conductive or non- conductive or which may be metallic or non-metallic.

Although the first and/or second components may be heated by passing an electric current through the first and/or second components, the first and/or second components may be heated using any alternative method. The first and/or second components may be heated by generating heat in or supplying heat to the first and/or second components. The first and/or second components may, for example, be heated by magnetic induction, by the action of friction or by supplying heat from an external heat source such as a flame, or any other method, or any combination thereof.

Although the movements of the pipes 4 and 6 in the welding system 2 of Figures 1 and 2, are described as being controlled by the actuators 20 and 22, it should also be understood that the weight of the pipes 4 and/or 6 may at least contribute to the forces acting to establish the interference.

Furthermore, it should be understood that the actuators 20, 22 may be used to test the weld. The actuators 20, 22 may, for example, be operable so as to apply a force to at least one of the first and second components to test weld strength.

It should also be understood that at least some of the elements constituting the system 2 of Figures 1 and 2 may be provided on a single assembly for ease of positioning with respect to and/or for ease of use for welding the first and second components together.

Claims

CLAIMS:

1. A method for welding a first component to a second component, comprising: heating at least one of the first and second components; and

establishing a predetermined interference between the first and second components before a temperature of at least one of the first and second components falls below a predetermined temperature.

2. The method according to claim 1 , wherein the predetermined interference is established between the first and second components by compressing the first and second components together over a predetermined relative distance.

3. The method according to claim 1 or 2, comprising applying a force to at least one of the first and second components so as to compress the first and second components together to establish the predetermined interference.

4. The method according to any preceding claim, wherein the step of establishing the predetermined interference at least partially overlaps the step of heating at least one of the first and second components.

5. The method according to any one of claims 1, 2 or 3, wherein the step of establishing the predetermined interference follows the step of heating at least one of the first and second components.

6. The method according to any preceding claim, comprising controlling the movement of at least one of the first and second components over a predetermined relative distance.

7. The method according to any preceding claim, wherein the predetermined interference is established substantially simultaneously with the instant when the temperature of at least one of the first and second components falls to the predetermined temperature.

8. The method according to any preceding claim, comprising predicting the instant when the temperature of at least one of the first and second components will fall to the predetermined temperature.

9. The method according to any preceding claim, comprising controlling the velocity of at least one of the first and second components so as to establish the predetermined interference before a temperature of at least one of the first and second components falls below the predetermined temperature.

10. The method according to any preceding claim, comprising sensing the temperature of at least one of the first and second components.

11. The method according to any preceding claim, comprising sensing the temperature at multiple points of at least one of the first and second components.

12. The method according to any preceding claim, comprising sensing the temperature at multiple points around at least a portion of an interface between the first and second components.

13. The method according to claim 11 or 12, wherein the temperature of at least one of the first and second components is defined by the minimum temperature measured across all the multiple points.

14. The method according to any preceding claim, comprising monitoring the relative positions of the first and second components.

15. The method according to any preceding claim, comprising controlling an alignment system to move at least one of the first and second components.

16. The method according to any preceding claim, comprising sensing data representative of the forces applied to at least one of the first and second components.

17. The method according to any preceding claim, comprising:

establishing the predetermined interference between the first and second components before a temperature of at least one of the components falls below a first predetermined temperature; and then

holding the first and second components together by a predetermined force to maintain the predetermined interference at least until the temperature of at least one of the first and second component falls to a second predetermined temperature.

18. The method according to any preceding claim, comprising electrically heating at least one of the first and second components.

19. The method according to any preceding claim, comprising inductively heating at least one of the first and second components.

20. The method according to any preceding claim, comprising welding the first component to the second component in a controlled environment.

21. The method according to any preceding claim, comprising heat treating the components subsequent to welding together.

22. The method according to any preceding claim, comprising heat treating a weld region defined between the joined components.

23. The method according to any preceding claim, configured for welding first and second tubular bodies together.

24. A system for welding a first component to a second component comprising: a heating arrangement for heating at least one of the first and second components; and

25. The system according to claim 24, comprising a temperature sensor arranged to measure the temperature of at least one of the first and second components.

26. The system according to claim 25, wherein the temperature sensor is configured to measure a temperature distribution around at least a portion of an interface between the first and second components.

27. The system according to claim 24, 25 or 26, comprising an alignment system configured to be controlled by the controller to move at least one of the first and second components in response to the temperature of at least one of the first and second components.

28. The system according to claim 27, wherein the alignment system comprises an actuator.