Clamp for an orbital welding system and orbital welding system with such clamp

Abstract

An orbital welding system with a first pipe comprising a straight portion and a substantially bent portion, and a second pipe. An orbital welder is arranged to orbitally weld open faces of the pipes. A clamp having two opposing jaws (122) moveable between an unclamped position and a clamped position. Each jaw (122) comprises a curved surface (150) arranged to, in the clamped position, engage with at least a part of the straight portion of the first pipe so as to hold it in place for the orbital welder. Each curved surface comprises a first edge cutaway (130) arranged adjacent to the bent portion of the first pipe such that a first part of the bent portion of the first pipe passes through each first edge cutaway (130).

Description

[0001] XA24121

[0002] - 1 -

[0003] ORBITAL WELDING CLAMP

[0004] FIELD

[0005] The present invention relates to an orbital welding system. In particular, but not exclusively, the present invention relates to an orbital welding system for clamping and welding closer to a curved portion of a pipe.

[0006] BACKGROUND

[0007] Orbital welding is an efficient and repeatable method for welding two pipes together. In operation, each pipe is clamped such that their corresponding open faces - the open faces to be welded together - are held in contact, or substantially proximate to one another, to form the basis of a weld seam. An orbital welder is thus positioned adjacent to the seam and is be able to rotate circumferentially about the outer surfaces of the pipes so as to weld along the seam - as such, it is perceived to “orbit” about the pipes.

[0008] For an orbital welder to accurately rotate about a weld seam in a circular motion, a bulky jig arrangement is required to hold the orbital welder in close proximity to the pipes. Orbital welders require a servomotor(s) or the like to move the welding head (i.e. the arcing electrode) in a circular path about the pipes, while a clamping arrangement is used to secure the welding head to the pipes. For orbital welders operated in situ - for example welding pipes in a confined compartment within a ship - a compact profile is required so that they can be deployed in cramped environments. As such, the clearance space immediately between the pipes to be welded and the welder itself is often as small as possible. Additionally, large-scale engineering projects (e.g. ship building) can require a high rate of use of orbital welders, such that reducing turnaround time between welds is critical.

[0009] Conventionally, an orbital welder will be secured to linear portions of the two pipes - this is because the orbital welder needs to follow a uniform circular path to ensure sufficiently high efficacy of welds. The clamps are sized and position so as to provide sufficient pressure on respective pipes while simultaneously not clashing with the orbital welder.

[0010] However, there are situations where at least one of the two pipes needs to be welded relatively close to a bend in the pipe. Present orbital welders require XA24121

[0011] - 2 - a relatively large clearance between the adjacent clamp and the beginning of the bent portion of the pipe, such that more complex and / or difficult-to-access welds are not possible with conventional orbital welders.

[0012] The present invention seeks to improve the ability of orbital welders to weld bent pipes.

[0013] SUMMARY

[0014] According to an aspect of the present invention, there is provided an orbital welding system comprising a first pipe comprising a straight portion and a substantially bent portion and a second pipe. The system further comprises an orbital welder arranged to orbital ly weld an open face of the straight portion of the first pipe to a corresponding open face of the second pipe. The system further comprises a clamp comprising two opposing jaws moveable between an unclamped position and a clamped position. Each jaw comprises a curved surface arranged to, in the clamped position, engage with at least a part of the straight portion of the first pipe so as to hold it in place for the orbital welder. Each curved surface comprises a first edge cutaway arranged adjacent to the bent portion of the first pipe such that, in the clamped position, a first part of the bent portion of the first pipe passes through each first edge cutaway.

[0015] The present invention permits pipes with bent portions to be orbitally welded far closer to the bend than has previously be possible. The straight portion is advantageously maintained in the required orientation for orbital welding, since the first part of the bent portion - which would otherwise clash with the clamp - does not deflect the first pipe. This permits more complex and often compact pipework to be orbitally welded with improved speed and reduced repair rate, since minimal modification to the clamp is required between welds. It also has the added benefit of greater accuracy and reduced deformation risks.

[0016] Each first edge cutaway may be arranged such that the curved surface is arranged to, in the clamped position, engage with at least a second part of the bent portion of the first pipe. Alternatively, the curved surface may not engage with the bent portion of the first pipe at all so as to not deflect the first pipe. However, the curved surface is arranged such that some of the bent portion - i.e. the second part - may contact one another without unduly deflecting, thus providing more surface area for increased grip. XA24121

[0017] - 3 -

[0018] Each first edge cutaway may be arranged at a location on the corresponding jaw distal to the orbital welder.

[0019] Each jaw may further comprise an arm arranged on an opposing edge of the curved surface to the first edge cutaway. Preferably, each arm may be arranged at a location on the corresponding jaw distal to the orbital welder. By providing the arm with sufficient clearance from the orbital welder, this prevents clashing or interference between the arm and any ancillary equipment of the orbital welder. This favourably allows the orbital welder to operate closer to the bent portion.

[0020] Each curved surface may comprise at least two clamping surfaces, wherein the clamping surfaces are arranged to engage with pipes of different diameters. Preferably, the clamping surfaces may comprise a first clamping surface having a first cylindrical radius of curvature, and, a second clamping surface having a second cylindrical radius of curvature that is smaller than the first cylindrical radius of curvature. The second clamping surface may be set within the first clamping surface such that they form a continuous surface. The orbital welding system can clamp and weld a greater range of pipes with bent portions each having different diameters. As such, only one clamp can be used to clamp a variety of pipes, reducing the cost of requiring clamps of different sizes and shapes, and improving the efficiency at which complex pipework arrangements can be welded.

[0021] Preferably, the second clamping surface may be off-centre relative to the first clamping surface.

[0022] Each jaw may further comprise a second edge cutaway arranged on an opposing edge of the curved surface to the first edge cutaway, and at a location proximal to the orbital welder. Preferably, the portion of the curved surface may be arranged adjacent to the second edge cutaway is arranged such the first and second clamping surfaces are set symmetrical about a centre line of the second clamping surface. This further reduces the risk of clashing between the orbital welder and the clamp, in particular where smaller diameter pipes are being orbitally welded.

[0023] According to a second aspect of the present invention, there is provided a clamp for an orbital welder, the clamp comprising two opposing jaws moveable between an unclamped position and a clamped position. Each jaw comprises a XA24121

[0024] - 4 - curved surface arranged curving inwards relative to a longitudinal axis of the clamp. Each curved surface is arranged to, in the clamped position, engage with at least a part of a straight portion of a pipe such that the straight portion is substantially co-axially aligned with the longitudinal axis. Each curved surface comprises a first edge cutaway arranged at a corner of the curved surface to allow a part of a bent portion of the pipe to pass through each first edge cutaway, such that the pipe is held fixed without deflecting the straight portion from co-axial alignment.

[0025] The clamp is far more versatile to secure pipes with bent portions of various angle or size, and permits orbital welding to be performed far closer to the bend than has previously be possible.

[0026] According to a third aspect of the present invention, there is provided an orbital welding system according the first aspect of the present invention, wherein the clamp is a clamp according to the second aspect of the present invention.

[0027] BRIEF DESCRIPTION OF THE FIGURES

[0028] Embodiments of the invention will now be described by way of example only with reference to the figures, in which:

[0029] Figure 1 shows a profile view of an example orbital welding system according to the present invention;

[0030] Figure 2 shows a front view of an example orbital welding system according to the present invention;

[0031] Figure 3a shows a profile view of an example jaw according to the present invention;

[0032] Figure 3b shows a profile view of an example jaw engaged with a first pipe portion according to the present invention;

[0033] Figure 4 shows a front view of an example clamp according to the present invention;

[0034] Figure 5 shows a perspective view of an example jaw of a clamp according to the present invention; and,

[0035] Figure 6 shows perspective view of an example orbital welding system according to the present invention.

[0036] DETAILED DESCRIPTION XA24121

[0037] - 5 -

[0038] The present invention provides an orbital welding system for welding a pipe in relative close proximity to a bend in the pipe. In particular, provided is a clamp which abuts with a bend in a pipe to be welded.

[0039] Figure 1 shows an example orbital welding system 100 according to the present invention. The orbital welding system 100 comprises a first pipe 102 comprising a straight portion 102a and a substantially bent portion 102b. The orbital welding system 100 further comprises a second pipe 104. The second pipe 104 comprises a straight portion 104a, wherein the open face of the straight portion 102a of the first pipe 102 is to be welded to a corresponding open face of the straight portion 104a of the second pipe 104. The second pipe 10 may comprise a substantially bent portion, or may comprise straight portions.

[0040] It will be appreciated by the skilled person that a bent portion of a pipe is a substantially arcuate or curved section. The bent portion may curve in only one plane. The bent portion may form a “U” shape. The bent portion may form a right angle. Indeed, the bent portion may form any arc having any suitable radius of curvature, the arc having any angle above 0 degrees. The bent portion may curve in more than one direction, for example an “S” shape.

[0041] The system 100 further comprises an orbital welder 110 arranged to orbital ly weld the open face of the straight portion 102b of the first pipe 102 to the corresponding open face of the second pipe 104. The orbital welder 110 may be any known type of orbital welder, for example a tungsten inert gas (TIG) welder. In this example, the orbital welder 110 may comprise a welding head and a welding electrode (not shown) arranged to move in an orbiting plane 0--0 immediately adjacent to the open faces. The orbital welder 110 may also comprise an inert gas feed pipe (not shown) arranged to feed the welding head and orbit a full revolution of the pipes 102, 104 without interfering with the weld melt pool.

[0042] The orbital welder 110 may further comprise a servomotor(s) or the like (not shown) to move the welding head in a circular path on the orbiting plane O- -O while maintaining contact (or substantially near contact) between the welding electrode and the pipes 102, 104. The servomotor may be arranged to move the welding head along a track or the like (not shown) disposed around the weld area, for example a circular track arranged concentrically about the pipes. Alternatively, the welding head may be attached to the jig arrangement in such a manner that XA24121

[0043] - 6 - it can rotate, and the motor may be arranged to move the welding head relative to the jig arrangement. The welding head may be moveable via an electronic rotating gear or the like. The orbital welder 110 may further comprise a subsequent servomotor or linear actuator arranged to move the welding held radially on the orbiting plane 0--0 so as to increase and / or decrease the radius of orbit. The present invention is not limited to any specific type of orbital welder, and is envisioned to operate with all known orbital welders.

[0044] The orbital welder may comprise a jig arrangement 112 arranged to support the orbital welder 110 and any ancillary equipment, i.e. a welding head, a servomotor(s), an inert gas feed pipe, a track(s), a clamp(s) 120 (see below), and / or any other equipment that the skilled person would understand as part of an orbital welding system.

[0045] The system 100 further comprises a clamp 120 (see figure 4 for the clamp 120 in isolation) comprising two opposing jaws 122 (only one shown in figure 1 ) moveable between an unclamped position and a clamped position so as to clamp the first pipe 102. Figure 1 shows the clamp 120 in the clamped position, i.e. the first pipe 102 is fixed in position such that the orbital welder 110 can perform welding orbits. Please see figure 3a for a detailed description of the jaw 122 of figure 1 .

[0046] The second pipe 104 may be clamped by a clamp substantially the same as the clamp 120, but reversed direction - this would permit two pipes, both having respective straight and bent portions to be orbitally welded together. However, the present invention is not limited to a second clamp 120 for the second pipe 104. The second pipe 104 may be clamped by any conventional clamp where the second clamp 104 is only straight, or has a sufficiently long straight portion to permit use of a conventional clamp. Alternatively, the second pipe 104 may not be clamped at all, for example where it is already held in place to a fixture (e.g. a bulkhead in a ship) or is already part of a semi-completed pipe network. The present invention is not limited to a clamp for the second pipe 104, but it will be appreciated that the clamp 120 may be used with either pipes 102, 104 without modification.

[0047] Figure 2 shows the example orbital welding system 100 from the front. Figure 1 shows the two opposing jaws 122a, 122b in the clamped position. Each jaw 122a, 122b comprises a curved surface 150 (see figure 3a) arranged to, in XA24121

[0048] - 7 - the clamped position, engage with at least a part of the straight portion 102a (see figure 1 ) of the first pipe 102 so as to hold it in place for the orbital welder 110. Each curved surface is arranged curving inwards relative to a longitudinal axis L of the clamp, i.e. running in the same direction as a central axis of the straight portion 102a of the first pipe 102. In other words, the longitudinal axis L of the clamp 120 is arranged substantially perpendicular to the orbiting plane 0--0 and such that the longitudinal axis L intersects with the centre of orbit of the orbital welder 110.

[0049] Referring briefly to figure 3b, the curved surface of each jaw 122 is arranged to, in the clamped position, engage with at least a part of a straight portion 102a of a pipe 102 such that the straight portion 102a is substantially coaxially aligned with the longitudinal axis L. Returning to figure 2, this co-axial alignment can be seen with both the first pipe 102 and the jaws 122a, 122b centred on the longitudinal axis L.

[0050] Figure 3a shows one jaw 122 of the present invention in isolation, with the curved surface 150 shown. Each curved surface 150 comprises a first edge cutaway 130 arranged at a corner of the curved surface 150 to allow a part of a bent portion 102b of the first pipe 102 to pass through each first edge cutaway, such that the first pipe 102 is held fixed without deflecting the straight portion from co-axial alignment. Referring briefly to figure 3b, the first edge cutaway 130 is arranged adjacent to the bent portion 102b of the first pipe such that, in the clamped position, a first part of the bent portion 102b of the first pipe 102 passes through each first edge cutaway 130.

[0051] Generally, but not exclusively, the surface of the bent portion 102b proximate to the inner curve of the bent portion 102b will pass through each first edge cutaway 130.

[0052] Each first edge cutaway 130 may be arranged at a location on the corresponding jaw 122 distal to the orbital welder 110. Referring briefly to figure 1 , the orbital welder 110 is shown to the right of the jaw 122 and the edge cutaway is arranged at the distally left end of the jaw 122.

[0053] Each jaw may further comprise an arm 124 arranged on an opposing edge of the curved surface 150 to the first edge cutaway 130. In the example of figure 3a, the arm 124 is arranged at a top edge of the curved surface 150, and the first edge cutaway 130 is arranged at a bottom edge of the curved surface 150. It will XA24121

[0054] - 8 - be appreciated by the skilled individual that top and bottom are relative in this context, and indeed the jaws 122 may be orientated in any suitable direction without deviating from the present invention.

[0055] Each arm 124 may be arranged at a location on the corresponding jaw distal to the orbital welder. In the example of figure 3a, the arm 124 is arranged at the extremity of the curved surface 150 so as to improve the clearance between the orbital welder 110 (and any ancillary equipment).

[0056] Each curved surface 150 may comprise at least two clamping surfaces 150a / c, 150b, wherein the clamping surfaces 150a / c, 150b are arranged to engage with pipes 102 of different diameters.

[0057] Figure 4 shows the clamp 120 of the present invention with at least two clamping surfaces 150a / c, 150b. The clamp comprises a pair of jaws 122a, 122b, a respective pair of arms 124a, 124a, a main body 126 for the arms 124 to attach to, and a respective pair of actuators 128a, 128b for moving respective jaws 122a, 122b between unclamped and clamped positions. The jaws 122a, 122b are lever operated - in an alternative arrangement, the jaws 122a, 122b may be linearly operated, or any suitable means for moving the jaws between positions. The main body 126 may be any suitable or known arrangement. The actuators 128a, 128b may be any suitable or known actuators, e.g. manually operated, electronically operated, and pneumatically operated.

[0058] A first clamping surface 150a / c has a first cylindrical radius of curvature R1 and a second clamping surface 150b has a second cylindrical radius of curvature R2. The second cylindrical radius of curvature R2 is smaller than the first cylindrical radius of curvature R1. The first clamping surface 150a / c comprises an upper first clamping surface 150a and a lower first clamping surface 150c. The second clamping surface 150b is set within the upper first clamping surface 150a and the lower first clamping surface 150c, such that they form a continuous surface, i.e. the curved surface 150. As such, the jaws 122a, 122b each form a compounding radius suitable for engaging with pipes of varying diameters.

[0059] The first clamping surface 150a / c and the second clamping surface 150b each have respective longitudinal axes extending perpendicularly relative to their respective cylindrical radii of curvature R1 , R2. These longitudinal axes are substantially parallel to the longitudinal axis L of the clamp. As such, each XA24121

[0060] - 9 - clamping surfaces 150a / c, 150b forms a surface arranged to engage with the straight portion of the first pipe.

[0061] As will be appreciated by the skilled person, the longitudinal axis L of the clamp does not necessarily have to overlap with centre of radii R1 , R2 - whether in a clamped or unclamped position, or any position there in-between. Indeed, while the clamping surfaces 150a / c, 150b have a respective cylindrical radii of curvature R1 , R2, this does not limit each to only engaging with pipes having exactly the same radii - rather, the clamp 120 is suitable to engage with a greater range pipes with different radii above R1 , between R1 and R2 (inclusive), and below R2.

[0062] The clamping surfaces 150a / c, 150b may have profiles that do not exactly match a cylindrical radius of curvature without deviating from the present invention. For example, the clamping surfaces 150a / c, 150b may be formed of an elliptic cylinder having respective semi-major and semi-minor axes. Alternatively, the clamping surfaces 150a / c, 150b may be formed of a collection of polygons or any other suitable high surface-friction concaved shape. Crucially, the clamping surfaces 150a / c, 150b - and more generally the curved surface 150 - are shaped such that it is suitable to reversibly engage with, and fixedly hold, a pipe in place such that it may be orbitally welded in a manner described by the present invention.

[0063] In an alternative arrangement, there may be a third, fourth or any number of clamping surfaces each set within one another. Preferably, each subsequent clamping surface is set within the preceding clamping surface, and the radii or curvature decreases each time.

[0064] Figure 5 shows one jaw 122 of the present invention in isolation, with the first clamping surface 150a / c and the second clamping surface 150b. The second clamping surface 150b is off-centre relative to the first clamping surface 150a / c. In other words, the second clamping surface 150b is misaligned with the centre line of the curved surface 150 in general. In the example, the second clamping surface 150b is arranged towards the bottom of the curved surface 150, such the lower extremity of the second clamping surface 150b is bordered by the first edge cutaway 130. As such, a portion of the lower first clamping surface 150c at the end distal to the orbital welder is removed to form the first edge cutaway 130. This permits the bent portion of the first pipe to pass through the first edge XA24121

[0065] - 10 - cutaway 130 unhindered. Alternatively, the second clamping surface 150b may be arranged towards the top of the curved surface 150, or elsewhere in a misaligned manner.

[0066] Depending on the diameter of the pipes 102, 104 being welded together, it may be that only the second clamping surface 150b engages with the first pipe 102 (where the first pipe has a small enough diameter). As such, the first edge cutaway 130 in the lower first clamping surface 150c permits the bent portion 102a to pass through. In particular, by having the first edge cutaway 130 border the lower extremity of the second clamping surface 150b, the bent portion 102a does not clash with any part of the lower first clamping surface 150c. Alternatively, it may be that only the first clamping surface 150a / c engages with the first pipe 102 (where the first pipe has a small enough diameter).

[0067] Each jaw 122 further comprises a second edge cutaway 140 arranged on an opposing edge of the curved surface 150 to the first edge cutaway 130, and at a location proximal to the orbital welder. In the example, the second edge cutaway 140 is a single rectangular cutaway. Alternatively, the second edge cutaway 140 is any suitable shape. The second edge cutaway 140 may comprise a series of at least two stepped or notched edges.

[0068] A portion 142 of the curved surface 150 arranged adjacent to the second edge cutaway 140 is arranged such the upper and lower first clamping surfaces 150a, 150c are set symmetrical about a centre line C of the second clamping surface 150b. For example, where the second clamping surface 150b is engaged with a smaller diameter pipe, the second edge cutaway 140 permits the orbital welder and any ancillary equipment to be positioned so as to perform orbital welding without clashing with the jaws 122. This is because the symmetrical nature of the portion 142 provides the same clearance at the top of the jaw 122 as at the bottom of the jaw 122. For example, where a servomotor is located immediately next to the welding head, the servomotor is able to pass through the second edge cutaway 140 without clashing with the jaw 122.

[0069] A fundamental requirement of any clamp is to have sufficient clamping surface area to apply the required pressure to fixedly hold an article in place. In the case of the example in figure 5, the jaws 122 of the clamp 120 are extended in the longitudinal axis L to ensure that there is sufficient clamping surface 150a / c, 150b. In particular, the portion 142 permits for a first pipe with a bent portion to XA24121

[0070] - 11 - be held securely, while the first edge cutaway 130 permits the bent portion to pass there through without deflecting the first pipe from the optimal orientation to be welded by the orbital welder. Without the portion 142 extending towards the orbital welder, the clamp 122 would not provide sufficient support. The second first and second edge cutaways 130, 140 facilitate welding of more complex pipework, and with the ability to clamp both large and small diameter pipes without clashing and / or negatively affecting the quality of the weld.

[0071] Figure 6 shows the orbital welding system 100 and the clamp 120 according to the present invention in a perspective view. The jig 112 is arranged to hold both the orbital welder 110 and the clamp 120 in place. Alternatively, the clamp 120 may be held in place by a different jig, or some other arrangement. The clamp 120 may positioned entirely within the confines of the orbital welder 110, further reducing the size of the system 100 and permitting orbital welder 110 to be operated in confined and packed environments.

[0072] A first pipe 102 and a second pope 104 are shown clamped in situ. As can be seen, the jaws 122a, 122b are engaged a part of the bent portion of the first pipe 102, wherein the first edge cutaway 130 (only visible for jaw 122a) permits the bent portion to pass there through without deflecting the straight portion of the first pipe (not visible) from the required position for the orbital welder 110 to perform welding operations. As such, the system 100 and clamp 120 of the present invention permits orbital welding to be performed far closer to the bend in the first pipe 102 than has been possible in the prior art. In particular, the weld may be located around 50% closer to a bend than is possible in the prior art. In an example, welds that were previously around 125-200mm from a bend can be welded, with the present invention, around 50-100mm from a bend. The diameter of the pipes may have a range of around 20-100mm, or preferably around 30- 50mm.

Claims

XA24121- 12 -CLAIMS1. An orbital welding system comprising: a first pipe comprising a straight portion and a substantially bent portion; a second pipe; an orbital welder arranged to orbitally weld an open face of the straight portion of the first pipe to a corresponding open face of the second pipe; and, a clamp comprising two opposing jaws moveable between an unclamped position and a clamped position, wherein each jaw comprises a curved surface arranged to, in the clamped position, engage with at least a part of the straight portion of the first pipe so as to hold it in place for the orbital welder, and, wherein each curved surface comprises a first edge cutaway arranged adjacent to the bent portion of the first pipe such that, in the clamped position, a first part of the bent portion of the first pipe passes through each first edge cutaway.

2. An orbital welding system according to claim 1 , wherein each first edge cutaway is arranged such that the curved surface is arranged to, in the clamped position, engage with at least a second part of the bent portion of the first pipe.

3. An orbital welding system according to claim 1 or 2, wherein each first edge cutaway is arranged at a location on the corresponding jaw distal to the orbital welder.

4. An orbital welding system according to any preceding claim, wherein each jaw further comprises an arm arranged on an opposing edge of the curved surface to the first edge cutaway.XA24121- 13 -5. An orbital welding system according to claim 4, wherein each arm is arranged at a location on the corresponding jaw distal to the orbital welder.

6. An orbital welding system according to any preceding claim, wherein each curved surface comprises at least two clamping surfaces, wherein the clamping surfaces are arranged to engage with pipes of different diameters.

7. An orbital welding system according to claim 6, wherein the clamping surfaces comprises: a first clamping surface having a first cylindrical radius of curvature; and, a second clamping surface having a second cylindrical radius of curvature that is smaller than the first cylindrical radius of curvature, wherein the second clamping surface is set within the first clamping surface such that they form a continuous surface.

8. An orbital welding system according to claim 7, wherein the second clamping surface is off-centre relative to the first clamping surface.

9. An orbital welding system according to any preceding claim, wherein each jaw further comprises a second edge cutaway arranged on an opposing edge of the curved surface to the first edge cutaway, and at a location proximal to the orbital welder.

10. An orbital welding system according to claim 9 when dependent on claim 7 or 8, wherein the portion of the curved surface arranged adjacent to the second edge cutaway is arranged such the first and second clamping surfaces are set symmetrical about a centre line of the second clamping surface.XA24121- 14 -11. A clamp for an orbital welder, the clamp comprising two opposing jaws moveable between an unclamped position and a clamped position, wherein: each jaw comprises a curved surface arranged curving inwards relative to a longitudinal axis of the clamp; each curved surface is arranged to, in the clamped position, engage with at least a part of a straight portion of a pipe such that the straight portion is substantially co-axially aligned with the longitudinal axis; and, each curved surface comprises a first edge cutaway arranged at a corner of the curved surface to allow a part of a bent portion of the pipe to pass through each first edge cutaway, such that the pipe is held fixed without deflecting the straight portion from co-axial alignment.

12. An orbital welding system according any of claims 1 to 10, wherein the clamp is a clamp according to claim 11 .

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