WO2000041488A2

WO2000041488A2 - Welding machine

Info

Publication number: WO2000041488A2
Application number: PCT/GB2000/000077
Authority: WO
Inventors: Leslie Ernest Power; Reginald Taylor; Michael Anthony Brennan
Original assignee: Meltax Gmbh
Priority date: 1999-01-13
Filing date: 2000-01-13
Publication date: 2000-07-20
Also published as: WO2000041488A8; AU1993700A; WO2000041488A3

Abstract

An internal pipe welding machine (10) including at least one welder assembly (50) rotatable relative to a chassis (11) of the internal pipe welding machine for welding a joint between a pipeline (1) and a pipe (3), the welder assembly being supplied by a cable (385) which carries at least one of a welding current and a control signal and a cable slack adjuster for taking up slack in the cable including a first disc arrangement having at least a first disc (924) rotatably mounted on a first pivot, the first pivot (929) being fixed relative to the internal pipe welding machine chassis, and a second disc arrangement having at least a second disc (925) rotatably mounted on a second pivot (930), the second pivot (930) being moveable relative to the chassis, the cable being wound around the at least one first and the at least one second disc, with the cable slack being taken up by movement of the first disc arrangement relative to the second disc arrangement.

Description

WELDING MACHINE

The present invention relates to mternai pipe welding macmnes.

Thus accorαing to the present invention there is provided an internal pipe welding machine including at least one welder assembly rotatable relative to a chassis of the internal pipe welding machine for welding a joint between a pipeline and a pipe, the welder assembly being supplied by a cable which carries at least one of a welding current and a control signal ana a cable slack adjuster for taking up slack in the cable including a first disc arrangement having at least a first disc rotatably mounted on a first pivot, the first pivot being fixed relative to the internal pipe welding machine chassis, and a second disc arrangement having at least a second disc rotatably mounted gμ a second pivot, the second pivot being movea-ble relauve to the chassis, the cable being wound around the at least one first and the at least one second disc, with the cable slack being taken up by movement of the first disc arrangement relative to the second disc arrangement.

According to a further aspect of the present invention there is provided an internal pipe welding machine including at least one welder assembly rotatable relauve to a chassis of the internal pipe welding machine for welding a joint between the pipeline and the pipe, the or at least one of the welder assemblies being supplied by a slip πng which carries at least one of a welding current and a control signal.

According to a further aspect of the present invention there is provided an internal pipe welding machine including a motor arrangement having pipe engaging means for propelling the intemai pipe welding machine from a welded joint or a pipeline to an open end of a pipeline, and a control arrangement capable of varying the power of the motor arrangement.

According to a further aspect of the present lnventiόT-vthere is provided an internal pipe welding macnine including a pipeline wail sensor, the sensor in use acting to detect the end of a pipeline, in which the sensor does not contact the pipeline in use. The present invention will now be described by way of example only with reference to the accompanying drawings in which:-

Figures 1-5 are successive composite cross-sectional views of an internal pipe welding machine according to the present invention;

Figures 1A-5A correspond to figures 1-5 with different components labelled for clarity

Figures 6-8, 10,15 and 17-21 show enlarged views of various components as shown in figure 2;

Figure 9 is a view on arrow A3 of figure 8;

Figure 11 is a view on arrow B3 of figure 3 showing a clamp shaft;

Figure 12 is a view similar to figure 1 showing shaft 376;

Figures 13 and 13A are developed views taken in the direction of arrow C3 of figure 3;

Figure 14 is a schematic view of the arrangement of the roller assemblies when viewed from the front of the welding machine;

Figure 16 is an axial view taken from the rear of the machine of the front clamp support 324B, also shown for convenience is the arrester rod guide lug 418A which is only present on rear clamp support 324A;

Figure 22 is a radial view of rod 399 and associated components

Figure 6A is an enlarged view of part of figure 4A; Figure 7A is a cross-section view taken along the mounting axle of track laying idle arrangement 612;

Figure 8A is a cross-section view taken along the rear idle sprocket axle 644 of track laying idle arrangement 612;

Figure 9A is an isometric schematic view of a track laying drive arrangement 612;

Figure 23 is a schematic view of a slack adjuster according to the present invention;

Figure 24 is a view in the direction of arrow 980 of figure 23;

Figures 25 and 26 are flow diagrams showing control arrangements for a motor arrangement 950;

Figure 27 is a view similar to figure 18 showing a further embodiment of the present invention; and

Figure 28 is a schematic view of the internal pipe welding machine advancing along the pipeline.

With reference to figures 1-5 there is shown an internal pipe welding machine 10 positioned within a pipeline 1. The pipeline 1 comprises a series of pipes each of which have been welded together to ensure a fluid tight pipeline.

The internal pipe welding machine 10 enables the joint 6 between the end 4 of pipeline 1 and end 5 of adjacent pipe 3 to be welded from the inside. Additionally the joint 6 can be welded from the outside by the use of a separate external pipe welding machine.

The internal pipe welding machine 10 comprises the following major components:-

a) Nose cone assembly 20 b) Thruster assembly 30 c) A plurality of arrester assemblies 40 d) A plurality of automatic welder assemblies 50 e) An articulated joint assembly 60 f) A drive assembly 70 g) An air receiver 80 h) A command rod coupling 85, and i) A chassis 11

The nose cone assembly 20 includes a manual welder 19 including a welding torch 21 along with a spool of welding wire 22. The nose cone assembly 20 includes a plate 23 ^"to which the thruster assembly 30 is connected. The nose cone assembly also includes a plurality of circumferentially equispaced pivotal guide arms 24 (in this case six) which are also connected to the thruster assembly 30.

Thruster assembly 30 includes a plurality of circumferentially equispaced pipe engaging clamps 31, a pair of guide wheels 32 and a rotatable ring member 33.

Mounted on ring member 33 is a plurality (in this case six) of circumferentially equispaced automatic welder assemblies 50.

A plate 61 of articulated joint assembly 60 is attached to the back of the thruster assembly 40. Attached to plate 61 is a plurality (in this case three) of circumferentially equispaced arrester assemblies 40. Each arrester assembly 40 includes an extendable shaft 41 with a positioning abutment 42 at one end.

The articulated joint assembly 60 allows the front subframe 12 of chassis 11 to articulate relative to the rear subframe 13 of chassis 11 and includes an articulated joint 62 and a plurality (in this case two) of loading wheels 63.

A plate 71 of the drive assembly 70 is attached to the back of the articulated joint assembly 60. Drive assembly 70 includes a plurality (in this case three) of circumferentially equispaced track laying arrangements 72. Drive assembly 70 also includes 2 batteries 73 and a tank 74 of inert welding shield gas. A plate 75 of the drive assembly 70 is connected to the air receiver assembly 80.

The air receiver assembly 80 includes an air receiver tank 81.

At the front of the nose cone assembly 20 there is positioned a command rod rear coupling 85 which is releasably connected to a command rod 86. Command rod 86 is of a length such that it projects beyond the end of pipe 3 and includes at that end a command ^"rod control panel 981 (see figure 28) which can be used to control various functions of the machine and a command rod front coupling (not shown) which releasably connects the command rod to a supply of services eg. compressed air, battery charging current and welding current generators. Control signals pass down the command rod, to the machine, along with service supplies such as compressed air, welding current, and welding shield gas.

Once the internal pipe welding machine has completed a weld sequence, continued operation of the machine is as follows:-

1) An operator standing at the open end of the pipeline, ie. at the open end of the pipe that has newly been welded into place, adjacent the command rod control panel disconnects the command rod front coupling from the services and then operates the panel so as to retract the clamps and then start the air motors which in turn drive each track drive 72 so as to advance the machine along the pipeline 1 with the front subframe 12 being carried on guide wheels 32. The air motors are supplied by pressurised air from the air receiver tank 81.

The machine is advanced, pushing the control rod before it, the control rod being fed into the next pipe 982 to be welded which has previously been located proximate the end of the pipeline (see figure 28). A pipeline wall sensor 910 mounted on the machine detects the presence of the pipeline wall. When the nose cone assembly 20 projects from the open end of the pipeline 1 to such an extent that the pipeline wall sensor no longer detects the presence of the wall, the machine is automatically stopped (see further description below).

2) If necessary the operator further advances the machine by operating a machine control panel 983, situated within the nose cone assembly and accessible to the operator, such that the automatic welder assemblies 50 project beyond the open end of the pipeline.

3) The extendable shaft 41 of each arrester assembly 40 is then extended and rotated such that the positioning abutment 42 is axially aligned with a weld plane of the welder assemblies 50 and radially aligned with the end of the pipeline.

4) The operator then reverses the machine until the positioning abutments 42 contact the pipeline and prevent further rearward movement of the machine. At this position the weld plane of the automatic welder assemblies are now aligned with the end of the pipeline (see fig 1).

5) The rearmost pipe-engaging clamps 31 A are then deployed to clamp the machine securely relative to the pipeline.

6) Each positioning abutment 42 is then rotated about the axis of the extendible shaft 41, and the extendible shaft is then withdrawn such that each positioning abutment lies between two adjacent rear pipe-engaging clamps 31 A, clear of the path of the automatic welder assemblies (see below).

7) The section of pipe is then moved such that its end to be welded abuts the end 4 of the pipeline.

8) The operator then deploys the front pipe -engaging clamps 3 IB by using the command rod control panel. 9) At some convenient time following stage 1) above of the operation of the machine, and prior to welding (see below) the control rod front coupling is reconnected to the supply of services and the air receiver tank 81 can be re -pressurized if necessary.

10) Welding of the joint 6 between the pipe 3 pipeline 1 then occurs in two stages:

Firstly the automatic welder assemblies positioned at 12 o'clock, 2 o'clock and 4 o'clock (when viewing from the front of the machine) weld the joint 6 whilst the ring member 33 rotates clockwise by approximately 60 degrees to weld one half of the joint 6. It should be noted that the automatic welder assemblies originally positioned at 6 o'clock, 8 o'clock and 10 o'clock are now positioned at 8 o'clock, 10 o'clock and 12 o'clock respectively. These latter automatic welder assemblies are then operated whilst the ring member is rotated sixty degrees anti-clockwise to weld the remaining half of the joint 6. ^"

11) The operator then unclamps the front and rear pipe-engaging clamps via the command rod control panel and the machine can be advanced further along the pipeline to the next weld position.

With reference to figure 1 there is shown a pipeline wall sensor 910. The sensor is an ultrasound sensor and is capable of transmitting ultrasound substantially in the direction of arrow 911. Such ultrasound is reflected off the inner wall of the pipeline 1. The sensor 910 is capable of detecting such reflected ultrasound. However when the internal pipe welding machine 10 is moved along the pipeline the nose cone will ultimately project beyond the end of the pipeline where upon ultrasound transmitted from sensor 910 will no longer be reflected due to the absence of the pipeline wall in the vicinity of the sensor 910. Thus the sensor acts to detect the end of the pipeline. In use, when the sensor detects the end of the pipeline, the air supply to the drive motor is stopped and the calliper 63 applies the brakes thus slowing the internal pipe welding machine 10 to a stand still.

It should be noted that the sensor 910 is protected by the nose cone assembly from inadvertent damage and can also be positioned towards the front of the nose cone assembly 20. This forward positioning allows early detection of the end of the pipeline allowing the brakes to be applied sooner resulting in less likelihood of the machine 10 projecting too far beyond the end of the pipeline resulting in possible damage to the machine or injury to the operators.

With reference to figures 2 there is shown a thruster assembly 30, the major components of which are a front clamp arrangement 310, a rear clamp arrangement 316, a hub 314, a plurality of cable guide arrangement 315, a ring member 33 and a plurality of guide wheels 32.

Front clamp arrangement 310 includes a plurality of front pipe engaging clamps 3 IB, an actuating arrangement 312 and a lock arrangement 313.

Rear clamp arrangements 316 is substantially similar to front clamp arrangement 310.

At the front of the thruster assembly 30, three pneumatic actuators 330 (only one shown) are mounted via their respective bodies 331 in a circumferentially equispaced manner on plate 23 of nose cone assembly 20. A plate 333 is secured to the rearmost portion of each actuator body. Plate 333 includes three holes 334 (only one shown) through which a corresponding portion of the actuator ram 332 can pass.

A lock body 336 of a lock arrangement 313 is secured between plate 333 and plate 322. Plate 322 includes holes through which a lock shaft 337 can pass, holes 339 through which a corresponding portion of an actuator ram can pass, and also a central hole 340 in which is secured hub shaft 342.

Each actuator 330 is a double-acting actuator which can bias the corresponding actuator ram 332 in a forward or rearward direction. Each actuator ram 332 is secured at a rearward end to a thruster collar 344.

Thruster collar 344 (see figure 6) includes two annular flanges 345 and 346 separated by a spacer 346A to provide an annular recess 347. Flange 346, spacer 346A and flange 345 are all releasably secured together by bolts (not shown). Flange 346 is of larger diameter than flange 345 and includes hole 348 in which one end of lock shaft 337 is secured, and holes 349 (only one shown) in each of which is secured, by bolt 350, a respective end of a corresponding ram 332. Thruster collar 344 also includes a central hole 351 with bush recesses 351 A for receiving bushes 35 IB. Thruster collar 344 is slidably mounted on hub shaft 342.

Plate 322 is secured at circumferentially spaced locations to each guide arm 24 and also at circumferentially spaced locations to annular front clamp support 324B. Front clamp support 324B has a first substantially cylindrical portion 325 with circumferentially spaced lever mounting lugs (not shown) secured thereto, a second pipe engaging clamp guide portion 326, a third cable guide mounting portion 327 and a fourth flange portion 328 which is secured to hub 314 by bolts 328A (only one shown).

On each pair of lever mounting lugs of the first cylindrical portion 325 there is pivotally mounted, via pivot pin 355, a lever 354 (see figures 8 and 9). Lever 354 is generally of an L shape and has a first arm 356 and a second forked arm 357. First arm 356 terminates in a thruster collar engaging boss 358 which has two part cylindrical surfaces 359A and 359B. Second forked arm 357 terminates in a pipe clamp engaging fork 360 having prongs 360A and 360B. Each prong includes a part cylindrical surface 361A and 361B. In use engaging boss 358 sits between flanges 345 and 346 of thrust collar 344, and each prong 360A and 360B sits in a respective recess 366A and 366B of a pipe clamp 3 IB (see below).

Each pipe engaging clamp 3 IB (in this case there are 24 pipe engaging clamps 3 IB) comprises a clamp head 363 secured via a bolt (not shown) to clamp shaft 364 via thread hole 365 (see figure 11). Clamp shaft 364 is generally circular in cross-section but includes fork prong recess 366A and 366B each having engaging abutments 367 and retraction abutments 368. In use a first part 369 of clamp shaft 364 sits within a central hole 370 of housing 371 (see figure 10), which in turn is mounted in holes 371A (see figure 15) in the front clamp support 324, and secured thereto via bolts (not shown) which pass through holes 372 in a flange portion 373 of the housing 371.

Operation of the front clamp arrangement is as follows:

When the clamps are required to clamp the pipe 3, air is admitted into each actuator 330 via manifold 335 and pneumatic line 335A such that the rams 332 on each actuator are caused to move rearward which causes the thruster collar 344 to also move rearward. Because the engaging bosses 358 of each lever 354 are situated in the recess 347 of the thruster collar 344, each lever 354 pivots about its respective pivot pin 355 causing the respective pipe clamp engaging fork 360 to move substantially radially outwards. Since the fork prongs 360A and 360B are situated in respective recesses 366A and 366B of clamp shaft 364, they act on the engaging abutment 367 and force the pipe engaging clamps 3 IB radially outwards such that each clamp head 363 engages the pipe 3. During such movement of the actuating arrangement 312 the lock shaft 337 moves axially relative to the lock body 336. Once all pipe engaging clamps 3 IB are fully engaged with the pipe 3 the lock body 336 clamps onto the lock shaft 337 thus preventing release of the clamps in the event of loss of air pressure in one or more of the actuators 330. The lock body is capable of clamping the lock shaft in any relative position, and thus variations in pipe internal diameter can be accommodated by the lock arrangement 313 without requiring adjustment. It should be noted that each clamp shaft 364 does not move in a truly radial direction but is angled in a rearward direction such that when moving from a disengaged to an engaged position the clamp head 363 whilst moving in a substantially radial direction also moves in a rearward direction towards the joint 6. This helps in ensuring that pipe 3 firmly abuts the end of pipeline 1 prior to welding.

The rear clamp arrangement 316 is arranged similarly to the front clamp arrangement 310 and engagement and disengagement of the rear pipe engaging clamps 31A with the inner wall of the pipe line 1 is substantially as described for the front clamp arrangement.

The rear clamp arrangement additionally includes three circumferentially equispaced arrester rod guide lugs 418A shown for convenience in figure 16.

Hub 314 is rotationally and axially releasably secured to hub shaft 342 via radially acting ring clamps which engage the shaft and surfaces 390 of the hub. Hub 314 is generally disc-shaped and has bush recesses 343A to accept bushes 343, gas seal grooves 391 and gas distribution grooves 392A and 392B. Gas distribution groove 292B is connected to gas feed 393B and gas distribution groove 392A is similarly connected to a corresponding gas feed 393 (shown schematically in figure 17).

Ring member 33 is rotatably mounted on bushes 343 which acts to radially locate ring member 33. Ring member 33 includes track mounting holes 394 on which are mounted arcuate keyways 797, welding current terminal holes 395 in which are mounted welding current terminals, welding assembly control socket hole 396 in which are mounted welder assembly control sockets.

Three ring member gas feed holes 397A are associated with welder assemblies W1.W2 and W3 whilst three further ring member gas feed holes 397B (shown schematically in figure 21) are associated with welder assemblies W4, W5 and W6 respectively (see below). When assembled gas feed 397A aligns with gas feed 393A and similarly gas feed 397B aligns with gas feed 393B.

Secured to ring member 33 is an internally toothed ring 33A (see figure 7.)

Gear wheel 375 engages the toothed ring 33A and is secured for drive on a rearmost portion of shaft 376. Shaft 376 is mounted for rotation on front clamp support 324B and is driven by a ring member motor (not shown) having an encoder and being connected to end 377. Thus by starting and stopping the ring member motor as appropriate the ring member can be caused to rotate to any desired location by monitoring the position via the encoder.

Further ring member motors can be arranged to drive the ring member in a similar manner if necessary in the event that only one ring member motor is not powerful enough.

Also secured to ring member 33 is a double-sided ramp 398 against which acts a roller 399A of a rod 399 mounted on front clamp support 324B, and biased towards the ramp 398. Acting against the end of rod 399 remote from roller 399A is a proximity sensor which can determine when roller 399A has reached the top of the double-sided ramp 398. This arrangement thus acts to determine a datum position of the ring member relative to internal pipe welding machine chassis and can be used to established a datum position of the ring member motor encoder.

Bush 329 (see figure 7) is secured to front clamp support 324 and acts axially on toothed ring 33A. A similar bush 329B acts on a rear portion of ring member 33, to secure the ring member 33 axially relative to the internal pipe welding machine.

Bushes 329A and 329B and 343 are all electrically insulating bushes and therefore in the event of a short circuit in the electrical system of the internal pipe welding machine they do not provide a conductive path. This is particularly beneficial in view of the high currents used for welding since no damage occurs to the bearings in the event of a welding current short circuit. Cable guide arrangements 315 comprises a first cable guide 380 mounted on the ring member 33 a second cable guide 381 mounted on the front clamp support 324 and a third cable guide 382 also mounted on the front clamp support.

The second cable guide comprises two disc 383A and 383B (see figure 13) each having a V-shaped periphery. The discs 383 A is rotatably mounted on the front clamp support 324 in slot 378 (see figure 16) about an axis E which is radially orientated having regard to the pipe line axis F. Disc 383B (obscured by disc 383A in figure 7) is also rotatably mounted on front clamp support 324 about axis G which is also radially orientated. Discs 383A and 383B are arranged such that their peripheries co-operate to form an aperture 384 through which cable 385 can pass.

The first cable guide 380 is similar in arrangement to second cable guide 381 though mounted on ring member 33.

Cable 385 comprises a first portion 387 connected to a corresponding welder assembly via the welding current terminal, a second portion 388 which runs between the first and second cable guides and a third portion 389 connected to a slack tensioner (not shown). When the ring member 33 is in a start position the second cable portion 388 is parallel to pipe line axis F. Rotation of the ring member in a clockwise direction (when viewing from the front of the internal pipe welding machine) causes the first cable guide 380 to move in the direction of arrow H of figure 13 resulting in the cable being pulled through the aperture 384 with the second portion 388 becoming longer at the expense of the third portion 389. Continuing rotation of ring member 33 will cause second cable portion 388 to contact a third cable guide 382.

Third cable guide 382 is in the form of a cylindrical roller situated in recess 382A which can rotate about axis J which is parallel to the pipe line axis F. Continued rotation of ring member 33 will cause the second cable portion 388 to contact successive rollers 382. Thus a particular roller 382 can accommodate more than one cable 385 by supporting cables lying parallel to each other across the roller (see figure 13A). This is because the axial position of part 388A of the second portion 388 of the cable as it leaves the first cable guide is rearward of the axial position of part 388B of the second portion 388 of the cable as it arrives at the second cable guide. It is this relative axial positioning of the first and second cable guides that allows the successive cables to lie as shown in figure 13 A.

In further embodiments it is possible to mount the third cable guide for rotation with the welder assemblies.

During movement of the ring member 33 from an extreme clockwise position back to the start position the slack tensioner takes up any slack in the third portion 389 of the cable 385.

The cable guide aιτangement 315 allows the ring member 33 to rotate through 360 degrees, in this case 180 degrees clockwise from a start position and 180 degrees anti-clockwise from a start position. The advantage of winding the cable in both a clockwise and anti-clockwise direction is that the slack adjuster only has to take up half the slack, in this case 180° of slack, than if the cable were only wound in one direction wherein they would have to take up more slack, in this case 360° of slack, thus making them more complicated.

A camera (not shown) mounted for rotation with the ring member 33 and aimed at and focused on a pipe joint can be used for post- weld inspection of all of the 360 degree arc of the joint without the requirement of axially moving the internal pipe welding machine.

Where space is limited in the vicinity of the welder assemblies such a camera can be aimed and focused at a portion of the pipe line remote from the joint eg. 100mm behind the joint. Post-weld inspection can then be carried out by moving the internal pipe welding machine forwards by 100 mm and then rotating the ring member 33 through 360 degrees. A light source can be provided for the camera either by shining a light down the pipe or by providing a light source on the internal welding machine or preferably providing a light source which is mounted for rotation with the camera. Preferably a moveable protector can be arranged to cover the camera lens when the camera is not being used post weld inspection to protect the lens from weld spatter. A similar movable protector can protect any light sources which are provided in the vicinity of the welder assemblies and preferably where the camera and light source are provided adjacent to each other a single moveable protector can be provided to protect both the camera and the light source.

As described previously there are six welder assemblies numbered W1-W6 which are positioned at 12 o'clock, 2 o'clock, 4 o'clock, 6 o'clock, 8 o'clock and 10 o'clock respectively when the ring member 33 is in a start position. Welding is carried out whilst each welder assembly is moving downwards, thus welder assemblies W1,W2 and W3 will simultaneously weld a right-hand portion of the joint 6 whilst they are moving from the 12,2 and 4 o'clock positions to the 2,4 and 6 o'clock positions respectively.

During this welding process shield gas is fed through gas feed 393A and is distributed circumferentially around gas distribution groove 392A and passes into the three ring member gas feed holes 397 associated with welder ^"assemblies WI, W2 and W3. Lengths of gas pipe connect the welder torch head of each welder assemblies WI, W2 and W3 with the appropriate gas feed holes 397.

Similarly welder assemblies W4,W5 and W6 will weld a left-hand portion of the joint 6 when moving from an 8 o'clock, 10 o'clock and 12 o'clock position to a 6 o'clock, 8 o'clock and 10 o'clock position respectively whilst gas distribution groove 392B is supplied with welding shield gas from gas feed 393 to provide shield gas at the welding torches of welder assemblies W4, W5 and W6.

Movement of the welders during welding define a weld plane of the internal pipe welding machine which immediately following a welding operation and prior to axial movement of the internal pipe welding machine is clearly coincident with the joint 6.

If during a welding sequence one of the welder assemblies eg. WI fails to weld its arc of the joint, another welder assembly, in this case W2 or W3 can be used to weld that arc or part of arc welder assembly WI failed to weld. This is possible because whilst each welder assembly ordinarily only required to weld an arc of 60 degrees (since in this case there are 6 welder assemblies), the fact that the welder assemblies can move through substantially more than 60 degrees allows for this "automatic repair" facility.

It is not necessary for a repair facility for the welders to have to rotate through 360 degrees. For example provided the ring member can rotate by plus 120 degrees and minus 60 degrees from the start position full repair facility is available. Furthermore even if the ring member can only rotate by plus or minus 60 degrees from a start position a partial repair facility is still available (see table 1).

In a further embodiment in which only four welder assemblies are used each mounted at the 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock positions, full repair facility is available when the welder assemblies can rotate by at least 180 degrees eg. ±90 degrees.

An internal pipe welding machine having a camera capable of being rotated about the pipeline axis for post-weld inspection of the joint and an automatic weld repair facility can be extremely useful. Advantageously, the camera can be mounted for rotation with the welder assemblies rather than having an independent means to rotate the camera. When thus mounted the number of cameras required for full post-weld inspection is then dependent upon the angle through which the welder assemblies can rotate. Thus where the welder assemblies can rotate through 360 degrees only one camera is required and where the welder assemblies can rotate through only 180 degrees, two cameras are required and where the welder assemblies can only rotate through 120 degrees three cameras are required.

Figures 23 and 24 show a schematic view of a slack adjuster 920.

Discs 383A and 383B of the second cable guide 381 are as described previously. In this case the slack adjuster 920 is offset relative to the second cable guide due to an obstruction 922 of the pipe welding machine 10. Slack adjuster 920 includes four discs 924,925,926 and 927, each disc having a peripheral edge which accepts the cable 385. Discs 924 and 925 are both mounted for rotation on pivot 929 which is fixed relative to the internal pipe welding machine 10. Discs 926 and 927 are both mounted for rotation on pivot 930. However in this case pivot 930 is slidably mounted on rail 932, rail 932 being fixed relative to the pipe welding machine 10. Thus discs 926 and 927 can move laterally when viewing figure 23 in the directions of arrows 934 and 935.

Disc assembly 936 is comprised of the above mentioned discs 926 and 927 and pivot 930, and is biased in the direction of arrow 934 by tension spring 937. End 939 of tension spring 937 is fixed relative to the pipe welding machine 10. An obstruction 940 prevents tension spring 937 acting in a straight line thus a spring guide 941 fixed relative to the pipe welding machine 10 allows the spring 937 to alter its attitude and avoid obstruction 940.

Starting at where the cable 385 (in particular the third portion 389 of the cable) leaves the second cable guide 381, it is initially wound around disc 924, then disc 926, then disc 925, then disc 927, with the end 942 of the cable 385 being connected to a terminal block 943. Terminal block 943 is fixed relative to the pipe welding machine 10.

It is apparent that for every say 100 mm of cable drawn through the second cable guide 381 as the ring member 33 rotates, the disc assembly 936 moves along rail 932 by only 25 mm. This provides for an axially compact slack adjuster 920. Furthermore there is more freedom of design of the internal pipe welding machine 10 since the slack adjuster 920 is capable of avoiding obstructions such as obstruction 922 and obstruction 940.

In this case the rail 932 is straight, though in further embodiments a curved or otherwise non-straight rail could usefully be used to avoid other obstructions.

Figure 27 shows a further embodiment of a hub 960, the central portion of which is similar to hub 314. However in this case slip ring portions 961 and 962 have been added to the front and rear of the hub respectively. Slip ring portion 961 includes three slip rings 963,964 and 965, each having corresponding insulating portions 963A,964A,965A and brushes 963B,964B,965B. The brushes are mounted for rotation with the ring member 33.

Slip rings 963,964,965 supply weld current.

Brush 963B is connected to welder assembly WI and W4, brush 964B is connected to welder assembly W2 and W5 and brush 965B is connected to welder assembly W3 and W6. Such an arrangement is possible since when, say, welder assembly WI is welding welder assembly W4 is not welding and has its weld head in the parked portion.

Mounted on slip ring portion 962 are six further slip rings which provide control ^"signals such as control signals to, and feedback signals from the welder assemblies, such as weld head position and wire feed rate. Such control signals can be intermittent in their nature and thus by using a multi-plexing arrangement it is possible to provide a slip ring capable of carrying a plurality of control signals since the slip ring only carries one particular- signal at any one time.

With reference to figures 4A and 6A-9A there is shown a pipe wall engaging drive system 610 comprising two track laying drive arrangements 611 positioned at the 4 o'clock and 8 o'clock positions when viewing the internal pipe welding machine from the front, and a track laying idle arrangement 612 positioned at the 12 o'clock position.

An actuating arrangement 614 allows the tracks of the drive arrangement and idle arrangement to move between a pipeline engaged position, shown at El of figure 4A and a pipeline disengaged position shown chain dotted at E2 of figure 4A.

The actuating arrangement includes a double acting pneumatic actuator 620, having a body mounted on the rear subframe 13 and a ram 621 slidable relative to the body.

The ram moves within tube 622 also mounted on the rear subframe 13 at a right-hand end when viewing figure 4; tube 622 includes two diametrically posed slots 623 and 624 (see figure 6A). Slidable on tube 622 is a collar 625. A pin 626 is positioned within slots 623 and 624 and is secured in holes in ram 621 and also in holes in collar 625.

Actuation of the pneumatic actuator 620 between an extended and a retracted position causes the collar (also known as a actuator member) to move between a disengaged and engage position respectively ie. a position where the drive and idle arrangements are disengaged and engaged respectively with the pipeline.

The actuating arrangement includes three linkage arrangements 615, one being associated with the track laying idle arrangement and the other two being associated, one with each track laying drive arrangement. The linkage arrangements 615 are substantially similar thus only one will be described in detail as follows :-

Each linkage arrangement 615 comprises two opposite handed sets of linkage components 616 and 617 mounted one on either side of track 618.

The set of linkage components 616 includes a first pivot lug 630A secured to rear subframe 13. First link 632A is pivotally mounted via a first pivot 631 A to first pivot lug 630A. First link 632A is also pivotally mounted to axle 633 via a second pivot 634A. A second link 635A is pivotally mounted at a third pivot 636A to axle 633 and also at a fourth pivot 637A to a fourth pivot lug 638A secured to collar 625; components 630B, 63 IB, 632B, 634B, 635B, 636B, 637B, and 638B of the second set of linkage components 617 are equivalent to their correspondingly numbered components in the set of linkage components 616.

First pivot 631 therefore comprises the combination of first pivot 631 A and 63 IB. First link 632, second link 635, second pivot 634, third pivot 636 and fourth pivot 637 similarly comprise the combination of their two component parts.

In this case the second pivot 634 and the third pivot 636 have coincident axes but this need not necessarily be the case in further embodiments. The track laying drive arrangement or track laying idle arrangement is mounted on mounting axle 633 (see below).

Extending the ram causes the collar to move axially towards the right when viewing figure 4 such that the fourth pivot 637 moves away from the first pivot 631 and the second 634 and third 636 pivots move radially in board along with the axle 633. This causes the track laying drive arrangement or track laying idle arrangement as appropriate to disengage the pipeline wall. Retraction of the ram 621 causes the fourth pivot 637 to move towards the first pivot 631 thus re-engaging the drive arrangement or idle arrangement as appropriate with the pipeline wall.

The idle arrangement 612 includes a side plate 641 secured to a bearing housing 642, the bearing housing houses a self aligning rotating element bearing 643 having an outer bearing race with a spherical surface thus allowing the bearing housing 641 to yaw and roll relative to the bearing 643. An inner race of the bearing is secured rotationally fast to axle 633. Thus in addition to the roll and yaw movements just described, the track laying idle arrangement can also pitch relative to the axle 633 by virtue of the rotating elements within the bearing 643.

A similar arrangement allows each track laying drive arrangement to pitch, roll, and yaw relative to their respective mounting axles.

A second side plate 640 is secured in spaced apart relationship to side plate 641 by spacers (not shown).

Rear idle sprocket axle 644 (see figure 8A) is mounted in self-aligning bearings 645 and 646 secured to side plates 641 and 640 respectively. Sprocket 645 is secured rotationally fast to sprocket mount 646 which in turn is secured rotationally fast to rear sprocket axle 644. A similar arrangement (not shown) secures a front idle sprocket to side plates 641 and 640 but additionally allows movement of the front idle sprocket axle toward and away from the rear idle sprocket axle to tension the track 618. Each tracking laying drive arrangement (see figure 9A) includes side plates 650 and 651, mounting axle 652, front axle 653, front sprocket 654, track 655, rear axle 656 and rear sprocket 657 equivalent to those components on the track laying idle arrangement. The track laying drive arrangement 611 further includes a front sprocket air actuated motor 658 connected to the front axle via front gear box 659, rear air actuated motor 660 connected to the rear axle 656 via rear gear box 661, and brake rear disc 662 also connected to rear axle 656. Brake calliper 663 is mounted via mounting arrangement 664 onto side plate 651.

By operating the actuating arrangement the two track laying drive arrangements and the track laying idle arrangement can be forced into engagement with the pipeline wall to provide for increased friction between the tracks of the drive arrangements to enable the internal pipe welding machine to move along the pipeline under adverse conditions eg. up gradients, or when the pipeline wall is damp. The idle arrangement does not provide any drive but does allow the track laying drive arrangement to be loaded against the pipeline wall.

The reduction ratio in gear box 661 is different to that in gear box 659 thus when motor 660 is driving rear axle 656 (and motor 658 is idling) the internal pipe welding machine progresses at a first speed which is different from when motor 658 is driving front axle 653 (and motor 660 is idling). Thus it is possible to provide an internal pipe welding machine that can travel along a pipeline at two different speeds.

By actuating brake calliper 663 to brake the disc 662 the internal pipe welding machine can be braked through the pipe wall engaging drive system ie. through track 655.

In further embodiments the disc 662 and calliper 663 can be mounted on any of the front or rear sprocket axles of any of the track laying drive arrangements or the track laying idle arrangements.

Calliper 663 includes disengaging pistons which are biased towards the disc 622 by a braking spring. The callipers operate such that supply of compressed air forces the pistons away from the brake disc 662 to release the brake. This arrangement is therefore a fail-safe arrangement wherein loss of air pressure causes the brake to be applied.

It should be noted that such a braking system uses less air than heretofore known arrangements which act by forcing brake shoes into direct engagement with the inner wall of the pipeline.

It should also be noted that by providing an internal pipeline welding machine which can move at two different speeds the consumption of air is minimised when compared to heretofore known internal pipeline welding machines.

With reference to figure 25 there is shown a flow diagram of how a motor arrangement 950 can be controlled to vary the speed of the internal pipe welding machine.

Air from air receiver tank 81 is fed to diverter valve 951 controlled by control arrangement 952. The air then passes either to flow control valve 953 and then onto motor arrangement 950 or the air passes to flow control valve 954 and then onto motor arrangement 950.

The flow control valves 953 and 954 are adjustable by the operator and typically one would be set to allow a relatively low flow of air and the other would be set to allow a relatively high flow of air. The control arrangement 952 is arranged to instruct the diverter 951 to divert air to flow control valve 953 or 954 as appropriate.

Motor arrangement 950 is capable of driving the internal pipe welding machine along the pipeline and thus can take many forms. For example a single motor driving a single wheel, a pair of motors driving a pair of wheels, a single motor driving a single track laying arrangement or a pair of motors each driving a corresponding track laying arrangement.

The control arrangement 952 can also take several forms. In one form control arrangement 952 provides instructions for the diverter valve to change over at predetermined condition. Thus typically the air flow path might initially run through flow control valve 953 which provides a relatively high flow in order to speed the internal pipe welding machine up from. rest, and following a predetermined time period the flow diverter might change to supplying air to the motor arrangement 950 via flow control valve 954 which would be set to a relatively low flow rate thus conserving air.

Alternatively if the pipeline is being laid uphill the diverter valve might only supply the motor arrangement via flow control valve 953 which has been set to a relatively high flow rate to ensure the internal pipe welding machine is driven uphill until such time as the gradient of the pipeline falls below a predetermined angle relative to the horizontal where upon the diverter valve can change the supply to the motor arrangement to come via control valve 954 which has been set to a relatively low flow rate.

Correspondingly when a pipeline is being laid in a downhill direction the diverter valve 951 might only supply air to the motor arrangement 950 via flow control valve 954 which is set to ^"a relatively low flow rate until such time as the gradient returns to a near horizontal condition. Clearly this arrangement helps to ensure that the internal pipe welding machine does not "run away" as it descends.

Gradient information can be input into the control arrangement 952 either manually by an operator or automatically by a level sensor.

Figure 26 shows a further flow diagram of how a motor arrangement 950 can be controlled to vary the speed of the internal pipe welding machine. In this case air is supplied from air receiver tanks 81 via motorised flow control valve 955 to motor arrangement 950. Control arrangement 952 controls the setting of motorised flow control valve 955 and allows variable flow of air to the motor arrangement.

It can be seen from figure 28 that as the internal pipe welding machine 10 advances along the pipeline the machine control panel 983 is within the pipeline and therefore inaccessible to an operator. Furthermore the command control rod panel 981 has been fed into the next pipe 982 to be welded in to place and thus is also inaccessible to an operator. The applicant is the first to realise that even under such circumstances it is possible to vary the power of the motor arrangement to suit the prevailing conditions.

TABLE 1

* N = number of welder assemblies = 6

Claims

1. An internal pipe welding machine including at least one welder assembly rotatable relative to a chassis of the internal pipe welding machine for welding a joint between a pipeline and a pipe, the welder assembly being supplied by a cable which carries at least one of a welding current and a control signal and a cable slack adjuster for taking up slack in the cable including a first disc arrangement having at least a first disc rotatably mounted on a first pivot, the first pivot being fixed relative to the internal pipe welding machine chassis, and a second disc arrangement having at least a second disc rotatably mounted on a second pivot, the second pivot being moveable relative to the chassis, the cable being wound around the at least one first and the at least one second disc, with the cable slack being taken up by movement of the. first disc arrangement relative to the second disc arrangement.

2. Ah internal pipe welding machine as defined in claim 1 in which the first disc arrangement includes one first disc and the second ^"disc arrangement includes two second discs.

3. An internal pipe welding machine as defined in claim 1 in which the first disc arrangement includes two first discs and the second disc arrangement includes two second discs.

4. An internal pipe welding machine as defined in any preceding claim in which the second disc arrangement is biased away from the first disc arrangement by biasing means.

5. An internal pipe welding machine as defined in claim 4 in which the biasing means is a spring.

6. An internal pipe welding machine as defined in claim 4 in which the biasing means is a spring and a spring guide, the spring guide altering the attitude of the spring.

7. An internal pipe welding machine as defined in any preceding claim in which the second disc arrangement is guided for movement on a rail.

8. An internal pipe welding machine as defined in any preceding claim in which the cable carries a welding current and is mounted in front of the or each welder assembly.

9. An internal pipe welding machine as defined in any one of claims 1 to 7 in which the cable carries a control signal and is mounted at the rear of the or each welder assembly.

10. An internal pipe welding machine including at least one welder assembly rotatable relative to a chassis of the internal pipe welding machine for welding a joint between the ^"pipeline and a pipe, the at least one welder assembly, or at least one of the welder assemblies, being supplied by a slip ring which carries at least one of a welding current and a control signal.

11. An internal pipe welding machine as defined in claim 10 in which the slip ring carries a welding current and supplies a plurality of welder assemblies.

12. An internal pipe welding machine as defined in claim 10 or 11 in which the slip ring carries a welding current and is mounted in front of the or each welder assembly.

13. An internal pipe welding machine as defined in claim 10 in which the slip ring carries at least one control signal and is mounted at the rear of the or each welder assembly.

14. An internal pipe welding machine as defined in claim 10 or 13 in which the slip ring is capable of carrying a plurality of control signals, each control signal being intermittent with the slip ring only carrying one signal at any one time.

15. An internal pipe welding machine including a motor arrangement having pipe engaging means for propelling the internal pipe welding machine from a welded joint of a pipeline to an open end of a pipeline, and a control arrangement capable of varying the power of the motor arrangement.

16. An internal pipe welding machine as defined in claim 15 in which the control arrangement is capable of varying the power of the motor arrangement whilst the internal pipe welding machine is in motion.

17. An internal pipe welding machine as defined in claim 15 or 16 in which the control arrangement is capable of automatically varying the power of the motor arrangement whilst the control arrangement is inaccessible to an operator.

18. An internal pipe welding machine including a pipeline wall sensor, the sensor in use acting to detect the end of a pipeline, without contacting the pipeline wall.

19. An internal pipe welding machine as defined in claim 18 in which the sensor is able to detect the presence of a pipeline when substantially within the pipeline and the absence of the pipeline when substantially outside the pipeline.

20. An internal pipe welding machine as defined in claim 18 or 19 in which the sensor is an ultrasound transmitter and receiver.

21. An internal pipe welding machine as defined in claim 20 in which the sensor uses reflected ultrasound to detect the presence of the pipeline.