GB2052334A - Rotary arc welding equipment - Google Patents

Abstract

Equipment is provided to assist a welder to perform tube-to-tube or similar welds, particular where large numbers of such welds are required. The equipment has two relatively- rotatable parts 10, 12; part 10 carries a clamp 24, 26 and part 12 carries a welding electrode in a pivotted holder 32. The equipment is clamped to a tube at a position in which the electrode is aligned with the weld line. The welder strikes the arc and manually rotates part 12 relative to part 10 and manipulates the electrode holder 32 to effect the weld. T.I.G. welding is referred to. <IMAGE>

Description

SPECIFICATION Welding equipment The invention relates to welding equipment for use in effecting circular welds; and to methods of welding.

Circular welds, for example butt welds between tubular members, are commonly made by manual manipulation of a welding torch but where access to the weld zone is restricted considerable difficulties are encountered, especially where relatively large numbers of welds have to be made.

An object of the invention is to provide equipment which facilitates the making of circular welds; a further object is to provide a method of welding.

Welding equipment according to the invention is characterised by two relatively rotatable parts connected to one another, one part having means for securing the part to a workpiece and the other part carrying a welding electrode which is adjustable relatively to said other part.

One form of welding equipment will now be described by way of example to illustrate the invention with reference to the accompanying drawings, in which: Figure 1 is an elevation of the equipment; and Figure 2 is a section on the line II - II in Figure 1.

The equipment consists of two stainless steel parts 10 and 12, the part 10 being a generally circular plate having a radial slot 14, a circular groove 16, a central spigot 17 and carrying a smaller diameter stainless steel plate 18 having a radial slot 20 aligned with the slot 14. The plate 18 is secured on the spigot 17 by screws 22.

The plate 10 has an integral central semi-circular clamp part 24 at its side opposite to the spigot 17. A second clamp part 26 is secured to the part 24 by two screws (not shown). The clamp parts 24, 26 have semi-circular inner faces defining a central circular opening adapted to receive a workpiece (not shown) in the form of a tube of corresponding diameter.

The other part 12 is a semi-circular plate having a central semi-circular recess of diameter slightly greater than that of the spigot 17 and positioned between the plates 10 and 18. The plate 12 has a semi-circular flange 30 which is a close fit in the groove 16.

The part 12 is freely rotatable relatively to the part 10 but is "trapped" in relation to the part 10 by the plate 18 and the flange 30 fitting in the groove 16.

The plate part 12 carries a non-consumable tungsten electrode (not shown) mounted in a collet (not shown) which is held in a holder 32. The holder 32 is mounted in a torch body 34, which is made of an heat-resistant insulating material such as Tufnol and which carries a ceramic gas nozzle 36. The body 34 also has a connection 38 for a combined gas and current lead (not shown).

The body 34 is pivotally mounted on a pin 40 supported by a post 42 carried by the plate 12. The torch can thus pivot about an axis tangential to a circle centred on the axis of rotation of the plate part 12.

The longitudinal axis of the electrode is radial to the axis of rotation of the plate part 12 as shown in Figure 2 but the torch body 34 and the electrode can be tilted, in a plane radial to that axis, about the pin 40.

The equipment is typically, though not exclusively, used to facilitate orbital welding tubes of say 19 mm inside diameter or less made of crack sensitive materials such as steel ofthe 18 chromium 13 nickel 1 niobium type.

Especially, the equipment is used to facilitate the effecting of the "root" run of weld where, for example, the tubes have a "Y" type preparation.

Subsequent runs of weld are effected wholly manually using filler material but without use of the equipment.

The mode of welding is tungsten inert gas (TIG) welding using an inert gas such as argon which passes out of the nozzle 36 and shields the weld zone.

The welder rotates the plate part 12 manually and the equipment facilitates the keeping of the welding electrode moving along the weld line and at a constant radius over a portion of the run where required.

The pivotal mounting of the torch on the plate 12 facilitates such positioning.

Also, the pivotal mounting enables the electrode to be swung out of the weld line at the end of the run.

The welder manipulates the equipment to rotate the part 12 and, or, pivot the torch relatively to the part 12. Relatively less skilled welders can be used for achieving acceptable welds using the equipment.

Welder fatigue is reduced.

The equipment is applicable with advantage to the welding of tube or pipework in nuclear installations, for example.

Although autogenous TIG welding is a typical welding method facilitated by use of the equipment, other welding methods may be practised with its aid.

The invention includes a method of welding using equipment manipulated manually.

Modified equipment (not shown) according to the invention is applicable to the facilitating of effecting circular welds between tubes and plates such as seal welds, fillet welds etc; and to the effecting of internal welds, such as bore welds between tubes and plates or between tubes and tubular weld formations on plates or tubular stubs on plates; and effecting tack welds.

The invention includes methods of effecting such further welds.

With the clamp parts separated the equipment can be offered up to one of two pipes or tubes to be joined by welding, the slot receiving the pipe or tube and when the equipment has been positioned to ensure that the electrode is positioned properly in relation to the weld line, the clamp parts are secured together thereabout.

The welder manipulates the equipment after striking an arc between the workpieces and the electrode so as to achieve a sound root run by autogenous TIG welding. At the end of the run he manipulates the equipment accordingly including swinging the torch body 34 about its pivot to give a satisfactory weld profile before the arc is extinguished.

The clamp parts are then released and the equipment is removed from the joined pipes or tubes in the reverse manner to that in which it was originally offered up.

The welder then completes the joining of the pipes or tubes by manual welding using a filler rod, making a number of passes to fill up the "Y" preparation.

The method of welding is entirely new and is advantageous over wholly manual welding which involves considerable difficulty for the welder in ensuring satisfactory welds in every case where large numbers have to be effected; or where access is restricted.

The level of skill required is relatively less than that required in wholly manual welding yet welds can be achieved which have characteristics otherwise achievable only by "automatic" welding using powered orbital weld heads.

Claims (15)

1. Welding equipment comprises two manually relatively-rotatable parts connected to one another, one part having means for securing the part to a workpiece and the other part carrying a welding electrode which is adjustable relatively to said other part.

2. Welding equipment according to claim 1, in which the welding electrode is manually adjustable relatively to said other part.

3. Welding equipment according to claim 1 or 2, in which the part carrying the welding electrode is located between two members comprising the other part and is secured to that other part by a cooperating arcuate flange and groove arrangement on the parts, which arcuate flange and groove being centred on the axis of relative rotation of the parts.

4. Welding equipment according to any preceding claim, in which the part having the securing means comprises a plate member having a radial slot, the securing means comprising a first clamp part formed on the plate member adjacent the inner end of the slot and a second clamp part securable to the first clamp part.

5. Welding equipment according to claim 4, in which the clamp parts have semi-circular inner faces defining a circular opening centred on the axis of relative rotation of the parts.

6. Welding equipment according to claim 4 or claim 5 as dependent on claim 3, in which a second plate member is secured in spaced-apart relationship with the first plate member, the second plate member having a radial slot aligned with the radial slot in the first plate member.

7. Welding equipment according to any preceding claim, in which the welding electrode is pivotally mounted on the part carrying the welding electrode.

8. Welding equipment according to claim 7, in which the pivot axis is tangential to a circle centred on the axis of relative rotation of the parts.

9. Welding equipment according to any preceding claim, in which the longitudinal axis of the welding electrode is radial to the axis of relative rotation of the parts.

10. A method of welding comprises using welding equipment as claimed in claim 1.

11. A method according to claim 10, in which the equipment is used to perform an autogenous TIG weld run.

12. A method according to claim 10 or 11, in which the equipment is used to perform a root weld run.

13. A method according to claim 12, in which further weld runs are made using filler material after the equipment has been removed from a workpiece to complete the weld.

14. Apparatus according to claim 1 substantiany as described herein with reference to the accompanying drawings.

15. A method according to claim 10 substantially as described herein with reference to the accompanying drawings.