GB1333497A - Welding apparatus - Google Patents

Abstract

1333497 Welding by fusion LINCOLN ELECTRIC CO 19 April 1971 [2 Feb 1970] 20488/71 Heading B3R Apparatus, particularly for end-to-end arc welding of axially aligned large-diameter pipes presenting a landed V weld preparation groove, comprises an electrode support rotary carriage which is adapted to surround more than 180 degrees of at least one of the pipes and is provided with a pair of end guide wheels and an intermediate guide wheel, all of the guide wheels being coplanar and having parallel axes, and at least one of said end guide wheels being movable in use towards and away from at least one of said pipes to permit installation of said apparatus. The carriage may support one or two electrode heads. For fill passes, the carriage may have electrode heads spaced from the guide wheel plane, a wheel-engaged grooved guide being fastened to either pipe; or, as particularly described, the electrode heads are provided in the plane of the guide wheels which are engageable in the weld preparation groove. The carriage may comprise a single rigid unit with one of the end guide wheels mounted on a pivoted arm or, as particularly described, the carriage comprises two arms pivotably connected together. As shown, the carriage comprises two arms 20, 21 pivotably connected together at 22 and each having long and short branches 24, 25. End and intermediate guide wheels G, H, J, are rotatably mounted on the ends of the long branches 24 and at the pivot 22. Tangential axes rollers 61 are rotatably mounted on the ends of the short branches 25. The end guide wheels G, H are apaced 200-300 degrees about the joint. By actuation of an hydraulic, screw or, as shown, toggle mechanism K, the arms 20, 21 are movable between a "closed" position in which the guide wheels engage the weld preparation groove and an "open", installing, position in which the guide wheels are withdrawn from the groove and the rollers 61 engage the pipe periphery, the apparatus being movable, in the "open" position, axially along the pipe on the rollers 61. Rotation of the apparatus about the pipes is by an electric motor (70) acting via reduction gearing on the guide wheels G. To stabilize rotation, each guide wheel G, H is frictionally braked by friction shoes 73 acted on by adjustably loaded springs 77. Welding head D comprises an electrode wire drive 103 drawing from a reel 100 through an arcuate tube 104 and feeding through a nozzle 105. The electrode wire is supported close to the joint by a V-groove 115 of an electrically insulated guide L. Current may be fed to the electrode wire via the guide L or, to provide for pre-arc resistance heating, via the nozzle 105. The guide L and nozzle 105 are mounted on a support 110 provided with means for manual adjustment of the angle of the electrode with respect to the joint. The welding head E is similar but has a solenoid 121 whereby the electrode angle may be changed for welding in either direction. Each guide wheel has a periphery as shown in Fig. 3, a concavity at 31 providing for weld deposit clearance. For operation sequence timing, cams (136) on a pipe mounted ring (135) are disposed so as to engage arms of limit switches (138) on the arm 20. The arc welding may be gas-shielded or flux - submerged or may employ tubular electrodes. In operation, an aligning fixture 14 carrying a channelled backing ring C, e.g. of copper, is first positioned in one pipe end. The other pipe is then brought up and aligned so that the preparation groove lands 12 are spaced, and the fixture 14 is expanded. The carriage is then installed with the guide wheels engaging the weld preparation groove. The specification describes various welding sequences with one, or, as shown, two welding heads.