GB1477837A - Orbital welding apparatus - Google Patents

Abstract

1477837 Welding by fusion DARCHEM Ltd 16 Jan 1975 [16 Oct 1973] 48217/73 Heading B3R A gas-shielded, non-consumable electrode, rotary arc-welder 3 for end-to-end welding together of tubular sections, comprises a non-rotary plate ring 11 adapted to be mounted on the workpiece, a rotary split ring 14 rotatably mounted in the ring 11, and an electrode holder 21 which is carried on the ring 14 by way of a plate spring 22, supports a workpiece-engaging ceramic follower 23 ensuring maintenance of a desired distance between the workpiece and holder (and, hence, the electrode), and holds the electrode by way of a clamp 24 which holds the electrode eccentrically and is rotatably adjustable in a radial bore of the holder to adjust the electrode position axially of the workpiece. The electrode clamp 24 is of copper, is turnable, e.g. by a screw driver, and is retained in its adjusted position by a screw 27. A tungsten electrode 25 is retained in the clamp by a screw 29. The plate spring 22 is formed of copper shims. The rotary ring 14 halves are electrically connected together by a connector 39 comprising a plate spring 40 screw secured to one ring half and provided with a copper shoe 41 bearing on the other ring half. The ring 14 has screw secured thereto a spur ring 13 meshing a motor driven spur pinion (not shown) disposed adjacent a terminal box 30 secured to the non-rotary ring 11. Electrically insulating bearing rings 19, 20 are provided between the ring 11 and the rotary ring 14 and spur ring 13 assembly. The terminal box 30 houses a copper shoe 33 which is connected to a supply lead 34 and is screw adjustably spring-loaded into engagement with the rotary ring 14. The non-rotary ring 11 is supported and positioned on the workpiece by a split collar 2 comprising a workpiece engaging sleeve 5 and a rotatable U-section setting ring 6 having limbs 7, 8 respectively engageable with the sleeve 5 and the non-rotary ring 11. The halves of the welder 3 and the collar 2 may be clamped or hinged together. Inert gas, e.g. 100%A or 95% A, 5% H 2 , is introduced into the space bounded by the workpiece and the welder via two fittings 44 in the sleeve 55, a wire mesh seal 45 in a top plate 46 allowing gas purging during welding. Means providing a gas backing comprises a tubular body 53 disposable inside the workpiece and gas-sealable thereto by two ring seals 54 inflated by gas (e.g. air) via pipes 56, 57, inert gas (e.g. A or A, H 2 ) being fed to the space between the body 53 and the workpiece via pipes 58, 59. In the operations described, a tubular insert is interposed between the tubular sections to be welded together. The insert is provided with locating lips 49 which serve as weld filling. Locating rings 48 on the insert are embraced by steel inserts 51 in the sleeve 5 respectively for different axial positions of the welder. Pulsed current is fed to the electrode, the inter-pulse time allowing cooling. Welding is effected by one constant speed rotation of the electrode. To compensate for possible misalignment of upper and lower workpiece tubes, e.g. charge tubes of a reactor, one of the workpiece tubes is cut to present an inclined face and an insert is provided with one end perpendicular and the other inclined, the tube face and insert end inclinations being equal to half the expected maximum angular misalignment and say 1 or 2 degrees. In the event of the charge tubes being in alignment, as shown in Fig. 6, the insert is turned so that the tube and insert inclinations complement each other. To accommodate welding about an inclined joint, use is made of a setting ring 6 provided with one limb angled to the same inclination as that of the tube and insert ends.