Abstract: A mechanical guidance system for automatically guiding one or more electrodes of an arc-welding unit along a groove delimited by the facing chamfered end surfaces of two metal parts to be welded together, the guidance system being of the type comprising a main carriage which is moved along a fixed guide extending parallel to the groove, a secondary carriage hinged to the main carriage and fitted with an electrode support block, and a guidance device comprising running members in contact with the surfaces of the metal parts on either side of the groove and feeler members which penetrate into the groove, wherein the guidance device includes two feeler members which are in contact with respective ones of the two side walls of the groove and which are respectively situated towards the front and towards the rear of the secondary carriage relative to the displacement direction of the main carriage.

Abstract: In the welding of tubes with bevelled ends without heels or root-faces, all the weldings beads are made from the outside of the tubes with the tubes being in contact with local gap not exceeding 2 mm. The first and second welding beads are made both by the up-hill method and the down-hill method with the axis of the welding torches at the same inclination to the normal or the radius of the pipe and the accuracy of welding is improved by the use of mechanical guiding means for the welding means comprising at least one roller which bears on the bevelled ends of the tubes adjacent the welding zone.

Abstract: In the welding of tubes with bevelled ends without heels or root-faces, all the weldings beads are made from the outside of the tubes with the tubes being in contact with local gap not exceeding 2 mm. The first and second welding beads are made both by the up-hill method and the down-hill method with the axis of the welding torches at the same inclination to the normal or the radius of the pipe and the accuracy of welding is improved by the use of mechanical guiding means for the welding means comprising at least one roller which bears on the bevelled ends of the tubes adjacent the welding zone.