A method for welding two or more conduits includes aligning end portions thereof in an abutting relationship to define a gap. The method includes performing a spatter free root weld along the gap to configure a root layer while the inner circumferential surface side is unobstructed. After the root weld is complete, an outward thrust is applied along the inner circumferential surfaces of the conduits. During the application of the outward thrust, a filler weld is performed along the gap to fill the gap and to facilitate shrinkage of the filler and root weld materials longitudinally and radially outward while preventing pressing out of the filler and root weld materials radially inward of the inner circumferential surface.

Two parts are joined along a joining gap disposed therebetween by welding by illuminating the joining gap with an energy beam through a mobile vacuum chamber which is moved, on the side to be welded, on the parts being joined along the joining gap and in which a vacuum is generated. The vacuum chamber forms a first vacuum chamber in which, during welding, a vacuum having a first pressure level is generated, and a vacuum having a second pressure level is generated in a second vacuum chamber which adjoins the first vacuum chamber directly at a chamber wall thereof and which, during welding, regionally covers the joining gap. The pressure levels in the two vacuum chambers are matched to one another or the first pressure level is raised to above the second pressure level by way of a pressure regulating system.

A method for welding two or more conduits includes aligning end portions thereof in an abutting relationship to define a gap. The method includes performing a spatter free root weld along the gap to configure a root layer while the inner circumferential surface side is unobstructed. After the root weld is complete, an outward thrust is applied along the inner circumferential surfaces of the conduits. During the application of the outward thrust, a filler weld is performed along the gap to fill the gap and to facilitate shrinkage of the filler and root weld materials longitudinally and radially outward while preventing pressing out of the filler and root weld materials radially inward of the inner circumferential surface.