A method for welding tubes in a shell and tube heat exchanger, including forming ring-shaped tube sheet grooves on the tube sheet at the shell side, inserting tube joint members into the tube insertion holes of the tube sheet, producing ring wires by cutting a welding wire into pieces and bending the pieces into a ring shape, affixing the ring wire to the outer circumference of one end of the tube, inserting the end of the tube into the tube sheet such that the end of the tube contacts one end of the tube joint member and is located within the recessed distance range of the tube sheet groove, and performing shell side welding by inserting a welding torch into the tube joint member and welding the end of the tube joint member, the end of the tube and the joint part to the tube sheet at the shell side using the ring wire as filler metal.

The invention relates to an orbital welding device with a welding head that has a receptacle for positioning a joining area of two joining partners, in particular a fitting and a pipe end which joining partners are tubular at least in the joining area, wherein The welding head has an electrode ring segment which is arranged in the circumferential direction around the receptacle and is mounted in such a way that the electrode ring segment can be rotated about an imaginary longitudinal axis of the receptacle. The electrode ring segment has an electrode holder for a welding electrode and/or a welding electrode. The welding head has drive means, in particular one or more driven drive wheels, for driving the electrode ring segment about the imaginary longitudinal axis. The invention further relates to a system, with such an orbital welding device and an orbital welding method.