Resistance spot welding apparatus

A resistance spot welding apparatus for attaching a turbulence insert to an internal wall of a steam generator pipe, comprising:

• a welding head which is introduced into the steam generator pipe and which comprises a cylindrical lance made of an electrically conductive material;
• a spot welding electrode which projects radially from the cylindrical lance;
• and
• an active member and an insulating body which lies radially opposite the spot welding electrode and is moved by the active member toward the internal wall;
• wherein the cylindrical lance includes a tapered section that is tapered at a defined distance from an end of the welding head such that the cylindrical lance bends at the tapered section so that insulating body and the spot welding electrode press the turbulence insert against the internal wall of the steam generator pipe when the active member is activated;
• wherein the active member is a hydraulic cylinder embedded into the cylindrical lance;
• wherein, when a welding current is applied to the cylindrical lance, a punctiform welding current flows via the spot welding electrode to a counter electrode arranged outside the steam generator pipe.