Not sure what you are talking about; however, I will take a guess. If you are trying to attach a wire to a pipe for cathodic protection or grounding, thermite welding is one method that is used in many piping applications.
As stated above the method generally used is resistance welding. You will note in the description that they are welded two by two. The machine is just a very large version of the common stud welder.
Ok for the welding methods.
My problem is to understand which industrial method is employed. i.e. a robot? In a linear meter of a pipe you can easily have more than 1000 studs. I imagine more than one studs are welded in the same time... right?
If you mean external applied studs, yes these are typically done by automatic arc stud welding machine(s). Many of the boiler manufacturers routinely apply many thousands of external studs on furnace wall tubes to hold refractory. I don't see any difference between a pipe and boiler tube for this application.
![[worm]](/data/assets/smilies/worm.gif "[worm] [worm]")