This specific welding machine is intended for the circumferential welding of the inner cylinder of the solar water heater with the outer casing and the lids. It is equipped with 4 welding torches, achieving high productivity in short periods of time. The centering of the cylinder with the lids is done automatically through the use of special molds. This machine can be used for applications of rotary welding in solar and electric water heaters, LNG / LPG tanks, and many other applications.