Abstract: The invention relates to a hot gas nozzle adapted for heating an end section of a double tube, where the double tube comprises a first tube and a second tube, comprising a first and a second inner nozzle insert having outlet openings adapted to heat an internally located section in a double tube with hot air, where the hot gas nozzle further comprises a first and a second outer nozzle insert having outlet openings adapted to heat an externally and between the tubes located section of the double tube with hot air, which section after a sealing of the double tube will join the tubes. The invention further relates to a tube filling machine comprising a hot gas nozzle and a method for sealing and joining a double tube. The object of the invention is to obtain an improved sealing of double tubes.