Jacketed jet radiant tube heater enclosing a segmented flame tube held together by clasps

A jacketed jet radiant heater suitable for heating an industrial process furnace comprising a jacket tube (1), mounted, near one end thereof, in a furnace wall and closed at its other end, said jacket tube surrounding, at its furnace-wall end, a burner unit (9) mounted therein, and a flame tube (4) disposed within said jacket tube, said flame tube being aligned at one end with said burner unit so as to receive a flame therefrom and at its other end being positioned for discharging combustion product gas into said jacket tube near said closed end thereof, said flame tube being composed of axially aligned pipe pieces (16,16a) connected one to another in each case by a plurality of clasps, said clasps in some pipe piece connections spacing apart connected pipe pieces from each other for providing channels for exhaust gas flow between the inside of said flame tube and a ring duct (5) inside said jacket tube and outside said flame tube, said clamps (19) each having elements protruding perpendicularly into respective holes of pipe pieces respectively joined by a said clasp.