A multiple hearth furnace including a rabble arm with a tubular structure and a solid plug body. The latter is received in a socket arranged in an arm fixing node. It has an axial through boring and cooling fluid supply and return channels arranged around this through boring. A clamping bolt is rotatably fitted in the through boring. It has a bolt head, which can be brought by rotation into and out of hooking engagement with an abutment surface on the arm fixing node. A threaded end of the clamping bolt sticks out of the through boring at the rear end of the plug body. A threaded sleeve, which is screwed onto this threaded end, bears on an abutment surface at the rear end of the plug body for exerting a clamping force onto the clamping bolt.