12 



BULLETIN 1141, U. S. DEPARTMENT OF AGRICULTURE. 



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and the distribution of 

 the pipes under the 

 d r y i n g floor. In all 

 these systems a section 

 of double -thickness 

 Russia iron pipe. 10 

 inches in diameter and 

 4J feet long, is placed 

 on top of the furnace. 

 This reaches a point 

 about the same distance 

 from the drying floor. 

 The course of the hot 

 gases in the different 

 systems may be fol- 

 lowed by referring to 

 t h e illustration. The 

 outside row of pipes is 

 placed about *22 inches 

 from the wall of the 

 kiln. The whole pip- 

 ing system is given a 

 gradual rise from the 

 furnace to the flue and 

 is held in place by 

 wires or chains at- 

 tached to the joists. 

 Openings fitted with 

 covers are provided at 

 several points, in order 

 that the piping may be 

 cleaned out without 

 taking it down. At the 

 point where the pipe 

 enters the flue the pipes 

 are about 2 feet below 

 the joists of the drying 

 floor. Some furnaces 

 are fitted with two 

 openings for pipes, and 

 with this type of fur- 

 nace one opening is 

 used for each side of 

 the kiln and the pipes 

 are joined with a tee 

 just before entering the 

 chimney. The second 

 system illustrated is 

 used to a greater extent 

 than any of the others, 

 for the reason that the 

 third system, while giv- 

 ing greater radiating 

 surface, is very difficult 



