﻿KILN DRYING HANDBOOK. 



53 



invented and developed at the Forest Products Laboratory. Figure 11 

 illustrates in a general way the principles of construction. The heat- 

 ing coils are conveniently mounted on the side walls, and a steam-jet 

 line runs along the top and bottom of each wall. The two left lines 

 operate simultaneously, and likewise the two right lines. The arrows 

 indicate the direction of the circulation when the left lines are open. 

 With the right lines open the circulation will be reversed. 



\ CANVAS CURTAIN 



CANVAS C'J.i?TA/N 



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Fig. 10. — Cross section of internal-fan kiln. A number of disk fans are mounted at 

 intervals upon a shaft extending the full length of the kiln. 



PILING LUMBER FOR KILN DRYING. 



Lumber to be kiln dried is usually piled in layers with strips or 

 stickers between each two layers. Sometimes short- stock, like spoke 

 billets, handles, and shoe-last blocks, is simply dumped into the kiln 

 without any attempt at orderly arrangement, " This method is apt to 

 produce irregular drying unless only small amounts are dried at a 

 time. The piling and sticking of the lumber should provide suitable 

 air passage between the boards in each layer and between layers, and 



