UNITED STATES DEPARTMENT OF AGRICULTURE 
1 BULLETIN No. 894 
Contribution from the Forest Service 
WILLIAM B. GREELEY, Forester 
js^fr p< $Wu 
Washington, D. C. 
PROFESSIONAL PAPER 
October 18, 1920 
MANUAL OF DESIGN AND INSTALLATION OF FOREST 
SERVICE WATER SPRAY DRY KILN. 
By L. V. Teesdale, 
Engineer in Forest Products. 
CONTENTS. 
The water spray kiln 
Kiln construction material. 
Details of construction 
Heating installation 
Page. 
1 
10 
11 
16 
Water supply 31 
Condenser coil 44 
Control instruments 45 
Some points to be emphasized in specifications 46 
THE WATER SPRAY KILN. 
The best thing that can be said of any dry kiln is that when it 
is run by a properly informed operator the temperature, humidity, 
and circulation are constant and uniform. In an endeavor to pro- 
duce a kiln in which each of these could be regulated independently 
of the others, the Forest Products Laboratory designed and devel- 
oped the " Forest Service Humidity Regulated Water Spray Kiln," 1 
described in this bulletin. The principle of forced circulation and 
humidity control by means of sprays of water was the basis of the 
first patent taken out in 1912 and is the main feature of the present 
kiln. This dry kiln is well adapted to commercial use in the kiln 
drying of refractory hardwoods of large dimensions and of green 
lumber of all kinds, and has attracted attention wherever commercial 
practice has been forced to realize that drying equipment incapable 
of close operation will not dry green lumber economically. 
Experience has shown that the details of good design and work- 
manship are often disregarded, with the result that the kiln fails 
to function as intended. By adhering to the principles herein set 
forth any competent engineer should be able to design or construct an 
installation of the size suited to the peculiar needs of a given plant. 
1 For.mformation regarding method of operation, see Forest Products Laboratory report "Notes on the 
Operation of the Forest Service Water Spray Dry Kiln and Theoretical Considerations of Heat Relations, " 
by H. D. Tiemann. 
187385°— 20 1 
