FOREST SERVICE WATER SPRAY DRY KILN. 25 
Table 5.- -Capacity of steam pipes 100 feet in length with separate returns. 
Diameter 
of supply. 
Diameter 
of return. 
Radiating surface. 
2 pounds 
pressure. 
5 pounds 
pressure. 
Inches. 
1 
li 
1* 
2' 
2h 
3 
3* 
4 
4| 
5" 
6 
7 
8 
9 
10 
12 
14 
16 
Inches. 
1 
1 
li 
li 
2 
2| 
2i 
3" 
3 
34 
3i 
4" 
4 
4* 
5" 
6 
7 
8 
Sq. feet. 
36 
72 
120 
280 
528 
900 
1,320 
1,920 
2,760 
3,720 
6,000 
9,000 
12,800 
17,800 
23,200 
37,000 
54,000 
76,000 
Sq. feet. 
60 
120 
200 
480 
880 
1, 500 
2,200 
3,200 
4,600 
6,200 
10,000 
15,000 
21,600 
30,000 
39,000 
62,000 
92,000 
130,000 
The amount of heating surface a steam.main will supply is reduced 
in excessively long runs or where frequent obstructions occur. For 
pipe of greater length than 100 feet, reduce the amount of radiation 
for a given diameter pipe according to Table 6. 
Table 6. — Constant for reducing radiation on account of length of pipe. 
Lenerth of 
Reduction 
pipe. 
factor. 
Feet. 
200 
0.71 
300 
.58 
400 
.50 
500 
.45 
600 
.41 
700 
.38 
800 
.35 
900 
.33 
1,000 
.32 
In estimating the length of mains and supplies consider the length 
of pipe increased by all obstructions such as elbows, tees, valves, etc. 
Such increase in length may be expressed in terms of diameters as 
follows: Eight angle elbows, 40 diameters; globe valves, 125 diam- 
eters; tees, 60 diameters. 
The steam main should be gradually increased in size as it 
approaches the source of supply in proportion to the amount of 
radiation taken off to supply the kilns on the main. 
There are two rules in common use by steam fitters for deter- 
mining the approximate size of steam mains and supply pipes which 
will give fairly satisfactory results when applied to short runs of 
Pipe- . 
Rule J. 3 — Diameter of steam main in inches should equal —-. \ 
Radiating surface 
in square feet. 
s Mr. George Babcock. 
