The rate of evaporation is given at 8 lbs. of water (from and at 212° Fahr.), for which the fuel required is

148,105 ÷ 8 = 18,513 lbs. of coal per hour.

For a rate of combustion of 15 lbs. of coal per hour per square foot of grate,

grate area = 18,513 ÷ 15 = 1,234 sq. ft.

For stationary boilers the usual ratio of heating surface to grate area is 35:1, accordingly the heating surface corresponding to this ratio is

1,234 × 35 = 43,190 sq.ft.

The above calculation is based on a rate of evaporation of 8 lbs. of water per lb. of coal and a rate of combustion of 15 lbs. of coal per sq. ft. of grate. For other rates the required grate area may be obtained from the following table:

GRATE SURFACE PER HORSE POWER (KENT)
Pounds
of water
from and
at 212°
per pound
of coal		Pounds
of coal
per h.p.
per hour		 Pounds of coal burned per square foot of grate per hour
8 1012 1520 2530 3540
Square feet grate per horse power
Good coal and boiler 103.45 .43.35 .28.23 .17.14 .11.10 .09
93.83 .48.38 .32.25 .19.15 .13.11 .10
Fair coal or boiler
8.61
4. 
.50
.40
.33
.26
.20
.16
.13
.12
.10
84.31 .54.43 .36.29 .22.17 .14.13 .11
74.93 .62.49 .41.33 .24.20 .17.14 .12
Poor coal or boiler
6.9
5. 
.63
.50
.42
.34
.25
.20
.17
.15
.13
65.75 .72.58 .48.38 .29.23 .19.17 .14
56.9 .86.69 .58.46 .35.28 .23.22 .17

Lignite and poor boiler
3.45
10. 
1.25
1.00
.83
.67
.50
.40
.33
.29
.25

General Arrangement of Station.—In designing an electrical station, it is preferable that whatever rooms or divisions of the interior space are desired should determine the total outside dimensions of the plant in the original plans of the building than that these latter dimensions be fixed and the rooms, etc., be fitted in afterward.