463 OF ENGINEERING formulæ.
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Mcltitübular Boileks.
d = Diameter of tubes in inches.
I = Length of tubes in inches.
n = Number of tubes.
II = Horse-power. .
A — Sectional area of tubes in inches.
KH -ISSitd
Assuming the tube surface to be about ’9 of the total
beating surface.
The values of K and A. vary
K. A.
from 670-20 in ordinary boilers
400-8 with very strong draught
to 250-2; „ artificial blast.
Relative Steam and Water Space.
Simula boiler—total capacity = 1-63 cub. ft. per sq. ft.
heating surface.
• 98 „
• 82 »
• 33 to 49 >,
• 26 >.
•18
Simple boiler—total capacity =
Boiler with two heaters . • < >
Lancashire boiler __________
Marine multitubular .. ..
Portable engine..............
Locomotive .. _.............
The ratio of steam space to water space is in—
Locomotives .. • • 1-00 steam to 2-00 water space.
Marine multitubular .. 1*00 „ „1'08 »
Cornish boilers .. .. 1’00 „ „1’33 „
The best distance for tbe fire below the heating surface of
the flue in Cornish or Lancashire boilers is about 20 or 22
Cornish or Lancashire Boilers,
general memoranda.
Thickness of fire-bars, 1 to f inch.
Width of fire-bar spaces, f to i inch..
Inclination of fire-bars, 1 in 10, to 1 12.
Height of dead plate above floor of boiler-shed or
stoke-hole, 2 ft. 8 in.
Minimum height of water over flue .. 4 inches.
Average „ \
Inclination of cylindrical boilers towards blow-off
cock in setting, i inch in 10 feet.