BOILERS FOR MARINE PURPOSES.
51
of the two former boilers—namely, 95, 105, and 112 Ibs. pressure,that it may be accepted as the ultimate strain that boilers of thisconstruction can bear after being twenty years in use. It is muchless than that due to the formula usually given for a new boiler.”
This boiler was twenty-five years old. Some of the plates andrivets showed little or no change, but brittleness appeared in theangle-iron.
BOILERS FOR MARINE PURPOSES.
It is not our intention to treat upon the old flue-boiler, with itsmultitudinous arrangements, as that dass has now become nearlyobsolete, though there is still a demand for them in particular cases,such as for dredgers. The arrangement of this type of boilershould be as simple as possible, and all the flues ought to run inthe same direction, and be of uniform width, commencing at thepart where the flame and gases meet from the furnace. When
Fig. 25.
AA, Furnaces.
b, Combustion chamber.
c, Tubes.
D, Smoke*box.e, Uptake.
A
N
D
1 ' 1
1 0 1
B
r .1
r=— . i
c -:-:-[
A
J
Fig. 24.—Flue Boiler for Dredger.
Fig. 25.—Tubulär Boiler for Dredger.
Longitudinal and Horizontal Sections.
more than one furnace is adopted all flues from the furnaces whichjoin into one large flue should taper from the furnace farthest fromthe large main flue. This is obvious, as the flame and gases fromthat furnace mix with the next, and so on; care ought to be taken