The Locomotive - Lighthouse Survival Blog

layy.J THE LOCOMOTIVE. 83
lltf urmngement of the furnace is substautially tlic .saiMo for boilers of tlie locomotive
type. Fig. 1 is a front view of the furnace, showing a section of it tlirough the middle
•of tlie front tiring-hole. Fig. 2 is a side elevation of the whole, showing it in section
i»s it would appear if cut throiigii at the center line of setting and Ijoiler.
The gLMieral arrangement of the furnace, when applied to nprjght boilers, is the
same as when a|)plied to tliose of the horizontal type. The products of combustion pass
-(jut of the detached furnace through an opening in the bridge-wall having approxinnitely
the shape of tlie vena contmcta. This allows the freest flow of the gases, and
lends to mingle them in sucli a manner as to secure as perfect combustion as ])ossible.
riie furnace is supplied with fuel through lioles in the top, which are fitted witli remov-
4ible covers. The air required for combustion conies tlirougli the ash-pit, as in ordinary
furnaces. (We call attention to this point because it is sometimes overlooked when
using these external furnaces, the draft being needlessly checked by boxing up the fur-
nace front in some way, so that air does not have the requisite freedom of access to it.)
A cleaning door is placed in the rear wall, on a level with tlie flame-bed, for the removal
of ashes.
The furnace itself is .so placed that the top of it is flush with the boiler-room floor.
This may be done either by sinking the furnace in the ground, or by grading the general
surface up to the proper level. A pit or cellar extends in front of the furnace for from
1) to 12 feet, as may be convenient. This is floored over either with sleepers and planks,
or with I-beams and brick arches. The arches are preferable, being less likely to yield
or "give""; but the planking has.been used with this furnace, although we do not recommend
it. In level ground it is not necessary to excavate below the flame-bed for the
rear wall of the furnace, except to secure a good foundation.
The especial features of the particular arrangement of Mr. Allen's furnace shown in
the accompanying cuts, are its applicability to fire-box boilers, and its utility when
space does not allow of the erection of horizontal boilers, and also its adaptability to
burning either wood or coal. This lust feature is of con.siderable importance, for in
some localities w-aste fuel can be obtained for only a part of the boilers, or for only a
part of the year. With the fire-box boiler and extension furnace arranged as here described,
it is possible to use waste in some of the boilers, and coal in the others; or wood
a part of the year, and coal when the wood- waste is unobtainable. When burning wood
the ordinary coal-burning grates are removed. The ring around the bottom of the fire-
box is protected, when burning wood, l^y the four courses of fire-brick shown in Fig. 2
as coming well up on the water si)ace of the leg of the boiler. In burning coal these
bricks are taken down and laid away, and the regular grate is put in the furnace, the
covers are placed over the feed-holes in the extension furnace, and the boiler is fired in
the usual manner, the combustion-chamber of the wood-burning furnace forming the
nsh-])it when l)urning coal, and the ashes being removed from the cleaning-door men-
tioned above.
This arrangement affords as good combustion of fuel, in burning coal, as is ob-
tained in ordinary practice, and has the additional advantage of the extension furnace
in burning waste fuel. Furthermore, when wood fuel is burned in fire-box boilers the
condensation of the wood gases on the plates of the furnace and in the tubes causes a
rapid deterioration and wasting of the plates. This trouble is eliminated in the exten-
.sion furnace, for by the time the gases strike the comparatively cool boiler the combus-
tion is nearly perfect and the corrosive substances distilled from the wood have been