[Illustration]
This figure exhibits the interior of the furnace of a locomotive
engine, which varies greatly from the furnace of either a land or
marine boiler. This difference is largely caused by the method of
applying the draught for the air supply; in the locomotive this is
effected by conducting the exhaust steam through pipes from the
cylinders to the smoke-box and allowing it to escape up the smoke
stack from apertures called exhaust nozzles; the velocity of the steam
produces a vacuum, by which the products of combustion are drawn into
the smoke-box with great power and forced out of the smoke stack into
the open air.
To prevent the too quick passage of the gases into the flues an
appliance called a fire brick arch has been adopted and has proved very
efficient. In order to be self supporting it is built in the form of
an arch, supported by the two sides of the fire box which serve for
abutments. The arch has been sometimes replaced by a hollow riveted
arrangement called a water table designed to increase the fire surface
of the boiler.
FIRING A LOCOMOTIVE.—No rules can possibly be given for firing a
locomotive which would not be more misleading than helpful. This is
owing to the great variations which exist in the circumstances of the
use of the machine, as well as the differences which exist in the
various types of the locomotive.
These variations may be alluded to, but not wholly described. 1. They
consist of the sorts of fuel used in different sections of the country
and frequently on different ends of the same railroad; hard coal, soft
coal, and wood all require different management in the furnace. 2. The
speed and weight of the train, the varying number of cars and frequency
of stopping places, all influence the duties of the fireman and tax
his skill. 3. The temperature of the air, whether cold or warm, dry
weather or rain, and night time and day time each taxes the skill of
the fireman.
Hence, to be an experienced fireman in one section of the country and
under certain circumstances does not warrant the assurance of success
under other conditions and in another location. The subject requires
constant study and operation among not only “new men” but those longest
in the service.
More than in any other case to be recalled, must the fireman of a
locomotive depend upon the personal instruction of the engineer in
charge of the locomotive.
FIRING WITH TAN BARK.—Tan bark can be burned upon common grates and
in the ordinary furnace by a mixture of bituminous screenings. One
shovel full of screenings to four or five of bark will produce a more
economical result than the tan bark separate, as the coal gives body
to the fire and forms a hot clinker bed upon which the bark may rest
without falling through the spaces in the grate bars, and with the
coal, more air can be introduced to the furnace.
The above relates to common furnaces, but special fire boxes have
been recently put into operation, fed by power appliances, which work
admirably. The “point” principally to be noted as to the efficacy of
tan bark as a fuel, is to the effect, that like peat, the drier it is
the more valuable is it as a fuel.