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THE COAL TRADE BULLETIN. 33
ELECTRICAL COMPRESSOR PLANT, CHICAGO AND NORTHWESTERN
RAILWAY TERMINAL, CHICAGO.
The air power plant at the terminal station of
the Chicago & Northwestern railway in Chicago
is a fine example of the best modern piactice in
the application of electric power to the compression
of air for the many purposes so characteristic
of railway yard work.
The air compressor plant is made up of two
Ingersoll-Sergeant standard power-driven compressors,
of the type designated by the makers
as class "JC." They are duplex two stage machines,
with air cylinders, frames and bearings,
mounted on a solid cast-iron bed-plate which encloses
the horizontal intercooler between the cylinders.
Both high and low pressure cylinders are
fitted with the standard Ingersoll-Sergeant pistcn
inlet valve, and regulation
is secured by the makers'
standard choking controller
on the low pressure intake.
This device, acting
to throttle the air intake
passage, is controlled by
receiver pressure and automatically
regulates the
volume of air compressed
and consequently the
amount of power consumed—to
the demand for
air from the power system.
The compressors run at
constant speed, the controller
simply varying the
effective piston displacement
with varying load.
The machines have a stroke of 12 inches, with
air cylinders 12 Vi an d 18Vi inches in diameter.
At their speed of 130 R. P. M. the free air capacity
of each unit is 455 cubic feet per minute. The
pressure used in this plant is 70 to 80 pounds
gauge.
The driving motors are General Electric direct
current machines, rated at 80 H. P. and 510 P. M..
on 220 volts. The illustration shows the arrangement
of the air plant. The machines are side by
side, the switch-board, rheostats, meters, etc.,
mounted in front of and between them. An intake
duct, supplying both compressors, leads under
the floor to the open air and rises beside the
power house, terminating in a screen cover for
the exclusion of dust and cinders from the yards.
The discharge pipes from the two unite in an
air main leading to the primary receiver outside
the plant. Provision is made for draining this
receiver. From this point, the line leads to a
system of cooling tubes to the west of the power
house, made up of a large upper and lower horizontal
header, connected by a number of small
vertical pipes. This arrangement freely exposed
to the air, precipitates whatever moisture may remain
in the air after leaving the primary receiver;
and this water is withdrawn from the lower
hj'ader. From this cooler, air lines radiate
throughout the yard, supplying power to the pneumatic
switch and signal system and a small portion
is diverted to the boiler room, where it is
applied in a small air lift pumping outfit which
supplies water to the terminal.
Interior of Power House.
England uses 32,000,000 tons a year for household
purposes, 13,000,000 tons in her railroads,
53.000,000 in factories, 18,000,001) tons in mining
processes, 28,000,000 tons in iron and steel industries,
and 15,000,000 tons in gas works. In a
third of a century England has doubled her coal
output. Germany has increased hers more than
four-fold, while the United States has multiplied
its production by ten. In 1870 the wholesale price
of bituminous coal in the American market ranged
from $6.25 to $7.25 per ton. Anthracite ranged
from $5.25 to $6.25.
The amount of coal docked at Milwaukee for
June of this year exceeded that for the same
month of any previous year. The receipts for
May were light, and coal men are trying to make
up the deficit.