i STEAM COAL - Clpdigital.org

34 THE COAL TRADE BULLETIN.
\ AIR COMPRESSOR PLANT OF THE HOMESTAKE MINING COMPANY.
Probably twenty localities, scattered over all
parts of the world, claim for some one of their
producing mines the distinction of being "the
greatest gold mine in the world." Perhaps no
where are facts so hard to obtain as in mining
operations. Yet the passing years have a way of
sifting facts from fancies, and the highest authorities
to-day unite in assigning to the great Homestake
mine, at Lead. South Dakota, the first place
among the gold mines of the world. Its monthly
yield of the yellow metal averages in the neighborhood
of $425,000, the value of over 2.000 ounces
of fine gold. This is secured by the treatment of
about 125.000 tons of ore per month.
A singular, and at first thought inexplicable,
fact is that the Homestake, while unquestionably
the world's richest gold producer, is relatively one
of the poorest mines. The average ore values are
only about $3.60 per ton, while mining and treatment
charges, run about $2.40 per ton. The explanation
of the mine's value lies in the enormous
tonnage and in the cheap operative and productive
charges. The secret of low charges lies in
the adoption of the latest methods, the best machinery
and a careful consideration of the small
economies. The handling of immense quantities
of ore by the most refined machine methods has
made this "low grade" property the greatest bonanza
in the world. The success of this great
enterprise is a remarkable example of what modern
productive methods can bring about, and a description
of a part of the equipment will be of
interest. Compressed air has long been recognized
as a powerful factor in economical mine
operation and in the Homestake mine its possi­
One'of the Air Compressor Plants of the Homestake Mine.
bilities have been developed to the utmost.
As is eminently fitting, this greatest mine in
the world has in its power plant the largest air
compressor in the world, and this giant must receive
the first mention in the list of machines
on the Homestake lode. It is located at the Ellison
shaft and is a cross compound condensing
two-stage Corliss machine, built by the Ingersoll-
Sergeant Drill Co. of New York. The high and
low pressure steam cylinders have a diameter of
32 and 60 inches, respectively, the air cylinders
are 52% and 32% inches in diameter, and the
stroke is 72 inches. At the rated speed of 50
R. P. M. the free air capacity is 9,000 cubic feet
per minute, this volume being sufficient, under
average conditions of mine work, to operate 125
rock drills. The steam pressure is about 130
pounds. The exhaust steam is received by a
Wheeler surface condenser, in connection with a
cooling tower. The well known Ingersoll-Sergeant
piston inlet valve is used on both high and
low pressure air cylinders, between which a horizontal
inter-cooler is placed in the air circuit.
The total weight of this huge compressor with its
accessories, is about 300 tons. It is placed beside
the great Ellison hoist, the mountain being
blasted out to make space for the engine room.
The output of this great machine is used exclusively
for [operating machine drills in the
underground workings. It is assisted by two
smaller machines, built by the same maker and
both of the Corliss type, with piston inlet valve.
One of these machines, located at what is known
as the Old Abe shaft, is a duplex machine, with
steam cylinders 24 inches in diameter, air cylin-
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