Apparatus of the first type, weighing 20 lb., supplies enough air to
last about 3 hours, and the products of breathing pass through a
check-valve directly into space. Apparatus of the second type supplies
oxygen obtained from oxygen-producing chemicals, and also provides means
of absorbing the carbonic acid gas produced in respiration. They contain
also the requisite tubes, valves, connections, etc., for the
transmission of the fresh air and the respired air so as to produce
sufficient oxygen while in use; to absorb and purify the products of
expiration; and to convey the fresh air to the mouth without
contamination by the atmosphere in which the apparatus is used. Three
oxygen-generating cartridges are provided, each supplying oxygen enough
for 1 hour, making the total capacity 3 hours. Changes of cylinders can
be made in a few seconds while breathing is suspended. This apparatus
weighs from 20 to 25 lb., according to the number of oxygen generators
carried. The cartridges for generating oxygen, provided with this
apparatus, are of no value after having been used for about an hour.
The third type of apparatus is equipped with strong cylinders charged
with oxygen under high pressure; two potash regenerative cans for
absorbing the carbon dioxide gas exhaled; a facial helmet; the necessary
valves, tubes, etc., for the control of the oxygen; and a finimeter
which registers the contents of the cylinders in atmospheres and minutes
of duration. The two cartridges used for absorbing the carbonic acid gas
are of no value after having been in use for two hours.
If inhalation is through the mouth alone, a mouthpiece is attached to
the end of the breathing tube by which the air or oxygen is supplied,
the nose is closed by a clip, and the eyes are protected by goggles. To
inhale through both nose and mouth, the miner wears a helmet or headgear
which can be made to fit tightly around the face. The helmet has two
tubes attached, one for inspiration and the other for expiration. In the
oxygen-cylinder apparatus these tubes lead to and from rubber sacks used
for pure-air and bad-air reserves.
Mine-Rescue Training.
It has been found in actual service that when a miner, equipped with
breathing apparatus for the first time, enters a mine in which an
explosion has occurred, he is soon overcome by excitement or nervousness
induced by the artificial conditions of breathing imposed by the
apparatus, the darkness and heat, and the consciousness that he is
surrounded with poisonous gases. It has also been found that a brief
period of training in the use of such apparatus, under conditions
simulating those encountered in a mine after a disaster, gives the miner
confidence and enables him to use the apparatus successfully under the
strain of the vigorous exertion incident to rescue work.
The rescue corps consists of five or six miners under the direction of
a mining engineer who is experienced in rescue operations and familiar
with the conditions existing after mine disasters. The miners work in
pairs, so that one may assist the other in case of accident, or of
injury to the breathing apparatus, and so that each may watch the
condition of the oxygen supply, as shown by the gauges in the other’s
outfit.
The training is given in the gas-tight room of Building No. 17, or in
similar rooms at sub-stations (Fig. 2, Plate XII). This room is made
absolutely dark, and is filled with formaldehyde gas, SO_{2}, CO_{2}, or
CO, produced by burning sulphur or charcoal on braziers. At each period
of training, the miners enter and walk a distance of about 1 mile, the
average distance usually traveled from the mine mouth to the working
face or point of explosion. They then remove a number of timbers; lift a
quantity of brick or hard lump-coal into wheel-barrows; climb through
artificial tunnels, up and down inclines, and over surfaces strewn with
coal or stone; operate a machine with a device attached to it, which
automatically records the foot-pounds of work done; and perform other
vigorous exercise, during a period of 2 hours. This routine is repeated
daily during 1 week, after which the rescue corps is considered
sufficiently trained for active service.
The apparatus used for recording the foot-pounds of work done by the
person operating the work machine within the gas-tight rescue room,
comprises a small dial with electrical connections, which records the
number of strokes made by the machine, and a pencil point which rests on
a paper diaphragm, fastened to a horizontal brass disk. This disk is
driven by clockwork, and makes one complete revolution per hour. When
the machine is in operation, the pencil point works back and forth,
making a broad line on the paper; when the operator of the machine
rests, the pencil point traces a single line. The apparatus thus records
the number of strokes given by the operator during a given time. From
the weight lifted, the height of lift, and the number of strokes in the
given time, the foot-pounds of work are readily calculated.
Electric Testing Apparatus.
On the ground floor of Building No. 10, two rooms are occupied as
laboratories for investigating the electrical equipment used in mining
operations. The purpose of these investigations is to ascertain the
conditions under which electricity of various voltages may be used with
safety--in mine haulage, hoisting, pumping, or lighting--in the presence
of dangerous mixtures of explosive gases or of dust. It is also proposed
to test various kinds of insulation and insulators in this laboratory,
and to determine the durability of such insulation in the presence of
such corrosive gases and water as are found in mines.
A water-proof wooden tank, measuring 15 by 5 by 5 ft., is installed, in
which insulation and insulating materials are tested under either pure
or polluted water. Various electric lighting devices and equipment can
be connected from a switch-board in Building No. 17 with Gas-and-Dust
Gallery No. 2, for testing the effect of such lighting apparatus in the
presence of explosive mixtures of gas and dust, as set forth on page
220.
In the electrical laboratory, Building No. 10, is a booster set
developing 60 kw., and an appropriate switch-board for taking direct
current at 220 volts from the turbo-generator and converting it into
current varying from 0 to 750 volts. There are also transformers for
developing 60-cycle, alternating current at voltages of from 110 to
2,200. The switch-board is designed to handle these various voltages and
to communicate them to the apparatus under test in Building No. 10,
Gallery No. 2, or elsewhere.
Tests are in progress of insulating materials for use in mines, and of
electric fuses, lights, etc., in Gallery No. 2 (Fig. 3, Plate X), and in
the lamp-testing box (Fig. 2, Plate XI). It is proposed, at the earliest
possible date, to make comparative tests of the safety of various mine
locomotives and mine-hoisting equipment through the medium of this
laboratory, and it is believed that the results will furnish valuable
information as a guide to the safety, reliability, and durability of
these appliances when electrically operated.
_Electric Lamp and Fuse Testing Box._--An apparatus for testing safety
lamps and electric lights and fuses, consists of ¼-in. iron plates,
bolted together with 1½ in. angle-irons to form a box with inside
dimensions of 18 by 18 by 24 in. The box is placed on a stand at such a
height that the observation windows are on a level with the observer’s
eye (Fig. 2, Plate XI), and it is connected, by a gas-pipe, with a
supply of natural gas which can be measured by a gas-holder or meter
alongside the box.
By the use of this apparatus the effect of explosive gas on flames, of
electric sparks on explosive mixtures of gas and air, and of breaking
electric lamps in an explosive mixture of gas and air, may be studied.
The safety lamps are introduced into the box from beneath, through a
hole 6 in. square, covered with a hinged iron lid, admission to which is
had through a flexible rubber sleeve, 20 in. long.
The behavior of the standard safety lamp and of the safety lamps
undergoing test may be compared in this box as to height of flame for
different percentages of methane in the air, the effect of such flames
in igniting gas, etc.
In each end of the box is an opening 1 ft. square, over which may be
placed a paper diaphragm held by skeleton doors, the purpose of which
is to confine the gas in such a manner that, should an explosion occur,
no damage would be done. In the front of the box are two plate-glass
observing windows, 2⅝ by 5½ in. In the side of the box, between the
two windows, is a ⅜-in. hole, which can be closed by a tap-screw,
through which samples for chemical analysis are drawn.
The gasometer consists of two iron cans, the lower one being open at
the top and filled with water and the upper one open at the bottom and
suspended by a counterweight. The latter has attached to its upper
surface a scale which moves with it, thereby measuring the amount of
gas in the holder. A two-way cock permits the admission of gas into the
gasometer and thence into the testing box.
_Gas-and-Dust Gallery No. 2._--This gallery is constructed of sheet
steel and is similar to Gallery No. 1, the length, however, being only
30 ft. and the diameter 10 ft. It rests on a concrete foundation (Fig.
3, Plate X). Diaphragms can be placed across either extremity, or at
various sections, to confine the mixtures of gas and air in which the
tests are made. The admission of gas is controlled by pipes and valves,
and the gas and air can be stirred or mixed by a fan, as described for
Gallery No. 1, and as shown by Fig. 1.
Gallery No. 2 is used for investigating the effect of flames of various
lamps, of electric currents, motors, and coal-cutting machines, in the
presence of known mixtures of explosive gas and air. It is also used for
testing the length of flame of safety lamps in still air carrying
various proportions of methane, and, for this purpose, is more
convenient than the lamp gallery. In tests with explosive mixtures,
after the device to be tested has been introduced and preparations are
completed, operations are controlled from a safe distance by a
switch-board in a building near-by.
Among other investigations conducted in this gallery are those of the
effect of sparks on known gas mixtures. These sparks are such as those
struck from a pick on flint, but in this case they are produced by
rubbing a rapidly revolving emery wheel against a steel file. The effect
of a spark produced by a short circuit of known voltage, the flame from
an arc lamp, etc., may also be studied in this gallery.