--------+---------+--------------------------
| | Permissible Explosives.
| Black |-------------+------------
| powder. | Maximum. | Minimum.
--------+---------+-------------+------------
CO_{2} | 22.8 | 14.50 | 21.4
CO | 10.3 | 27.74 | 1.3
N | 10.3 | 45.09 | 74.4
--------+---------+-------------+------------
In addition to investigations as to explosives for use in coal mining,
the Explosives Section of the Geological Survey analyzes and tests all
such materials, fuses, caps, etc., purchased by the Isthmian Canal
Commission, as well as many other kinds used by the Government. It is
thus acquiring a large fund of useful information, which will be
published from time to time, relative to the kinds of explosives and the
manner of using them best suited to any blasting operations, either
above or under water, in hard rock, earth, or coal. There has been
issued from the press, recently, a primer of explosives,[7] by Mr.
Clarence Hall, the engineer in charge of these tests, and Professor C.
E. Munroe, Consulting Explosives Chemist, which contains a large amount
of valuable fundamental information, so simply expressed as to be easily
understandable by coal miners, and yet sufficiently detailed to be a
valuable guide to all persons who have to handle or use explosives.
In the first chapters are described the various combustible substances,
and the chemical reactions leading to their explosibility. The low and
high explosives are differentiated, and the sensitiveness of fulminate
of mercury and other detonators is clearly pointed out. The various
explosives, such as gunpowder, black blasting powder, potassium chlorate
powders, nitro-glycerine powders, etc., are described, and their
peculiarities and suitability for different purposes are set forth. The
character and method of using the different explosives, both in opening
up work and in enclosed work in coal mines, follow, with information as
to the proper method of handling, transporting, storing, and thawing the
same. Then follow chapters on squibs, fuses, and detonators; on methods
of shooting coal off the solid; location of bore-holes; undercutting;
and the relative advantages of small and large charges, with
descriptions of proper methods of loading and firing the same. The
subjects of explosives for blasting in rock, firing machines, blasting
machines, and tests thereof, conclude the report.
The work of the chemical laboratory in which explosives are analyzed,
and in which mine gases and the gases produced by combustion of
explosives and explosions of coal-gas or coal dust are studied, has been
of the most fundamental and important character. The Government is
procuring a confidential record of the chemical composition and mode of
manufacture of all explosives, fuses, etc., which are on the market.
This information cannot but add greatly to the knowledge as to the
chemistry of explosives for use in mines, and will furnish the basis on
which remedial measures may be devised.
A bulletin (shortly to go to press) which gives the details of the
physical tests of the permissible explosives thus far tested, will set
forth elaborately the character of the testing apparatus, and the method
of use and of computing results.[8]
This bulletin contains a chapter, by Mr. Rutledge, setting forth in
detail the results of his observations as to the best methods of using
permissible explosives in getting coal from various mines in which they
are used. This information will be most valuable in guiding mining
engineers who desire to adopt the use of permissible explosives, as to
the best methods of handling them.
_Electricity in Mines._--In connection with the use of electricity in
mines, an informal series of tests has been made on all enclosed
electric fuses, as to whether or not they will ignite an explosive
mixture of air and gas when blown out. The results of this work, which
is under the direction of Mr. H. H. Clark, Electrical Engineer for
Mines, have been furnished the manufacturers for their guidance in
perfecting safer fuses, a series of tests of which has been announced. A
series of tests as to the ability of the insulation of electric wiring
to withstand the attacks of acid mine waters is in progress, which will
lead, it is hoped, to the development of more permanent and cheaper
insulation for use in mine wiring. A series of competitive tests of
enclosed motors for use in mines has been announced, and is in progress,
the object being to determine whether or not sparking from such motors
will cause an explosion in the presence of inflammable gas.
In the grounds outside of Building No. 10 is a large steel gallery, much
shorter than Gallery No. 1, in fact, but 30 ft. in length, and much
greater in diameter, namely, 10 ft. (Fig. 3, Plate X), in which electric
motors, electric cutting machines, and similar apparatus, are being
tested in the presence of explosive mixtures of gas and dust and with
large amperage and high voltage, such as may be used in the largest
electrical equipment in mines.
The investigation as to the ability of insulation to withstand the
effects of acid mine waters has been very difficult and complicated. At
first it was believed possible that mine waters from nearby Pennsylvania
mines and of known percentages of acidity could be procured and kept in
an immersion tank at approximately any given percentage of strength.
This was found to be impracticable, as these waters seem to undergo
rapid change the moment they are exposed to the air or are transported,
in addition to the changes wrought by evaporation in the tank. It has
been necessary, therefore, to analyze and study carefully these waters
with a view to reproducing them artificially for the purpose of these
tests. Concerning the insulation, delicate questions have arisen as to a
standard of durability which shall be commensurate with reasonable cost.
These preliminary points are being solved in conference with the
manufacturers, and it is expected that the results will soon permit of
starting the actual tests.
_Safety-Lamp Investigations._--Many so-called safety lamps are on the
market, and preliminary tests of them have been made in the lamp
gallery, in Building No. 17 (Fig. 2, Plate X). After nearly a year of
endeavor to calibrate this gallery, and to co-ordinate its results with
those produced in similar galleries in Europe, this preliminary inquiry
has been completed, and the manufacturers and agents of all safety lamps
have been invited to be present at tests of their products at the
Pittsburg laboratory.
A circular dated November 19th, 1909, contains an outline of these
tests, which are to be conducted under the direction of Mr. J. W. Paul,
an experienced coal-mining engineer and ex-Chief of the Department of
State Mine Inspection of West Virginia. The lamps will be subjected to
the following tests:
(_a_).--Each lamp will be placed in a mixture of air and explosive
natural gas containing 6, 8, and 10% of gas, moving at a velocity of
from 200 to 2,500 ft. per min., to determine the velocity of the air
current which will ignite the mixture surrounding the lamp. The current
will be made to move against the lamp in a horizontal, vertical
ascending, and vertical descending direction, and at an angle of 45°,
ascending and descending.
(_b_).--After completing the tests herein described, the lamps will be
subjected to the tests described under (_a_), with the air and gas
mixture under pressure up to 6 in. of water column.
(_c_).--Under the conditions outlined in (_a_), coal dust will be
introduced into the current of air and gas to determine its effect, if
any, in inducing the ignition of the gas mixture.
(_d_).--Each lamp will be placed in a mixture of air and varying
percentages of explosive natural gas to determine the action of the gas
on the flame of the lamp.
(_e_).--Each lamp will be placed in a mixture of air and varying
percentages of carbonic acid gas to determine the action of the gas on
the flame.
(_f_).--Lamps equipped with internal igniters will be placed in
explosive mixtures of air and gas in a quiet state and in a moving
current, and the effect of the igniter on the surrounding mixture will
be observed.
(_g_).--The oils (illuminants) used in the lamps will be tested as to
viscosity, gravity, flashing point, congealing point, and composition.
(_h_).--Safety-lamp globes will be tested by placing each globe in
position in the lamp and allowing the flame to impinge against the globe
for 3 min. after the lamp has been burning with a full flame for 10
min., to determine whether the globe will break.
(_i_).--Each safety-lamp globe will be mounted in a lighted lamp with
up-feed, and placed for 5 min. in an explosive mixture of air and gas
moving at the rate of 1,000 ft. per min., to determine whether the heat
will break the glass and, if it is broken, to note the character of the
fracture.
(_j_).--Safety-lamp globes will be broken by impact, by allowing each
globe to fall and strike, horizontally, on a block of seasoned white
oak, the distance of fall being recorded.
(_k_).--Each safety lamp globe will be mounted in a safety lamp and,
when the lamp is in a horizontal position, a steel pick weighing 100
grammes will be permitted to fall a sufficient distance to break the
globe by striking its center, the distance of the fall to be recorded.
(_l_).--To determine the candle power of safety lamps, a photometer
equipped with a standardized lamp will be used. The candle-power will be
determined along a line at right angles to the axis of the flame; also
along lines at angles to the axis of the flame both above and below the
horizontal. The candle-power will be read after the lamp has been
burning 20 min.
(_m_).--The time a safety lamp will continue to burn with a full charge
of illuminant will be determined.
(_n_).--Wicks in lamps must be of sufficient length to be at all times
in contact with the bottom of the vessel in which the illuminant is
contained, and, before it is used, the wick shall be dried to remove
moisture.
_Mine-Rescue Methods._--Mr. Paul, who has had perhaps as wide an
experience as any mining man in the investigation of and in rescue work
at mine disasters, is also in charge of the mine-rescue apparatus and
training for the Geological Survey. These operations consist chiefly of
a thorough test of the various artificial breathing apparatus, or
so-called oxygen helmets. Most of these are of European make and find
favor in Great Britain, Belgium, France, or Germany, largely according
as they are of domestic design and manufacture. As yet nothing has been
produced in the United States which fulfills all the requirements of a
thoroughly efficient and safe breathing apparatus for use in mine
disasters.
At the Pittsburg testing station there are a number of all kinds of
apparatus. The tests of these are to determine ease of use, of repair,
durability, safety under all conditions, period during which the supply
of artificial air or oxygen can be relied on, and other essential data.
In addition to the central testing station, sub-stations for training
miners, and as headquarters for field investigation as to the causes of
mine disasters and for rescue work in the more dangerous coal fields,
have been established; at Urbana, Ill., in charge of Mr. R. Y. Williams,
Mining Engineer; at Knoxville, Tenn., in charge of Mr. J. J. Rutledge,
Mining Engineer; at McAlester, Okla., in charge of Mr. L. M. Jones,
Assistant Mining Engineer; and at Seattle, Wash., in charge of Mr. Hugh
Wolflin, Assistant Mining Engineer. Others may soon be established in
Colorado and elsewhere, in charge of skilled mining engineers who have
been trained in this work at Pittsburg, and who will be assisted by
trained miners. It is not to be expected that under any but
extraordinary circumstances, such as those which occurred at Cherry,
Ill., the few Government engineers, located at widely scattered points
throughout the United States, can hope to save the lives of miners after
a disaster occurs. As a rule, all who are alive in the mine on such an
occasion, are killed within a few hours. This is almost invariably the
case after a dust explosion, and is likely to be true after a gas
explosion, although a fire such as that at Cherry, Ill., offers the
greatest opportunity for subsequent successful rescue operations. The
most to be hoped for from the Government engineers is that they shall
train miners and be available to assist and advise State inspectors and
mine owners, should their services be called for.
It should be borne in mind that the Federal Government has no police
duties in the States, and that, therefore, its employees may not direct
operations or have other responsible charge in the enforcement of State
laws. There is little reason to doubt that these Federal mining
engineers, both because of their preliminary education as mining
engineers and their subsequent training in charge of mine operations,
and more recently in mine-accidents investigations and rescue work, are
eminently fitted to furnish advice and assistance on such occasions. The
mere fact that, within a year, some of these men have been present at,
and assisted in, rescue work or in opening up after disasters at nearly
twenty of such catastrophes, whereas the average mining engineer or
superintendent may be connected with but one in a lifetime, should make
their advice and assistance of supreme value on such occasions. They
cannot be held in any way responsible for tardiness, however, nor be
unduly credited with effective measures taken after a mine disaster,
because of their lack of responsible authority or charge, except in
occasional instances where such may be given them by the mine owners or
the State officials, from a reliance on their superior equipment for
such work.
Successful rescue operations may only be looked for when the time, now
believed to be not far distant, has been reached when the mine operators
throughout the various fields will have their own rescue stations, as is
the practice in Europe, and have available, at certain strategic mines,
the necessary artificial breathing apparatus, and have in their employ
skilled miners who have been trained in rescue work at the Government
stations. Then, on the occurrence of a disaster, the engineer in charge
of the Government station may advise by wire all those who have proper
equipment or training to assemble, and it may be possible to gather,
within an hour or two of a disaster, a sufficiently large corps of
helmet-men to enable them to recover such persons as have not been
killed before the fire--which usually is started by the explosion--has
gained sufficient headway to prevent entrance into the mine. Without
such apparatus, it is essential that the fans be started, and the mine
cleared of gas. The usual effect of this is to give life to any
incipient fire. With the apparatus, the more dense the gas, the safer
the helmet-men are from a secondary explosion or from the rapid ignition
of a fire, because of the absence of the oxygen necessary to combustion.
The miners who were saved at Cherry, Ill., on November 20th, 1909, owe
their lives primarily to the work of the Government engineers. The
sub-station of the Survey at Urbana, Ill., was promptly notified of the
disaster on the afternoon of November 13th. Arrangements were
immediately made, whereby Mr. R. Y. Williams, Mining Engineer in Charge,
and his Assistant, Mr. J. M. Webb, with their apparatus, were rushed by
special train to the scene, arriving early the following day (Sunday).
Chief Mining Engineer, George S. Rice, Chief of Rescue Division, J. W.
Paul, and Assistant Engineer, F. F. Morris, learned of the disaster
through the daily press, at their homes in Pittsburg, on Sunday. They
left immediately with four sets of rescue apparatus, reaching Cherry on
Monday morning. Meantime, Messrs. Williams and Webb, equipped with
oxygen helmets, had made two trips into the shaft, but were driven out
by the heat. Both shafts were shortly resealed with a view to combating
the fire, which had now made considerable headway.
The direction of the operations at Cherry, was, by right of
jurisdiction, in charge of the State Mine Inspectors of Illinois, at
whose solicitation the Government engineers were brought into conference
as to the proper means to follow in an effort to get into the mine. The
disaster was not due to an explosion of coal or gas, but was the result
of a fire ignited in hay, in the stable within the mine. The flame had
come through the top of the air-shaft, and had disabled the ventilating
fans. A rescue corps of twelve men, unprotected by artificial breathing
apparatus, had entered the mine, and all had been killed. When the
shafts were resealed on Monday evening, the 15th, a small hole was left
for the insertion of a water-pipe or hose. During the afternoon and
evening, a sprinkler was rigged up, and, by Tuesday morning, was in
successful operation, the temperature in the shaft at that time being
109° Fahr. After the temperature had been reduced to about 100°, the
Federal engineers volunteered to descend into the shaft and make an
exploration. The rescue party, consisting of Messrs. Rice, Paul, and
Williams, equipped with artificial breathing apparatus, made an
exploration near the bottom of the air-shaft and located the first body.
After they had returned to the surface, three of the Illinois State
Inspectors, who had previously received training by the Government
engineers in the use of the rescue apparatus, including Inspectors Moses
and Taylor, descended, made tests of the air, and found that with the
fan running slowly, it was possible to work in the shaft. The rescue
corps then took hose down the main shaft, having first attached it to a
fire engine belonging to the Chicago Fire Department. Water was directed
on the fire at the bottom of the shaft, greatly diminishing its force,
and it was soon subdued sufficiently to permit the firemen to enter the
mine without the protection of breathing apparatus.
Unfortunately, these operations could be pursued only under the most
disadvantageous circumstances and surrounded by the greatest possible
precautions, due to the frequent heavy falls of roof--a result of the
heating by the mine fire--and the presence of large quantities of
black-damp. All movements of unprotected rescuers had to be preceded by
exploration by the trained rescue corps, who analyzed the gases, as the
fire still continued to burn, and watched closely for falls, possible
explosions, or a revival of the fire. While the heavy work of shoring
up, and removing bodies, was being carried on by the unprotected rescue
force, the helmet-men explored the more distant parts of the mine, and
on Saturday afternoon, November 20th, one week after the disaster, a
room was discovered in which a number of miners, with great presence of
mind, had walled themselves in in order to keep out the smoke and heat.
From this room 20 living men were taken, of whom 12 were recovered in a
helpless condition, by the helmet-men.
This is not the first time this Government mining corps has performed
valiant services. Directly and indirectly the members have saved from
fifteen to twenty lives in the short time they have been organized. At
the Marianna, Pa., disaster, the corps found one man still alive among
150 bodies, and he was brought to the surface. He recovered entirely
after a month in the hospital.
At the Leiter mine, at Zeigler, Ill., two employees, who had been
trained in the use of the oxygen helmets by members of the Government’s
corps, went down into the mine, following an explosion, and brought one
man to the surface, where they resuscitated him.
Equally good service, either in actual rescue operations, or in
explorations after mine disasters, or in fire-fighting, has been
rendered by this force at the Darr, Star Junction, Hazel, Clarinda,
Sewickley, Berwind-White No. 37, and Wehrum, Pa., mine disasters; at
Monongah and Lick Branch, W. Va.; at Deering, Sunnyside, and Shelburn,
Ind., Jobs, Ohio, and at Roslyn, Wash.
_Explosives Laboratory._--The rooms grouped at the south end of Building
No. 21, at Pittsburg, are occupied as a laboratory for the chemical
examination and analysis of explosives, and are in charge of Mr. W. O.
Snelling.
Samples of all explosives used in the testing gallery, ballistic
pendulum, pressure gauge, and other testing apparatus, are here
subjected to chemical analysis in order to determine the component
materials and their exact percentages. Tests are also made to determine
the stability of the explosive, or its liability to decompose at various
temperatures, and other properties which are of importance in showing
the factors which will control the safety of the explosive during
transportation and storage.
In the investigation of all explosives, the first procedure is a
qualitative examination to determine what constituents are present.
Owing to the large number of organic and inorganic compounds which enter
into the composition of explosive mixtures, this examination must be
thorough. Several hundred chemical bodies have been used in explosives
at different times, and some of these materials can be separated from
others with which they are mixed only by the most careful and exact
methods of chemical analysis.
Following the qualitative examination, a method is selected for the
separation and weighing of each of the constituents previously found to
be present. These methods, of course, vary widely, according to the
particular materials to be separated, it being usually necessary to
devise a special method of analysis for each explosive, unless it is
found, by the qualitative analysis, to be similar to some ordinary
explosive, in which case the ordinary method of analysis of that
explosive can be carried out. Most safety powders require special
treatment, while most grades of dynamite and all ordinary forms of black
blasting powder are readily analyzed by the usual methods.
The examination of black blasting powder has been greatly facilitated
and, at the same time, made considerably more accurate, by means of a
densimeter devised at this laboratory. In this apparatus a Torricellian
vacuum is used as a means of displacing the air surrounding the grains
of powder, and through very simple manipulation the true density of
black powder is determined with a high degree of accuracy. In Building
No. 17 there is an apparatus for separating or grading the sizes of
black powder (Fig. 1, Plate X).
By means of two factors, the moisture coefficient and the hygroscopic
coefficient, which have been worked out at this laboratory, a number of
important observations can be made on black powder, in determining the
relative efficiency of the graphite coating to resist moisture, and also
as a means of judging the thoroughness with which the components of the
powder are mixed. The moisture coefficient relates to the amount of
moisture which is taken up by the grains of the powder in a definite
time under standard conditions of saturation; and the hygroscopic
coefficient relates to the affinity of the constituents of the powder
for moisture under the same standard conditions.
Besides the examination of explosives used at the testing station, those
for the Reclamation Service, the Isthmian Canal Commission, and other
divisions of the Government, are also inspected and analyzed at the
explosives laboratory. At the present time, the Isthmian Canal
Commission is probably the largest user of explosives in the world, and
samples used in its work are inspected, tested, and analyzed at this
laboratory, and at the branch laboratories at Gibbstown and Pompton
Lakes, N.J., and at Xenia, Ohio.
Aside from the usual analysis of explosives for the Isthmian Canal
Commission, special tests are made to determine the liability of the
explosive to exude nitro-glycerine, and to deteriorate in unfavorable
weather conditions. These tests are necessary, because of the warm and
moist climate of the Isthmus of Panama.
_Gas and Dust Gallery No. 1._--Gallery No. 1 is cylindrical in form,
100 ft. long, and has a minimum internal diameter of 6⅓ ft. It consists
of fifteen similar sections, each 6⅔ ft. long and built up in in-and-out
courses. The first three sections, those nearest the concrete head, are
of ½-in. boiler-plate steel, the remaining twelve sections are of ⅜-in.
boiler-plate steel, and have a tensile strength of, at least, 55,000 lb.
per sq. in. Each section has one release pressure door, centrally placed
on top, equipped with a rubber bumper to prevent its destruction when
opened quickly. In use, this door may be either closed and unfastened,
closed and fastened by stud-bolts, or left open. Each section is also
equipped with one ¾-in. plate-glass window, 6 by 6 in., centrally placed
in the side of the gallery (Fig. 1, and Figs. 1 and 2, Plate VI). The
sections are held together by a lap-joint. At each lap-joint there is,
on the interior of the gallery, a 2½-in. circular, angle iron, on the
face of which a paper diaphragm may be placed and held in position by
semicircular washers, studs, and wedges. These paper diaphragms are used
to assist in confining a gas-and-air mixture.
[Illustration: Fig. 1.