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Electric Detonators—
90. All electric detonators, aud leads thereto,
shall he suitable for the conditions under which
the blasting is carried on and shall he of a type
approved by the Testing Station of the Federal
Bureau of Mines. Detonators shall be kept in a
dry place and never stored with any other explosive.
Portable Firing Machines and Batteries—
91. Portable shot firing machines, sometimes
called generators, shall be enclosed in a tightly
constructed case when employed in any portion of
the mine. All contacts, when made or broken,
shall be within the case, except that the bindingposts
for making connections to the firing leads
may be outside.
92. Primary or secondary batteries used for
shot firing shall be provided with a suitable case
covered by rule 91. The batteries shall be constructed
so that if the wires of a detonator or
leads should accidentally, or otherwise, come in
contact with the binding posts, no current will be
discharged. They shall be provided with a detachable
handle, plug, or key, without which the current
cannot be closed, or provided with one or
more safety contact buttons, which are well countersunk
or protected by a non-conducting housing.
The plugs, handles, or keys, shall be detached
when not actually in use for firing a shot and shall
not, under any circumstances, pass from the personal
custody of the person commissioned to fire
the shots while on duty.
93. All portable devices for generating, or supplying,
electricity for shot filing, when in a mine,
shall be in charge of the person commissioned to
fire the shots.
94. No firing machine or battery shall be connected
to the shot firing leads until all other steps
preparatory to the firing of a shot have been com­
THE COAL TRADE BULLETIN. 57
pleted and all persons have moved to a place of
safety, and no person other than the shot firer
shall make such connection.
Disconnecting of Leads—
95. Immediately after the firing of a shot the
firing leads shall be disconnected from the supply,
or source, of electricity, and no person shall approach
a shot which has failed to explode until
the firing leads have been so disconnected by the
shot firer from the device, and an interval of five
minutes has elapsed since the last attempt to fire
the shot.
Tests of Generators 1 and Batteries—
96. Frequent tests shall be made of all devices
covered ny rule 93 to insure that their capacity has
not been decreased by use or accident.
Special Systems—
97. The use of special electrical shot firing systems
or equipment not covered by the foregoing,
shall receive the approval of the Testing Station
of the Federal Bureau of Mines.
Section 9.—Electric Signaling.
Precautions—
98. All proper precautions shall be taken to
prevent electric signal and telephone wires from
coming into contact with other electric conductors,
whether insulated or not.
Character of Equipment—
99. Bells, wires, insulators, contact-makers, and
other apparatus, used in connection with electric
signaling underground, shall be of suitable design,
of substantial and reliable construction, and
erected in such a manner as to reduce the liability
of failures or false signals to a minimum.
Maximum Potential—
100. fn any gaseous portion of a mine the potential
used for signal purposes shall not exceed
L'4 volts and bare wires shall not be used for signal
circuits except in haulage roads. •
ARGYLE COAL COMPANY
SOUTH FORK,
MINERS AND SHIPPERS OF THE
„ FAMOUj
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"ARGYLE"
SMOKELESS
C O ^ A V
PENNSYLVANIA.