The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1914-03-05

The bureau Of mines has recently
issued an interesting pamphlet on 1.-THE
Factor Of Safety in Mine Electrical In
stallations," from which the following
is taken:
In analyzing the relation that the
use of electricity in mines bears to the
accidents that occur there, the first
step is to classify the different ways In
which electricity can cause injury,
death or disaster.
rent with which everybody Is familiar
is its ability to produce electric shocks.
The conditions underground are fav-
orabe to their occurrence. There Is a
well known fire risk in connection with
the use of electrical apparatus. The
use of electricity in the vicinity of gas,
explosive dust or explosives. all of
which may be found in mines, Is at
tended with danger There are, there
fore. in connection with the use Of
electricity in mining work three posi-
BILE dangers-shocks fires and explo-
sions.
Electric Shocks.
/ The conditions under which electro
city can start a fire or cause an explo-
sion may be absent from mine at any
or all times, but the chance of receiy-
ing an electric shock is always present
in any mine in which electricity is
used and men are at work.
Many conditions that are peculiarly
favorable to the occurrence of electric
shocks are found in mines. Most Of
these such as dampness, dust, limited
space, and scanty light, are unavoid-
ably associated with mining work. In
addition, many underground employees
are unfamiliar with electrical apparat-
us and the proper way to regard it.
They may have no responsibility as to
its operation or condition, nor any d.
rect interest in it whatever. TO some
of them electricity may be not even
name or at most only something
about which conflicting and confusing
statements are made. Yet though the
conditions underground favor electric
shocks and though the men may be
unfamiliar with electricity, trolley
wires and uninsulated feeders are fire.
nuently found operating at $50 and $50
volts, the earth being used almost uni
versally as the common return for all
! direct pIr,ent apnaratl
Danger From Ground Return Circuits.
Under the best of conditions ground
return circuits offer more chances for
shock than do completely insulated
circuits. The risk is increased where
workmen are obliged to stand upon the
ground when handling apparatus OPP
grating with ground returns. In the
ground return systems one side of the
generator is connected to the earth, to
the track rail network and to the re.
turn feeders which are in parallel with
both. AS result anyone who stands
upon the ground stands upon one side
of the electric circuit and only sin,
gle contact with the other side of tn,
circuit is necessary to give shock.
Danger From Trolley Wires or Bar,
Conductors.
Trolley wires in mines present :
most fruitful source of electric shock
Trolley wires are necessarily bar,
conductors; they may extend for Ion,
distances throughout mine, and Of
ten they must be installed less than
mans. height above the track raj
which is used as a part of the return
circuit. A low trolley wire is especial
~ dangerous in places where men mus
work in making up trips of cars al
at partings where loaded trips ar,
brought out to the foot of a rope haul
age system. Under such crcum
stances both the loaded and the empt,
trips are in the parting at the sam,
time and manipulation is required t
make up the loaded trip to be taker
out on the rope and to split up tn.
empty trip to be taken in by the var.
ious locomotives. 1t is often desirabl,
to do this work rapidly, and if tn.
trolley wires are lower than a mans
head the chance for shock Is consid.
cradle. Even If the men are familiar
with the conditions their attention
while hurrying to get the trips away
from the parting, can not be constantly
on the trolley wire.
Trolley wire feeders and the wires
of circuits that operate motors of any
description, If exposed to the same eX
: tent, offer the same chance of shocl
as does the trolley wire. Usually such
exposure is not necessary, however, al
the wires can be strung along the side.
of entries in positions less accessible
to perons passing. 1t is also possible t.
insulate or protect the wires.
Danger From Accidental Charging o.
Equipment.
Apparatus that has accidentally
come in contact with the ungroundeG
side of an electric circuit is almost as
dangerous as the trolley wire. If such
apparatus is metallic and is insulated
from the earth 1t offers all the neces
sary conditions for giving severe
shock and the danger from such a
shock is accumulated by the fact that
the victim. being unaware Of his prox-
unity to danger, may firmly grasp the
charged part If shock is received