The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1914-03-05
Classification of Mine Accidents Due
to Electricity

Oo
ing material but are not designed to
carry current they can not become
charged with electricity to a potential
above that OF the earth; consequently
a shock can not be obtained by per-
sons establishing contact between
such parts and the ground.
Shocks From Locomotives and Cars.
There are certain ways in which
shocks can be received from locomo-
tives and mine cars. The frames of
locomotives are connected to the cur
rent carrying parts Of the motors and
become charged whenever the motors
or headlights are in operation. If the
locomotive loses its ground or contact
with the rail by reason of oversanding
or from any other cause, the full line
potential exists between the frame OF
the locomotive and the rail. Under
such circumstances as severe shock
can be obtained from the locomotive
frame as from the trolley wire
Since the drawbars of the mine cars
are connected to the locomotive frame
and are continuous throughout the
length of the trip, 1t follows that
whenever the locomotive loses it's con
tact with the rail all the drawbars are
raised to the potential of the trolley
wire unless some of them are in con-
tact with the car axles, axle boxes, OF
some Of their connections.
Relative Danger From Different Volt
ages.
An electric shock is caused by the
passage of current through the human
body, the severity of the shock de-
pending upon the amount Of current
passed. The amount of current de-
ponds upon the voltage and the resist
ance of the circuit, the latter including
the resistance of the body, the resist
ance of it's contact with the source OF
current, and any resistance that may
be in series with the body. such as
ground resistance. Obviously, there
fore, all other factors being equal, the
severity of the shock varies with the
voltage causing it There are voltages
so small that they are not capable OF
passing through the body current suf-
voltages are exceeded, a value is
reached at which shocks begin to be
felt AS the voltage is further in
creased a value is reached such thai
shocks may be fatal if the contact is
maintained for a sufficiently long time
At still higher voltages the period O.
contact necessary to cause death be-
comes shorter.
! The effect Of any shock depends 81
much upon the particular conditions
involved that no specific values o
voltage can be assigned to any of tn
conditions mentioned. The physica
makeup of a man greatly affects tn
outcome. Some men seem PRACTICAL,
immune from shocks from potential
as high as 500 volts, while others ma,
be killed by much lower voltage
AS regards the relative danger of
current having a potential of $50 volt
and one having potential of so
volts. both have been known to caus
fatal shocks. Compared with a $50
volt potential, 55O-volt potential no
only passes more current through
mans body under given set of con
ditions, but 1t is also more likely t
break through insulation to ground
The higher voltage will pass the sam
current through poorer contacts an
greater resistances than will the low
Ter.
Fires Caused by Electricity.
The danger from fires caused b.
electricity arises principally from de
fective installation, careless upkeep, O
from Injuries to equipment resultin
from falls of roof or similar causes
short circuit or a ground that does no
Iblow the circuit breaker nor the fuse
may produce heat enough to start
fire by leaking across coal or timber
ing. The blowing of an open fuse i
accompanied by sufficient heat to liz
mite combustible material that is YER
close to the fuse, especially if for an
reason the arc is long drawn out. TIL
presence of inflammable materia
|around electric motors or starting
boxes may prove to be a source o
trouble. Incandescent lamps produc
heat enough to ignite combustible ma
terals if the dissipation of heat from
the bulbs of the lamps is allowed t.
become restricted. With conductor
bare and with both sides Of the circui
strung side by side there is a chanc
that leakage from one side to the othe
across coal or damp timbering ma,
produce heat enough to start fire.
The conductivity of coal, especially
dry coal, is usually very low. Thi