TM 9-1375-213-12
may initiate electrical firing circuits. Effects of remote
lightning strikes are multiplied by proximity to conduc-
ing elements, such as those found in buildings, fences,
railroads, bridges, streams, and underground cables or
conduit. The only safe procedure is to suspend all
blasting activities during electrical storms and when one
is impending.
c. Electric Power Lines. Electric firing will not be
performed in training within 155 meters of energized
power transmission lines. When it is necessary to con-
duct blasting operations at distances closer than 155
meters to electric power lines, nonelectric firing systems
should be used or power lines deenergized (AR 385-63).
2-10. Detonating Cord Firing Systems-
Methods of Use
Of all the firing systems for explosives, a detonating
cord firing system is probably the most versatile and in
many cases the most easily installed. The detonating
cord firing system is especially applicable for under-
water and underground blasting because the blasting
cap of the initiating system may remain above water or
ground.
a. A detonating cord system utilizes detonating cord
as a relay element between the initiator and the main ex-
plosive charge. A detonating cord firing system has the
following advantages:
(1) It allows a long distance between the sensitive
initiator element (blasting cap or delay detonator) and
the main charge.
(2) It allows simultaneous detonation of a
number of charges with a single initiator.
(3) The detonating cord itself is moisture resistant
Table 2-4.
and thus can be used to run the priming system into
damp areas or even underwater.
(4) Since most charges can be primed with
detonating cord, its lack of sensitivity to accidental in-
itiation reduces the danger of misfires underground (i.e.
digging into a misfired detonating cord primed charge is
less dangerous than digging into a blasting cap primed
charge).
b. The set-up of a detonating cord firing system is
optional. The charge may be primed with encircling
loops of detonating cord or knots of it within plastic ex-
plosive or by means of a nonelectric blasting cap
crimped onto the end of the detonating cord. Details are
given in the priming section (pars. 2-2 and 2-17). The
length of the detonating cord lead-in can be as short or
long as desired-even hundreds of feet. The detonating
cord may be initiated by an electric or non-electric
blasting cap, or a delay detonator. The method of in-
itiating the detonating cord may be an electric or non-
electric blasting cap or a delay detonator. A firing
and nonelectric blasting caps. A strike or a nearby miss
device or time fuze may be used to initiate a non-electric
is almost certain to initiate either type of cap and other
cap. A standard blasting machine will be used to initiate
sensitive explosive elements such as caps in delay
electric caps.
detonators. Lightning strikes, even at remote locations,
c. Connection of the initiating cap (or detonator)
may cause extremely high local earth currents which
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