short in it. Further checking is required to
(g) If blasting caps still fail to function, short
the firing wire conductors and check circuit and all com-
differentiate between a proper circuit or one
with a short in it.
(2) Refer to nonelectric misfire procedures (para
(3) When using galvanometers, touch free ends of
2-3) for handling underground charges.
firing wire to galvanometer posts. This should cause a
wide deflection of needle. Magnitude of deflection
Detonation by induced Currents
depends upon number of caps and length of firing wire.
The circuit is defective if galvanometers indicates con-
siderably more or less resistance than it should for the
circuit, or if galvanometers does not respond to the
If electric blasting caps are to be transported
near mobile transmitter (e. g., in helicopter)
e. Checking Defective Circuits. If firing circuit is
defective, proceed as follows:
in a metal container. Cover of container
(1) Shunt firing wires.
must be snug fitting and overlap container
(2) GO clown range and recheck circuit, repeating
body by a minimum of M-inch. Caps will
a and b above.
not be removed from container while close
(3) If a splice is found defective, resplice wires.
to an operating transmitter until the hazard
(4) If a cap is found defective, replace it.
has been fully evaluated and determined to
(5) Test all caps and wires in circuit.
(6) Test entire circuit again to make sure that all
Premature detonation of electric blasting caps by induc-
problems have been located before attempting to fire
ed current from radio frequency (RF) signals is possible.
Table 2-2 showing the minimum safe distance
to transmitter power, indicates distance beyond which it
is safe to conduct electrical blasting even under the most
adverse conditions. If blasting distances are less than
To minimize the occurrence of misfires,
make one individual responsible for all elec-
formation required to use them, the only safe procedure
trical wiring in a demolition circuit.
is to use a nonelectric system. If, however, use of an
a. Cause of Electric Misfires. Common specific
electric blasting cap is necessary to retain precise com-
causes of electric misfires include:
mand firing, use detonating cord priming of charge.
(1) Inoperative or weak blasting machine.
Run detonating cord from charge to firing point and at-
(2) Improperly operated blasting machine.
tach a shunted electric cap to the detonating cord when
(3) Defective and damaged connections, causing
ready to fire. Run cap lead wires to a protected position,
either a short circuit, a break in the circuit, or high
remove shunt, and fire charge electrically.
(4) Faulty blasting cap.
(5) The use in the same circuit of blasting caps
made by different manufacturers (other than M6).
(6) The use of more blasting caps than blasting
machine rating permits.
b. Procedures@ Electric Misfires.
(1) If blasting caps fail to fire:
(a) Check connections to machine.
(b) Try functioning machine again with max-
(c) Change operators.
(d) For dual firing systems, use secondary
(e) After three unsuccessful tries, check circuit
using galvanometers or test set M51.
(f) Try second machine (if available).
Wait hour before approaching any
misfire unless it can be positively ascertained
that failure is strictly electrical. If misfire is
strictly electrical in nature, corrective action
may be taken immediately.