TM 9-1375-213-12
b. Precautions.
2-4. Electric Firing System
(1) Two or more caps. If two or more electric
WARNING
blasting caps are connected in same circuit, be sure that
they are of same type and made by same manufacturer
WHEN HANDLING ELECTRIC
BLASTING CAPS, DO NOT HOLD
(except for blasting cap M6. Refer to 1-11a(1) (a) and
THE EXPLOSIVE END OF THE
(b)).
CAP. HOLD THE END OF THE
CAP WHICH IS CONNECTED TO
(2) Firing the circuit. For safety reasons, only one
THE LEAD WIRES.
individual must be detailed to connect blasting machine
to firing circuit and to fire the circuit. He must be respon-
one in which electricity is used to fire the primary initiat-
sible for care and security of the blasting machine at all
ing element. An electric impulse supplied from an elec-
times during blasting activities. He also should either
tric blasting machine travels through the firing wire and
connect the blasting wires in the circuit or check their
cap lead wires to fire an electric blasting cap. The chief
connection by on-the-spot visual examination.
components of the system are the electric blasting cap,
firing wire, and the blasting machine. The preparation of
c. Placing Charges. Prepare and place all explosive
the explosive charge for detonation by electric means is
charges as prescribed by methods in FM 5-250.
called electric priming. The proper methods and se-
quence of operation of electric priming are described be-
d. Laying Firing Wire.
low in detail and summarized in table 2-1.
(1) After locating a firing position a safe distance
away from charges, (ref para 5-2 FM 5-250), lay out fir-
WARNING
ing wire from charges to firing position.
BLASTING MACHINE WILL
NOT BE CONNECTED TO FIR-
(2) Test firing wire as described in paragraph 2-
ING WIRES UNTIL COMPLE-
TION OF PREFIRING TESTS
(3) Twist free ends of firing wire together at firing
AND UNTIL READY FOR FIR-
position to prevent a static electric charge from building
ING.
up in firing wire.
Table 2-1. Outline (Checklist) of Basic Electric Blasting (Setup and Firing)
1. Check circuit test instrument.
2. Install charges--do not install electric blasting caps--any nonelectric priming may be done.
3. Check firing wire continuity.
4. Short firing site end of firing wire leads.
5. Lay firing wire.
6. Check firing wire continuity again.
7. Electrically check each blasting cap.
8. Connect blasting caps in desired arrangement but NOT to firing wire. Do not install caps in charges yet.
9. Keeping away from caps, check for RF induced currents by connecting cap circuit to firing wire.
10. Install caps in charges and assure blast area is clear of personnel.
11. Retire to firing site.
12. Unshort firing wire leads and electrically check completed blasting circuit.
13. Exercise blasting machine.
14. When ready to fire, attach firing wire leads to blasting machine.
15. Actuate blasting machine.
Change 19
2-6.1
