PREVENTION OF ELECTRIC MISFIRES

TM 9-1300-277

or nonmetallic tool. Avoid accidental digging into the

WARNING

charge. When the earth has been removed within one

UPON REACHING THE MISFIRED

foot, place a new 1 to 1-1/2 kilograms (2 to 3 pounds)

CHARGE, IMMEDIATELY REMOVE

charge over the failed charge and prime as before.

THE

FAILED

DETONATOR/

INITIATOR.

5-27. PREVENTION OF ELECTRIC MISFIRES

All safety precautions will be followed. In

(2) Insert a new fused detonator/

addition, the probability of a misfire may be reduced if

initiator into the charge. Destroy the failed components

the following procedures are adhered to:

by placing them along side the newly primed charge. If

this is not practical, place a new charge next to the

a. Ensure use of proper blasting cap.

misfired charge and prime as required.

b. All blasting caps are included in firing circuit.

b. Detonating Cord Misfire.

c. All connections between blasting cap wires,

(1) Allow a minimum of 30 minutes

connecting wires, and firing wires are properly made.

after expected detonation before starting investigation,

except if initiating blasting cap is electric.

d. Short circuits and grounds are avoided.

WARNING

UPON REACHING THE MISFIRED

e. The number of blasting caps in any circuit does

CHARGE, IMMEDIATELY REMOVE

not exceed the rated capacity of blasting machine being

THE MALFUNCTIONED BLASTING

used.

CAP FROM THE DETONATING

CORD.

f. A dual electric firing system should be used or

all charges should be dual primed.

(2) Attach a new initiating blasting cap

to detonating cord, taking care to fasten properly. Place

5-28. HANDLING ELECTRIC MISFIRES

failed blasting cap on or near the newly primed charge

to ensure destruction.

Electric misfires will be handled as follows:

(3) If detonating cord still fails, remove

WARNING

earth cover and reprime explosive charge with new

WAIT AT LEAST 30 MINUTES AFTER

detonating cord. Failed detonating cord will be disposed

EXPECTED

DETONATION

of by placing in the pit. Replace earth cover.

IGNITION BEFORE APPROACHING

ANY MISFIRE.

IF IT CAN BE

POSITIVELY ASCERTAINED THAT

c. Explosive Charge Misfire. After determining in

accordance with paragraphs a and b above that blasting

THE

FAILURE

STRICTLY

cap and/or detonating cord are satisfactory, replace

ELECTRICAL IN NATURE, AND IT IS

failed explosive charge as follows:

POSITIVELY KNOWN THAT THE

EXPLOSIVES ARE NOT BURNING,

CORRECTIVE ACTION MAY BE

(1) Allow a minimum of 30 minutes after

TAKEN IMMEDIATELY.

expected detonation before starting investigation,

except if initiating blasting cap is electric and if it is

positively known that the charge is not burning.

a. Check firing wire connections to blasting

machine terminals to be sure that contacts are good.

(2) Replace charge as follows:

b. Make two or three more attempts to fire the

circuits.

(a) If failed charge has not been buried,

place a new charge (counter-charge) at the side of the

failed charge and prime as before.

c. Disconnect blasting machine and check firing

wire for continuity. If continuity exists, attempt to fire

again using another blasting machine. If con-

(b) If failed charge has been covered

with earth, carefully remove earth cover with a wooden

Change 2

5-23