Figure 5-10. Splicing two pairs of wires

TM 9-1300-277

Figure 5-10. Splicing two pairs of wires.

Figure 5-11. Common series circuit.

WARNING

(4) Circuit splices, not taped or insulated,

INDUCED CURRENTS FROM RADIO

should not lie on moist ground. Splices should be

FREQUENCY (RF) SOURCES CAN

supported on rocks, blocks, or sticks so that only

INITIATE

BLASTING

CAPS

insulated portions of wires touch ground.

CONNECTED TO LONG LEAD OF

WIRE.

BEFORE CONNECTING

d. Common Series. This is used for connecting

ELECTRIC BLASTING CAPS TO THE

two or more charges fired electrically by a single

FIRING WIRES, THE BLASTING

blasting machine (fig. 5-11). A common series circuit is

CIRCUIT MUST BE TESTED FOR

prepared by connecting one blasting cap lead wire from

THE PRESENCE OF EXTRANEOUS

the first charge to one lead wire in the second charge

ELECTRICITY AND RF ENERGY.

and so on until only two end wires are free. Connecting

wires (usually annunciator wire) are used when the

FACE AWAY FROM CAPS WHEN

distance between blasting caps is greater than the

length of the usual cap lead wires.

CIRCUIT

COMPLETED

MINIMIZE FACE INJURIES FROM

5-10. PRIMING AND TESTING FIRING CIRCUIT

ACCIDENTAL INITIATION. IF AT ALL

POSSIBLE,

MAINTAIN

COVER

NOTE

BETWEEN BLASTING CAPS AND

At firing position, keep free ends of

TESTING PERSONNEL.

firing wire twisted together and

grounded until ready to connect to

b. Check for presence of RF energy and/ or

galvanometer or to blasting machine.

extraneous electricity as follows:

a. Splice one of the free cap lead wires to a firing

(1) Arrange a dummy test circuit, essentially

wire conductor.

the same as the actual blasting circuit except that a No.

47 radio pilot lamp of known good quality inserted in

place of the blasting cap shall be used without applying

electric current to the circuit. Any glow of the radio pilot

lamp, viewed in the darkness, is to be construed as

evidence of the presence of possible dangerous

amounts of RF energy, and/or extraneous electricity;

blasting operations in such areas must be performed

with nonelectric blasting caps and safety fuse.

Change 2

5-10