Newer 10-cap and 50-cap machines have significantly higher electrical output than their predecessors. These
machines also include a built-in safety circuit. This circuit allows no current to reach the terminals until the
machine's handle or plunger has been actuated with sufficient energy to produce nearly the maximum output from
the machine.
Older 10-, 30-, 50-, and 100-cap machines include a switch that delays the flow of current from the generator to
the output terminals until the handle or plunger is near the end of its travel. This switch ensures that the output
produced by the machine's mechanism does not reach the terminals until the operator is using maximum force.
The M32 is a small, light-weight blasting machine intended to replace the larger, heavier machines. Instead of a
shunt-wound generator, this machine uses a small alternator that is gear-driven by the handle-actuated plunger.
The electrical output from the alternator is rectified and fed into storage capacitors. When sufficient energy is
available in the capacitors, (which may require 3 or 4 strokes of the handle) an internal switching circuit
discharges the electrical energy to the output terminals and, through them, to the blasting circuit. This machine is
capable of initiating ten M6 electric blasting caps.
The M34 blasting machine is similar to the M32, but is capable of initiating fifty M6 electric blasting caps.
Ensure that the blasting machine you are using is capable of carrying the load. For example, do not try to use a
10-cap machine to set off 50 caps.
Firing Cable. The firing cable consists of a DR-8 firing wire reel, an RL-39 reeling machine, and 500 feet of
AWG Number 18 firing wire or WD-1/TT telephone wire. The firing cable is used to transfer electrical current
from the blasting machine to the electric blasting cap. Based on the size of the storage facility and associated
fragment hazards, it may be necessary to splice firing cables together to reach a safe distance.
Strip the insulating material from the ends of insulated wires before splicing. Expose approximately three inches
of bare wire, and remove any foreign matter (such as enamel) by carefully scraping the wire with the back of a
knife blade or another suitable tool. Do not nick, cut, or weaken the bare wires. Twist multiple-strand wires
lightly after scraping them.
Two wires may be spliced as shown in Figure 1-22. This is called the Western Union pigtail splice. Protect the
splices from pull damage by tying the ends in an overhand or square knot, allowing sufficient length for each
splice. Point the free ends in opposite directions as shown in detail A, join them with a few tight twists, and bend
the remaining ends up and away from the joint as shown in detail B. Twist these ends to form a pigtail at a right
angle to the connected wires as shown in detail C. Push the pigtail to one side to lie along one of the wires as
shown in detail D. Tape the connection to ensure that it is completely insulated.
Another method of splicing two wires is to place the two wires to be connected side by side, with their free ends
pointing in same direction, wind them together by twisting, then tape them to ensure that they are completely
insulated.
If certain precautions are not observed, a short circuit may easily occur at a splice. If pairs of wires are to be
spliced, stagger the two separate splices, and tie them with twine or tape. An alternate method of preventing a
short circuit at the point of a splice is shown in Figure 1-23. In. this alternate method, the splices are separated,
not staggered. Insulate the splices from the ground and from other conductors by wrapping them with friction
tape or with other electric insulating tape. Circuit splices that are not taped or insulated must not lie on moist
ground. Support the splices on rocks, blocks, or sticks, so that only the insulated portions of the wires touch the
ground. Protect the splices by inserting them in the cardboard cap spools. Bend the spools to hold the splices
firmly inside.
1-31
MM0170
Previous Page
