R. Meyer J. Köhler A. Homburg Explosives

Blasting Machines
Blasting Machines
Zündmaschinen; exploseurs
Blasting machines are used for electric firing of explosive charges by
sending an electric pulse (indicated in mW·s/ohm) through the firing
circuit to the round of electric detonators connected in series. Except
during the moment of actuation of the blasting machine, the entire
electrical system is tensionless (unlike: W Blasting Switch).
In mines endangered by a potential firedamp explosion, the duration of
the electric pulse must be limited to 4 ms with the aid of a triggering
switch in the blasting machine, so that flying fragments cannot strike
the firing circuit while the latter is still live, and then generate a shortcircuit
spark. Also, the housing must withstand an internal pressure of
1 MPa (10 atm), so that it cannot be destroyed by a burst due to
intruded methane. These special conditions are only requested in
blasting areas endangered by firedamp.
Two types of blasting machines are used:
1) blasting machines with direct energy supply, equipped with a selfinduction
or a permanent magnet generator, which are made to rotate
with the aid of a twist knob, impact knob or a spring extension, and
2) blasting machines with an indirect energy supply, in which the
generated electrical energy is stored in a capacitor and, after the
discharge voltage has been attained, the breakthrough pulse is sent to
a blasting train (“CD Type”). A misfire due to incorrect handling is
impossible.
Capacitor machines have now superseded direct-generation machines.
In order to set off W Bridgewire Detonators, which are connected
in parallel, the output of the machines must be particularly
high, since more than 95% of the electric energy becomes lost in the
blasting circuit. Special powerful machines are required to set off
“HU”-(highly unsensitive) detonators for blastings carried out in high
mountain areas and in other locations endangered by high-voltage
induction; a very strong (3000 mW · s/ohm) priming pulse must be
applied in such cases.
W Bridgewire Detonators.
Blasting Mat
Sprengmatte; réseau de fils d’acier
A mat of woven steel wire, rope, scrap tires, or other suitable material
or construction to cover blast holes for the purpose of preventing rock
missiles against flying debris.
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