collapse event was from August 5, 2010 to October 14, 2010. During the 69 days, 33
miners were trapped in 700 m underground. Pneumatic DTH is used to hammer into
rock drilling, and finally the trapped miners are rescued from the underground
through the hole.
11.2 Principle and Classification of Pneumatic DTH
Hammer
11.2.1 Classification of Pneumatic DTH Hammer
Pneumatic DTH hammer is a pneumatic impact tool with foam agent as well as
flushing medium. The impact energy produced by it is transmitted directly to the
drill bit at a certain impact frequency, and then driven by the drill rig and the drill
pipe by rotation, resulting in the pulsating breakage of rock. At the same time, the
compressed air discharged by the impactor is used to cool the drill bit, and the
broken rock particles are discharged so as to realize the impact, rotation, and
drilling at the bottom of the hole.
(1) Pneumatic DTH hammer can be divided into valve-type and valveless type
according to the valve distribution mode and structure of impactor. As shown in
Fig. 11.3, the valve-type pneumatic DTH hammer makes the compressed air
enter the front and rear chambers alternately through various forms of control
valves, which promotes the reciprocating motion of the piston to produce
impact effect. The piston moves to the front and back dead points of the
cylinder block, which generates pressure signals to push the control switch and
cause the piston to change impact direction. The valve-type DTH hammer
cylinder has a simple valve distribution process, and the compressed air only
undergoes two-valve distribution processes: intake and exhaust. Figure 11.4
shows that the valveless pneumatic DTH hammer has no valve. The valve
Fig. 11.2 Application of
pneumatic DTH hammer in
copper mine disaster in Chile
198
11 Pneumatic Down-the-Hole Hammer
miners were trapped in 700 m underground. Pneumatic DTH is used to hammer into
rock drilling, and finally the trapped miners are rescued from the underground
through the hole.
11.2 Principle and Classification of Pneumatic DTH
Hammer
11.2.1 Classification of Pneumatic DTH Hammer
Pneumatic DTH hammer is a pneumatic impact tool with foam agent as well as
flushing medium. The impact energy produced by it is transmitted directly to the
drill bit at a certain impact frequency, and then driven by the drill rig and the drill
pipe by rotation, resulting in the pulsating breakage of rock. At the same time, the
compressed air discharged by the impactor is used to cool the drill bit, and the
broken rock particles are discharged so as to realize the impact, rotation, and
drilling at the bottom of the hole.
(1) Pneumatic DTH hammer can be divided into valve-type and valveless type
according to the valve distribution mode and structure of impactor. As shown in
Fig. 11.3, the valve-type pneumatic DTH hammer makes the compressed air
enter the front and rear chambers alternately through various forms of control
valves, which promotes the reciprocating motion of the piston to produce
impact effect. The piston moves to the front and back dead points of the
cylinder block, which generates pressure signals to push the control switch and
cause the piston to change impact direction. The valve-type DTH hammer
cylinder has a simple valve distribution process, and the compressed air only
undergoes two-valve distribution processes: intake and exhaust. Figure 11.4
shows that the valveless pneumatic DTH hammer has no valve. The valve
Fig. 11.2 Application of
pneumatic DTH hammer in
copper mine disaster in Chile
198
11 Pneumatic Down-the-Hole Hammer