The piston is not only the working element that generates mechanical impact
energy, but also the control element of reciprocating motion, and the only moving
part. Therefore, the failure rate of DTH hammer is low and its life is long. The
piston completes an impact, and the front and rear chambers each experience an
expansion stroke. Because the stroke does not need air supply, the air consumption
is greatly reduced.
Valveless pneumatic DTH hammer has the following characteristics:
(1) Simple air distribution system, direct pressure blowing, short air path, low gas
pressure loss, and the elimination of complex air distribution machine.
(2) By using compressed gas expansion to work, the gas consumption of DTH
hammer is greatly reduced.
(3) The service life of DTH hammer parts is approximately the same, and the
maintenance work of DTH hammer has been improved.
(4) Valveless DTH hammer requires high processing accuracy, and it is difficult to
design its structure and size.
11.2.4 Large Diameter Pneumatic DTH Hammer
Large diameter pneumatic DTH hammer is important equipment for rock drilling.
During the construction of large-scale projects, such as high-rise buildings,
important factory buildings, ports, wharfs, highways, railways, bridges, water
conservancy, and Hydropower junctions, drilling construction of large-diameter
hard rock and gravel is involved. In recent years, large diameter ( ! 400 mm)
pneumatic DTH hammers have been developed in the United States, Japan, South
Korea, and other countries for the construction of rock entry pile foundations and
anti-slide piles. At present, domestic large diameter drilling equipment over
400 mm mainly depends on imports. Drilling diameter of DTH hammer in China is
less than 400 mm, which is called medium and small diameter DTH hammer.
Figure 11.5 shows the picture of 800 mm large diameter pneumatic DTH hammer
and matching drill bit imported by Shanghai Zhenzhong Machinery Manufacturing
Co., Ltd. in 2011 by Japan Construction and Adjustment Corporation.
American Ingersoll-Rand Company first produced pneumatic DTH hammers
with single-head and Cluster Drills series, a total of 40 models, which are used for
drilling and grouting construction of large-caliber projects. Single-head DTH
hammer is suitable for 90 $ 762 mm aperture range; cluster DTH hammer is
composed of 16 single hammers at most, and suitable for 610 $ 1980 mm aperture
range. At present, Ingersoll-Rand large diameter pneumatic DTH hammer has been
widely used in the construction of foundation pile holes, diaphragm wall and hard
rock drilling in deep water wells, and has achieved high drilling efficiency. For
large diameter pile holes and engineering holes, cluster DTH hammer is used to
form holes at one time. In order to adapt to the construction of “multi-aperture”
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11 Pneumatic Down-the-Hole Hammer
energy, but also the control element of reciprocating motion, and the only moving
part. Therefore, the failure rate of DTH hammer is low and its life is long. The
piston completes an impact, and the front and rear chambers each experience an
expansion stroke. Because the stroke does not need air supply, the air consumption
is greatly reduced.
Valveless pneumatic DTH hammer has the following characteristics:
(1) Simple air distribution system, direct pressure blowing, short air path, low gas
pressure loss, and the elimination of complex air distribution machine.
(2) By using compressed gas expansion to work, the gas consumption of DTH
hammer is greatly reduced.
(3) The service life of DTH hammer parts is approximately the same, and the
maintenance work of DTH hammer has been improved.
(4) Valveless DTH hammer requires high processing accuracy, and it is difficult to
design its structure and size.
11.2.4 Large Diameter Pneumatic DTH Hammer
Large diameter pneumatic DTH hammer is important equipment for rock drilling.
During the construction of large-scale projects, such as high-rise buildings,
important factory buildings, ports, wharfs, highways, railways, bridges, water
conservancy, and Hydropower junctions, drilling construction of large-diameter
hard rock and gravel is involved. In recent years, large diameter ( ! 400 mm)
pneumatic DTH hammers have been developed in the United States, Japan, South
Korea, and other countries for the construction of rock entry pile foundations and
anti-slide piles. At present, domestic large diameter drilling equipment over
400 mm mainly depends on imports. Drilling diameter of DTH hammer in China is
less than 400 mm, which is called medium and small diameter DTH hammer.
Figure 11.5 shows the picture of 800 mm large diameter pneumatic DTH hammer
and matching drill bit imported by Shanghai Zhenzhong Machinery Manufacturing
Co., Ltd. in 2011 by Japan Construction and Adjustment Corporation.
American Ingersoll-Rand Company first produced pneumatic DTH hammers
with single-head and Cluster Drills series, a total of 40 models, which are used for
drilling and grouting construction of large-caliber projects. Single-head DTH
hammer is suitable for 90 $ 762 mm aperture range; cluster DTH hammer is
composed of 16 single hammers at most, and suitable for 610 $ 1980 mm aperture
range. At present, Ingersoll-Rand large diameter pneumatic DTH hammer has been
widely used in the construction of foundation pile holes, diaphragm wall and hard
rock drilling in deep water wells, and has achieved high drilling efficiency. For
large diameter pile holes and engineering holes, cluster DTH hammer is used to
form holes at one time. In order to adapt to the construction of “multi-aperture”
202
11 Pneumatic Down-the-Hole Hammer