Do You Know What Is Conventional DTH Hammers?

A down-the-hole hammer (DTH hammer) is a pneumatic rock drilling tool that differs from other tools in that it remains at the bottom of the hole during drilling, directly impacting the rock through its own drill bit. High-pressure air enters the DTH hammer through the drill pipe and is then expelled from the drill bit; this expelled air is used to blow rock cuttings out of the hole. The rotational power acting on the DTH hammer comes from the rotary motor on the drilling rig, and the thrust comes from the feed mechanism, with the energy being transmitted to the DTH hammer through the drill pipe.

The components of a DTH hammer include: a piston, inner cylinder, air distribution valve, check valve, and drill bit attachment, all mounted inside the outer cylinder. The top of the outer cylinder has an upper connector connected by connecting threads and a wrench, and the other end of the outer cylinder is threaded to a drive chuck. The drive chuck contains splines, mainly used to transmit feed force and rotational force to the drill bit. A retaining ring controls the axial movement of the drill bit, and a check valve prevents rock cuttings and other foreign matter from entering the DTH hammer when the air supply is stopped. During drilling, the drill bit is pushed into the DTH hammer and pressed against the drive chuck, at which point the piston directly impacts the drill bit to break the rock. When the drill bit is lifted from the hole, the DTH hammer begins to clean the bottom of the hole by blowing air.

1. The drill bit is pressed against the rock.
2. High-pressure air rushes in from the drill pipe through the check valve, entering the front chamber of the DTH hammer.
3. The volume of the front chamber increases, pushing the piston upwards.
4. When the piston moves upwards to a certain extent, the front chamber is vented, and compressed air enters the rear chamber. The piston continues to move upwards due to inertia.
5. When the piston moves to a certain extent, due to the pressure in the rear chamber, the air pressure increases, and the piston begins to impact downwards, forming an impact stroke. The above process is repeated for upward movement, achieving impact and completing the rock drilling operation.

• Classified by the method of rock cutting removal: conventional DTH hammers and reverse circulation DTH hammers (RC hammers).
• Classified by the air distribution method and structural characteristics: valved DTH hammers and valveless DTH hammers.
• Classification of down-the-hole hammers:
  • By rated working pressure: Low-pressure down-the-hole hammers (rated working pressure ≤ 0.7 MPa), medium-low pressure down-the-hole hammers (0.7 MPa - 2.5 MPa), and ultra-high pressure down-the-hole hammers (rated working pressure > 2.5 MPa).
  • By whether the matching drill bit has a bottom valve: Down-the-hole hammers suitable for drill bits with a bottom valve and down-the-hole hammers suitable for drill bits without a bottom valve.
  • By the outer diameter of the down-the-hole hammer: 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, 5.5 inches, 6 inches, 7 inches, 8 inches, 9 inches, 10 inches, 12 inches, 15 inches, 24 inches, etc.

Down-the-hole hammers are widely used in geological exploration, civil engineering, water well drilling, and building foundation engineering.