Unveiling the Working Principle of the Down-the-Hole (DTH) Hammer
The DTH hammer acts like an "electric toothbrush" for geological strata, utilizing high-pressure air to drive the hammer body in high-frequency impacts against the drill bit:
Power Transmission: Compressed air drives a piston in a reciprocating motion, generating impact forces exceeding 2,000 strikes per minute.
Rock Crushing and Debris Removal: The drill bit rotates to cut through rock layers, while the airflow simultaneously expels rock fragments through the annular space between the drill rod and the borehole wall.
Depth Advantage: Compared to standard drilling rigs of equivalent power output, the DTH hammer allows for an increase in drilling depth of over 30%.
The Five-Step Standardized Operation Protocol
Adhering to standardized procedures is the key to ensuring construction efficiency:
Site Survey: Verify the layout of underground pipelines and mark areas where rock hardness varies.
Equipment Assembly: Connect components in the sequence of Drill Rod → DTH Hammer → Drill Bit, ensuring that all connections are properly sealed.
Parameter Configuration: Adjust air pressure (typically 0.7–2.5 MPa) and rotation speed (20–60 rpm) according to the specific rock formation.
Staged Drilling: Pause drilling every 3 meters to inspect the drill tools for wear and tear.
Borehole Completion: Thoroughly purge the borehole using a high-pressure airflow before retracting the drill rod.
Solutions for Common Issues
Do not panic if you encounter these situations:
Sudden Drop in Drilling Speed: This may indicate the presence of an interlayer or excessive drill bit wear; retract the drill string to inspect.
Poor Debris Removal: Increase the air pressure by 10% or inject an appropriate amount of foaming agent to improve debris evacuation.
Excessive Borehole Deviation: Employ a centralizer in conjunction with low-speed drilling to correct the borehole trajectory.
Prevention of Drill String Sticking: Inspect the straightness of the drill rods at the start of every shift; immediately replace any rod exhibiting a bend exceeding 2 mm.