In South African quarries, especially in granite and dolerite formations, DTH drilling faces extreme wear conditions. Many operators accept short bit life as “normal”, but in practice, service life can be extended by up to 2× with the right technical adjustments.
Case Background
Location: South Africa hard-rock quarry
Rock type: Granite (UCS > 200 MPa)
Drilling method: DTH drilling, 115–127 mm
Original bit life: 500–700meters
Key Improvements That Doubled Bit Life
- Correct Button Grade Selection (Critical)
Instead of standard cobalt grades, the quarry switched to:
Higher cobalt content
Improved toughness (not just hardness)
Result:
✔ Reduced button cracking
✔ Significantly lower button breakage in abrasive zones
- Optimized Air Pressure & Volume
Previously, air pressure was pushed too high to chase penetration rate.
Adjustment made:
Slightly reduced pressure
Increased airflow stability
Result:
✔ Less thermal fatigue on buttons
✔ Lower impact stress on carbide tips
- Controlled Rotation Speed (RPM)
Excessive RPM caused:
Button flatting
Micro-cracks on gauge buttons
By reducing RPM and maintaining proper impact energy:
✔ More uniform wear
✔ Gauge buttons stayed intact longer
- Improved Flushing & Hole Cleaning
Enhanced air flushing reduced cuttings recirculation.
Result:
✔ Less secondary abrasion
✔ Lower temperature at the bit face
Final Result
Bit life increased to 1000-1400 meters
Cost per drilled meter reduced by over 35%
Fewer bit changes → higher rig utilization
Key Takeaway
In hard rock drilling, bit life is not decided by price, but by system matching:
Carbide grade + air system + operating parameters.
South African quarries prove that with the right setup, doubling DTH bit life is absolutely achievable.
