Recently, at an iron ore project in Ghana, the client encountered a situation engineers love to joke about:
👉 The drill bit’s flushing grooves were blocked, stopping penetration
The rig kept spinning, but the bit wouldn’t advance. One operator jokingly said: “Is there a little monster living in the hole?”
Site Conditions
- Rig: 6″ high-pressure DTH hammer
- Bit: Spherical buttons + medium-hard carbide
- Formation: Hard iron ore + highly abrasive fragments
- Issue observed:
- Bit rotated but debris accumulated in the hole
- Rig load spiked
- Frequent downtime for cleaning
Cause Analysis
1️⃣ Flushing groove too narrow → debris couldn’t escape → blockage
2️⃣ Impact rhythm mismatched → debris compressed → stuck
3️⃣ Insufficient air pressure → debris not blown out → blockage worsened
Solution
- Enlarge flushing grooves → give debris room to escape
- Adjust impact rhythm → let the bit advance steadily
- Increase air pressure → blow debris out
- Optimize button layout & type → spherical buttons + slightly convex face, debris evacuates naturally
Result
- Penetration speed returned to normal
- Stuck holes almost disappeared
- Bit life increased by ~30%
- Operators joked: “The little monster is gone!”
Takeaway
In hard rock formations, bit flushing groove blockage is often due to:
- Too narrow grooves
- Impact too aggressive
- Insufficient air
Make the bit “comfortable,” and it will work efficiently, letting you drill smoothly.
