1. Broken drive sub
Probable causes:
- Gap between drive sub shoulder and out tube
- The joint is loose
- Insufficient feed pressure
- Threads lacking lubrication
Suggested actions:
- Implement appropriate tightening torque
- Enhance feed force in soft and unconsolidated rock conditions
- Ensure sufficient feed pressure
- Replace drive sub
- Use appropriate type and amount of grease to the drive sub threads
2. Cracked drive sub
Probable causes:
- Mishandling with sledge hammer
Suggested actions:
- Utilize tongs or chains to detach the drive sub from out tube

3. Broken piston
Probable causes:
- Galling
- Corrosion at piston undercut
Suggested actions:
- Clean the hammer with foam after drilling
- Check lubrication regularly; use the correct type and quantity of hammer oil
4. Piston cracked
Probable causes:
- Incorrect wrenching location
- Inadequate lubrication
- Stuck in the hole
- Hole deviation
Suggested actions:
- Inspect the lubrication system and ensure oil film is formed in bit flushing holes
- Use wrenching areas to prevent distortion on out tube
- Use water when stuck because friction can cause distort

5. Cracked out tube
Probable causes:
- Gripping on wrong location with jaw wrench
- Worn out tube
- Corrosion
Suggested actions:
- Apply correct tong placements
- Replace out tube upon reaching the discard limit on the outside diameter
- Apply a corrosion protector for storage
6. Broken Top Sub
Probable causes:
- Improper torque between joints
Suggested actions:
- Use minimum recommended torque
