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
