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