Making sure your drill rods are in good condition is a good way to keep drilling operations productive. Drillers need to get in the habit of checking drill rods before using them. There are 5 common problems that can affect drill rods so let’s look at what causes these problems and how to fix them.

High torque or loading without proper lubrication can cause galling of the drilling rod threads. This can also occur when there is dirt and dust on the threads, when the wrong kind of thread lubricant is used or not enough of it is used. Care needs to be taken when you are making a joint to make sure there is no overheating or misalignment of the threads.

What you should do

• Clean the threads properly before making the joint
• Always use thread compound with 50% zinc content or some other metal component in the compound
• Use equipment that is compatible with your rods – do not mix rods or other equipment that come from different manufacturers (water swivels, hoisting plugs, etc)
• Make sure your rods are properly aligned when making a joint
• Use your hands when you start joining the threads
• Use a slow rotation speed when making the joint

2) Threads that are cracked

Over torqueing and excessive vibration can both cause drill rods to crack. You can read more about reducing vibrations here. Rods can crack when they are too thin (worn out). Weak points in the material can occur when you are joining threads that are galled, improperly cleaned or when there is prior damage that leads to fatigue failure.

What you should do

• Inspect all drill rods and throw out ones that are worn or damaged
• Make sure that the drill rods are properly aligned when making a joint and that they come from the same manufacturer
• Make sure the drill rig is properly aligned with the collar and that the drill rig set-up does not move.
• Avoid putting lateral force on the rod joints
• Use soft-tipped (brass) hammers to hit the rods if needed
• Reduce vibration by lubricating the rods and by using drilling fluid additives

3) Threads belling

Conditions to that cause thread galling can also cause belling of the threads, and these include over torqueing, over-tightening and excessive vibration in a dry hole. Belling will occur if the drill rods are too thin or worn out, and if there is too much weight placed on the rod and core bit. Using bent rods will cause premature wear at the box ends.

What you should do

• Use hydraulic pressure reducer on the drill rig to fine tune rotation torque
• Avoid rotating the rods while in low gear
• Inspect all drill rods and throw out ones that are worn or damaged
• Make sure to choose the right core bit matrix for the ground conditions
• Lubricate the rod string properly to reduce or avoid vibration

4) Leaking drill rods

Drill rod threads that are worn, cracked or otherwise damaged prematurely will eventually leak. This will reduce the water flow to the core bit. Little or no lubrication of the drill rods can cause more vibration and increased torque which in turn increase wear and tear of the rods. Leaking joints are an indication of a bigger problem, meaning that the mechanical strength of the threaded joint has been substantially reduced. The continued use of leaking rods will lead to more severe down-hole problems, such as broken rods and lost tooling.

What you should do

• Adopt better maintenance and handling routines for drill rods
• Inspect all drill rods and throw out ones that are worn or damaged
• Avoid using cotton thread as “wicking” as this procedure does not eliminate leaking

5) Dents and other damage

Imprints and dents occur on the pin and box thread ends when two drill rods hit each other due to poor storage and handling. “Stabbing” is another common problem that occurs when two rods are being made up and the pin “stabs” the box thereby damaging both rods. These rods can then damage others if they are not removed from the system. The problem can compound quickly. Dents also occur when drill rods are misaligned on the hole collar.

What you should do

• Adopt better maintenance and handling routines for drill rods
• Inspect all drill rods and throw out ones that are worn or damaged
• Make sure the drill rig is properly aligned with the collar and that the drill rig set-up does not move.
  
  

CONCLUSION:

When worn drill rods are used, they can snap or break while in the hole leading to expensive downtime while you stop operations to retrieve your equipment. Rods that are in poor condition lead to decreased weight on the bit and a poorer rate of penetration, while cracked, leaking rods lead to poor water circulation and shorter bit life. Care and proper maintenance of your drill rods, and all drilling equipment, will improve your rate of penetration and extend bit life.