NGWA Air Rotary Practice Exam 2026 – The Complete All-in-One Guide to Exam Success!

In this drilling method, lubrication and cooling rely on circulating water. The water serves as the lubricant film and, as it flows through the system, it removes heat from the hammer mechanism and carries away cuttings. This keeps the hammer operating smoothly without introducing oily residues into the borehole, which is important for maintaining well cleanliness and protecting the surrounding formation.

Using oil mist or injection would introduce oil into the well and could contaminate the water, foul equipment, and complicate operations. A grease-based automatic lubrication system isn’t compatible with the circulating water path and would also create contamination and flow issues. A dry-running approach would lead to excessive heat and rapid wear since there’s no lubricant to reduce friction. Hence, water-only cooling is the appropriate choice for DHH drilling.