Air Rotary Drilling

The air-rotary technique is much more efficient than other rock drilling techniques (i.e., cable tool) because the high-flow air constantly cleans the bottom of the borehole, which allows for consistent contact between the drill bit and intact bedrock.

The size of the air compressor and borehole determine the achievable depth, since the compressor must maintain an up hole velocity of approximately 3,000 feet per minute to effectively remove the drill cuttings. In bedrock formations where cuttings removal is more difficult, foam can be added to the injected air to increase the viscosity and help lift cuttings from the borehole.