Which factors are used to size air rotary rigs?

• A. Air compressor capacity (CFM/PSI) only
• B. Air compressor capacity (CFM/PSI), drilling depth capacity, and mast height
• C. Drilling depth capacity only
• D. Mast height only

Answer: (B)

Sizing air rotary rigs requires matching the air supply and the rig’s physical capabilities to the job at hand. The air compressor capacity, shown by CFM and PSI, sets how much air and at what pressure is available to power the drill bit and to efficiently clear cuttings. If the air supply is too small for the demanded operation, you’ll lose drilling speed and performance.

Drilling depth capacity is essential because deeper holes demand more controlled power delivery, longer tool strings, and greater endurance from the rig’s systems. Knowing the target depth helps ensure the rig can handle the required load, cycle times, and air demand throughout the drilling program.

Mast height matters because it affects the rig’s reach, clearance, and how easily the drill string can be raised and lowered over the borehole. Adequate mast height supports proper alignment, stability, and the ability to work efficiently at the planned depths and hole sizes.

Together, these factors—air supply, depth capability, and mast height—define the appropriate size and configuration of an air rotary rig. Focusing on just one aspect would risk undersizing or mismatching the rig to the job.