Air Compressors in Underground Mining Operations
What compressed air does underground
Compressed air is the workhorse utility in underground mining. It powers the tools that break rock, clears water, and supports ventilation. The main consumers are:
- Rock drills and jumbos: pneumatic drifters and jumbos are the largest air users, often running at 6–8 bar (90–120 psi) at the tool.
- Loaders and utility vehicles: pneumatic starters, brakes, and controls on LHDs and service equipment.
- Ventilation and pumping aids: air-driven fans, venturi blowers, and diaphragm pumps for sumps and dewatering.
- Service air: greasing, cleaning, and small tools at workshops and refuges.
Pressure and volume at the face
Air tools are rated at a working pressure, typically 6–8 bar. If the system cannot hold that pressure at the face, performance drops: drilling slows, bits wear faster, and fuel or power per metre rises. The number that matters is measured pressure at the face, not at the compressor outlet. A compressor rated at 7 bar may deliver only 5 bar at the last drill if the network is undersized or leaking. Size the compressor for the total simultaneous demand plus a margin, then verify with a gauge at the face.
Pressure drop, leakage, and pipework
Long pipe runs, bends, and undersized hoses cause pressure drop. In a mine, leakage is often the largest single waste—commonly 20–40% of generated air in older networks. Leaks at joints, hoses, and tools are silent and continuous. A disciplined leak survey and repair programme usually pays back faster than adding compressor capacity. Use adequately sized mains, minimise bends, and keep hoses as short as practical.
Moisture, contamination, and safety
Compressed air carries water vapour and oil carry-over. Condensate corrodes tools, washes lubricant from drills, and can freeze in cold sections. Oil carry-over is a safety issue in confined spaces and can affect downstream equipment. Fit aftercoolers, moisture separators, and filters appropriate to the duty. Drain traps must be maintained—water in the line is a common cause of tool failure and downtime.
Electric vs diesel drive
Where mine power is available, electric drive is preferred. It removes engine exhaust and heat from a ventilation-limited environment, reduces ventilation load, and lowers maintenance. Diesel units remain necessary for development headings without power, portable or emergency duty, and remote sites. The trade-off is ventilation cost and exhaust management versus the flexibility of a self-contained unit.
Filtration, cooling, and maintenance
Dust-laden air clogs intake filters and coolers, raising temperatures and reducing output. Specify filtration and cooling matched to the site, and schedule cleaning or replacement by condition, not just hours. In a confined, high-demand environment, maintenance access is limited: choose units with service points that can be reached safely, and keep critical spares on site. Measured pressure at the face, leak rate, and filter condition are the three numbers to track.
For a matched compressor and piping recommendation for your underground operation, contact Kaishan engineers with your face pressure, total air demand, and power availability.
Frequently Asked Questions
What size air compressor do I need for underground mining?
Size for total simultaneous demand at the face, not the sum of all tools. Add the air consumption of drills, loaders, and service air running together, then add a margin for leakage and future use. Because leakage often wastes 20–40% of generated air, measure actual flow and pressure at the face before adding capacity. A compressor rated at 7 bar may only deliver 5 bar at the last drill if the network is undersized.
Why is pressure at the face more important than at the compressor?
Air tools are specified at a working pressure, typically 6–8 bar. Pressure drop through long mains, bends, and hoses means the compressor outlet reading can be much higher than what the tool receives. If the face pressure is low, drilling slows, bits wear faster, and energy per metre rises. Always verify with a gauge at the face, not at the compressor.
Can I use a diesel compressor underground?
Yes, where mine power is not available or for portable and emergency duty. However, diesel exhaust and heat add to the ventilation load in a confined environment. Electric drive is preferred wherever power is available because it removes exhaust and heat, reduces ventilation cost, and lowers maintenance. The trade-off is flexibility versus ventilation and exhaust management.
How do I control moisture and oil in underground compressed air?
Fit aftercoolers, moisture separators, and filters matched to the duty, and maintain drain traps. Water and oil carry-over corrode tools, wash lubricant from drills, and can freeze in cold sections. Oil carry-over is also a safety issue in confined spaces. Regular draining and filter replacement by condition, not just hours, keeps air quality within tool specifications.