TL;DR
Low drill air pressure is usually a dirty air filter, worn compressor valves, or a leaking rotary head seal. Check the filter first because it is the fastest and easiest fix.
What you might see
- drill bit penetration rate dropping
- air pressure gauge below setpoint
- compressor unloader cycling rapidly
- hole flushing insufficient, cuttings not clearing
Likely causes
Air filter element plugged with dust reducing compressor inlet flow
Compressor inlet valve worn or damaged reducing volumetric efficiency
Rotary head shaft seal worn allowing compressed air to bleed back
Air line leak at a coupling or fitting in the drill string air path
Required tools
- Calibrated air pressure gauge
- Replacement air filter element
- Soapy water or leak detector spray
- LOTO kit
Safety first
- High-pressure compressed air on drill rigs can cause serious injury. Bleed the system before working on any component.
- Lockout the engine start before removing the air filter housing or any air-side component.
- Dust explosion risk in certain mineral formations. No ignition sources near the drill air exhaust.
Procedure
- 1
Stop drilling and shut down the compressor. Lock out the engine start.
Warning: Compressed air lines on drill rigs retain pressure after shutdown. Bleed the air system before opening any fitting. - 2
Bleed the compressed air circuit at the drain valve before working on any component.
- 3
Remove and inspect the air filter element. Replace if discolored or visibly plugged.[1]
- 4
Restart the compressor and read the steady-state delivery pressure at the drill string inlet. Compare to the specification for the formation being drilled.[1]
- 5
If pressure is still low after filter replacement, check for audible air leaks along the drill pipe, rotary head, and couplings.
- 6
Test the compressor unloader valve. Rapid cycling indicates the delivery pressure is not holding, confirming an upstream leak or valve fault.
- 7
If compressor valve wear is suspected, measure the flow and pressure under load. Values outside specification confirm valve overhaul is needed.
Sources
Sandvik Sandvik DR / DI / DT Drill Rig (Surface / Underground) general technical documentation, Sandvik
Sandvik drill rig operation and service documentation, compressor and air system maintenance procedures (general)
More guides for Sandvik Sandvik DR / DI / DT
How to diagnose rotary head hydraulic faults on a Sandvik DR / DI / DT drill rig
Low rotary head speed means the rotation hydraulic motor or its control valve is restricting flow. Measure rotation circuit pressure and compare to the relief valve setting.
How to inspect track drive and undercarriage faults on a Sandvik DR / DI / DT drill rig
A rig that pulls to one side has a track tension or drive motor imbalance. Check and equalize track tension before looking at the hydraulic drive motors.
Stop fixing the same fault twice.
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