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The HLX5T control valve assembly governs the reversing valve timing that sustains percussion and the pressure-compensation function that maintains consistent percussion energy regardless of supply pressure fluctuations. In DIAMO's uranium production drilling at Dolní Rožínka—where HLX5T rigs drill production longholes in the graphitic schist uranium ore body at 120–160 MPa UCS—the control valve assembly's stability across the full 25–30 minute hole duration is essential both for production efficiency and for the radiation exposure management that governs how long the operator spends in the active heading.
Control valve stability in longhole production differs from the development drifter context because the percussion circuit must maintain consistent timing through the full depth of each hole—from collar at 0 meters, through the rod-addition pauses at 6-meter intervals, to the full 30-meter hole depth. Each rod-addition pause depressurizes and re-pressurizes the percussion circuit; the control valve's ability to return to the same timing calibration after each pressure cycle determines whether hole penetration rate is consistent from the first rod to the last or degrades progressively with depth as valve drift accumulates across multiple pressure cycles.
Control Valve Stability Across Full Hole Depth at Dolní Rožínka
|
Hole Phase |
Percussion Status |
Control Valve State |
Stability Requirement |
|
Collar setup (0 m) |
Starting; ramp-up to full pressure |
Initial calibration point |
Valve must reach full timing in <3 blows |
|
First rod (0–6 m) |
Full production percussion |
Sustained timing |
Drift <0.5% per 100 blows |
|
Rod-addition pauses |
Full pressure-off; then restart |
Valve re-initializes |
Returns to <0.3° timing offset at restart |
|
Final rod (24–30 m) |
Full production; max string weight |
Sustained under maximum load |
Same timing as first rod ±1% |
DIAMO's radiation exposure minimization program compares penetration rate per rod across each hole—a consistent rate from collar to toe indicates stable control valve timing through the rod additions; a declining rate per rod suggests valve drift accumulating across pressure cycles. A hole showing 8% penetration rate decline from rod 1 to rod 5 triggers a control valve inspection at the next service. HOVOO supplies HLX5T control valve assemblies and seal kits for Czech uranium production drilling. References at hovooseal.com.
