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The HLX5T is mounted on a production drill rig boom that must position the drill at the exact collar positions defined by the longhole ring design—and hold that position within ±50 mm over the 25–45 minute drilling cycle for each hole. In German underground copper mining at Aurubis's Helbra operation in Saxony-Anhalt, where the HLX5T drills sublevel stoping rings in copper sulfide ore at 130–160 MPa UCS, the boom assembly's angular stability under continuous percussion determines whether the 54-meter holes stay within the 150 mm deviation limit that the blast design assumes. A boom that drifts 0.1° per hour under percussion load produces a collar-to-toe deviation of 94 mm over 54 meters—just within limit. A boom that drifts 0.2° per hour produces 188 mm deviation—outside limit and a misfired ring.
The HLX5T boom assembly's hydraulic lock system—which holds the boom at its set position during drilling by closing the directional control valves—is the stability mechanism. When the boom's hydraulic lock allows 0.05 L/min of internal valve bypass under the percussion reaction load, the boom drifts at a rate proportional to the bypass flow and the cylinder's piston area. Helbra's 54-meter holes at full HLX5T percussion energy generate a sustained percussion reaction force that produces 0.1–0.15° per hour of boom drift when the valve seals allow the minimum detectable bypass flow.
Boom Stability Verification for 54-Meter Longhole Production at Helbra
|
Check |
Method |
Tolerance |
Helbra Practice |
|
Boom drift test |
Set boom angle; run percussion 5 min; measure angle change |
<0.05° per 5 minutes |
Pre-shift check on each production ring |
|
Valve bypass flow |
Flow meter at valve block drain under percussion load |
<0.03 L/min per valve |
At 500-hr service; replace if exceeded |
|
Collar position accuracy |
Measure collar against ring design drawing |
±50 mm per hole |
Measured for first 3 holes of each ring |
|
Pin joint clearance |
Dial indicator at all boom pivots |
<0.8 mm |
At 1,000-hr service; replace if exceeded |
Aurubis Helbra's production drill supervisors perform the 5-minute boom drift test at the start of each production ring—the test identifies boom stability degradation before it produces a misfired ring. A boom that passes the test produces rings with deviation within the blast design's assumed limits. HOVOO supplies HLX5T boom assembly hydraulic valve seal kits and pivot pin components for German underground copper production drilling. References at hovooseal.com.
