High-Reliability Percussion Mechanism of Sandvik HLX5T Rock Drill in Poland

KGHM's underground copper operations in Poland use HLX5T longhole rigs for sublevel stoping production in the Legnica-Głogów copper belt's Kupferschiefer ore zone. Unlike the hard crystalline formations where many HLX5T fleets operate, KGHM's ore is hosted in dolomite and anhydrite at 120–150 MPa UCS—significantly softer than Scandinavian formations. That lower UCS means the HLX5T's heavy percussion mechanism delivers more energy per blow than strictly necessary for crack initiation in the dolomite, which raises the question of whether the production drill's heavy percussion class is appropriate or whether it's over-spec for the formation.

The answer at KGHM Sieroszowice is that the HLX5T's heavy percussion is appropriate not because the dolomite needs 300+ J per blow, but because the 35-meter holes in the steeply dipping copper ore pass through multiple anhydrite interlayers at 200 MPa UCS within each hole. Those interlayer contacts are what the heavy percussion is designed for—the dolomite drills quickly between them, and the anhydrite requires full percussion energy to maintain advance rate. A medium-duty drifter would stall in the anhydrite; the HLX5T maintains consistent penetration through the full 35-meter ring.

Percussion Mechanism Reliability in Polish Dolomite-Anhydrite Production

KGHM Sieroszowice's HLX5T rigs run with blank-fire detection active throughout each hole—the auto-stop function that cuts percussion within 200 ms of detecting unloaded percussion prevents the housing stress that occurs when the heavy-percussion HLX5T runs without rock contact in the fast-penetration dolomite zones. Without this protection, the heavy percussion mechanism accumulates disproportionate housing fatigue in a formation that's too soft for the machine's rated percussion class. HOVOO supplies HLX5T percussion mechanism seal kits and valve components for Polish production drilling. References at hovooseal.com.