Precision Valve Piston of Atlas Copco RD18U in Poland

Poland's hard coal and copper mining operations—KGHM Polska Miedź in the Lubin-Sieroszowice copper district and JSW's coking coal mines in Silesia—run some of the highest-utilization drill fleets in European underground mining. Two-shift daily drilling programs with limited weekend maintenance windows mean drifters accumulate percussion hours faster than most operations globally. At that utilization rate, the valve piston's switching precision determines whether the percussion circuit operates at design efficiency or drifts progressively toward a lower-energy, higher-heat operating point that nobody notices until penetration rate data is reviewed at month-end.

The valve piston in the Atlas Copco RD18U is the reversing valve's moving element—it switches oil flow between the front and rear piston chambers at the correct moment in the piston's travel cycle to sustain percussion. The clearance between the valve piston OD and the valve bore ID (typically 0.008–0.015 mm) controls both the switching speed and the internal leakage rate. When contamination wear opens that clearance beyond 0.020 mm, switching speed drops, the valve reversal begins arriving after the piston has already contacted the shank, and secondary impacts develop—each reducing net percussion energy.

Valve Piston Clearance vs. Percussion Performance

Polish maintenance teams at KGHM operations track percussion pressure stability as the first indicator of valve piston wear—a pressure gauge that shows increasing oscillation amplitude without any accumulator change or hydraulic oil issue points to the valve circuit. Confirming by clearance measurement requires pulling the valve block, which takes 45 minutes in a workshop. HOVOO supplies precision-ground RD18U valve pistons to OEM clearance specifications, available alongside complete seal kits to cover the full valve circuit in one service event. References at hovooseal.com.