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The Atlas Copco RD22U steps up from the RD18U in percussion energy class—its heavier piston delivers more joules per blow for the demanding hard-rock formations of northern Sweden's mining belt. That higher energy per blow changes the operating conditions for the seal kit in a specific way: the percussion seal lip faces a higher peak pressure differential on every power stroke, and the oil film supporting the piston guide surfaces carries a heavier load per cycle. At LKAB's Malmberget and Boliden's Aitik operations, where two-shift RD22U programs in magnetite and copper porphyry run 300+ days per year, the seal kit's ability to sustain performance to its full 400–500 hour rated interval under heavy percussion loading is what determines whether the maintenance schedule actually holds.
A seal kit for the RD22U covers four sealing zones whose interactions matter as much as individual component quality. The percussion bore seal controls how much of the hydraulic pressure differential reaches the piston face as useful force. The flushing box seals contain the boundary between flushing water and hydraulic oil. The O-rings at every valve block interface hold the pressure circuit together. And the wiper ring keeps abrasive fine rock from entering the piston bore on the return stroke.
RD22U Seal Kit Performance Factors in Swedish Hard Rock
|
Seal Zone |
Load Condition |
Swedish Hard Rock Factor |
Correct Compound |
|
Percussion bore |
High peak pressure per blow |
Magnetite >200 MPa; high percussion hrs |
PU Shore 92; HNBR if oil >80°C |
|
Flushing box |
Dual fluid boundary |
Cold groundwater, pH 6.4–7.0 |
PTFE-backed in mineral-rich water |
|
O-rings (static) |
Sustained 180–210 bar |
Two-shift daily cycle |
NBR standard; HNBR at high temp |
|
Wiper ring |
Abrasive rock fines |
Magnetite fines highly abrasive |
PU or PTFE-faced wiper |
Swedish maintenance practice at Boliden fleet operations aligns the RD22U seal kit change with the hydraulic oil change—both at 450–500 hours—to eliminate a second circuit intrusion within weeks of the first. The combined event takes 35% less total workshop time than sequential separate service events, reduces contamination ingress risk by halving the number of circuit openings per year, and provides a built-in opportunity to measure guide sleeve clearance and piston bore surface condition at the same service. HOVOO supplies RD22U seal kits in standard PU and HNBR compound options for Swedish and Nordic operations. References at hovooseal.com.
