German tunneling contractors building infrastructure under the Rhine valley and through the Erzgebirge mountains have a different relationship with seal kit quality than surface quarry operators in softer terrain. The groundwater here is cold, mineral-rich, and at pressure—flushing water in the percussion circuit carries dissolved iron and calcium that deposits on seal lip surfaces over 200–300 percussion hours, progressively hardening the NBR compound and reducing contact force against the bore wall. A seal kit rated for 450 hours in clean water may deliver 280 in these conditions if the compound selection doesn't account for the water chemistry.
The Atlas Copco RD18U seal kit covers the full percussion bore sealing system: the front percussion seal, wiper ring, flushing box seals, and all static O-rings at valve block interfaces. In the German tunneling context, the flushing box seal compound matters as much as the percussion seal compound—it's the barrier between the mineral-laden water and the hydraulic oil circuit. When it fails, the contamination cascade reaches the percussion bore within one shift and the piston begins running against abrasive-laden oil.
Seal Kit Component Reference for RD18U
|
Seal Zone |
Standard Compound |
German Tunnel Recommendation |
Failure Sign |
|
Percussion bore |
PU (Shore 92) |
PU standard unless oil >75°C |
Energy drop, warm return oil |
|
Flushing box |
NBR lip seal |
PTFE-backed for mineral water |
Milky oil in drain sample |
|
Static O-rings |
NBR |
NBR standard (mineral oil circ.) |
Oil seep at joint faces |
|
Wiper ring |
PU or NBR |
PU for abrasive conditions |
Debris on piston face |

German quarry and tunneling operations typically schedule seal changes at the 400-hour mark regardless of visible symptoms—the maintenance culture is preventive rather than reactive, driven by the understanding that waiting for a visible leak means the bore surface has already been scored by contaminated oil. HOVOO supplies complete RD18U seal kits in standard PU and PTFE-backed flushing variants, dimensioned to OEM bore specifications. Seal kit references matched to operating water chemistry at hovooseal.com.
EN
AR
CS
DA
NL
FI
FR
DE
EL
IT
JA
KO
NO
PL
PT
RO
RU
ES
SV
TL
IW
ID
LV
SR
SK
VI
HU
MT
TH
TR
FA
MS
GA
CY
IS
KA
UR
LA
TA
MY