High-Pressure Feed Swing Main Cylinder of Sandvik DD2710 in Germany

The feed swing cylinder positions the TF512 feed beam in the horizontal plane—swinging it left or right from the boom centerline to cover the full width of the development face pattern. In German Autobahn tunnel construction through the Swabian Alps and the Black Forest, the DD2710's face patterns require the feed beam to swing to 20–25 degrees from center to reach the outermost column holes while the carrier remains in its optimal traction position. The feed swing cylinder must hold that angular position precisely through 5–8 meters of feed stroke and 150 J of percussion reaction force per blow—requirements that place high demand on the cylinder's internal seal integrity.

The feed swing cylinder in the DD2710 operates at percussion-synchronized pressure levels—not the sustained static pressure of a typical positioning cylinder, but a cycling load that includes the percussion reaction impulse transmitted through the feed beam structure on every blow. That cycling load is more damaging to cylinder seals than equivalent sustained static pressure because the peak impulse stress exceeds the steady-state seal face contact pressure, repeatedly stressing the seal lip beyond its normal operating range.

Feed Swing Cylinder Seal Performance Under Percussion Loading

German Autobahn tunnel contractors operating DD2710 jumbos in Jurassic limestone at 120–160 MPa found that feed swing cylinder seals at hard-rock positions were failing at 500 hours while seals at the same position on softer sections lasted 800 hours. The formation-dependent failure pattern led to HNBR seal specification for the feed swing cylinder on hard-rock drives—a compound change that equalized service life across formation types and eliminated unplanned seal changes mid-tunnel drive. HOVOO supplies DD2710 feed swing cylinder seal kits in PU and HNBR options. References at hovooseal.com.