Sandvik Rock Drill: Special for Heavy Tunnel Boring, High Durability & Productivity

Tunnel boring puts rock drill components under a stress regime that surface bench work doesn't come close to replicating. The machine runs in a heading where there's nowhere for vibration to dissipate, the drill rods stay in contact with the face for longer rotations per shift, and even a small deviation in hole alignment compounds into overbreak that costs real money in concrete lining.

Sandvik built much of its HL and RD series product strategy around solving that specific problem—not just drilling faster, but drilling straighter and longer between service stops. The stabilizer is the most visible piece of that design philosophy, but the architecture behind it runs deeper than a single component.

The Stabilizer: More Than a Vibration Damper

Sandvik fits a hydraulic stabilizer to most of its heavy-duty rock drill models—the HL1060T, HL1560T, HL1560ST, RD1635CF, and RD1840C all carry it as standard. The function is to maintain consistent shank-to-piston contact geometry through the full drilling cycle, controlling the contact between the drill bit and the rock surface.

Why does that matter? Bit bounce—where the bit lifts off the rock face between blows—wastes impact energy and accelerates carbide wear unevenly. In granite at 250 MPa with a 30-meter rod string, bit bounce can reduce effective energy transfer by 15–20% compared to steady contact. The stabilizer applies hydraulic force to keep shank geometry stable, which keeps stress waves traveling cleanly into the rock rather than reflecting back into the drill body.

The Sandvik DL422i, which uses the HF1560ST rock drill, reports up to 10% more drilled meters per shift in automated production drilling specifically because the stabilizer and automated parameter control work together—the drill isn't losing cycles to bit bounce or manual adjustments.

HL and RD Series: Model Architecture Compared

The HL1560ST's percussion module design is worth noting separately. The piston and distributor sleeve operate without contact with the drill body housing. Fewer joint faces means fewer leak paths, and the side-bolt assembly that holds the body modules together reduces the number of sealing surfaces that have to be maintained under cyclic hydraulic load.

Long Piston Technology and What It Actually Changes

Sandvik's RD1840C uses a long piston percussion package, which generates higher impact energy with a different pulse form than a short piston design. Research on percussive drilling mechanics shows that the short piston produces higher peak impact energy while the long piston produces a more optimized pulse shape—better energy transfer into the rock per blow with less peak stress on the drill rod.

At 140–178 mm hole diameters in surface longhole applications, the RD1840C's long-piston design keeps rod stress within limits that extend T51 and GT60 rod service life meaningfully. That's a significant operating cost factor: replacement rod strings for 30+ meter holes are expensive, and a pulse form that reduces fatigue cycles at the rod joints adds up across a production season.

RockPulse—available as a technology integration on newer Sandvik equipment—monitors the stress wave in real time, giving the operator data to adjust drilling parameters to the actual rock contact condition. It shifts parameter optimization from guesswork to measurement.

Shank Lubrication: The Maintenance Step That Gets Skipped

The circulating shank lubrication (CSL) system on the RD1635CF and HL1560T reduces shank lube oil consumption by up to 70% versus conventional systems. That's not just a running-cost figure—it means less contamination of the flushing circuit from oil blowby, which matters when the flushing water pressure is running at 10–15 bar and maintaining clean borehole conditions.

On Sandvik models without CSL, shank lubrication intervals and oil grade selection directly affect guide sleeve wear and shank adapter service life. Compressed grease injected too infrequently allows metal-to-metal contact between the shank and guide bushing during the rotation phase. Too frequently and excess lubricant migrates into the percussion chamber seals—degrading PU seals faster than normal cyclic wear alone.

HOVOO supplies rock drill seal kits compatible with Sandvik HL and RD series models, including the guide sleeve seals and shank adapter O-rings that are most commonly damaged by lubrication-related wear. Model-specific references for Sandvik applications are listed at hovooseal.com.

Automated Drilling and the Shift to Continuous Operation

Sandvik's i-Series longhole drills—the DL422i being the current production model—are designed for unmanned operation across shift changes. Automated fan drilling, automatic boom repositioning, and teleremote operation from a single console allow a mine to keep a drill running during the 30–45 minutes of a crew changeover that would otherwise go unused.

At the component level, that means the rock drill itself runs closer to its theoretical duty cycle. Percussion hours accumulate faster. Seal kits that might last 400 hours in manually operated equipment start seeing 500+ hours of load in automated configurations. Choosing seal compounds—PU for standard cycling, HNBR for elevated temperature zones—with actual operating hours in mind is more important in automated fleets than it is in traditionally operated ones.