High-Thrust, High-Stiffness Anti-Vibration Construction
The barrel is manufactured from high yield-ratio quenched & tempered alloy steel forgings or ultra-heavy-wall tube, with FEA-optimized gland, cap, and clevis geometries. All welds undergo 100% UT/MT with stress relief. The piston rod is a large-diameter solid forging or heavy-wall rod, precision hard-chrome plated (HV900–1100, Ra≤0.1μm). Fatigue life exceeds 1.5 million full-load pressurization cycles, withstanding continuous severe vibration at the face and cutter impact without weld cracking or structural deformation.
Grouped Zone Propulsion for Precision Steering
Main thrust cylinders are divided into independent upper, lower, left, and right control zones. Differential pressure adjustment across groups, combined with built-in magnetostrictive displacement sensors (±0.2 mm accuracy), enables real-time correction of TBM roll, pitch, and yaw, precisely tracking the designed tunnel alignment. Closed-loop propulsion control and surface remote monitoring are fully supported.
Main/Auxiliary Coordination for Multi-Mode Operation
The hydraulic system can be linked with the auxiliary thrust cylinders. In competent rock (ample gripper reaction), the main cylinders work independently; in weak zones or during gripper repositioning, thrust automatically transfers to the auxiliary cylinders for uninterrupted advance. The transition is smooth and shock-free, ensuring advance rate and alignment continuity.
Ultra-Low Breakaway, Smooth Penetration
The main seal uses a filled PTFE and polyurethane low-friction composite with wear-resistant guide rings, achieving breakaway pressure as low as 0.3 MPa. The entire stroke is smooth and stepless, free of stick-slip or judder. In jointed, fractured, or mixed-face ground, this allows stable low-speed penetration and effectively controls rock disturbance and overbreak.
Specialized Rock-Dust-Resistant High-Pressure Sealing
The gland exterior is equipped with multiple wipers, a stainless steel scraper ring, and a labyrinth structure. The main seal — a hydrolysis-resistant polyurethane + filled PTFE composite with an accumulator buffer chamber — completely blocks rock dust, cuttings, and fissure water ingress while absorbing high-frequency pressure pulsations. Sealing design life corresponds to over 15 km of continuous drive.
Integrated Counterbalance Valve for Safe Self-Locking
Each cylinder comes standard with a high-flow counterbalance valve or dual pilot-operated check valve. Even if a hydraulic hose bursts or power is lost, the cylinder instantly locks, maintaining thrust at its current level. This prevents cutterhead retreat that could trigger face collapse or gripper slippage, ensuring work safety.
Fast Retract for Efficient Gripper Reset
Large-diameter ports and low backpressure flow paths achieve retract speeds of up to 100 mm/s, significantly reducing gripper stepping auxiliary time and increasing net boring time and overall productivity.
Comprehensive Anti-Corrosion & Temperature Resistance
External surfaces are finished with moisture-resistant epoxy. The piston rod is available with hard chrome, Ni/Cr alloy plating, laser cladding, or ceramic thermal spray. Seals can be upgraded to high-temperature grades for deep, hot rock conditions; all fasteners are stainless steel.
Maintenance-Free Pivots & Compact Mounting
Standard self-lubricating composite bushings in both clevises eliminate daily greasing and maintain low wear and long life under sustained high loads and frequent gripper repositioning. Mounting dimensions, pin sizes, and port orientations are fully customized to the TBM gripper shield and main thrust frame design.
