Massive Thrust with High-Stiffness Construction
The barrel is manufactured from high yield-ratio quenched & tempered alloy steel heavy-wall tube or forging, with FEA-optimized gland, cap, and clevis geometries. The piston rod is a large-diameter solid forging or ultra-heavy-wall tube, precision hard-chrome plated (HV900–1100, Ra≤0.1μm). Welds undergo 100% UT/MT. Fatigue life exceeds 1.5 million double-acting cycles, maintaining structural integrity and precise linear motion under sustained high ground and water pressure.
Grouped Zone Control for Precise Steering
Thrust cylinders are typically divided into four or more independently controlled groups (upper, lower, left, right). Differential pressure regulation across groups, combined with built-in displacement sensors, actively corrects shield roll, pitch, and yaw — enabling tight-radius curves and axis tracking. Sensor resolution is ±0.2 mm, supporting closed-loop control and remote monitoring.
Integrated Counterbalance Valve for Safe Pressure Resistance
Each cylinder comes standard with a high-flow counterbalance valve or dual pilot-operated check valve. In water-rich ground under high face pressure, this prevents unintended shield rebound. Even if a hydraulic line bursts or power is lost, the cylinder immediately self-locks, bracing the face and segment ring to ensure work safety.
Ultra-Low Breakaway, Smooth Propulsion
The main seal utilizes a filled PTFE and polyurethane low-friction composite with wear-resistant guide rings, achieving breakaway pressure as low as 0.3 MPa. The advance motion is free of stick-slip and shudder, especially important in soft or mixed ground to maintain a constant slow advance rate and effectively control surface settlement.
Specialized High-Pressure Sealing & Slurry Exclusion
The guide bushing area features multi-lip wipers, stainless steel retainer rings, and hydrolysis-resistant O‑rings, together with a dense hard-chrome rod surface. This completely blocks mud, rock fines, and groundwater ingress, enabling zero-leak, zero-contamination operation over drives exceeding 10 km.
Comprehensive Anti-Corrosion & Durable Coatings
External surfaces receive a moisture- and salt-spray-resistant epoxy coating. The piston rod can be specified with Ni/Cr plating, laser cladding, or ceramic thermal spray for enhanced protection. All fasteners are made of stainless steel, suitable for long-term use in mildly acidic groundwater and highly mineralized environments.
Fast Retract for High Productivity
Large-diameter oil ports minimize return backpressure. Together with the shield’s main pump station, retract speeds of up to 120 mm/s shorten segment erection auxiliary time and boost overall advance efficiency.
Maintenance-Free Pivots & Compact Mounting
Standard self-lubricating composite bushings at both clevises eliminate daily greasing and maintain low wear under long-distance drives and frequent pad repositioning. Mounting dimensions, pin sizes, and port orientations are fully customizable to any shield OEM design.
