Double Shield Tunnel Boring Machine Main Thrust Cylinder

The Double Shield Tunnel Boring Machine Main Thrust Cylinder is the primary hydraulic actuator responsible for pushing the tunnel boring machine forward through various ground formations. This main thrust cylinder absorbs and converts hydraulic power into mechanical force, generating the necessary push to advance the cutterhead assembly through soft to medium‐hard rock layers. Installed between the cutterhead shield and the gripper shield, the main thrust cylinder operates in conjunction with high‐precision gripper shoes to maintain stable reaction forces against the tunnel walls, ensuring continuous forward motion in a controlled manner.

Featuring a robust single‐acting design, the Double Shield Tunnel Boring Machine Main Thrust Cylinder extends under hydraulic pressure up to 35 MPa and retracts via an integrated accumulator system. The accumulator captures energy during extension and releases it for retraction, optimizing cycle efficiency and minimizing pump load. Custom bore diameters from 220 mm to 380 mm and rod diameters from 150 mm to 280 mm, combined with strokes ranging from 1 100 mm to 1 700 mm, allow each main thrust cylinder to be tailored precisely for tunnel diameter and ground conditions.

Double Shield Tunnel Boring Machine Main Thrust Cylinder Technical Specifications

Design Features and Technical Advantages

The Double Shield Tunnel Boring Machine Main Thrust Cylinder integrates multiple advanced technologies to withstand the extreme demands of continuous tunneling operations:

• High‐Strength Materials: Cylindrical barrels and piston rods are forged from 42CrMo or 4140 alloy steel, heat‐treated for optimized tensile strength and durability.
• Precision Machining: Bore and rod straightness and roundness controlled within 0.02 mm to ensure leak‐free operation and minimal side loads on seals.
• Premium Sealing Systems: NOK, Trelleborg, Hallite seals selected to maintain zero leakage under cyclic pressures up to 35 MPa and temperatures between –20 °C and +80 °C.
• Automated Surface Protection: Robotic coating lines apply epoxy primers and polyurethane topcoats with ≥ 1 000 hours of salt spray resistance, ensuring corrosion protection in wet and abrasive environments.
• Full Data Traceability: Advanced CNC testing equipment with cloud‐based data storage tracks dimensional and performance measurements throughout manufacturing and testing.
• 100% Factory Testing: Each main thrust cylinder undergoes pressure, leakage, extension/retraction speed, and endurance cycle testing before shipment.

Tunnel Boring Machine Cylinder Family

In addition to the main thrust cylinder, the Tunnel Boring Machine Cylinder family includes Auxiliary Thrust Cylinders, Torque Cylinders, and specialized Gripper Actuators. These cylinders work in harmony to control advance, rotate the cutterhead, and anchor the machine against tunnel walls:

• Auxiliary Thrust Cylinder: Provides supplemental push during segment lining installation and single‐shield operations, allowing continuous tunneling without interruption.
• Torque Cylinder: Transmits rotational torque to the cutterhead motor housing, adjusting cutterhead orientation and torque output for optimal rock penetration.

Torque Cylinder Integration

The Torque Cylinder is integrated within the cutterhead drive assembly to deliver precise rotational control. By modulating hydraulic flow and pressure, the torque cylinder regulates cutterhead RPM and torque, ensuring consistent performance across varying ground conditions.

torque cylinder head sequence

The torque cylinder head sequence consists of five critical phases: initial pressure ramp‐up, torque application under load, load hold for steady cutting, pressure release for cycle reset, and repositioning for the next cut. This sequence ensures smooth torque transitions and prevents shock loading on the cutterhead bearings.

Thrust Cylinder Arrangement

A coordinated network of Thrust Cylinders supports both advance and lining installation. The Main Thrust Cylinder delivers the principal driving force, while Auxiliary Thrust Cylinders stabilize the shield during ring erection. This dual arrangement allows the machine to switch seamlessly between excavation and segment installation modes.

Auxiliary Thrust Cylinder and Main Thrust Cylinder

During a typical advance cycle, the Auxiliary Thrust Cylinder clamps the rear shield to the freshly installed concrete segment, then the Main Thrust Cylinder pushes the cutterhead shield forward. Once the next segment is in place, the auxiliary cylinder retracts, and the cycle repeats.

Working Principle and Cycle Efficiency

The working principle of the Double Shield Tunnel Boring Machine Main Thrust Cylinder relies on hydraulic power transmission and energy recovery. In the extension phase, hydraulic fluid pressurizes the cylinder chamber, pushing the piston rod out and advancing the machine. In the retraction phase, the accumulator stores excess fluid energy, which is then released to retract the rod with minimal pump consumption. This regenerative action enhances hydraulic system efficiency by up to 20 %.

Cycle times can be adjusted by controlling fluid flow rates and accumulator precharge pressures. Optimized control algorithms minimize cycle variation, improving tunnel advance rates by reducing dwell times between pushes.

Applications and Industry Uses of Double Shield Tunnel Boring Machine Main Thrust Cylinder

The Double Shield Tunnel Boring Machine Main Thrust Cylinder is employed in a wide range of tunneling projects:

• Urban metro and subway systems
• High‐speed rail and conventional railway tunnels
• Highway and road underpasses
• Hydroelectric and water conveyance tunnels
• Underground utility and service ducts

Its robust design also makes it suitable for mixed‐face and variable geology where high thrust forces and precise cycle control are essential.

Materials and Manufacturing Process

• Key components of the Double Shield Tunnel Boring Machine Main Thrust Cylinder undergo rigorous manufacturing steps:
• Forging and Heat Treatment: Alloy steel billets are forged and heat‐treated for maximum strength and fatigue resistance.
• CNC Machining: Precision turning, boring, and grinding ensure dimensional tolerances within ±0.02 mm.
• Honing and Polishing: Bore and rod surfaces are honed to Ra 0.2 µm for optimum seal life.
• Seal and Accessory Assembly: Installation of premium seals, rod bearings, and pressure gauges.
• Surface Coating: Automated priming and finishing layers with epoxy and polyurethane coatings.
• Final Testing: Pressure, leakage, cycle life, and load tests with full data logging and certification.

Company Introduction and Related Products

We are a leading manufacturer of heavy-duty hydraulic cylinders for mining, tunneling, and material handling industries. Adhering to ISO 9001 and TS 16949 quality systems, we deliver reliable, high-performance products backed by comprehensive after-sales support and global 24×7 service.

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