LTZC Develops China’s Largest 8-Meter TBM Main Bearing

Against the backdrop of continuous development in national infrastructure construction towards "deeper, longer, larger, and more challenging" projects, super-large tunnel boring machines (TBMs) have become critical equipment in urban rail transit, cross-river and cross-sea tunnels, and complex geological engineering projects. As one of the most critical components of a TBM, with the highest technical threshold and manufacturing difficulty, the performance and reliability of the main bearing directly determine the construction efficiency, safety, and service life of the entire machine.

Recently, LTZC successfully delivered a super-large diameter main bearingfor a tunnel boring machine. This main bearing has a diameter of 8 meters and a single-piece weight of 41 tons, making it currently the largest diameter and heaviest main bearing for TBMs manufactured in my country. This bearing will be used in a 16-meter-class super-large TBM, serving a major national-level tunnel excavation project.

This achievement not only marks a significant technological breakthrough for LTZC in the field of super-large diameter slewing bearings and TBM main bearings, but also further strengthens my country's independent manufacturing capabilities in high-end core components for basic industries.

1. Why are Tunnel Boring Machine (TBM) Main Bearings So Critical?

1. The "Heart" of the TBM：

The TBM main bearing, located between the cutter head and the main drive system, is a core component that connects the cutter head, transmits loads, and enables continuous rotation. It needs to operate stably for extended periods under extreme conditions:

Ultra-large axial loads

Huge overturning moments

Complex radial loads

Long-term low-speed, heavy-load operation

Impact loads and uneven ground resistance

If the main bearing fails, the TBM will face prolonged downtime, high repair costs, and potentially even engineering risks. Therefore, the main bearing is widely considered one of the most technically challenging and demanding bearing products in a TBM.

2. New Challenges Posed by Super-Large TBMs to Bearings

As TBM diameters increase from 10 meters to 16 meters and even larger sizes, the main bearing faces exponentially increasing technical challenges in terms of size, weight, load capacity, structural stability, and manufacturing precision:

Bearing diameter exceeding 8 meters

Single-piece weight exceeding 40 tons

Dramatically increased difficulty in machining, heat treatment, and inspection

Significantly increased transportation and assembly risks

The 8-meter-class TBM main bearing successfully developed by LTZC was created against this backdrop.

3. Case Overview: 8-Meter Class Tunnel Boring Machine Main Bearing Project Background

1. Project Application Scenario

Equipment: 16-meter diameter ultra-large tunnel boring machine

Engineering Type: Ultra-large tunnel engineering (urban rail transit / cross-river and cross-sea tunnels / complex geological engineering)

Operating Characteristics: Low speed, heavy load, long-term continuous operation

2. Customer's Core Requirements

The main bearing must withstand ultra-large axial loads and overturning moments.

Maintain stable rotation under complex geological conditions.

Long-life design to meet the entire service life of the machine.

High reliability and extremely low failure rate.

Domestic replacement of similar high-end imported products.

LTZC, as a leading Chinese manufacturer of large slewing bearings and heavy-duty bearings, undertook the research and development and manufacturing tasks of the main bearing for this ultra-large diameter tunnel boring machine.

3. Basic Parameters

Bearing Type: Tunnel boring machine main bearing

Structure: Multi-row roller structure

Outer Diameter: Approximately 8000 mm

Single Piece Weight: Approximately 41 tons

Design Life: 6 years

Operating Conditions: Low speed, heavy load, continuous operation

Manufacturing Precision Grade: P5

4. How did LTZC successfully manufacture the 8-meter main bearing?

1. Structural Design Capabilities for Ultra-Large Diameter Bearings

LTZC has been deeply involved in the bearing industry for over 20 years and is a leading slewing bearing supplier in China, possessing extensive technical expertise in shield machine bearings, slewing rings, and ultra-large diameter bearings. In this project, the LTZC technical team conducted a detailed analysis of load life and systematically optimized the bearing structure, ensuring sufficient safety margin and operational stability even under extreme loads.

2. Advantages in Materials and Heat Treatment Technology——View LTZC bearing manufacturing capability

LTZC invests 10% of its annual sales revenue in the research and development of production processes.  The manufacturing of this shield machine slewing bearing utilizes specialized steel and a comprehensive heat treatment and quenching process, ensuring consistent raceway hardness. This lays a solid foundation for the bearing to maintain stable performance during long-term heavy-duty operation.

3. Rigorous Testing and Quality Control System——View LTZC bearing quality and certificates

In terms of quality control, LTZC implemented multiple tests and verifications on the main bearing: full-process testing of dimensions and geometric accuracy, assembly accuracy, and rotational performance testing. This ensures that the shield machine main bearing meets high reliability standards for engineering applications before leaving the factory.