LTZC Four Point Contact Ball Slewing Bearing for 7000mm Shield Tunnelling Machine

I.What is a shield tunneling machine bearing?

Shield machine bearings refer to the main bearings that serve as the core drive component within the cutterhead system. By facilitating rotational movement, they drive the cutterhead to rotate, thereby enabling the cutting of rock and soil and the advancement of the tunnel; consequently, they are known as the "heart" of the machine and are critical for power transmission and load-bearing across the entire assembly.

During operation, these bearings must simultaneously withstand multiple complex loads, including immense axial thrust, radial forces, and overturning moments, as well as dynamic torque generated by the motor or reducer drive systems. These extreme and fluctuating load conditions place exceptionally high demands on the bearing's structural strength and reliability.

Currently, shield  machine bearings predominantly utilize a three-row roller slewing bearing design. This configuration offers high load-bearing capacity, superior rigidity, and excellent resistance to overturning moments, enabling the machine to effectively handle extreme operating conditions while ensuring safe and stable performance.

It is worth noting that the shield machine in this project features a 14-meter diameter cutterhead; the slewing bearing for its associated segment erector utilizes a four-point contact ball bearing design to meet specific operational requirements regarding precision, rigidity, and rotational flexibility.

II. Technical Requirements for the Φ7000mm Shield Tunnelling Machine Bearing Project

This project serves a Southeast Asian manufacturer of shield tunnelling equipment, specifically for a large-scale machine featuring a 14-meter diameter cutterhead. The core component is a slewing bearing with a diameter of approximately 7000mm, designed for the segment erector system. LTZC successfully secured the order by leveraging its exceptional technical responsiveness and extensive experience in manufacturing heavy-duty bearings.

2.1 Key Technical Requirements

Product Structure and Interfaces: Utilizes a single-row, four-point contact ball slewing bearing structure with an internal gear design, ensuring compatibility with the client's existing main drive hydraulic motor meshing system.

Specifications:Outer diameter of 7000mm, precisely matched to the cutterhead drive unit of a 14-meter class shield tunnelling machine.

Operating Conditions: Designed for continuous, low-speed rotation; subjected to frequent, intense impact loads from rock fragmentation during excavation; operates in high-humidity, high-sediment environments, posing challenges for sealing and pressure resistance in the lubrication system.

Load Performance: Must simultaneously withstand bidirectional axial forces, high-magnitude radial forces, and overturning moments; requires a safety factor of at least 3.2 under short-term impact loads to ensure reliability and safety in extreme conditions.

Qualification Thresholds: Suppliers must possess independent manufacturing capabilities for large slewing bearings and provide comprehensive documentation—including material certificates, heat treatment curves, inspection reports, and non-destructive testing (UT/MT) reports—while accepting inspections by authoritative third-party agencies.

2.2 LTZC Value-Added Service Commitments

 Provide on-site technical guidance for installation and clearance adjustment;

Compile detailed operation and maintenance manuals;

Support long-term spare parts supply and full-lifecycle technical services.

2.3 LTZC Project Execution and Competitive Advantages

Upon receiving the operating parameters, LTZC’s technical team responded rapidly, conducting multiple specialized technical discussions with the client to precisely define design constraints. After completing the preliminary design drawings and obtaining client approval, the team immediately initiated load simulation and verification. Using a finite element analysis (FEA) model based on actual operating conditions, they ensured that the structural strength and fatigue life met all design requirements.

IV. LTZC 7000mm Shield Tunneling Machine Bearing Solution

As a specialized manufacturer of four-point contact ball slewing bearings with over 30 years of experience, LTZC operates workshops equipped with multiple sets of precision CNC machine tools and standardized assembly areas, capable of producing bearings with diameters ranging from 200mm to 15,000mm.

4.1 Selection of High-Quality Forgings

High-strength alloy structural steel (42CrMo) is selected as the primary material for the inner and outer rings of this 7000mm four-point contact ball slewing bearing. Suppliers provide ultrasonic and flaw detection reports for the forgings; upon arrival, LTZC conducts a secondary internal inspection to control quality at the source and prevent substandard forgings from entering production.

4.2 Quenching and Tempering Pre-treatment and Precision Raceway Induction Hardening

After rough turning, the inner and outer rings undergo integral quenching and tempering. Quenching and tempering temperature curves are strictly controlled to stabilize the base hardness between 230HB and 270HB, ensuring overall ring toughness to withstand sudden impact loads during tunneling operations.

4.3 Precision CNC Machining

To meet the customer's specified internal gear structure, large-scale floor-type CNC gear shaping equipment is used, followed by gear surface strengthening treatment. Gear profile accuracy meets the customer's required grade, with no machining burrs or impact defects on the gear surfaces. After gear machining, magnetic particle testing (MT) is conducted to detect micro-cracks at the gear roots, preventing tooth breakage under long-term torque loads.

4.4 Comprehensive Non-Destructive Testing (NDT)

Upon completion of all machining processes, a comprehensive NDT procedure is carried out—including ultrasonic testing, magnetic particle testing, dimensional inspection, and axial runout testing—and a complete inspection report is provided to the customer. 4.5 Multi-layer Protective Sealing and Assembly Inspection

To address the high-sediment operating conditions faced by the shield machine, the sealing system for this four-point contact ball slewing bearing has been upgraded to a composite design: the outer side features a labyrinth-style debris guard combined with dual-layer fluororubber seals, ensuring resistance to slurry abrasion and water immersion.

Following assembly, a slow, full-circle manual rotation test is conducted to verify smooth movement—free from binding or abnormal impact noises—and the no-load slewing torque is recorded as a key metric for factory acceptance.

Looking for bearing solutions? Speak with LTZC engineers today.

V. Why Choose LTZC for Custom Large-Scale Slewing Bearings

1.  Dedicated Manufacturing Facility: We operate an independent bearing factory with comprehensive production lines, capable of supplying slewing bearings ranging from 200mm to 15,000mm in diameter.

2.  Extensive Application Expertise: We possess a rich database of shield tunneling operating conditions and offer collaborative design services to meet specific customer customization requirements.

3.  Proven Experience & Certification: With over 30 years of bearing manufacturing experience and certifications such as ISO, CCS, and BV, we are a highly trusted partner.

4.  Broad Product Range & Customization:We offer a wide range of specifications and support diverse customization options, catering to applications requiring large-diameter and extra-heavy-duty slewing bearings, such as port cranes and excavators.

5.  Comprehensive Service System: We provide end-to-end support, offering free technical consultation and drawings during the initial stages, followed by technical guidance on bearing installation.

VI. FAQ on Shield Tunnelling Machine Slewing Bearings

Q1: Can large-diameter four-point contact ball slewing bearings be manufactured as segmented structures?

A: Yes. When the outer diameter of a full-ring bearing is too large and constraints exist regarding road transport or factory lifting capabilities, LTZC can design large segmented slewing bearings. However, for the main drive bearings of shield machine cutterheads, an integrated full-ring design is preferred whenever conditions permit; this offers superior overall rigidity and impact resistance compared to segmented structures, thereby reducing the likelihood of future failures. For the recent 7000mm project, as the client's factory facilities and road transport conditions were suitable, an integrated full-ring four-point contact ball slewing bearing was ultimately selected.

Q2: Which manufacturing factors primarily influence the service life of shield machine bearings?

A: Key factors include raw forging materials, heat treatment quality, and sealing structure design. When purchasing heavy-duty slewing bearings, buyers should carefully verify the manufacturer's capabilities regarding heat treatment and raceway machining, and discuss technical specifications with the supplier to prevent premature bearing failure caused by technical issues.

Q3: What is the maximum diameter of slewing bearings that LTZC can manufacture?

A: LTZC’s existing production lines support the customization of various slewing bearings with outer diameters up to 15,000mm. We are capable of fulfilling orders for ultra-large slewing bearings across a range of heavy equipment sectors, including shield tunnelling machinery and large-scale cranes.