INDUSTRY COMPONENT

Main Bearing

Main bearing is a critical rotating component in tunnel boring machines that supports the cutterhead and transmits thrust loads.

Component Specifications

Definition
The main bearing in a tunnel boring machine (TBM) is a large-scale, precision-engineered rolling-element bearing assembly that serves as the primary load-bearing interface between the rotating cutterhead and the stationary main drive system. It supports radial loads from cutterhead weight and rotational forces, axial thrust loads from excavation pressure, and moment loads from uneven ground conditions. This component enables continuous 360-degree rotation under extreme mechanical stresses while maintaining precise alignment and minimal friction.
Working Principle
The main bearing operates on rolling-contact mechanics where hardened steel rollers or balls circulate between inner and outer raceways, converting sliding friction into rolling friction. It distributes massive loads (typically 5,000-15,000 kN) across multiple rolling elements while allowing smooth rotation at 0-10 RPM. The bearing transfers rotational torque from the drive motors to the cutterhead while simultaneously handling thrust forces generated during excavation. Lubrication systems maintain oil films between contact surfaces to prevent metal-to-metal contact and dissipate heat.
Materials
Bearing rings: Forged AISI 52100 chromium steel (1.0-1.1% C, 1.3-1.6% Cr) or case-hardened 42CrMo4 steel; Rolling elements: Through-hardened 100Cr6 steel (SAE 52100); Cage/separator: Machined brass (CuZn39Pb3) or glass-fiber reinforced polyamide; Seals: Nitrile rubber (NBR) or polyurethane with steel reinforcement
Technical Parameters
ParameterTypical rangeNotes & selection driver
Diameter3,000-8,000 mm
MountingHydraulic shrink-fit or heated mounting
LubricationForced oil circulation with filtration
Service Life10,000-15,000 hours
Load Capacity5,000-15,000 kN axial, 2,000-6,000 kN radial
Rotation Speed0-10 RPM
Precision ClassP5 or higher (ISO 492)

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards
ISO 281, ISO 76, ISO 355, DIN 5412, DIN 620

Parent Products

This component is used in the following industrial products

Engineering Analysis

Risks & Mitigation
  • Catastrophic bearing seizure leading to project delays
  • Contamination-induced spalling and fatigue
  • Thermal runaway from inadequate cooling
  • Misalignment causing uneven load distribution
FMEA Triads
Trigger: Lubrication contamination with abrasive particles
Failure: Surface pitting and spalling on raceways
Mitigation: Implement dual filtration systems (10μm absolute), regular oil analysis, and magnetic plugs
Trigger: Insufficient bearing preload during assembly
Failure: Skidding of rolling elements under light load
Mitigation: Apply controlled hydraulic preload (0.05-0.10mm deflection), verify with strain gauges
Trigger: Seal degradation in abrasive environments
Failure: Contaminant ingress and lubrication loss
Mitigation: Use multi-labyrinth seals with grease purge systems, implement quarterly seal inspection

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance
Radial runout < 0.05mm, axial runout < 0.03mm, raceway roundness < 0.01mm
Test Method
Ultrasonic testing (DIN 54120), magnetic particle inspection (ISO 4986), dimensional verification with laser trackers, full-scale load testing to 150% design load

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation
Request current drawings, revision history, and a signed specification sheet.
Manufacturing capability
Verify equipment lists, process limits, capacity, and representative production evidence.
Inspection readiness
Confirm test methods, calibrated equipment, sampling plans, and traceable reports.
Supplier transparency
Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Main Bearing

3 companies list this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

Chongqing Kyson Machinery Equipment Co., Ltd.
Guangxi, CN
Listed on the company's own website · profile compiled by CNFX from public sources
Listed there as: “main bearings”
View source page ↗ kysonpower.com · checked 2026-09-16
Jinan Zhongchuan Equipment Co., Ltd.
Jinan, Shandong, CN
Also makes: Double-End Stud, Diesel Engine, Cylinder Head and 6 more
Listed on the company's own website · profile compiled by CNFX from public sources
Listed there as: “Main Bearing Bolts”
View source page ↗ jnzcsb.com · checked 2026-09-17
Luoyang LYC Bearing Co., Ltd.
Luoyang, Henan, CN
Listed on the company's own website · profile compiled by CNFX from public sources
Listed there as: “Main Bearing”
View source page ↗ lycbearing.com · checked 2026-09-07

Manufacturer listings support early research and capability understanding. They are not certification, ranking, or transaction guarantees.

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Frequently Asked Questions

What is the typical service life of a TBM main bearing?

Properly maintained TBM main bearings typically achieve 10,000-15,000 operational hours, equivalent to 10-15 kilometers of tunnel excavation, depending on ground conditions and loading patterns.

How are main bearings lubricated in tunnel boring machines?

Main bearings use forced oil circulation systems with dual filtration (typically 10-25 micron filters), temperature monitoring, and sometimes grease backup systems. The oil serves both as lubricant and coolant.

What causes premature failure in TBM main bearings?

Common causes include contaminated lubrication (80% of failures), improper mounting/preload, shock loads from hard rock formations, seal failure allowing abrasive ingress, and misalignment exceeding 0.1mm/m.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification
This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

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