Choosing the Right Seals for Tunnel Boring Machine

Number of hits：132025-07-01 15:25:02　

In the world of underground construction, shield tunnel boring machine (TBM) face some of the harshest operating conditions. Working beneath the surface means exposure to high pressure, water ingress, abrasive soil, and continuous mechanical stress. One critical yet often underestimated component in the success of a TBM is the sealing system.

But how do you choose the right tunnel boring machine seals for such a demanding application?

Understanding the Role of Seals in TBM
Seals in a shield tunnel boring machine serve several functions:

Prevent water and soil from entering mechanical compartments

Retain grease or lubrication within key areas like the main bearing

Isolate pressure differentials across the face or tail of the machine

The tail seal system and main bearing seal are especially crucial. Failure here can lead to costly downtime and safety risks.

Key Selection Factors
Rather than relying on a single criterion, multiple technical factors must be evaluated:

Material resistance: Seals must endure contact with slurry, chemicals, and varying temperatures. Elastomers like NBR, FKM, and HNBR are often used depending on the zone of application.

Structural integrity: Multi-lip sealing elements, reinforced with metal springs or composite fabrics, are essential for durability in dynamic motion and pressure.

Environmental pressure: High underground pressure and the presence of groundwater require seals capable of handling axial and radial loads without deformation.

Grease compatibility: Since sealing systems often work in tandem with special greases, material compatibility must be confirmed to avoid chemical degradation.

Common Questions Engineers Ask
Q1: Can general industrial seals be used in shield tunnel boring machine?
Not recommended. TBM seals must be designed for large-scale motion, uneven pressure, and extreme dirt exposure. Standard industrial seals lack the reinforcement and configuration needed.

Q2: How often should seals be inspected or replaced in TBM?
Routine inspection intervals are project-specific but often occur every 300–500 working hours. Tail seal replacement depends on wear indicators and grease consumption rate.

Q3: Is material the most important factor in seal selection?
Material is key, but geometry, installation method, and grease type are equally important. A well-chosen material with poor lip structure won’t perform as expected.

Q4: How do environmental conditions impact seal performance underground?
Temperature variation, abrasive soil, and unexpected rock layers can all cause premature wear. Seals must therefore be tested and rated for project-specific geological conditions.

When it comes to shield tunnel boring machine, sealing isn’t just a supporting role—it’s a critical element in machine reliability and project continuity. The right combination of materials, multi-lip design, and grease compatibility, along with a solid understanding of site conditions, ensures that the seals do their job silently but effectively beneath the surface.