Tunnel boring machine (Figure 1), also known as shield machine, is an advanced operating equipment of underground tunneling, a large complex structure, poor working conditions. For example, in Hamburg, Germany over the Elbe river tunnel construction site of a tunnel boring machine, cutter diameter of 14.2m, the total length of the device 58m, the total weight of 2500t, worth 3 million euros. TBM main bearing seal on the system is a key component of equipment located in the drive spindle and cutter shield between the steel shell, its role is to isolate the earth and the operation area of ​​mechanical transmission equipment and electrical control and prevent mud into the main bearing, importance can be imagined. Because it is underground, the sealing system is difficult to replace in the field, its life must be to ensure that tunnel boring machine operations to complete the entire tunnel.

Figure 2 is designed for the tunnel boring machine main bearing seal design Seal TBM series of large-size rotation, the material is oil and water resistant high-strength wear-resistant nitrile rubber B248, the structural design of seals to ensure a good seal lip to follow the nature with the rotation axis to maintain the best contact point; in ensuring the sealing effect of the dynamic seal while reducing the contact area, to the maximum extent to reduce friction and heat seal lip wear, so that can be used to pressure conditions (such as soil pressure balance working condition).

Tunnel boring machine under working conditions, it is recommended to use multiple tandem sealing system seals the structure, as shown in Figure 3. Suggested that the first set before sealing a TBM labyrinth seal, and continuous use of oil "wash" lubrication, oil consumption, as the condition may be, is about an hour weeks per meter seal oil consumption 0.1-0.3kg. Between the former three seals also need to grease, the last two oil seals for circulation lubrication between the application, or at least a 0.5m high level of oil bath lubrication. Because seals have a certain "pumping" ability, oil bath lubrication oil to be added in time.

TBM back pressure seal, the seal lip opening pressure of about 0.1-0.2 bar (1bar = 0.1MPa), the main bearings, oil (fat) pressure should not exceed 0.1 bar. If more than 0.1 bar, to be the final seal this road towards the turn towards the direction of the main bearings.

TBM seals installed, you need to axial compression. According to experience, required weeks per mm axial compression force of about 14N.