Tail seal greases for TBM

Tail seal greases
CONDAT, world leader in sealants for TBM tail seals.



Protection of the wire brushes and tightness of the tail seal are essential in tunnel excavation. Tail sealants, thanks to their composition, are viscous, resistant to wash-out, and adhere to any damp surface.

Pumped continuously as the tunnel boring machine advances, CONDAT sealing compounds for tail seals allow for good filling of the interbrush chambers to:

  • act as a barrier to water, mortar, and soil fines
  • offer controlled consumption

Brushes protected in this way by sealants are more flexible and more durable.
The sealants are injected in 2 stages:

  • at the start-up phase
  • as the tunnel boring machine advances

1st filling

Before starting to bore, it is imperative that a first filling of the brushes should be carried out.mastic-joint-queue-tunnelier

The first-filling sealant WR 90 New Generation must be injected deep into the brushes until reflux on brush surfaces. All the brushes must be prepared in this way to ensure an uninterrupted sealing of the tail brushes . The consistency and adherence of the first-filling sealant ensures protection during the entire lifetime of the brushes.


As the TBM advances, a so-called "operating" sealant is continuously pumped between the rows of brushes to perfect the sealing of the tail joint. This ensures that the chambers are properly filled, extends the service life of the brushes and is perfectly compatible with the WR 90 New Generation. Its performance guarantees good containment and therefore optimum safety for operators and equipment.

Depending on the type of geology crossed, CONDAT offers you a complete range of tail sealants that will provide you with optimum TBM protection at the best possible cost.

Product benefits

CONDAT tail sealants have the following advantages:

  • Minimal environmental impact
  • Eco-responsible range
  • Resistance to ignition and self-extinguishing for greater safety
  • Wash-out resistance
  • Resistance to all types of mortar
  • Compatible with emergency sealants
  • Controlled consumption
  • Homogeneous filling of chambers
  • Maintains containment → reduces the risk of subsidence
  • Approved by TBM manufacturers


In the event of heavy pressure compressing and deforming the brushes, a WRS emergency sealant can be used to counter the ingress of water, mortar and soil fines.

This emergency sealant is injected in place of conventional sealant, using the same pump, pipes and injection points. By reacting with the water, the emergency mastic seals off the water inlets to form a watertight barrier.

To continue boring in critical conditions, WR 21 can be injected after WRS.


Associated services

For more information about the products, their implementation, and a good match between the situation encountered and the solution to be considered, contact a CONDAT representative.