Simultaneousness within wide movements – Fabric Expansion Joints

Negative pressure

A multilayer fabric expansion joint can absorb the movements of ducts, thanks to the amount of material which is considered in the design phase.

There is a well-defined link among movements, length of installation and construction length. Therefore, it is clear that the more extensive the movements are, the greater the amount of material that must be used, especially in the presence of elongation movements.

In case of negative pressure where large movements are foreseen or along the three reference axes (axial, vertical, lateral) – it might happen that the expansion joint, sucked inward, interferes with the metal parts (in particular the baffle), thereby causing:

  • possible internal lacerations caused by contact with sharp objects;
  • transmission of the baffle surface temperature by conduction on the inner wall of the expansion joint.

Furthermore, in an external concavity, without adequate external protection, debris, rain water, etc.

The installation of a Isolmat bolster bag, inside the expansion joint, provides a valid support that avoids the above mentioned phenomena.