Sealing types
Tightness and mechanics- Notion of tightness and associated measures

Theoretically, the seal is no longer satisfactory if there is a leak, which translates into the flow of confined fluid from one side of the containment wall to the other under the action of a pressure or concentration difference on either side of the wall.

A leak can take one of two forms:

• material permeability: even at ordinary temperatures, certain materials can let fluid through through a succession of more or less complex absorption, diffusion and desorption phenomena; elastomers, for example, are relatively permeable materials, especially with certain gases, whereas...