Diaphragm seal

The flexible nature of this seal allows pressure effects to cross the barrier but not the material being contained.

Since diaphragm seals need to be highly flexible, elastomers are commonly used, and include a wide variety of both general purpose and speciality rubbers.

Elastomers are limited to low pressure applications and those that are chemically compatible with the various plastics and rubbers used.

Metal diaphragms of stainless steel (several grades), Carpenter 20, Hastelloy, Monel, Inconel, tantalum, titanium and several other metals are in common use where high pressure ratings and specific chemical compatibility are required.

Depending on the PSI levels of the sealing application, the diaphragm may require fabric reinforcement.

An example of a diaphragm seal (in green) used to protect a pressure sensor.
Environmental scanning electron microscope image of ozone cracks in NBR diaphragm seal formed at sharp corners in seal