A diaphragm seal is a flexible membrane that seals and isolates an enclosure. The flexible nature of this seal allows pressure effects to cross the barrier but not the material being contained.
Common uses for diaphragm seals are to protect pressure sensors from the fluid whose pressure is being measured.
Diaphragm seals (also known as chemical seals) are also used to protect a process fluid from the pressure sensor. Examples of this use are:
- Sanitary processes (food, pharmaceuticals, etc.) where allowing process fluid to accumulate in the pressure port of the sensor would compromise the purity of the fluid (such as milk getting into the pressure port of a pressure gauge and spoiling)
- Very pure process fluids, where the metal surface of the pressure sensor might contaminate the fluid (such as copper ions from brass leaching into ultra pure water.)
- Pneumatic systems where small changes in pressures must be eliminated, such as those controlling air bearings.