Diaphragm seal

Typically connected to a pressure gauge, process transmitter, or pressure switch, a diaphragm seal is a thin, flexible wall that separates the media being measured from the pressure measuring instrument. The space between the diaphragm and the measuring instrument is filled with a system fluid (transmitting fluid), which hydraulically transmits pressure from the flexible diaphragm. The contact surface between the media and the diaphragm is relatively large, which ensures more accurate pressure measurements – especially for very low pressures (< 600 mbar).

Diaphragm seals are also known as Isolation diaphragms or isolating diaphragm seals.

The purpose of a diaphragm seal is to isolate a pressure measuring instrument from the process media. It is often used for the most difficult measuring tasks, such as when the environment is extremely hot or cold, or when a process connection is difficult to attach to the measuring instrument. Diaphragm seals are also used when the media being measured is corrosive, viscous, sticky, or easily solidified, or when the process isn’t chemically compatible with the instrument material.

Diaphragm seals are often made from materials with different corrosion properties such as Stainless Steel 316L, Hastelloy C276, Duplex, Titanium, Tantalum or Monel, expanding the media compatibility of a product.