Diaphragm seal pressure transmitters

What is Diaphragm seal?

Diaphragm seals are also referred to as chemical seals. It is a flexible material that separates the process fluid or material from intering the measuring instrument and also transfer the fluid pressure to the meter without contact.

Why to use a seal?

High pressure, the High temperature can affect the meter gauge directly, Also fluid entering the meter gauge can cause corrosion in it.

Seals are widely used in the pharmaceutical and food industries, where highly viscous fluid can get trapped in the meter seals.


The measuring gauge or meters are separated from process fluid using a diaphragm as shown at the bottom of the above picture.

The internal space between this diaphragm and the pressure measuring instrument is completely filled with a system fill fluid. This system could transfer the mechanical pressure of diaphragm to the measuring elements of the gauge.

The process pressure is get transmitted to the diaphragm and into the process fluid and from there to the measuring element. Diaphragm seal, capillary and measuring instrument form a closed system. The sealed fling screws on the diaphragm seal and the measuring instrument must therefore never be opened, since the function of the system is affected following any escape of filling liquid.

The diaphragnm material should meet the requirements in pressure withstand, corrosion, Temperature.


  • For the process fluid is corrosive

  • For the medium is highly viscous and fibrous, thus causing measuring problems due to dead spaces.

  • The medium which has the tendency for crystallisation

  • For very high-temperature medium

  • For the process fluid is toxic.