Diaphragm seals are used for the protection of pressure measuring instruments in applications with difficult media. In diaphragm seal systems, the diaphragm of the diaphragm seal effects the separation of the instrument and the medium.
The pressure is transmitted to the measuring instrument via the system fill fluid which is inside the diaphragm seal system. For the implementation of demanding customer applications, there are a wide variety of designs, materials and system fill fluids available. For further technical information on diaphragm seals and diaphragm seal systems see IN 00.06"Application, operating principle, designs".

The model 990.31 diaphragm seal with threaded connection in a plastic version is suitable for versatile application areas in the water supply and wastewater treatment industries. Mounting of the diaphragm seal to the measuring instrument may be made via a direct connection or a flexible capillary. The WIKA model 990.31 diaphragm seal is used successfully in chemical plant construction, electroplating and wastewater treatment applications.