Diaphragm seals are used to protect the pressure measuring instrument from aggressive, adhesive, crystallising, corrosive, highly viscous, environmentally hazardous or toxic media. A diaphragm made of the appropriate material provides for the separation from the medium to be measured. Thus even the most difficult measuring requirements can be met by combining measuring instruments with diaphragm seals. A system filled fluid inside, which can be chosen to suit the particular application, hydraulically transmits the pressure to the measuring instrument. Almost limitless application possibilities exist due to the large number of available variants, such as diaphragm seal designs or materials. The type of process connection (flange, threaded and sterile connection) and the basic method of manufacture are important design differentiation criteria. For further technical information on diaphragm seals and diaphragm seal systems see IN 00.06 "Application, operating principle, designs".

The model L990.41 diaphragm seal with flange connection and internal diaphragm is ideally suited for applications with small process connections. Due to the internal diaphragm (large diaphragm diameter) low measuring ranges can be realised. When the temperature changes, the diaphragm counteracts the volume expansion of the system fill fluid, thus ensuring a lower deviation at the measuring instrument. Assembly of the diaphragm seal and measuring instrument is made via a direct assembly as standard or optionally via a cooling element or a flexible capillary. For the material selection WIKA offers a variety of solutions, in which the upper housing, the diaphragm and the lower housing can be made of identical or different materials. The diaphragm and the lower body can also be offered coated or covered with foils. Measuring systems with model L990.41 WIKA diaphragm seals are successfully used worldwide in the chemical process and petrochemical industries with high measuring requirements.