981.18 981.19 981.20 981.21 INLINE™ Diaphragm Seal with Sterile Connection

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.

The model L981.18 in-line diaphragm seals with threaded connections, due to their circular design, can be mounted directly into the pipeline, meaning no special measuring point connection is required. Through the integration into the process line, turbulences, dead spaces, corners and other obstructions can be avoided. For this diaphragm seal WIKA uses a completely round diaphragm, which, due to the unobstructed flow of the media, produces an automatic cleaning of the chamber.

The diaphragm seal systems can withstand the cleaning vapour temperatures occurring in the SIP processes and thus ensure a sterile connection between the medium to be measured and the diaphragm seal.

Special Features

  • Completely round diaphragm (Europ. Pat. No. 0609846) to avoid dead spaces
  • Self-draining in all mounting positions
  • Quick measuring point cleaning without residues
  • Suitable for SIP and CIP


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  • For direct, quickly removable installation in pipelines
  • For flowing, pure media
  • Food and beverage production
  • For dairies, dairy products, breweries, soft drink production

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. Even the most difficult measuring requirements can be met by combining measuring instruments with diaphragm seals.

A fluid inside the system that hydraulically transmits the pressure to the measuring instrument can be chsoen to suit the particular applicaiton.

Assembly of the diaphragm seal and measuring instrument is made via a direct assembly as standard. It can also be done optionally via a cooling element or a flexible capillary.

The main housing and the diaphragm are made of identical materials. Stainless steel 316L (1.4435) is used as standard material. Other special materials are available on request.