WIKA In-line Diaphragm Seal with Sterile Connection (981.18, 981.19, 981.20, 981.21)

With union nut (milk thread fitting)


  • Gases, compressed air, vapour; liquid, pasty, crystallising and flowing media
  • Food and beverage production
  • Dairies and dairy products
  • Breweries, filling systems
  • Filtration, separation, pasteurisation

Special Features

  • For direct, quickly removable installation in pipelines
  • Self-draining in all mounting positions
  • Quick cleaning, without residue
  • Suitable for COP, SIP and CIP
  • Dead-space free installation in pipes

Sales Contact (Wika.sales@asyatrafo.com)




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 is 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”.

Due to their hygienic process connection, the model 981.18, 981.19, 981.20 and 981.21 diaphragm seals are particularly well suited for food production. The diaphragm seals 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.

Mounting of the diaphragm seal to the measuring instrument may be made via a direct connection, for high temperatures via a cooling element or via a flexible capillary.

The availability of the diaphragm seals for common pipe standards and nominal widths simplifies integration into already existing pipe cross-sections.