Precise Flow · Calibration · Test Equipment

Critical venturi nozzles according to DIN EN ISO 9300

Venturi nozzles, also called Laval nozzles, have a flow-optimised inlet radius and outlet cone. In this way these nozzles have a low pressure drop and a very good pressure regain. Venturi nozzles with throat diameters larger than 1 mm can be critically operated with a differential pressure between inlet and outlet of 120 up to 200 mbar.


Flows of air or gases can be adjusted with very high stability by critical nozzles. Therefore, they are perfect for the calibration of all kind of mass flow and volume flow measuring devices for air and gases, as, e.g., gas meters, LFEs, mass flow meters and all other kind of flow meters.

Venturi nozzles
Venturi nozzles

Product features include:

  • Nozzle throat diameter d of 170 μm up to 100 mm
  • Inlet radius 2 x d, outlet cone 8° full angle
  • Inlet diameters of DN 15 up to DN 400
  • Connection by adapters or flanges
  • Suction or overpressure operation
  • Short response time and high accuracy
  • Very good long-time stability, no moving parts

Calibrating options

  • Type: Calibration in pressure and suction operation
  • Medium: air or pure gases
  • Certificate: factory, DAkkS-DKD- or PTB calibration

Operating instructions

Suction operation is the preferred operation mode for these nozzles, since the atmospheric density is very constant at the inlet. For pressure operation a very stable pressure control should be used. Optimally free and undisturbed incoming flow is observed at high-capacity conditions at the inlet section of the nozzle: No barrier gets closer to the nozzle axis and the inlet level than 5 times the nozzle diameter.

Venturi nozzles
of the series SNZ

for critical operation

More information and technical details can be
found in the data sheet

Additional information
on this subject:


Flow calibration

Flow element software

To our contact page