Adjustable Area Venturi Valves

Fox Variable Sonic Chokes Adjustable Venturi Valves

For High-Precision Throttling and Adjustment of Liquid and Gas Flows Unaffected by Downstream Pressure


Fox Adjustable Area Venturi Valves are designed to provide high accuracy flow regulation, over a broad flow range, while maintaining critical flow (with gasses) or cavitation (with liquids). This means that with a fixed inlet pressure, the valve can be set to create a fixed, accurate flow rate that is unaffected by changes or fluctuations in downstream pressure.

Fox Venturi Valves have been used both in industrial research, for ground support test equipment, and qualified for flight hardware.

Sealing/Temperature Range

Fox Venturi Valves are used with fluids ranging from -300° F to 500° F. Spring loaded TFE seals are used for cryogenic fluids like LOx and LH2. Kalrez o-rings enable simple o-ring sealing up to 500° F.

Pressure Range

Standard valve bodies, in 300 series stainless, are supplied with AN ends and are rated up to 3000 psig.


The effective throat area (CdA) is directly related to needle position. Carefully machined surfaces on the knob enable quick, precise measurement of a calibration reference dimension. Calibration then relates this external dimension to flow rate, defining a highly repeatable flow characteristic.

Adjustable area venturi valves can be calibrated to ±1/2% traceable to NIST, establishing a CdA vs. valve position relationship. This data can then be used to predict flow of any fluid at any given inlet pressure. A less expensive calibration to ±2% is also available.