When used in flow systems, cavitating venturis limit max flow of fluids regardless of downstream pressure. These are passive devices that operate in a non cavitating mode until their design (cavitating) point (inlet pressure and flow) is reached. Cavitation occurs when the absolute pressure of the fluid equals its vapor pressure. The cavitation (formation of bubbles) restricts any increase in flow.
Cavitating venturis can be used to limit flow as a result of a design basis accident (guillotine break) or as an alternative to an active control loop to control flow for a bypass or recirculation line. They have historically been used in the Chemical and Volume Control System and Auxiliary Feed Water systems. Lacking any moving parts, our venturis require no maintenance whatsoever.