Flow limiting valve

[MEPumpMan]

Does anyone know if there exists a valve that allows unrestricted flow up to a given flow rate but restricts any flows that would exceed that given flow rate? For example, I would like to allow free flow into my system at flow rates of 0-6gpm with little or no pressure drop, but in the event of a sudden pressure drop in my system I don't want to allow more than 6gpm to enter my system.

Does this valve exist?

Thanks!

 

[JLSeagull]

You are looking for an excess flow valve. I have seen these for piping from a storage tank and small tubing for carrier and calibration gas entering an analyzer shelter. I think that models can be selected to trip the flow at about three times the normal flow.

 

[SteveWag]

These valves will allow flow up to a specified rate and then no more;

http://www.plastomatic.com/fc.html

the drawback is the 15 PSI or so pressure drop.

Steve