normally-open vacuum-actuated valve?

[Altairus]

I am looking for a small vacuum-accuated valve that will accept something close to 5/16" - 3/8" fittings. I will be using it to control the flow of compressed air with a maximum pressure of 75psi. Now here's the tricky part... I need the valve to fully close under approx 20 in. Hg of vacuum and fully open under no vacuum. Does such a thing exist? Any info is appreciated.

 

[btrueblood]

Build or purchase a pneumatic actuator with spring return, and set it up to respond the way you want. A small (about 3" or 4" diameter) cylinder should have enough force to open/close a 3/8" ball valve at 75 psi.