Excess Flow Valves are normally open valves that close automatically at a predetermined flow rate. Models are designed to operate in the lower flow ranges, i.e. 120 SCFM air, 20 GPM water or less. In this auto reset model, after actuation, the piston rests on a metal to metal seat which allows a controlled bleed. To reset the unit, pressure must be equalized on both sides of the piston. If the source is turned off, either upstream or downstream, the bleed will equalize the pressure and the valve will automatically reopen by magnetic repulsion from the fixed magnet located in the valve body. Datasheet