Abstract

A flow limit valve for limiting the flow rate of a pressurized fluid includes a valve body with an interconnecting cavity of circular cross section. Within the cavity if a piston that slides within the cavity under force generated by a pressure differential across the piston to a closed position which prevents fluid flow through the valve. A pin is provided that is attached to the piston and that protrudes through the piston seat into the outlet side of the cavity when the piston is at the closed position. Opposite the pin is an encapsulated magnet within the valve body that can be moved in response to another magnet outside the valve body to contact the pin attached to the piston to move it to the open position. The magnetic forces applied through the valve body affect internal valve operation via the pin attached to the piston and this avoids the danger of noxious fluids escaping through sliding seals or flexible membranes.