A pressure regulator has a pressure chamber connected to an inlet flow area which receives liquid flow. As liquid flows into a forward chamber of the pressure chamber, pressure is exerted on the forward face of the piston, which in turn causes the piston to slide longitudinally through the pressure chamber. A bypass fluidically connects the forward pressure chamber and rear pressure chamber such that as the piston slides into the rear pressure chamber pressure increases at the rear pressure chamber, which in turn forces the piston to move forwardly, thus regulating flow out of the pressure chamber. A hand wheel is configured to turn a movable plate located inside the pressure chamber, with the movable plate configured to impede the piston from moving rearwardly. Pressure sensors and vents with a pressurized air source may be used to keep the pressure within a desired range.

A fluid regulating device includes a regulator valve having an inlet, an outlet, and a valve port disposed between the inlet and the outlet. An actuator is coupled to the regulator valve and includes a valve disc that displaces between a closed position and an open position. The device also includes an overpressure protection device adapted to stop flow from the inlet to the outlet when pressure in a control cavity reaches a predetermined level. The overpressure protection device includes a sensing tube having a first end in fluid communication with the control cavity and a second end in fluid communication with the outlet. The sensing tube has a first portion extending parallel to the flow axis. One or more apertures are disposed in the sensing tube adjacent to the second end, and each of the apertures has a centerline that is perpendicular to the flow axis.