Abstract: A typical flow-control valve has a housing forming a flow passage and a valve seat. An upstream and downstream valve bodies are is engageable with the seat and form upstream and downstream restrictions. A control piston defines therein outer and inner control compartments. This control piston is coupled to the downstream valve body for joint movement therewith. High-pressure and low-pressure conduits connect the outer and inner control compartments to the flow passage upstream of the upstream restriction and to the flow passage between the upstream and downstream restrictions. A connector element or stem connected to the upstream valve body extends through the control piston and has an outer end projecting out of the housing. A pressure reliever between the control piston and the outer end exerts on the connector element a force urging the upstream valve body upstream and generally equal to a pressure differential across the upstream restriction.