Systems for Filling a Gas Cylinder

A flow control valve includes a housing defining a cavity therein. The housing has an input port for receiving a gas from a gas supply, and an output port for delivering the gas to a gas cylinder. The cavity defines a staging area fluidly connected to the input port, a delivery area fluidly connected to the output port, and a pressurization area fluidly connected to a feedback sensing port. The feedback sensing port is configured to receive pressurized fluid that is pressurized to a pressure level representative of a pressure level of gas delivered to the gas cylinder. The flow control valve includes a piston slidably positioned in a channel extending between the pressurization area and the delivery area. The position of the piston changes a rate of flow of gas through the flow control valve. The piston position moves in response to a pressure at the feedback sensing port.