Excess flow valve devices, which are responsive to pressure and flow conditions in a bi-directional system, including structures to restrict flow in one direction through openings of a stopper of an excess flow valve based on balancing forces from at least a spring and a frictional force caused by the flow. Bi-directional system employing at least one pressure delayer responsive to pressure and flow impulses to protect a tank valve of a storage tank or a regulator during a refill phase or a discharge phase.