Passive valve

A passive in-line valve configured to be actuated without an external control, comprising:

• a valve housing defining an inlet, an outlet, and a flow path between the inlet and the outlet;
• a piston housing extending inwardly from the housing;
• a valve piston movably disposed within the piston housing, the valve piston including an upstream side and a downstream side, wherein the valve piston is configured to define an upstream cavity between the piston housing and the upstream side of the valve piston and wherein the downstream side is in fluid communication with outlet static pressure, wherein the valve piston is configured to move between an open position where fluid can flow from the inlet, through the flow path, to the outlet, and a closed position where the valve piston prevents flow from the inlet to the outlet,
• a control mechanism disposed at least partially within the housing and configured to port outlet static pressure to the upstream cavity in a first state such that pressure is equalized on the valve piston, wherein the control mechanism is configured to port inlet pressure to the upstream cavity in a second state such that a differential pressure on the valve piston acts on the valve piston, wherein the control mechanism is configured to transition from the first state to the second state at a first threshold valve delta pressure, wherein the control mechanism is configured to transition from the second state to the first state at a second threshold valve delta pressure.