Abstract: A purge valve for expelling liquid contaminants from a fluid conduit which is normally unpressurized but is at times pressurized with a gas which contains liquid contaminants. It has a housing, a diaphragm mounted within the housing, a control chamber on a first side of the diaphragm, an exhaust passage on a second side of the diaphragm and a valve seat surrounding the exhaust passage. The valve seat is positioned so that the diaphragm can seal against it. A spring on the second side of the diaphragm presses it away from the seat. An annular chamber is on the second side of the diaphragm, surrounding the exhaust passage. The annular chamber is open to the exhaust passage when the diaphragm is unseated from the valve seat. The valve has a low impedance flow path between the control chamber and the fluid conduit. The valve also has a high impedance discharge flow path connected to the annular chamber.

Abstract: The invention is a valve for expelling a liquid contaminant from a gas in a conduit. It is used for a conduit with a pressure subject to variations in time. The valve has a housing containing a diaphragm with a control chamber on one side of the diaphragm and an exhaust passage on the other side. A valve seat surrounds the exhaust passage. A spring presses the diaphragm against the valve seat so that the valve is normally closed and an annular chamber surrounds the exhaust passage. A low impedance discharge passage is connected to the annular chamber and to the conduit. A high impedance control passage is connected to the control chamber and is either connected to the discharge passage or to the conduit. When the conduit pressure remains constant in time, the pressure in the control chamber equilibrates with it so that a net pressure force on the diaphragm plus the spring force presses the diaphragm against the valve seat so that the valve is closed.