Dynamically-monitored double valve with anti-tiedown feature

摘要

A double valve is reset when a source of pressurized fluid is connected to a reset port. When the source of pressurized fluid is removed from the reset port, a first reset piston is retracted so that a second pilot chamber receives pressurized fluid while a first pilot chamber continues to be vented. A second reset piston is retracted after a predetermined delay time following retraction of the first reset piston, the predetermined delay time being sufficient to allow the second pilot chamber to become substantially pressurized. If a second pilot valve is actuated when the second reset piston is retracted, then the pressurized fluid in the second pilot chamber drives the second movable valve unit out of a deactuated position during a time that pressurized fluid in the first pilot chamber is insufficient to drive the first movable valve unit out of a deactuated position.