FORCE ACTUATED CONTROL VALVE

摘要

The disclosed embodiments include a force actuated modulating control valve such as a direct acting solenoid valve or pilot actuated bellows valve with a knife edge seat so that the metering location on the seat is at the very outer diameter. In one embodiment, a portion of the valve seat outside of the metering edge is removed to substantially the outside diameter to reduce contact with high velocity fluid flow. In certain embodiments, a flow shield may be positioned just outside of the metering edge of the seat to prevent the high velocity fluid from circulating toward parts of the spool assembly. In some embodiments, the flow shield may be fixed to the body of the instrument so all fluid forces are transmitted to the body. Embodiments of the force actuated modulating control valve may be employed in a mass flow controller for controlling fluid flow.