Use of fluid valve assemblies in control of fluid valve assemblies, process valve positioners and process valves

摘要

Fluid valve assembly 60 includes a central bore 202 and a stem 203 that is moveable axially within the central bore and is actuated by an axial pilot force F_pil and an axial counter force F_sup . An internal supply pressure chamber 202E is provided to maintain a stabilized supply pressure that provides an axial counter force acting on the stem. A seal member 603 is arranged on the common axis with the stem between the inner supply pressure chamber and the outer supply pressure chamber connected to the supply pressure input line S. [ The metering edges PR3 and PS3 are arranged in common with the stem to control fluid flow from the externally supplied pressure chamber to the actuator chamber 202D. For a sudden pressure drop in the externally supplied pressure chamber, means 605 are provided for stabilizing the supply pressure of the inner chamber.