EMERSON Process Management has released one-inch, two-inch, three-inch and four-inch Class 600 globe-style bodies for the Fisher NotchFlo DST control valve. These bodies are available in carbon steel, chrome moly, and stainless steel. NACE materials are available for corrosive applications.
The NotchFlo DST control valve minimises the cavitation and clearance-flow problems typical in high-pressure liquid applications within the power generation industry, in oilfield production use, and in refinery recirculation and letdown services. The trim has a longitudinal flow path that incorporates a series of pressure staging notches. The notches achieve the required pressure drop while avoiding conditions that would cause cavitation and result in trim damage.
The pressure staging design and separation of shutoff and throttling locations prevent high pressure drops from occurring at the trim seat under low flow conditions. This avoids clearance flow erosion of the seat line, thereby extending the already long-term shutoff capability of the NotchFlo DST control valve trim. As an added benefit, the relatively large flow passageway through the NotchFlo DST control valve trim allows control of liquids with entrained solids. Flow range ability is 50:1.
The NotchFlo DST control valve trim is pressure-balanced, which yields smoother operation and reduces actuator size requirements. The valve plug has a large-diameter stem and added rigidity against high-pressure conditions.