Emerson Process Management has introduced the Fisher NotchFlo DST (dirty service trim) for its control valves. NotchFlo DST prevents 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 NotchFlo DST control valve trim features 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 shut-off and throttling locations prevent high-pressure drops from occurring at the trim seat at 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 Fisher NotchFlo DST control valve trim design allows control of liquids with entrained solids. Flow rangeability is 50:1. The NotchFlo DST control valve trim is pressure-balanced, which yields smoother operation and reduces actuator size requirements. The valve plug features a large-diameter stem for added rigidity against high-pressure conditions. NACE materials are available for corrosive applications. The new NotchFlo DST control valve trim is offered in globe and angle body styles.
