Result

These use simplified, widely-taught sizing equations — liquid Cv = Q·√(SG/ΔP), and standard compressible-flow forms for gas and saturated steam — and are intended for preliminary sizing and study. The choked-flow check uses a simplified critical pressure-drop ratio near 0.5; real valves have a manufacturer-specific pressure-recovery factor that shifts this point, and liquids can flash or cavitate before it. Suggested valve sizes come from typical Cv ranges, not any specific product, and a good rule of thumb is that the required Cv should fall around 60–80% of the valve's rated Cv so the valve controls in a stable part of its travel. Always confirm the final selection against the manufacturer's actual Cv and characteristic data, including their FL, xT and viscosity corrections.