Chemline Exner characterized control valves provide precise flow control of aggressive fluids. The valves’ flow characteristics follow theoretical linear or equal percentage curves through the entire range of stem travel. This is accomplished with precision made replaceable seats and plugs in a wide variety of Cv values. These valves have Teflon® bellows shaft seals which provide almost frictionless stem movement and provide over 10 years of maintenance-free operation on aggressive chemical services. They also respond smoothly and quickly to small changes in signal and deadband and hysteresis is negligible.