Cv varies with position based on the trim characteristics. For example, a butterfly valve will have poor control at 10% open compared to a cage guided globe with anti-cav trim at 10% open. The full open Cv will also vary greatly between valve styles. Globe valve are available with...
I have supplied isolation valves for brackish sea water applications in a variety of different materials with a mixture of success. The best material, disregarding cost, has been Titanium. These were metal seated butterfly valves for bi-directional Class VI shutoff. I think the best material...