I am designing a 1", quarter-turn ball control valve and in need of some overall guidance.The inlet and outlet seat trims are modified with a pattern of holes intended to help reduce flow. The valve is required to pass water at a flow rate of 19 gpm, with inlet pressures ranging from 750 psig to 350 psig, while maintaining an outlet pressure of at least 150 psig. Plugging this data into Cv = q (SG / dp)1/2, tells me that my valve must have a Cv ranging from .77 to 1.34. My unknown is obviously pressure drop, as unless a prototype is produced and tested, the resultant p.out from the inlet pressure range is unknown. How do I go about determining what the pressure drop will be at differing degrees of valve travel without a flow test/ CFD software? I have been studying ANSI/ISA-75.01.01 and it seems as if these equations are geared towards globe and butterfly valves.The inlet of the valve is 1" in diameter. The seat trim pieces have a pattern of various diameter holes, so when the valve is cycled and the ball is turned to a certain position, only certain diameter holes are exposed to flow.If a flow rate of 19 gpm is fed into the 1" inlet bore, that flow rate will remain constant as it enters and exits the smaller holes in the seat trim, granted the upstream pressure is enough to maintain it, correct? The velocity of the fluid as it goes through those holes will have to increase, however, from what it is traveling at through the 1" bore.

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