A typical Choke Valve Design Specification should include but is not limited to;
Mechanical Requirements
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Body - Inlet and Outlet size and ratings, body type (eg., angle), Rated Pressure and Temperature, Standard (eg., API 6A), Materials, NACE Requirements, Bonnet requirements.
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Trim - Size, Design, Flow Direction, Material for trim, stem, plug and seals, Leakage class, Maximum allowable noise.
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Actuator - Type, Air/Hydraulic, Operating medium pressures, Failure Mode, Actuator torque, Orientation, Stroke and Stroking Time and Limit stops.
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Positioner - Positioner type (eg., Pneumatic, Hydraulic, Electric), - Input signal, Output Pressure, Tube fittings, Material and Cable Entry.
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Accessories - Handwheel, Limit Switches, Pressure Trip Valve, Position Indicator, Filter Regulator, Volume Tank.
Process Data -
Gas and Liquid Flow Rates (Including initial start up, Max flow for the life of the well), Production Profile over the life of the well, Wellsteam Composition, Fluid Type (eg., Natural Gas, Crude Oil, Condensate), Water, Fluid State (eg., oil), Compressibility. Design Pressure, Pressure Inlet and Outlet, Pressure Drop, Liquid Density, Design Temperature, SG, Vapour Pressure, Critical Pressure, Molecular Weight, Specific Heat Ratio, H2S content, Sand content and Actuator Sizing Differential Pressure. When selected the vendor should be requested to advise the Calculated Cv of the valve, percentage opening for the Cv selected for the Flow rates specified and predicted noise of the valve.