Equations for control valve flow in SI units

The historical dominance of US valve manufacturers has led to valve characteristics often being given in standard US units (US gallons, standard cubic feet per hour, etc.). A particularly important influence because of its extensive research into and testing of control valves was the Fisher Controls Company of Marshalltown, Iowa (now part of Fisher-Rosemount Ltd.) This appendix converts the basic liquid-flow equation from US to SI units. The appendix then goes on to derive Fisher s Universal Gas-Sizing Equation ( FUGSE ) from the basic liquid-flow equation and shows how this may be converted into SI units. 

Some of the important variables in the text to follow will be superscripted with an asterisk when given in US units in order to differentiate them from the equivalent or related variables given in standard SI units. 

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Appendix 3 Equations for control valve flow in SI units... 

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