Valves with a "Full Port" have an internal seat diameter that is the same as the nominal pipe size, i.e. a 1 inch pipe size valve with a full port has a 1 inch diameter seat. Valves with a "Reduced Port" have an internal seat diameter that is smaller than the nominal pipe size.
The valve's flow coefficient, Cv, is a value that is determined by flow testing for each valve size. Full port valves will have a higher Cv than reduced port valves. The Cv rating for each valve is listed in the tables found in the valve catalog.
The definition of Cv is the # of gallons of water that will flow through the valve with a 1 PSI pressure differential when the valve is open.
The equations below can be used to determine:
Cv = Valve's flow coefficient (dimensionless value)
S = Specific Gravity (1.0 for air or water)
T = Absolute Temperature in °R (°R = °F + 460)
ΔP = Pressure Differential in PSI across valve in the open position
V = Specific Volume in Cubic Feet per Pound
The CV factor is the number of U.S. gallons per minute that will pass through a valve with a pressure drop of (1) PSI.
|Port Size in Inches||3/32"||1/8"||5/32"||3/16"||1/4"||5/16"||3/8"||1/2"||3/4"||1"||1-1/4"||1-1/2"||2"||2-21/2"||3"|