CV Correction Factor Formulas For HVAC Control Valves

Опубликовано: 08 Февраль 2026
на канале: AAA Mechanical Contractors Inc.

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More than 2 pipe sizes then base valve CV off the Piping Correction Formula:
Corrected CV:
Cvc = Corrected Valve Coefficient because of the reducers hooked to the valve. This matters more with high-capacity valves (standard ball valves and butterfly valves). Characterized Control Ball Valves and Globe valves are affected less by FP = Pipe Correction Factor (Piping Geometry Factor).

FP= [1+ (∑K)/890 (C_V/d^2 )^2 ]^(-.5)

FP= 1/√(1+[[1.5(1-d^2/D^2 )^2 ][(C_V/d^2 )^2 ]/890] )

The formula for corrected Cv is Fp x Cv = Cvc.
Cv = Valve Coefficient of flow which is what is the flow with a 1 psi drop across the valve.
Cvc = Corrected Valve Coefficient because of the reducers hooked to the valve.

Variables:
Cv = Valve Coefficient of flow which is what is the flow with a 1 psi drop across the valve.
d = Valve Diameter
D = Pipe Diameter
∑K = sum of fittings factors

Example:
Pipe Size = 6” D
Valve Size = 1.5” d
The 1.5” has a 28 CV.
FP= [1+ (∑K)/890 (C_V/d^2 )^2 ]^(-.5)

Step 1: ∑K=[1.5(1-d^2/D^2 )^2 ]

Step 2: ∑K=[1.5(1-〖1.5〗^2/6^2 )^2 ]

Step 3: ∑K=[1.5(1-(2.25)/36)^2 ]

Step 4: ∑K=[1.5(1-0.0625)^2 ]

Step 5: ∑K=[1.5(0.9375)^2 ]

Step 6: ∑K=[1.5 x .87890625]

Step 7: ∑K=1.318359375

FP= [1+ (∑K)/890 (C_V/d^2 )^2 ]^(-.5)

Step 8: FP= [1+ (1.318359375)/890 (28/〖1.5〗^2 )^2 ]^(-.5)

Step 9: FP= [1+ (1.318359375)/890 (28/(2.25))^2 ]^(-.5)

Step 10: FP= [1+ 0.00148130266853932584269662921348(12.4444444444444444)^2 ]^(-.5)

Step 11: FP= [1+ 0.00148130266853932584269662921348 x 154.86]^(-.5)

Step 12: FP= [1.22939453125]^(-.5)

Step 13: FP= 0.90189164052975176554437307994671

FP= 1/√(1+[[1.5(1-d^2/D^2 )^2 ][(C_V/d^2 )^2 ]/890] )
Variables:
Cv = Valve Coefficient of flow which is what is the flow with a 1 psi drop across the valve.
FP = Pipe Correction Factor (Piping Geometry Factor)
d = Valve Diameter
D = Pipe Diameter

Example:
Pipe Size = 6” D
Valve Size = 1.5” d
The 1.5” has a 28 CV.

Step 1:
FP= 1/√(1+[[1.5(1-〖1.5〗^2/6^2 )^2 ][(28/〖1.5〗^2 )^2 ]/890] )
Step 2:
FP= 1/√(1+[[1.5(1-(2.25)/36)^2 ][(28/(2.25))^2 ]/890] )
Step 3:
FP= 1/√(1+[[1.5(1-0.0625)^2 ][(12.44)^2 ]/890] )

Step 4:
FP= 1/√(1+[[1.5(0.9375)^2 ][154.86]/890] )
Step 5:
FP= 1/√(1+[[1.50 x .87890625][154.86]/890] )
Step 6:
FP= 1/√(1+[[1.318359375][154.86]/890] )
Step 7:
FP= 1/√(1+[(204.1611328125)/890] )
Step 8:
FP= 1/√(1+0.22939453125)
Step 9:
FP= 1/√(1.22939453125)
Step 10:
FP= 1/(1.10878)
Step 11: FP= 0.90189164052975176554437307994671