Valve Sizing With Cv = 1 Table
This method can be used if the required air flow is known or has been calculated with the formulas as shown below:
Air Flow Q (SCFM) for Cv = 1
Example 2: Find Cv if air flow Q (SCFM) is given.
low through valve from Table 28 for Cv = 1:30 SCFM
Cv = Air Flow Q (SCFM)
Air Flow at Cv = 1 (SCFM)
Cv = 60 SCFM
30 = 2.0
A valve with a Cv of minimum 2 should be selected.
Example 3: Find Cv if air flow Q (SCFM) to atmosphere is given.
Primary Pressure P1 = 90 PSIG
Air Flow to atmosphere Q = 100 SCFM
Flow to atmosphere through valve from Table 28 for Cv = 1:51 SCFM
Cv = Air Flow to atmosphere Q (SCFM)
Air Flow to Atmosphere at Cv = 1 (SCFM)
Cv = 100
Flow given is equivalent to valve with Cv = 2. This conversion is often necessary to size a valve properly, since some manufacturers do not show the standard Cv to allow a comparison.