What is Critical Flow Factor (Cf)?

Critical Flow Factor (Cf)

A coefficient that defines how the pressure will recover after it drops to its lowest point (the vena contracta) inside the valve.  Each valve has one Cf, and it doesn’t change due to % open, like the Cv does.  Cf is a factor that is needed in order to calculate Cv or Flow Rate for valve sizing purposes.  The Cf  for each Kimray valve can be found on its detail page or on the Sizing Page in the Valve Coefficients dropdown.  The Critical Flow Factor is also referred to as the Pressure Recovery Factor (FL).  Below is an illustration of how Cf is determined.