What is the Kv, Cv and Qn Value?

What is the Kv Value?

Kv value is the metric measure for the flow of a valve. It is defined as: The volume flow in cubic metres per hour of water at a temperature of between 5° and 40° Celsius with a pressure drop across the valve of 1 bar.

What is the Cv Value?

Cv is the imperial measure for the flow of a valve. It is defined as: The volume flow in US gallons per minute of water at a temperature of 60° Fahrenheit with a pressure drop across the valve of 1 psi. For example, a Cv of 150 would then equate to 150 gpm of water at 60°F with a differential pressure of one psi.

What is the Qn Value?

Qn value is used in pneumatics to define the flow of a valve. It is defined as: The volume flow in litres per minute of air at a temperature of 20° Celsius, with an input pressure of 6 bar and a pressure drop across the valve of 1 bar.

Conversion : Kv, Cv & Qn

Kv = 0.86 × Cv
Kv = Qn / 1078
Cv = Kv / 0.86
Cv = Qn × 0.0008
Qn = Kv × 1078
Qn = Cv / 0.0008


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