Below are some definitions and conversion factors for the three valve flow coefficients Kv, Cv and Qn.
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.
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.
Converting between Kv, Cv & Qn
Kv = 0.86 x Cv
Kv = Qn / 1078
Cv = Kv / 0.86
Cv = Qn x 0.0008
Qn = Kv x 1078
Qn = Cv / 0.0008
'We're a building company and don't normally get involved in pneumatics but I found the PVC tubing quickly on the web and the Airlines-Pneumatics site clearly showed the specification that we needed. I'm a Layman when it comes this type of product and dealing with Airlines-Pneumatics was absolutely fantastic.'
John Lee, Moorcroft Construction Ltd, Ellesmere Port
Security & Payment Options
Your online payment will be handled by SecureTrading, the leading independent internet payment processor in the UK.
Credit card details are entered on a secure page (https secure padlock). They are fully encrypted using the most sophisticated e-payment software and also incorporate Verified by Visa & MasterCard SecureCode to ensure that your payment is secure.