The Kv-value is a measure of the flow rate through a valve for a given medium and pressure drop. The larger this value, the higher the flow rate through the valve will be at a given pressure drop. Usually, the Kv-value is given in the product description or datasheet. It provides a more accurate indication than for example the pipe connection size or orifice diameter. The Kv-value is measured as the flow rate of water in m3/h with a pressure drop of 1 bar at 20°C.
If the medium characteristics, the pressure drop and the desired flow rate are known, the minimal required Kv-value for the valve can be calculated. Different formulas apply for fluids and gases.
Fill a value for the inlet pressure, the outlet pressure and the minimal required flow rate. Click calculate and the Kv and Cv value will be calculated. Choose a valve with a Kv-value equal or higher than the calculated value.
Choose a gas type and the inlet temperature. Choose the inlet pressure, the outlet pressure, the required flow rate and click calculate. Choose a valve with an equal or higher Kv-value to achieve the desired flow rate. The N in the flow rate stands for normal conditions (atmospheric pressure and 0 degrees Celsius).
QN= Normal Flow rate [m3/hour]
Kv = Hydraulic factor
T = Inlet gas temperature [K]
p1 = Inlet Pressure [bar]
p2 = Outlet Pressure [bar]
dp = Pressure differential [bar]
SG = Specific Gravity (Air = 1)