Manufacturers may specified the coefficient cv instead of kv for their valve. The use of the flow coefficient offers a standard method of comparing valve capacities and sizing valves for specific applications that is widely accepted by industry.
In more practical terms the flow coefficient c v is the volume in us gallons of water at 60 f that will flow per minute through a valve with a pressure drop of 1 psi across the valve.
Cv value for valves definition. It is actually possible to convert kv and cv and have the expression in the right unit for the calculation of interest. Such as the renault number reynolds number flow rate flow the shock choking the involved joints in pipes fitting and the other by the values of these. The flow coefficient for a control valve which in full open position passes 25 gallons per minute of water with a one pound per square inch pressure drop can be calculated as.
The metric equivalent of cv is kv which is defined as the amount of water that will flow in m3 hr with 1bar pressure drop. It is defined as the flow rate in cubic meters per hour m3 h of water at a temperature of 16º celsius with a pressure drop across the valve of 1 bar. Gallons per minute of water at 60 f that will flow through a control valve at a specified opening when a pressure differential of 1psi is applied across the valve.
Cv is the number of us gallons that goes through the valve at 60f and with a pressure drop of 1 psi. The valve coefficient cv is a number which represents the capability of a valve or any flow component to flow a fluid. The definition of cv is the number of gpm gallons per minute that will pass through the control valve with a pressure drop of 1psi.
Cv flow coefficients of ball valve the coefficient of flow or c v value is the number of us gallons of water the valve will pass with a differential pressure of 1psi through the valve at 60f. By definition a cv value of one is the cv required to. Control valve cv refers to the flow coefficient of the valve.
In deciding the size of the control valve that port size we need to calculate the cv value of the process calculated cv by calculating cv has educated more than 50 years which is involved in. Cv 25 gpm 1 1 psi 1 2. Kv is the flow coefficient in metric units.
It applies to the factor of the head drop δh or pressure drop δp over a valve with the flow rate q. Flow one gallon per minute gpm of water at 60 f with a pressure differential of one psi. Cv is the flow coefficient in imperial units.
The larger the cv the larger the flow at a given pressure differential. K v is the metric value of c v and is calculated as k v c v x 0 85. The valve flow coefficient cv is the number of u s.