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.
The cv was designed for use with liquid flows it expresses the flow in gallons per minute of 60º f water with a pressure drop across the valve of 1 psi.
Valve cv formula gas. The formula will differ depending on the product the valve regulates such as liquid gas or steam. Control valve cv refers to the flow coefficient of the valve. Valve cv formula gas.
The coefficient of flow cv is a formula which is used to determine a valve s flows under various conditions and to select the correct valve for a flow application. Mathematically the flow coefficient c v or flow capacity rating of valve can be expressed as. It describes the relationship between the pressure drop across an orifice valve or other assembly and the corresponding flow rate.
Example flow coefficient liquid. Than 1 2 p1 use 1 3 p1 for p2 in formula. 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 volumetric flow rate of gas through a valve can be calculated from the valve cv thanks to the following formula. Find valve size and valve position of an unlined valve with flow at 200 gpm and an actual pressure drop of 5 psi for a liquid with a specific gravity of 1 8. The flow coefficient of a device is a relative measure of its efficiency at allowing fluid flow.
C v 25 gpm 1 1 psi 1 2 25 flow coefficient c v for saturated steam since steam and gases are compressible fluids the formula must be altered to accommodate changes in. It applies to the factor of the head drop δh or pressure drop δp over a valve with the flow rate q. Control valve cv formula for gas free tool for control valve cv calculation microsoft excel cv valve calculation 5 simple moves that can make a good cv calculation etrealap basics of control valve sizing key terms concepts magnatrol formulas control valve sizing dwyer instruments blog control valve sizing dwyer instruments blog.
Q is the rate of flow expressed in us gallons per minute. How do we get value 1 156 conversion factor in formula cv 1 156kv or cv 1 156 q sqrt g delta p. G specific gravity air 1 0 t flowing temperature absolute ºf 460 q 34 3 cv p g the rate of flow of a liquid or gas through a valve depends upon numerous factors such as gravity the temperature and pressure drop of the liquid or gas through the valve.
Q v flow rate m3 h at 15c and 101325 pa abs f l critical flow factor c v valve flow coefficient gpm p 1 upstream pressure bar abs. Pressure and temperature of fluid at valve inlet and to differential pressure p across the valve. The valve coefficient cv in imperial unit the number of us gallon per minute of water at 60 f that will flow through a valve at specific.
For measuring the valve capacity of control valves the coefficient cv or its metric equivalent kv is adopted. 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.