What is the Cv rating on a control valve?
All control valves have a rated flow capacity expressed as the Cv rating. The valve flow coefficient (Cv) is the number of US gallons per minute of 60 degree Fahrenheit water that will pass through a fully open valve with a 1 psi pressure drop.
How do you size a globe valve?
When sizing a control valve, the rule of thumb is to size it so that it operates somewhere between 20-80% open at maximum required flow rate and whenever possible, not much less than 20% open at the minimum required flow rate.
How do you calculate the flow rate of a globe valve?
The volume flow rate for liquids can be calculated by multiplying the fluid velocity times the flow area. Thus, Cv is numerically equal to the number of U.S. gallons of water at 60°F that will flow through the valve in one minute when the pressure differential across the valve is one pound per square inch.
How do you read valve sizes?
The basic valve sizing equation Q = Cv√∆P can be used to calculate pressure drop, flow rate, or the flow coefficient. For solutions other than water, a correction for a difference in specific gravity of the solution is necessary. This revised formula would be: Q = Cv[√∆P/Sg] with Sg = specific gravity of the liquid.
What is Cv in flow control valve?
Valve Flow Coefficient (Cv) is a valve’s capacity for a liquid or gas to flow through it. It is technically defined as “the volume of water at 60°F (in US gallons) that will flow through a valve per minute with a pressure drop of 1 psi across the valve.”
How do you calculate valve CV?
Cv by definition is the number of gallons per minute (GPM) a valve will flow with a 1 psi pressure drop across the valve. For example a valve with a Cv of 10 will flow 10 GPM with a 1 psi pressure drop. The formula used to select the valve Cv with the specified differential pressure is: Cv=GPM/((SQ RT(∆P)).
For example a valve with a Cv of 10 will flow 10 GPM with a 1 psi pressure drop. The formula used to select the valve Cv with the specified differential pressure is: Cv=GPM/ ( (SQ RT (∆P)). If the specified ∆P is 4 psid and full flow is 10 GPM the calculated CV is 10/SQ RT of 4 = 5.
What does CV rating mean on a water valve?
CV stands for the “coefficient of flow” of a valve , and is further defined as the flow rate in gallons of 60°F water that will pass through a valve in one minute at one-pound pressure drop. A CV of 1 then, means that one gallon of water passed through a valve in 1 minute at 1 pound DP.
What is the use of CV in control valve designing?
The flow coefficient or valve coefficient denoted by “Cv”, is used to determine the valve size that will best allow the valve to pass the required flow rate while providing stable control of the process fluid. Most valve manufacturers publish Cv data in product catalogues for various valve styles.
What is ball valve CV?
Ball Valves. The below CV values are used to give an indication of flow rates for ball valves. CV value is an imperial measure of flow in US gallons per minute of water at 60° fahrenheit with a pressure drop of 1 psi across the valve. This is used as a guide and is not a linear progression.
