The instrumentation on the line show that the pressure drop through the valve is 0 1 bar. The relationship between control valve capacity and valve stem travel is known as.
The density of water at 15 c is 999 13 kg m 3.
Control valve cv curve. When sizing a control valve the most common approach is to calculate the flow coefficient cv which is a measure of the capacity of the valve body and trim. Trim design of the valve affects how the control valve capacity changes as the valve moves through its complete travel. 5 dresser valve division masoneilan liquid flow equations cv valve flow coefficient n numerical constants based on units used see table 1 fp piping geometry factor reducer correction ff liquid critical pressure factor 0 96 0 28 pv pc fl liquid pressure recovery factor for a valve flp combined pressure recovery and piping geometry factor for a valve with attached fittings.
Example flow coefficient liquid. It is water at 50 c. 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.
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. The valve flow coefficient cv or its metric equivalent kv has been adopted universally as a comparative value for measuring the capacity of control valves. 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.
What is the flow through the valve. The linear flow characteristic curve allows the flow rate to be directly proportional to the valve travel δq δx equals a constant or in terms of the inherent valve characteristic f x x. An equal percentage valve starts initially with a slow increase in flow rate with valve position which dramatically increases as the valve opens more.
Calculation example of the flow through a valve of coefficient cv. A control valve has a cv of 5. The flow characteristic of the control valve.
For measuring the valve capacity of control valves the coefficient cv or its metric equivalent kv is adopted. The valve flow coefficient cv is the number of u s. 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.
How do we get value 1 156 conversion factor in formula cv 1 156kv or cv 1 156 q sqrt g delta p. A valve cv can be described as the number of gallons per minute gpm at 60 o f 15 5 o c that will pass through a valve with an associated pressure drop of 1 psi. Into the control valve dialog box or a set of data can be generated using the control valve cv calculator by entering a single cv value at any valve position and selecting the type of valve and characteristic curve as shown in figure 2.
Because of the variation in trim design many valves are not linear in nature.