The Ultimate Valve Cv Sheets

What is a Cv?

Control valve CV refers to the flow coefficient of the valve. It applies to the coefficient of pressure drop(ΔP) or head drop (Δh) on the valve of Q(flow capacity).

For more definitions and related information, please read this article.

Flow Coefficient Calculation Cv

The flow rate of a liquid or gas through a valve depends on many factors such as density, temperature, gravity, and the pressure drop of the liquid or gas through the valve. The design type and flow path of the valve has different effect on the flow rate through the valve. Considering the relationship between temperature, gravity, and pressure drop through the valve, a “flow coefficient” can be calculated to determine the theoretical flow rate through the valve. This coefficient is called Cv (coefficient of flow) and it is developed by the flow capacity testing from the manufacturer.

Liquids: 

Equation Abbreviations – Liquids:

Q = Flow (Barrels/Day)

Cv= Flow Factor

ΔP = Pressure Drop Across Valve

G = Specific Gravity (Water=1.0)

Gas:

Equation Abbreviations – Gas:

Q = Flow (MMSCFD)

Cv = Flow Factor

P1 = Inlet Pressure (psia)

P2 = Outlet Pressure (psia)

ΔP = Pressure drop (P1-P2). When P2 is less than 1/2 P1, use 1/3 P1, for P2 in the formula.

G = Specific Gravity (air=1.0)

T = Flowing Temperature Absolute (°F + 460)

If flow capacity required is known and valve selection is desired, calculate Cv with the following formula and select the appropriate valve from the manufacturer’s Cv factor chart.

Liquids:     

Gas:

Butterfly Valve Cv Flow Rate

Generally, we work on metric systems, but many engineers still prefer to express flow coefficients in terms of Cv values. The imperial system measures flow in US GPM at 60 degrees Fahrenheit with a pressure drop of 1 psi across the valve. The following table shows the flow rate of a butterfly valve between 0°(fully closed) and 90° (fully open) with the valve at different openings. Please notice that the Cv value is not a linear increment, so it cannot be deduced just by looking at the value. These sheets of flow coefficients are just for your reference. 

Triple Offset Butterfly Valve Cv 150LB

Triple Offset Butterfly Valve Cv 300LB

High-Performance Butterfly Valve Cv

Resilient Seated Butterfly Valves Cv

Cv Value at different degrees of opening

Ball Valves Cv Flow Rate

The Cv values below are used to indicate the flow rate of the ball valve. Different ball type has different Cv flow rate. Hope it will be useful for your case. 

V-Port Ball Valve Cv

Flow Rate for two-way Full Bore Ball Valve Cv

3 Way Full Bore Flanged Ball Valve Cv

3 Way Reduced Port Threaded Ball Valve Cv

Globe Type Control Valve Cv Flow Rate

globe Control valve cv

For example: 1″ globe valve cv. The Cv (flow coefficient) of a 1″ globe valve will depend on a range of factors, including the valve design, the flow medium, and the pressure drop across the valve. The Cv value is a measure of a valve’s flow capacity, and it represents the number of gallons of water that can pass through the valve at a pressure drop of one psi. For a 1″ globe valve, the Cv value could range from 0.14 to 15, depending on the specific valve model and application requirements.

Class 150 – Class 600 Globe Control Valve CV

Class 900 – Class 1500 Globe Control Valve CV

Class 2500 Globe Control Valve CV

Manual Globe Valve Cv Table

Here is a table showing some typical Cv values for manual globe valves of varying sizes:

Please note that these Cv values are just examples and may vary depending on the specific valve model and application requirement.

Gate Valve Cv

Gate valves do not have a Cv curve like some other types of valves because they operate with the valve fully open or fully closed. The Cv value is not used to determine the flow rate through a gate valve, but rather to size the valve based on the required flow rate and pressure drop.

Bolted Bonnet Gate Valve Cv (Full Open）

Pressure Seal Gate Valve Cv (Full Open）

Pressure Seal Venturi Gate Valve Cv (Full Open）

Check Valve Cv

Bolted Cap Swing Check Valve Cv (Full Open）

Pressure Seal Tilting Disc Check Valve Cv (Full Open）

 Pressure Seal Venturi Tilting Disc Check Valve Cv (Full Open)

Globe Valve, Stop-Check Valve, and Lift-Check Valve Cv

Pressure Seal T-Globe Stop, Stop-Check, and Lift-Check Valve Cv (Full Open)

Pressure Seal Venturi Globe Stop, Stop-Check, and Lift-Check Valve Cv (Full Open)

Pressure Seal Venturi Y-Globe Stop, Stop-Check, and Lift-Check Valve Cv (Full Open）

Globe Valve Cv

Bolted Bonnet Globe Valve Cv (Full Open）

Seat Port Area For Pressure Seal Y-Type Globe Valves Cv (in²)

How to Use Valve Cv?

The valve coefficient (Cv) is a number that represents a valve’s ability to pass flow. The bigger the Cv, the more flow a valve can pass with a given pressure drop. A Cv of 1 means a valve will pass 1 gallon per minute (GPM) of 60oF water with a pressure drop (dp) of 1 PSI across the valve. A Cv of 350 means a valve will pass 350 GPM of 60oF water with a dp of 1 PSI.

Equation 1: Flow Capacity LBS/Hr (steam or water)

dp= pressure drop in PSI

F=flow rate in lbs./hr.

=square root of a specific volume in ft3/lb. (downstream of the valve)

Equation 2: Flow Capacity GPM (Water or other liquids)

dp= pressure drop in PSI

Sg=specific gravity

Q=flow rate in GPM

Restrictions

The velocity equation is invalid under the following conditions.

a. For compressible fluids, the pressure drop is more than half of the inlet pressure.

b. For incompressible fluids, when the pressure drop causes cavitation or flashing.

c. For two-phase flows, such as a mixture of steam and water.

The optimum operating speed should be within these ranges when sizing check valves as below.

Question A:

What is the pressure drop through a 14″ Class 900 pressure seal gate valve with 400oF water, 1500 PSIG, and 5,000,000 lbs/hr flow rate?

Answer A: Use Equation 1

F=5,000,000

=0.137 (from the chart for water at 400^oF)

Cv=9150 (from pressure seal gate valve Cv sheet)

Question B:

What is the pressure drop through a 14″x12″x14″ Class 900 Venturi pressure seal gate valve with the same conditions as question A.

Answer B: Use Equation 1

Cv = 6285 (from Venturi pressure seal gate valve Cv Sheet)

Question C:

What is the smallest Class 2500 gate valve that will have less than a 5 PSI pressure drop in 900oF, 1200 PSI steam service at a flow rate of 500,000 lbs/hr?

Answer C: Use Equation1.

F=500,000

=0.785 (from chart for steam at 900oF, 1200 PSIG)

==2.24

The closest higher Cv is a 10″ Class 2500 gate with a Cv of 3130. This is the smallest valve with a pressure drop of less than 5 PSIG.

Selected Properties of Water and Steam

For Water (Downstream)

Temperature	100oF	200oF	300oF	400oF	500oF	600oF
All Pressures	0.127	0.129	0.132	0.137	0.143	0.154

For Steam (Downstream)

Calculating Seat Port Velocity　

The following formulas can be used to calculate seat port velocity in any valve:

Flow (lbs/hr): vel: (fps) = F()2  /25A

Flow (GPM): vel: (fps) = 0.32Q/A

Where: F=flow (lbs/hr)

=square root of specific volume

A=seat port area (in2)

Q=flow (GPM)

Case A:

What is the seat port velocity in a 12″ Figure 58809 (Class 900) check valve with a flow rate of 90,000 lbs/hr of steam at 500 oF and 200 PSIG?

Solution A:

From the steam sheet is 1.61, and from the seat port area sheet A is 78.5 in².

Vel (fps) =F()² /25A    ⁼ 90,000 (1.61)²  /25(78.5)= 118.8 fps

Case B:

What is the seat port velocity in a 12″ Figure 180 (Class 150) Swing Check Valve with a flow rate of 90,000 lbs/hr of steam at 500oF and 200 PSIG?

Solution B:

From the Sheet is 1.61 and A is 113.1 in³.

Vel (fps) =F()² /25A =90,000 (1.61)²/25(113.1)= 82.5 fps

Figure 1 Bolted Bonnet Globe Valves

Characteristic Flow Curves for Globe Stop, Stop-Check, Lift-Check Valves

Estimating Cv For Less Than Fully Open Valves

Figure 2. Globe Stop, Stop-Check, and Lift-Check Valves

Figure 3. Y-Globe Stop, Stop-Check and Lift-Check Valves

The flow coefficient (Cv) listed in the tables applies to fully open valves only. Flow coefficients other than fully open may be approximated by use of the characteristic flow curves for tilting disc check and globe valves. Gate valves are not recommended for throttling service.

Case 3:

What is the Cv of a 12 inch Class 900 Pacific pressure seal globe valve 1/4 open?

Solution 3:

From the flow coefficient table above, the fully open Cv for a 12 inch, Class 900 globe valve is 1820.

Consulting Figure 2, the percent of fully open Cv at 1/4 valve open is 52%.

The Cv at 1/4 open is then computed as:

0.52 x 1820 = 946.

The above information is only for general use, all the data and formulae may not be suitable for all engineers, plant experts, and purchasing managers. Some data may be delayed or changed and we do not assume any responsibility for any failure to notify you at the first opportunity.

THINKTANK is a major valve manufacturer and optimal fluid solution provider, which supplies control valves, self-operated pressure regulators, butterfly valves, ball valves, eccentric plug valves, knife gate valves, globe valves, fusible link valves, and gate valves around the world.