1. What is Control Valve Cv Calculation?

Definition: This calculator determines the flow coefficient (Cv) for control valves based on flow rate, pressure drop, and specific gravity.

Purpose: It helps engineers and technicians properly size control valves for fluid systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( C_v \) — Flow coefficient (dimensionless)
• \( Q \) — Flow rate (gallons per minute)
• \( \Delta P \) — Pressure drop across valve (psi)
• \( SG \) — Specific gravity of fluid (dimensionless)

Explanation: The Cv represents the flow rate in GPM of water at 60°F that will pass through a valve with a 1 psi pressure drop.

3. Importance of Cv Calculation

Details: Proper valve sizing ensures optimal flow control, prevents cavitation, and maintains system efficiency.

4. Using the Calculator

Tips: Enter the flow rate in GPM, pressure drop in psi, and fluid specific gravity (default 1.0 for water). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What does Cv represent?
A: Cv is a measure of a valve's flow capacity - the number of GPM of water at 60°F that will flow through the valve with a 1 psi pressure drop.

Q2: What's a typical Cv range?
A: Cv values vary widely from <1 for small valves to >1000 for large valves, depending on valve type and size.

Q3: When would I change the specific gravity?
A: When working with fluids other than water at 60°F. For example, gasoline has SG ≈ 0.72-0.78.

Q4: How does temperature affect Cv?
A: Temperature affects fluid density and viscosity, which are accounted for in the specific gravity value.

Q5: What if I have a gas instead of liquid?
A: Different formulas are needed for gases that account for compressibility and expansion factors.