Control Valve Sizing Calculator

Basis of Calculation

The calculations performed by this tool are based on the industry-standard ISA-75.01.01 (IEC 60534-2-1), Flow Equations for Sizing Control Valves.

• Liquid Sizing: The required flow coefficient (Cv​) for non-compressible fluids is calculated using the standard liquid sizing equation, which accounts for flow rate ($Q$), specific gravity (Gf​), and the pressure drop across the valve ($\Delta P$). The calculator also considers the potential for choked flow (flashing or cavitation) by using the liquid pressure recovery factor (FL​) and the liquid’s vapor pressure (Pv​).

• Gas & Vapour Sizing: For compressible fluids, the tool uses the appropriate gas sizing equation from the standard. This calculation incorporates the expansion factor ($Y$), which is determined using the specific heat ratio ($k$) and the valve’s pressure drop ratio factor (xT​) to accurately model the effects of fluid compressibility and potential choked flow conditions.

• Pressure: All calculations are performed using absolute pressure. The tool converts the user-entered gauge pressures to absolute by adding the specified atmospheric pressure.

• Valve Characteristics: The flow rate vs. opening curve is generated using idealized mathematical models for the selected inherent characteristic (Linear, Equal Percentage, or Quick Opening).

📜 Disclaimer

This calculator is provided for educational and preliminary estimation purposes only. The results generated should not be considered a substitute for a comprehensive engineering analysis and design review.

The user agrees to the following conditions:

1. No Guarantee of Accuracy: While based on recognized industry standards, this tool makes certain simplifying assumptions. The accuracy of the results is not guaranteed. The creators of this webpage provide no warranty, expressed or implied, for the calculations or data presented.

2. Professional Verification Required: All control valve sizing and selection for final design, procurement, or installation must be verified by a qualified engineer and cross-checked with the specific valve manufacturer’s proprietary sizing software and documentation. Real-world performance can vary based on factors not included in this tool, such as high-viscosity effects, two-phase flow, or noise generation.

3. Assumption of Risk: The user assumes all risks and liabilities associated with the use of this calculator. The authors and hosts of this webpage shall not be held liable for any damages, losses, or costs arising from the use of the information provided herein.