Control Valve Sizing

Required Cv / Kv for liquid, gas & steam per ISA-75.01.01 / IEC 60534-2-1, with reducer FLP/xTP, choked-flow, cavitation, flashing, noise checks and valve-size recommendation.

Service Type

Process Conditions

Normal is required. Toggle Min / Max to add optional cases.

Flow unit

Pressure unit

Temperature unit

Use	Case	Flow *	P1 *	P2 *	Temp
	min
	normal
	max

Fluid Properties

Fluid Name

Physical Properties

Specific gravity

Density — kg/m³

Viscosity — cSt

Phase Properties

Vapor pressure (Pv)

Critical pressure (Pc)

Valve & Trim

Valve size optional — blank = auto-recommend.

Valve type

Valve size — inch

Line size — inch

Flow characteristic

Override coefficients (vendor data)

Rated Cv

Rangeability

Ready to calculate

Enter values and press Calculate to see results.

Engineering Tips

Normal flow is required; Min and Max are optional but improve the controllability and capacity checks.

Leave Valve size blank to auto-recommend a size from the coefficient database, or enter one to check that specific size.

Reducers are auto-detected from valve vs line size. Coefficients are representative — verify final sizing against vendor data.

Sizing checks

Operating window: check minimum, normal, and maximum flow together. An undersized valve cannot pass peak demand; an oversized valve works near the seat, where gain is high and control can become unstable.
Cavitation: vapor bubbles form at the vena contracta and collapse after pressure recovery, creating noise, vibration, and possible trim or downstream-pipe erosion.
Flashing: when outlet pressure remains below vapor pressure, vapor persists downstream. The valve cannot eliminate flashing; review body geometry, velocity, and erosion-resistant materials.
Choked flow: lowering downstream pressure further no longer increases flow for the same valve opening. Review the reported choked limit instead of extrapolating the basic Cv equation.
Vendor confirmation: rated Cv and factors such as F_L, x_T, and F_d depend on the selected body and trim. Confirm the final size, noise, travel, and reducer corrections with certified vendor data.

Recommended values

Operating window: Normal flow at 40–60% travel, max < 90%, min > 10% of rated Cv.
Noise: Aim < 85 dBA; high ΔP gas or cavitating liquid needs low-noise / anti-cavitation trim.
Characteristic: Equal-% for most throttling (rangeability ~50:1); linear where valve ΔP is a large share of system ΔP.
Avoid oversizing: An oversized valve throttles near the seat — poor control and fast wear.

Limitations

Steady sizing: ISA/IEC installed-flow sizing only — no actuator/positioner dynamics or loop tuning.
Not included: Detailed aerodynamic noise spectra, trim erosion life, and multiphase flashing are separate studies.

About the standards

ISA-75.01.01: Flow Equations for Sizing Control Valves.
IEC 60534-2-1: Industrial-Process Control Valves.