Control Valve · Glossary

What is Piping Geometry Factor?

Symbol: Fpreducer correctionControl Valve

Piping geometry factor Fp corrects valve capacity for reducers and other fittings attached directly to the valve.

Piping Geometry Factor Explained

When a valve is smaller than the line, the reducer and expander add losses that reduce the effective capacity. Fp is below 1 and lowers the usable Cv.

It also affects the combined FL, written FLP, for choked flow calculations.

Piping Geometry Factor Formula

F_p = 1 ÷ √[1 + (ΣK ÷ N₂) × (C ÷ d²)²]

ΣK	sum of fitting loss coefficients
C	flow coefficient
d	valve size (mm)
N₂	0.00214 for Cv (0.0016 for Kv)

Calculators for Piping Geometry Factor

CalculatorPiping Geometry Factor Fp CalculatorFree online calculator with formula and worked example.CalculatorCv Calculator for LiquidsFree online calculator with formula and worked example.

Free Downloads

Free downloadControl Valve Sizing Excel SheetFree download in Excel and PDF.

Frequently Asked Questions

What is Piping Geometry Factor?

Piping geometry factor Fp corrects valve capacity for reducers and other fittings attached directly to the valve.

When can Fp be ignored?

When the valve is line size with no reducers; then Fp = 1.

Why is the valve often smaller than the line?

Sizing for proper opening often gives a valve one or two sizes below the pipe.

Learn more on the blog

Control valve flow coefficient (Cv and Kv)

A practical guide on instrumentationblog.in with more detail on piping geometry factor and how it is applied on real plants.

Read Full Article

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