Flow Measurement · Glossary

What is Pressure and Temperature Compensation?

gas and steam flow correctionFlow Measurement

Pressure and temperature compensation corrects gas or steam flow for density changes using live pressure and temperature measurements.

Pressure and Temperature Compensation Explained

A DP or volumetric gas meter is designed for one density. When line pressure or temperature changes, density changes and the uncompensated flow is wrong.

Compensation uses live absolute pressure and temperature, and Z where needed, to correct the flow in the DCS, a flow computer or a multivariable transmitter.

Pressure and Temperature Compensation Formula

Q_comp = Q_design × √[(p ÷ p_d) × (T_d ÷ T) × (Z_d ÷ Z)]

Q_design	flow from DP at design density (mass or standard volume)
p, T	actual absolute pressure and temperature
p_d, T_d	design conditions

Example: Design 6 bar a, 20 °C; actual 5 bar a, 30 °C: factor √(5 ÷ 6 × 293.15 ÷ 303.15) = 0.898, so 1000 kg/h reads 898 kg/h.

Calculators for Pressure and Temperature Compensation

CalculatorGas Flow Pressure and Temperature Compensation CalculatorFree online calculator with formula and worked example.CalculatorGas Density CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Pressure and Temperature Compensation?

Pressure and temperature compensation corrects gas or steam flow for density changes using live pressure and temperature measurements.

Why is the DP compensation a square root?

DP meter flow is proportional to √(DP × density), so the density correction enters under the square root.

Is compensation needed for liquids?

Rarely for pressure. For large temperature changes the density correction can matter, especially for oils.

Learn more on the blog

Mistakes in DP flow measurement

A practical guide on instrumentationblog.in with more detail on pressure and temperature compensation and how it is applied on real plants.

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More Flow Measurement Terms

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All flow measurement terms · Full glossary A to Z