Natural Gas Flow & Pressure Drop

Estimate steady-state gas flow from inlet and outlet pressure, gravity, pipe size, length, and line efficiency. Defaults are a 508 mm, 9.5 mm WT, 50 km metric example at 7000 / 5000 kPa abs, γg 0.60, and E 0.92. Switch to US Customary to convert those inputs. Results update as you edit.

Section 1

Units

Unit system

Switching units converts the numbers already in the form. Gas gravity and line efficiency stay the same.

Section 2

Line & Gas Parameters

Inlet pressure P1

kPa abs

Absolute pressure, not gauge.

Outlet pressure P2

kPa abs

Absolute pressure, not gauge. Must be lower than P1.

Gas specific gravity

γg

Air = 1.00. Typical pipeline gas is about 0.60. Dimensionless, does not convert.

Outside diameter

Wall thickness

Pipeline length

Line efficiency E

factor

Typical gathering 0.80 to 0.92. Dimensionless, does not convert.

Section 3

Flow & Pressure Drop

Inside diameter

489.0 mm

OD minus two wall thicknesses

Pressure drop

2,000 kPa abs

P1 minus P2

Weymouth flow

8,157 10³ m3/d

Shorter, higher-friction gathering estimate

Panhandle A flow

10,638 10³ m3/d

Medium-to-large transmission estimate

Panhandle B flow

10,293 10³ m3/d

Large, smooth, high-pressure line estimate

What this tool calculates

Inside diameter is OD minus two wall thicknesses. Pressure drop is P1 minus P2. Flow uses the encoded Weymouth, Panhandle A, and Panhandle B equations with a fully turbulent, horizontal-line assumption. Metric rates are shown in 10³ m3/d. US rates are shown in MMSCFD.

Phase 1 hardcodes flowing temperature, compressibility, and base conditions. Metric uses Tf = 288.15 K, Z = 0.88, Tb = 288.15 K, and Pb = 101.325 kPa. US Customary uses Tf = 520 R, Z = 0.88, Tb = 520 R, and Pb = 14.73 psia. Those values are not editable on this page.

Switching the unit toggle converts values already in the form: pressure by 0.145038, diameter and wall by 25.4, and length by 1.60934 (km to miles). Gas specific gravity and line efficiency are dimensionless and do not convert.

Weymouth is a better fit for shorter, higher-friction gathering. Panhandle A is commonly used on medium-to-large transmission. Panhandle B is intended for large, smooth, high-pressure lines. If length, gravity, or inside diameter is not greater than 0, or if P1² minus P2² is not greater than 0, results pause instead of showing NaN.