Gas Pipeline Sizing · Instrument Apps Hub

Setup

Main equationAll are compared below

Pipe

Pipe size Outside diameter Wall thickness Length Elevation changeOutlet minus inlet Internal roughnessNew steel ≈ 0.046 mm; coated ≈ 0.01 mm Pipeline efficiency E0.92–1.0 (1 = clean, new)

Gas and conditions

GasZ from AGA 8 at the average pressure Inlet pressure P1 Outlet pressure P2 Gas temperature ViscositycP Base conditions

Design pressure · ASME B31.8 / 49 CFR 192

Pipe grade (SMYS) Location class · design factor F Longitudinal joint factor E Temperature derating T Corrosion allowance

P = 2·S·t / D × F × E × T (t without corrosion allowance). Design factors and derating per 49 CFR 192.111–192.115; ASME B31.8 allows 0.80 for Class 1 Division 1. Check the code and your company's specification.

Flow capacity

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Velocity (inlet / outlet)

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Design pressure (MAOP)

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All equations compared

Empirical equations were fitted to different pipelines: Weymouth is conservative (often used for gathering and short lines), Panhandle A/B for large transmission lines, IGT for distribution, Spitzglass for small-diameter plant piping. The general equation with Colebrook-White friction is the most physical.

Pressure along the line

Details

Equations used

General: Q = 38.77·F·(Tb/Pb)·[(P1² − P2²)/(G·Tf·Le·Z)]^0.5·D^2.5, F = 2/√f, Colebrook-White friction Weymouth: Q = 433.5·E·(Tb/Pb)·[(P1² − P2²)/(G·Tf·Le·Z)]^0.5·D^2.667 Panhandle A: Q = 435.87·E·(Tb/Pb)^1.0788·[(P1² − P2²)/(G^0.8539·Tf·Le·Z)]^0.5394·D^2.6182 Panhandle B: Q = 737·E·(Tb/Pb)^1.02·[(P1² − P2²)/(G^0.961·Tf·Le·Z)]^0.51·D^2.53 IGT: Q = 136.9·E·(Tb/Pb)·[(P1² − P2²)/(G^0.8·Tf·Le·μ^0.2)]^0.555·D^2.667 Spitzglass: Q = 729.6087·E·(Tb/Pb)·[(P1² − P2²)/(G·Tf·Le·Z·(1 + 3.6/D + 0.03·D))]^0.5·D^2.5 (USCS: Q SCFD, P psia, T °R, Le miles, D in.) Elevation: P1² − e^s·P2², s = 0.0375·G·ΔH/(Tf·Z), Le = L(e^s − 1)/s. Average pressure Pavg = ⅔·(P1 + P2 − P1·P2/(P1 + P2)); Z at Pavg and Tf from AGA 8 DETAIL. Erosional velocity (API RP 14E): Ve = C/√ρ, C = 100 (ρ in lb/ft³, Ve in ft/s). Design pressure: P = 2·S·t/D·F·E·T.

Public textbook forms of the classic gas-flow equations. Steady, isothermal, single-phase gas. For study and screening; use your company's hydraulic software for final design.