Gas Pipeline Sizing (Weymouth & Panhandle)
Calculate gas transmission pipeline flow capacity, delivery pressure, required diameter, and Line Pack storage using Weymouth, Panhandle A, and Panhandle B equations.
Calculation Mode
Pressure & Route Conditions
Geometry & Fluid Properties
About This Tool
The Gas Transmission Pipeline Hydraulics Calculator is an essential design utility for midstream, pipeline, and gas gathering engineers. Unlike standard in-plant piping equations that assume incompressible or minor pressure drops, long-distance gas transmission lines experience massive compressible expansion over tens or hundreds of kilometers.
This tool evaluates cross-country pipelines using the industry standard Weymouth, Panhandle A, and Panhandle B formulations, simultaneously calculating delivery pressure, flow velocity, API 14E erosional limits, and dynamic Line Pack gas inventory.
Pipeline Equation Selection & Reynolds Regime
1. Weymouth Equation: Originally developed for high-pressure, high-velocity gathering and transmission systems. It assumes fully turbulent flow with a constant friction factor dependent only on pipe diameter (f ∝ 1/d^(1/3)). It is the most conservative of the three formulas.
2. Panhandle A Equation: Calibrated for moderate-pressure, medium-to-large diameter transmission lines operating in the partially turbulent regime (Reynolds numbers between 5 × 106 and 1.1 × 107).
3. Panhandle B Equation: Widely considered the modern gold standard for high-pressure, large-diameter, smooth transmission lines operating at very high flow rates (Reynolds numbers from 4 × 106 up to 4 × 107).
Line Pack & Average Pressure
Because pressure drops quadratically rather than linearly along a compressible gas pipeline, the effective average line pressure (P_avg) is higher than the arithmetic mean:
P_avg = (2/3) · [P_1 + P_2 - (P_1 · P_2) / (P_1 + P_2)]
Line Pack: Represents the total standard volume of gas physically stored within the line volume at operating conditions. Midstream operators rely on Line Pack as a temporary buffer to absorb supply interruptions or daily peak-demand swings without shutting down deliveries.
Frequently Asked Questions
The pipeline efficiency factor E accounts for internal surface roughness, liquid accumulation (condensate or lube oil carryover), slight bends, and aging. New, clean, epoxy-coated transmission pipelines typically operate at E = 0.95 to 0.98. Standard carbon steel pipelines with minor aging typically use E = 0.90 to 0.92, while older or sour gas lines with scale may drop to E = 0.80 to 0.85.
As gas flows downstream, frictional pressure drop causes pressure to decrease. Under the Real Gas Law (PV = ZnRT), lower pressure forces the gas to expand into a significantly higher actual volumetric flow rate (Q_actual). Since the internal pipe cross-sectional area is constant, the velocity must accelerate, reaching its maximum at the delivery terminal. Operators must verify that outlet velocity remains safely below the API 14E Erosional Velocity Limit.
Input / Output Units
Specific to the active calculator.