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Gas Pipeline Hydraulics Calculator

ASME B31.8 Compliant | Pressure Drop, Flow Capacity, or Pipe Sizing

Professional Gas Pipeline Hydraulics
Choose your calculation mode below, then select the appropriate flow equation per ASME B31.8. Includes AGA-8 compressibility corrections, Lee-Gonzalez-Eakin viscosity, erosional velocity checks, and line pack calculations.
Calculation Mode:
Flow Equation:

Pipeline Dimensions

in
miles
in
-

Operating Conditions

MMSCFD
psig
°F

Gas Properties

-
ft

Typical Values:
• Gas Gravity: 0.55-0.65 (natural gas)
• Roughness: 0.0007" (new), 0.002" (aged)
• Efficiency: 0.95 (new), 0.92 (good), 0.85 (fair)
• Elevation: + uphill, - downhill

📋 Mode 1: Calculate Pressure Drop

Use when designing a new pipeline or verifying an existing system. Input the desired flow rate and inlet pressure to find the resulting outlet pressure and pressure drop. Most common calculation for pipeline design.

Application: Pipeline sizing, capacity verification, operational planning

Given: Flow rate (Q), Inlet pressure (P₁), Diameter (D)

Calculate: Outlet pressure (P₂), Pressure drop (ΔP)

🔬 Equation Selection Guide

  • Weymouth: High-pressure transmission (>500 psig), D>12" - most conservative
  • Panhandle A: Older pipes, moderate roughness
  • Panhandle B: New/smooth pipes, fully turbulent - most optimistic
  • AGA: General purpose, uses Colebrook-White friction factor

Engineering Notes

Flow Equations (ASME B31.8)

Weymouth:
Q = 433.5 E (Tᵦ/Pᵦ) √[(P₁²-P₂²)D^(16/3)/(G·Tₐᵥ·Lₑ·Z)]
Q = Flow rate (scfd)
P₁, P₂ = Inlet/outlet pressure (psia)
D = Inside diameter (in)
E = Efficiency factor
Z = Compressibility factor

Standards & References

  • ASME B31.8-2020
    Gas Transmission and Distribution Piping Systems (Section 841, Appendix C)
  • API RP 14E
    Design and Installation of Offshore Production Platform Piping Systems
  • AGA Report No. 8
    Compressibility Factors of Natural Gas
  • Lee et al. (SPE 1340)
    Viscosity of Natural Gases

Important Notes

  • Base Conditions: 14.7 psia, 60°F (standard cubic feet)
  • Compressibility: Uses Standing-Katz correlation for Z-factor
  • Viscosity: Lee-Gonzalez-Eakin correlation
  • Erosional Velocity: API RP 14E check (Ve = 100/√ρ)
  • Elevation: Positive = uphill (increases ΔP)
  • Valid For: Single-phase gas only, steady-state flow
  • Professional Review: Verify with licensed PE for final design

Frequently Asked Questions

What equations does this gas pipeline hydraulics calculator use?

This calculator implements ASME B31.8 gas pipeline equations to calculate pressure drop, flow capacity, or required pipe size. It accounts for gas compressibility (Z-factor), temperature, specific gravity, and pipeline efficiency.

What are the three calculation modes for gas pipeline hydraulics?

The three modes are: calculate pressure drop given flow rate and pipe diameter, calculate flow capacity given inlet and outlet pressures, or calculate required pipe diameter given flow rate and pressure constraints.

How does gas compressibility affect pipeline hydraulics calculations?

Gas compressibility factor (Z) reduces gas density from ideal conditions. Higher Z-factors mean less gas mass per unit volume, affecting pressure drop calculations. The calculator uses the average pressure and temperature to determine Z at pipeline conditions.