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Compressor Station Piping – Gas Velocity, Pipe Diameter andWall Thickness

Contents

Introduction

This application uses gas velocity and flow rates to determine the minimum required pipe diameter for station piping.

Gas Velocity

v=\frac{127.3\times10^3QP_bT_fZ}{D^2P_fT_b}

v=\frac{127.3\times10^3QP_bT_fZ}{D^2P_fT_b}

Pipe Diameter

D=\sqrt{\frac{127.3\times10^3QP_bT_fZ}{vP_fT_b}}

D=\sqrt{\frac{127.3\times10^3QP_bT_fZ}{vP_fT_b}}

Wall Thickness

Wt=\frac{P\left( \frac{127.3\times10^3QP_bT_fZ}{vP_fT_b} \right)^{0.5}}{2S}FET

Wt=\frac{P\left( \frac{127.3\times10^3QP_bT_fZ}{vP_fT_b} \right)^{0.5}}{2S}FET

Where:
๐‘ฃ โˆ’ Gas Velocity (ft/min)
๐‘„ โˆ’ Flow Rate (MMCFD)
๐‘Š๐‘ก โˆ’ Wall Thickness (in)
๐‘ƒ โˆ’ Design Pressure (psi)
๐น โˆ’ Design Factor
๐ธ โˆ’ Longitudinal Joint Factor
๐‘‡ โˆ’ Temperature Derating Factor
๐‘ƒ๐‘ โˆ’ Base Pressure (psia)
๐‘‡๐‘“ โˆ’ Flowing Temperature (ยฐR)
๐‘ โˆ’ Compressibility Factor
๐ท โˆ’ Internal Pipe Diameter (in)
๐‘ƒ๐‘“ โˆ’ Flowing Pressure (psia)
๐‘‡๐‘ โˆ’ Base Temperature (ยฐR)
Note: Gas velocity in piping should not exceed 2000(ft/min)

CNGA/GPSA Compressibility Factor Approximation:

Z=\frac{1}{\left[1+\left(\frac{3.444\times10^5P\times10^{1.785G}}{T_f^{3.825}} \right)\right]}

Z=\frac{1}{\left[1+\left(\frac{3.444\times10^5P\times10^{1.785G}}{T_f^{3.825}}   \right)\right]}

Where:
๐‘ โˆ’ Compressibility Factor
๐‘ƒ โˆ’ Pressure
๐‘‡๐‘“ โˆ’ Gas Flowing Temperature (ยฐ๐‘…)

This approximation will produce results sufficiently accurate for preliminary calculations.

Brake Horsepower

BHP=\frac{HP}{n_m}

BHP=\frac{HP}{n_m}

Where:
๐‘›๐‘š โˆ’ Mechanical Efficiency ๐‘›๐‘š = 0.95/0.98

Case Guide

Part 1: Create Case

  1. Select the Compressor Station Piping application from the Compressor Module
  2. To create a new case, click the โ€œAdd Caseโ€ button
  3. Enter Case Name, Location, Date and any necessary notes.
  4. Fill out all required Parameters.
  5. Make sure the values you are inputting are in the correct units.
  6. Click the CALCULATE button to overview results.

Input Parameters

  • Pipe Internal Diameter (in)
  • Operating Temperature (ยฐF)
  • Operating Pressure (psig)
  • Base Temperature (ยฐF)
  • Base Pressure (psi)
  • Capacity/Required Flow Rate (MMSCFD)
  • Gas Specific Gravity (Relative to air)
  • Gas Molecular Weight
  • C – Factor
  • Compressibility Factor
  • Z – Compressibility Factor
  • Outside Diameter (in)
  • SMYS (psi)
  • Design Factor
  • Joint Type
  • Temperature Derating Factor
  • Design Pressure (psig)

Gas Velocity

Pipe Diameter

Wall Thickness

Part 2: Outputs/Reports

  1. If you need to modify an input parameter, click the CALCULATE button after the change.
  2. To SAVE, fill out all required case details then click the SAVE button.
  3. To rename an existing file, click the SAVE As button. Provide all case info then click SAVE.
  4. To generate a REPORT, click the REPORT button.
  5. The user may export the Case/Report by clicking the Export to Excel icon.
  6. To delete a case, click the DELETE icon near the top of the widget.

Results

  • Z – Compressibility Factor
  • Gas Velocity (ft/min)
  • Erosional Velocity (ft/min)
  • Sonic Velocity (ft/min)
  • Pipe Internal Diameter (in)
  • Minimum Pipe Wall Thickness (in)

Gas Velocity

Pipe Diameter

Wall Thickness

References

  • Engineering Data Book, Volume 1, Gas Processors Suppliers Association, Tenth Edition
  • Compressor Station Operation, Book T-2, GEOP, American Gas Association (A.G.A.)
  • Compressor Selection and Sizing, Royce N. Brown, Second Edition, Gulf Professional Publishing
Updated on January 4, 2024
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