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Linear Thermal Pipeline Expansion – Gas

Contents

Introduction

Buried pipe must include pre-existing operational stresses. These includes hoop, longitudinal stress due to thermal expansion. Outside force stress must be added to these stresses before any evaluations can be performed as in PLTB.

The thermal stress is difficult to estimate because of unknown installation temperature. It can be estimated from local climatic data.

Thermal Expansion – Linear

E=CL(T_1-T_2)

E=CL(T_1-T_2)

Where:
𝐸 βˆ’ Elongation (in)
𝐢 βˆ’ Coefficient of Linear Expansion (in/℉)
𝐿 βˆ’ Length of pipe (ft)
𝑇1 βˆ’ 𝑇2 = Temperature change (℉)

Material Coefficient:

Longitudinal Stress Due to Temperature Changes

S=EC(T_1-T_2)

S=EC(T_1-T_2)

Where:
𝑆 βˆ’ Stress (psi)
𝐢 βˆ’ Coefficient of Linear Expansion (in/℉)
𝐸 βˆ’ Modulus of Elasticity (psi)
𝑇1 βˆ’ 𝑇2 = Temperature change (℉)

Case Guide

Part 1: Create Case

  1. Select the Linear Thermal Pipeline Expansion application from the Design & Stress Analysis Module
  2. To create a new case, click the β€œAdd Case” 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 Length (ft)
  • Modulus of Elasticity (psi)
  • Coefficient of Linear Expansion (in/inΒ°F)
  • Temperature Change (Β°F)

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

  • Pipe Linear Elongation (in)
  • Longitudinal Stress due to Temperature Change (psi)

References

  • ASME B31.8 – Gas Transmission and Distribution Piping Systems
  • API 5L, API 5LS and API 5LX – Specification of Pipe Grade
  • ASTM – Various – Weld Joint Factor
  • CFR Code Part 192
  • USDA-SCS Modified (Permissible Velocity of Water and Soil Erodibility)
  • FHWA-HEC
  • Pipeline Rules of Thumb Handbook
  • Timoshenko, S – Theory of Elasticity Anchor Force

FAQ

  • Restrained versus Unrestrained Pipe (Difference in Gas vs. Liquid)?

    ASME B31.4 liquid and B31.8 gas codes include calculations for the net longitudinal compressive stress that must be applied only for a restrained line that equates to a low (less than 2%) longitudinal strain. This stress status is characteristic to underground pipelines located some distance away from above ground piping facilities.

    Unrestrained lines means those above ground sections of piping without axial restraint as with buried pipe with soil.Β  Β In others words the soil exerts substantial axial restraint, but not fully restrained. Check Out

  • What is the Maximum Span Length of rev1?

    Regarding span factors with and without water are based on bending stress and deflection.Β  Larger diameter pipe spansΒ  require saddles for stability. Many standards that require pipes to be filled with water are based on bending and shear stresses not to exceed 1,500 psi and a deflection between supports not exceed 0.1 inches. Check Out

  • What is the model used for Thrust at Blow-Off?

    HUBPL uses the equation from the DOT Inspectors Handbook:Β 

    TF = 0.5042 * G*Q^2/(P*D^2)

    Check Out

Updated on December 15, 2023
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