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Accidental Gas Release Full-Bore Pipeline Rupture

Contents

Release Rate Equations

Gas release rate is from peak initial release rate from single side and both sides. Some of the limiting factors include effective hole diameter and pressure differential. Q_m=C_d\frac{\pi d^2}{4}p\frac{\varphi}{a_o}

Q_m=C_d\frac{\pi d^2}{4}p\frac{\varphi}{a_o}

𝑄𝑚 − Peak Initial Release Rate from Single Side of Pipeline Rupture[lbm/sec]

\varphi=k(\frac{2}{k+1})^{\frac{k+1}{2(k+1)}} – Flow \, Factor

\varphi=k(\frac{2}{k+1})^{\frac{k+1}{2(k+1)}} - Flow \, Factor

a_o= \sqrt{\frac {kRT}{M}}- Sonic\ Velocity\ of\ Gas\ [ft/sec]

a_o= \sqrt{\frac {kRT}{M}}- Sonic\ Velocity\ of\ Gas\ [ft/sec]

𝐶𝑑 − Discharge Coefficient
𝑘 − Specific Heat Ratio of Gas
𝑅 − Universal Gas Constant=1545.3[ft ∙ lb/lb ∙ mol −°R]
𝑇 − Gas Temperature[°R]
𝑀 − Gas Molecular Weight
𝑑 − Effective Hole Diameter – LineDiameter[in]
𝑝 − Pressure Differential − Line Pressure[psi]

For the guillotine-type failure of pipeline rate release, the effective release: Q_{effm}=2\lambda Q_m=2\lambda C_d \frac{\pi d^2}{4}p\frac{\varphi}{a_o} – Effective \ Double – Ended \ Release \ Rate[lbm/sec]

Q_{effm}=2\lambda Q_m=2\lambda C_d \frac{\pi d^2}{4}p\frac{\varphi}{a_o} - Effective \ Double - Ended \ Release \ Rate[lbm/sec]

𝜆−Release Rate Decay Factor = 0.25−0

Case Guide

Part 1: Create Case

  1. Select the Accidental Gas Release Full-Bore Pipeline Rupture application in the AGR & GPRA module.
  2. To create a new case, click the “Add 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

  • Leak/Hole Location
  • Discharge Area
  • Outside Pipe Diameter
  • Wall Thickness
  • Internal Diameter
  • Specific Gravity
  • Molecular Weight of Gas
  • Specific Heat Ratio of Gas
  • Critical Flow Ratio of Gas
  • Operating Temperature
  • Base Pressure
  • Line Pressure at Rupture Location
  • Cd – Discharge Coefficient – Sharp Orifice
  • Release Rate

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

  • Critical Pressure Ratio
  • Flow Factor
  • Erosional Velocity
  • Sonic Velocity
  • Peak Initial Release Rate – From Single Side
  • Effective Release Rate – From Both Sides

References

  • GRI-00/0189, A Model for Sizing High Consequence Areas Associated with Natural Gas Pipelines, Gas Technology Institute
  • PHMSA – Final Report TTO Number 13, Delivery Order DTRS56-02-D-70036, Michael Baker Jr., Inc. –
  • PHMSA – Final Report TTO Number 14, Delivery Order DTRS56-02-D-70036, , Michael Baker Jr., Inc.
  • Crane Limited, Flow of Fluids through Valves, Fittings, and Pipe, Technical Paper No. 410-C, Crane Engineering Division
  • Schram, W., “Prediction of Crater Caused by Underground Pipeline Rupture”, N.V. Nederland se Gasunie, Report TR/T 97.R.2515
  • NEN 3651, Annex A: “Determining Disturbance Zone Dimension”
  • PRCI L51861, “Line Rupture and Spacing of Parallel Lines”, Battelle Memorial Institute
Updated on December 14, 2023
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