Natural Gas Pipeline Rupture – Width Radius Depth or Crater

Natural gas rupture includes three (3) models that determine depth, radius and Width of the crater. Gasunie, NEN 3651 Radius of Crater and PRCI/Gasunie/Battelle combined model.

GASUNIE MODEL
This model applies to a guillotine rupture wherein two separate pipe ends exists after the rupture.

Crater Depth:
𝑤 − Soil Parameter
𝐷𝑝 − Pipe Outside Diameter(m)
𝑝𝑜 − Pipe Pressure(Pa)
𝐷𝑐 − Depth of Cover from ground surface to center of the pipe(m)
𝐷 − Depth of Crater(m)
𝑅 − Soil Parameter Function

Soil Parameter Functions:

𝑅(𝑤) = 0.28+0.62(5 – 𝑤) − 0.07(25 − 𝑤2)

Allowable limits for R are between 0.28 and 1.3

if 𝑤 ≤ 0.6 𝐷 = 4.3𝐷_𝑝 + 𝐷_𝑐

if 0.6 < 𝑤 < 2

if 𝑤 ≥ 2 𝐷 = 2.2𝐷_𝑝 + 𝐷_𝑐

The crater angles are determined from empirical equations:

𝛼₁ = tan⁻¹(𝑤 + 1)

Considering crater and dimensions shown in Figure 1. The equation of the ellipse is given by

Differentiating this at the ground level and substituting for x give

Evaluating this on the ground level and half crater depth gives

These can be solved simultaneously

The width of crater W is given by

NEN 3651 MODEL RADIUS OF THE CRATER

Model may be applied for guillotine type rupture, NEN 3651 define radius of the crater as:

PRCI/GASUNIE/BATTELLE COMBINED MODEL

This model may be applied for guillotine type rupture only. Computation of the crater depth in combined PRCI/Gasunie/Battelle model is the same as described above for Gasunie model.

The crater width is calculated as:

Where:

𝑅_𝑝 =

𝑊_𝑤 = 𝐷_𝑐 + 𝑅_𝑝 − Distance from the Ground to the Center of the Pipe[m]

𝜌_{𝑠𝑜𝑖𝑙} − Soil Density[kg/m³]

𝛾 − Gas Specific Heat Ratio(1.031 for Natural Gas)

𝑢_𝑘𝑟= 2.54[m/s] − Critical Gas Velocity [m/s]

𝑢_𝑥− Velocity of the Explosive Gases[m/s]

Input Parameters

To create a new case, click the “Add Case” button
Select the Natural Gas Pipeline Rupture – Width, Radius, Depth of Crater application in the AGR & GPRA module.
Enter Case Name, Location, Date and any necessary notes.
Fill out all required fields.
Make sure the values you are inputting are in the correct units.
Click the CALCULATE button.

Pipe Outside Diameter
Pipe Internal Pressure
Depth of Cover
Average Unit Weight of Soil
Natural Gas Specific Heat Ratio
Soil Type
w – Soil Parameter
Alpha 1 – Crater Wall Angle at Ground Level
Alpha 2 – Crater Wall Angle at Half Depth

Outputs/Reports

View the results.
If an input parameter needs to be edited be sure to hit the CALCULATE button after the change.
To SAVE, fill out all required case details then click the SAVE button.
To rename an existing file, click the SAVE As button. Provide all case info then click SAVE.
To generate a REPORT, click the REPORT button.
The user may export the Case/Report by clicking the Export to Excel/PowerPoint icon.
To delete a case, click the DELETE icon near the top of the widget.

Gasunie Model
R – Soil Parameter Function
Depth of Crater
Width of Crater
NEN 3651 Model
Radius of Crater
PRCI/Gasunie/Battelle Model
Velocity of Explosive Gases
Depth of Crater
Width of Crater

Natural Gas Pipeline Rupture – Width Radius Depth or Crater

Input Parameters

Outputs/Reports

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