Z_b=\frac{1}{(1+0.0002)P_b}Z_b=\frac{1}{(1+0.0002)P_b}
Where:
𝑃𝑎𝑣𝑔 − Average Initial Pipeline Pressure (psi)
𝑃𝑏 − Base Pressure (psi)
𝑃 = 𝑃𝑎𝑣𝑔+𝑃𝑏
𝑡 − Temperature (℉)
F_{pv} = 1 + \frac{3.44410^6P(10^{1.875G})}{t^{3.825}} \~\ N_t = \frac{\pi(0.0833D)(0.0833D)PL5280}{4zRt}
F_{pv} = 1 + \frac{3.44410^6P(10^{1.875G})}{t^{3.825}} \\~\\ N_t = \frac{\pi(0.0833D)(0.0833D)PL5280}{4zRt}Where:
𝐿 − Length of Pipeline (mi)
𝐷 − Pipe Inside Diameter (in)
𝑧 − Shut in Time (hr)
𝑅 − Constant (10.7316)
𝑁𝑡 − Initial Test Pressure (psi)
𝑡 − Temperature (℉)
𝑇𝑏 − Temperature Base (°R)
Vb=0.001\frac{(N_tRZ_b)}{P_b}
Vb=0.001\frac{(N_tRZ_b)}{P_b}Where:
𝑉𝑏 − Volume Lost (MSCF)
𝑇𝑚 − Blowdown Time (min)
𝐷𝑠 − Inside Diameter of Blowdown Stack (in)
𝐺 − Gas Specific Gravity
𝑛 − Number of Blowdown Stacks
𝑓 − Choke Factor
T_m = 0.05888f \left( P_{\text{avg}} ^{0.3333} \right)\sqrt{G} \left(\frac{D}{D_s}\right)^2 \left(\frac{L}{n}\right)
T_m = 0.05888f \left( P_{\text{avg}} ^{0.3333} \right)\sqrt{G} \left(\frac{D}{D_s}\right)^2 \left(\frac{L}{n}\right)
Case Guide
Part 1: Create Case
- Select the Gas Pipeline Blowdown – AGA Manual application from the Testing Module
- To create a new case, click the “Add Case” button
- Enter Case Name, Location, Date and any necessary notes.
- Fill out all required Parameters.
- Make sure the values you are inputting are in the correct units.
- Click the CALCULATE button to overview results.
Input Parameters
- Outside Pipe Diameter (in)
- Wall Thickness (in)
- Reduced Wall Thickness (in)
- Pipe Grade
- Internal Pipe Diameter (in)
- Length of Pipeline (mile)
- Average Initial Pressure (psi)
- Inside Diameter of Blowdown Stack (in)
- Number of Blowdown Stacks
- Choke Factor (drop down)
Part 2: Outputs/Reports
- If you need to modify an input parameter, click 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 icon.
- To delete a case, click the DELETE icon near the top of the widget.
Results
- Blowdown Time (min)
- Volume Lost (MSCF)
References
- Pipeline Design for Hydrocarbons Gases and Liquids, Committee of pipeline planning, American Association of Civil Engineers, 1975
- Engineering Data Book, Volume II, Gas Processor Association, Revised Tenth Edition, 1994
- Pipeline Design & Construction, A Practical Approach, American Society of Mechanical Engineers, 2000
FAQ
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Gas Purging Calculations?
Purging is a process of removing gas from the pipeline. Controlled purging of gases from pipelines by direct displacement with other gases that have been safely practiced for many years with the recognition that some flammable mixture is present. Purging of gases from pipelines by direct displacement with another gas also has been similarly practiced. It works both ways; however, there will always be an atmosphere of type of a mixture. This is due to the densities of the gases. Check Out
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What are the differences between the Semiempirical Blowdown calculation and the AGA Blowdown calculation?
AGA blowdown calculation is based on the specification defined by American Gas Association. Semiempirical blowdown calculation was developed from the SW Research Report calculations for the blowdown time and mass of gas vented to atmosphere of a piping system. Check Out