Introduction
These stresses are used in most calculations for road and RR crossing, spans, blasting, streams, etc. before deciding on the safety of the pipe.
Live hoop and longitudinal stress must be below seam and girth weld fatigues limits. Outside force stresses must be known for proper evaluation.
Hoop Stress
S_H=\frac{PD}{2t}
S_H=\frac{PD}{2t}
Where:
ππ» β Hoop stress (psi)
π β Pipe internal pressure (psi)
π· β Pipe outside diameter (in)
π‘ β Pipe wall thickness (in)
Longitudinal Stress
S_L=\frac{PD}{4t}
S_L=\frac{PD}{4t}
Where:
ππΏ β Longitudinal stress (psi)
π β Pipe internal pressure (psi)
π· β Pipe outside diameter (in)
π‘ β Pipe wall thickness (in)
Case Guide
Part 1: Create Case
- Select the Hoop and Longitudinal Stress application from the Design & Stress Analysis Module
- To create a new case, click the βAdd Caseβ 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
- Nominal Pipe Size (in): (0.625β β 48β)
- Wall Thickness (in): (0.068β- >2β)
- Pipe grade: (24000psi-80000psi) (if unknown use Grade A 24000)
- Outside Pipe Diameter (in)
- Internal Pipe Diameter (in)
- Internal Pressure (psi)
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
- Hoop Stress( psi)
- Longitudinal Stress (psi)
References
- ASME B31.8 β Gas Transmission and Distribution Piping Systems
- API 5L, API 5LS and API 5LX β Specification of Pipe Grade
- ASTM β Various β 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 β Theory of Elasticity Anchor Force
FAQ
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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
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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
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