Abstract

Onshore pipelines are usually designed and constructed for burial conditions. However, pipeline exposures can develop from environmental and geohazard conditions such as creek crossing, soil washout due to significant rainfall events, short-term flooding, etc. Engineering assessment of the exposed pipeline sections is a vital consideration to assess the fitness of the exposed pipeline sections for continued service. A fitness for service engineering assessment methodology that was successfully used for the assessment of an NPS 10 onshore natural gas pipeline exposure is presented herein. The assessment is based on finite element analysis to evaluate several damage mechanisms, e.g., lateral and vertical longitudinal bending stresses and strains, buoyancy, hydrodynamic forces, vortex-induced vibration, mechanical damages due to foreign objects impact, and brittle fracture assessment as per failure assessment diagram approach. The proposed framework for the fitness for service engineering assessment of exposed pipe sections presented in this study helps identify potential integrity concerns and prioritize required corrective actions. The proposed methodology offers a robust framework that can significantly improve the operation and maintenance of the existing buried pipelines.

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