Session: 04-03-01 Geohazard Management Program - Part II

Paper Number: 87364

87364 - Fitness for Service Engineering Assessment of Exposed Pipeline Sections 

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. The fitness for service engineering assessment needs to identify the relevant damage mechanisms for evaluation in all the possible environmental conditions. A fitness for service engineering assessment methodology successfully used for an NPS 10 onshore natural gas pipeline exposure is presented herein. The assessment is based on analytical and finite element analysis to evaluate all the possible damage mechanisms, e.g. lateral and vertical longitudinal bending stresses/strains, buoyancy, hydrodynamic forces, vortex-induced vibration, denting and mechanical damages due to object impact, and brittle fracture assessment as per failure assessment diagram approach. Both beam-based and an advanced hybrid three-dimensional finite element model have been used in the present study. A strain-based evaluation is utilized to check for rupture, yielding, local buckling, and fatigue failure modes. A comprehensive parametric study on soil types, loading scenarios, size of the fallen objects, etc is also conducted in the present study. Finite element results show that not only the length of the exposed section and thereby the bending strain but also other damage mechanisms such as impact loading from the falling trees located nearby or vortex-induced vibration loading due to the creek flow can impact the fitness for service engineering assessment of an exposed pipe section. 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 unique framework that can significantly improve the operation and maintenance of the existing buried pipelines. 

Presenting Author: Alireza Kohandehghan Pacific Northern Gas Ltd.

Presenting Author Biography: Alireza Kohandehghan is an Asset Integrity Engineer at Pacific Northern Gas Ltd. (PNG). He has extensive experience in pipeline and facility integrity management processes, fitness for service (FFS) engineering assessments, engineering critical assessment (ECA), risk assessments and probability of failure, remaining-life assessments, welding and metallurgical assessments, stress analysis, and simulation and modeling. He is an active member of several industry proceedings and working groups. Alireza always strives for knowledge sharing across the industry, promotes a culture of excellence, and promotes strategic thinking. He has demonstrated initiatives by tackling challenges, solving problems, developing systems, processes, and procedures, and brainstorming ideas to provoke critical thinking.