Session: 03-01-01 Pipeline Remediation and Mitigation 1.1

Paper Number: 133795

133795 - Impact of Inline Isolation Tool on the Integrity of Onshore Pipelines 

Abstract: 

Inline isolation tools are widely used for offshore pipelines for planned maintenance and emergency repair work, e.g. valve replacement, repair, tie-ins. Design and engineering analysis of such tools for offshore application have been well developed, e.g. as outlined in DNV-RP-F113 Pipeline Subsea Repair. Because of its capability of providing reliable in-line isolation with significantly reduced blown-down length and methane emission for integrity and capital projects that traditionally require pipeline outages, the technology is getting increased attention from the onshore pipeline operators in recent years. Consequently, there is a growing need for better understanding of applicability and limitations of using established offshore design rules for onshore applications and developing engineering assessment workflow to ensure successful execution and prevent potential irreversible damage to existing assets.

In this paper, differences of onshore vs. offshore pipelines such as loading scenarios, restraint conditions, pipeline configurations are described. Typical challenges for onshore applications are also discussed. The in-depth analysis in this study investigates the stresses on the pipeline exerted by the inline isolation tools during operation by leveraging 3-D continuum finite element (FE) analysis using Abaqus FE software, with consideration of actual loading and boundary conditions that onshore pipelines could involve. The FE model was first calibrated with the full-scale test results to ensure accuracy and validity of the simulation. Subsequently, a total of 137 FE models were developed for a wide range of pipe sizes (NPS 10 to NPS 48) and wall thicknesses (4 mm to 26.4 mm). The resulting stresses are compared with the allowable stresses for the pipelines to check against potential failure modes such as plastic collapse and local failure. Furthermore, a sensitivity study is also performed for various pipe material properties to ensure that an adequate factor of safety is maintained throughout the analysis. Outcomes of the investigative study was fed into a streamlined assessment workflow that includes a series of simplified graphs for determining the allowable pressure for various pipe sizes for future applications. The results demonstrated advantages of using FE based streamlined approach over conservative case-by-case analytical solutions. The outcome of this study provides insight on the various stress conditions that could result from the inline isolation tool for onshore pipelines and could potentially impact pipeline integrity. A streamlined engineering assessment workflow for application of inline isolation tools for onshore pipelines is also provided.

Presenting Author: Suborno Debnath DNV

Presenting Author Biography: Suborno Debnath is working in DNV as a Pipeline Integrity Engineer in Training. He has over eight years of cumulative experience (six years of industrial and two years of research) and has gained extensive expertise in various aspects of engineering, specializing in designing new pipelines, fitness for service assessment of existing pipelines (i.e., crack, corrosion, dent, fatigue etc.), geohazard assessment, and design, repair, and rehabilitation of steel structures. Mr. Debnath has an in-depth knowledge of API 579-1, ASME B31 pipeline codes, CSA Z662, and local regulation of Alberta, British Columbia, Saskatchewan, and Ontario.

Authors:

Suborno Debnath DNV
Kshama Roy DNV
Tina Liu TC Energy
Ole Yin TC Energy
Ken Zhang TC Energy