Session: 07-05: Cracks Uncertainty Modelling

Submission Number: 186284

Accounting for Unreported Pipe Body Axial SCC Features in EMAT-Based Integrity Management and Long-Range Planning 

Electromagnetic Acoustic Transducer (EMAT) tools are widely used for Stress Corrosion Cracking (SCC) threat management in pipeline integrity programs. While EMAT offers unique advantages in detecting axially oriented cracks without direct liquid coupling, it is not without limitations. These tools can struggle to reliably identify small and moderate cracks, interacting crack colonies, and features located in noisy or geometrically complex pipe environments. As a result, a population of SCC features may remain unreported following an EMAT inline inspection (ILI). If this hidden population is not explicitly accounted for, it can introduce systematic bias into probability of failure estimates and reduce confidence in long range integrity planning decisions.

This paper presents a methodology to estimate and incorporate unreported SCC into a comprehensive SCC threat management framework. The approach begins with development of a logistic detection model calibrated using excavation validation data for SCC features. This model characterizes the probability of detection of an EMAT tool as a function of crack size and is used to estimate the size distribution of SCC features that may remain unreported following an EMAT ILI. The estimated unreported SCC size distribution is considered alongside EMAT reported features to support risk evaluation of a pipeline and future risk.

By explicitly accounting for EMAT detection limitations, the methodology enables more realistic evaluation of long term risk trends at the pipeline segment level. Comparisons of long range planning scenarios with and without the unreported SCC population demonstrate that omission of this population can lead to non-conservative assumptions regarding reassessment timing and mitigation prioritization. In contrast, explicitly incorporating detection uncertainty improves transparency in SCC risk estimation and supports more robust, risk informed decision making.

The proposed methodology provides a structured framework for integrating inspection limitations into long range SCC threat management, strengthening confidence in integrity decisions and supporting proactive risk management.

Presenting Author: Alexander Foster, ENBRIDGE, INC.

Presenting Author Biography: Alexander Foster is a Senior Engineer in the Risk Analysis & Diagnostics group at Enbridge, Gas Transmission and Midstream, where he supports pipeline integrity decision-making through risk and reliability assessments. He has over 10 years of industry experience in pipeline and facility integrity and threat assessment. Alexander holds a Bachelor of Science in Chemical Engineering and is a licensed Professional Engineer in the state of Texas.

Authors:

Alexander Foster ENBRIDGE, INC.
Huang Tang ENBRIDGE, INC.
Martin Di Blasi ENBRIDGE, INC