Session: 07-04-02 Crack Management

Paper Number: 87208

87208 - Implementation and Validation of Reliability-Based Crack Assessment for Natural Gas Pipeline 

Traditional in-line inspection (ILI)-based crack management programs use deterministic methods, where the calculated failure pressure ratio (FPR) and ILI-reported crack depth are compared with their respective thresholds. In recent years, TC Energy has developed a probabilistic crack assessment method, where annual probability of rupture (POR) and probability of leak (POL) are evaluated. The mitigation plan is then made by comparing the annual POR/POL with their respective thresholds. The advantage of probabilistic methods over deterministic methods is that they portray the reality better by explicitly accounting for the uncertainties associated with pipeline geometric and material properties, ILI-reported crack sizes, crack growth and burst pressure models. The framework of the probabilistic method for crack assessment has been presented in the IPC paper in 2020 (IPC 2020-9484).

This study demonstrates the safe implementation of the probabilistic assessment method for stress corrosion cracking (SCC) based on EMAT-reported data of three natural gas pipelines that are operated by TC Energy. The annual POR and POL of individual cracks are evaluated using a Monte Carlo simulation-based in-house tool. Comprehensive validation was conducted by comparing the EMAT-based mitigation plan with the in-ditch assessment of a large set of dig data. Three key questions were addressed in the validation: (1) Does the probabilistic method capture all critical features identified in the field? (2) Are the features avoided by the probabilistic method safe based on the in-ditch assessment? (3) What is the benefit of the probabilistic method in comparison with the traditional deterministic method?

The examination indicates that the developed probabilistic assessment process captures all the critical SCC features identified in the field. In comparison with the deterministic method, implementation of the probabilistic assessment method safely avoids a large portion of unnecessary digs that have been demonstrated by the in-the-ditch assessment results. The result proves that the reliability-based method can reduce a significant number of unnecessary digs without compromising safety

Presenting Author: Wei Xiang TC Energy

Presenting Author Biography: Wei Xiang is a data analytics and pipeline engineer in TC Energy. He has been working for TC<br/>Energy since April 2020 after he finished his PhD degree and Postdoctoral research work at the<br/>University of Western Ontario.