Session: 07-03-01 Risk Management

Paper Number: 87273

87273 - Prioritizing Retrofits of Non-Piggable Transmission Pipelines Using an Internal Corrosion Structural Reliability Model 

Internal Corrosion (IC) is a time dependent threat to pipelines that leads to wall loss due to a reaction between pipe material and the products or contaminants being transported. Certain vintage pipelines are not piggable, meaning that Inline Inspection measurement tools cannot be used to measure IC defects. Furthermore, being older, these pipelines are more susceptible to time dependent threats such as IC due to their longer exposure time. Operators often need to prioritize retrofits between different non-piggable pipelines, and the approach described in this study uses a structural reliability approach to estimate the expected frequency of failure for non-piggable pipeline segments and ranks them accordingly.

This model captures the severity of IC using defect length and depth corrosion growth rate (CGR) by building empirical distributions using data from inspected pipelines of different pipeline asset types (eg. laterals, transmission).  These asset types serve as an indirect measure of gas quality. The data on these inspected lines shows evidence of this through differences on the IC depth distributions and anomaly densities. By characterizing CGR as a distribution for different asset types and using the industry standard Growth-by-Rule method to model defect depth, the model considers both asset type and pipe age when predicting the defect depth distribution in the current year. This projected depth distribution is used with physical and operating parameters (eg. diameter, WT, pressure) in a structural reliability model to estimate the probability of failure for the segment under consideration. The importance of both asset type and age when modelling IC was confirmed using a supervised machine learning regression decision tree. This decision tree model describes the likelihood of corrosion existing by estimating the anomaly density for different pipeline types.

The structural reliability-based prioritization approach described in this paper provides a methodology to utilize physical and operating parameters of an un-piggable pipeline together with information from inspected pipelines to rank the expected severity of a given un-piggable line. These segment ranks were finally compared to a baseline rule-based approach to quantify the benefits of this more detailed analysis methodology.

Presenting Author: Gabriel Langlois-Rahme Enbridge

Presenting Author Biography: Gabriel Langlois-Rahme is an Integrity Assessments Engineer at Enbridge Gas Distribution and Storage. As a member of the Integrity Assessments team, he is responsible for the development and implementation of a variety of quantitative risk models on Transmission Pipelines. This includes the application of limit state designs, Bayesian and Classical statistics for engineering decision making, Spatial Analysis, Societal and Individual Risk Reporting, and model integration into database and software environments. He joined Enbridge in 2020 as an Engineer and has had increasing responsibility around engineering research and implementation. He currently has 6 years of engineering experience in the area of risk and reliability in the transmission, distribution and storage of natural gas pipelines.<br/><br/>Gabriel was born in Montreal and holds a Bachelor and Master’s degree in Chemical Engineering from McGill University. He is a licensed Engineer and a member of Professional Engineers Ontario, a project management professional (PMP), and an avid data science enthusiast. In his spare time, Gabriel enjoys skiing, swimming, playing tennis and spending time with friends and family