NDT Global Advancing pipeline integrity: Enhancing detection of complex cracking in LF-ERW Pipelines

By Christopher Newton, Jordi Aymerich, Sayan Pipatpan, Tannia Haro, Santiago Urrea, and Alex Hensley

Pipeline integrity remains a cornerstone of the energy industry’s commitment to safety and reliability. With aging infrastructure and evolving operational demands, operators constantly seek innovative methods to enhance detection and assessment of potential pipeline threats. A recent collaboration has advanced the detection and characterization of complex cracking in low-frequency electric resistance welded (LF-ERW) pipelines.

The Challenge: Detecting Complex Cracks

Cracks in LF-ERW pipelines, particularly those with complex geometries such as “hook cracks” or surface laps, pose significant challenges. These defects often originate from manufacturing anomalies and can compromise pipeline integrity. Traditional inline inspection (ILI) tools and non-destructive examination (NDE) methods sometimes struggle to accurately detect and size these anomalies due to their orientation or embedded nature.

The Two-Phase Approach

To tackle these challenges, a systematic, two-phase approach was used:

• Phase 1: This phase focused on analyzing ILI data to identify patterns indicative of complex cracking. Advanced signal analysis and pattern recognition techniques were applied, incorporating insights from NDE results to differentiate potential "hook cracks" from other anomalies.

• Phase 2: The findings from Phase 1 were validated through destructive testing of pipeline samples. This metallurgical evaluation provided ground-truth data to assess the accuracy of both ILI and NDE results.

Key Insights from Destructive Testing

The laboratory testing involved seven pipeline coupons containing nine linear anomalies. The results were illuminating:

• Anomalies confirmed as lack-of-fusion (LOF) defects at the weld bond line, resulting from manufacturing issues such as improper strip edge preparation.

• Anomalies identified as surface laps, caused by folding of the pipe’s external or internal surfaces during welding.

These findings not only validated the initial ILI data patterns but also underscored the importance of destructive testing in accurately characterizing complex anomalies.

Practical Applications

Using the destructive testing results, the pattern recognition methodology was refined and applied across a broader dataset of over 3,000 anomalies. The analysis reduced the list of potential "hook cracks" and surface laps to fewer than 20, enabling a more targeted and risk-based approach to remediation. This refined approach ensures a more effective allocation of resources and reduces unnecessary digs.

Industry Implications

This case study highlights several key takeaways for pipeline operators:

1. The Value of Ground-Truth Data: Destructive testing remains a gold standard for validating ILI and NDE results, enabling operators to refine detection methods and enhance confidence in their data.

2. Collaboration is Key: Partnerships between operators and technology providers can drive innovation, combining field expertise with advanced analytical tools to address complex integrity challenges.

3. Avoiding Over-Reliance on NDE: While NDE is a critical component of pipeline integrity programs, its limitations must be acknowledged. Adjustments to ILI sizing curves should be based on verified ground-truth data, not solely on NDE results.

4. A Systematic Approach: Employing a structured methodology, as outlined in industry standards like API 1163, ensures consistency and minimizes errors in pipeline integrity assessments.

Looking Ahead

This collaboration sets a benchmark for advancing pipeline safety. By leveraging destructive testing and sophisticated data analysis, this initiative demonstrates how operators can overcome the challenges of detecting and managing complex cracking in aging infrastructure.

As the industry continues to prioritize integrity and innovation, these lessons will undoubtedly shape the future of pipeline inspection and maintenance strategies.

Crack definitions and terms. Schematic of tilted and skewed ideal cracks.