Pipeline pigging and integrity management conference, Houston, February 2021
This paper is the continuation of a 3 year-long study in the use of magnetic based ultra-high sampling density in-line inspection (ILI) systems (up to 2,000 samples per square inch) to detect and size circumferential stress corrosion cracking (CSCC). The objective of the study is to enable a shift from the CSCC direct assessment approach to diagnostics by an ILI measurement system.
This phase of the study focuses on the detection of CSCC by multiple ILI systems that integrate axial and circumferential magnetic flux leakage (AMFL and CMFL) along with internal depth detection sensor arrays (IDD), a high precision geometry measurement unit (HP-GMU) and inertial mapping data (IMU).
To date a total of seven line segments have now been inspected for CSCC collecting a total amount of data exceeding 1 TB. This paper focuses on the five line segments inspected for Xcel Energy and the results from two other operators have been include in our data base. Individual line segments had collected data sizes that often exceeded 200 GB. This also required the development of detection and sizing algorithms along with data analysis processes that can categorize and prioritize relevant CSCC. This process was performed to differentiate CSCC amongst the hundreds of thousands of detected magnetic anomalies in any given line.
Included in this study are the CSCC inspection results from over 200 miles of natural gas pipelines in NPS 6”, 8” and 10” segments. These results are utilized to review susceptibility factors for CSCC and discuss best practices for excavation and inspection of CSCC anomalies. Field non-destructive examination (NDE) and metallurgical analysis from identified anomalies have been used to baseline the system’s probability of detection (POD) and probability of identification (POI) of critical and subcritical CSCC.
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