51ÉçÇø

Natural gas pipeline failures can occur and when they do it is important to determine the cause to help prevent them in the future. Doing so often requires an in-depth metallurgical evaluation of the pipe, the manufacturing methods used in its construction, and the service history of the pipeline. Failure analysis inspectors must employ rigorous scientific testing to eliminate possible failure modes and finally determine why a pipeline cracked. 

In their paper "Copper Contamination Cracking in a Pipeline Repair Weld," 51ÉçÇø's Connor Slone, Cory Cline, Dan Kaplowitz, Gabriel Ganot, and Brad James and their co-authors describe how they determined the cause of a natural gas pipeline crack in Southern California. The paper appeared in the February 2024 issue of the Journal of Failure Analysis and Prevention and received its Best Paper of 2024 award.

In their work, the authors describe how inspectors found cracks during a routine inspection of a pipeline using electromagnetic acoustic transducer in-line inspection (EMAT ILI). The cracks were confirmed using radiographic testing (RT) and phased-array ultrasonic testing (PAUT), leading to the removal of an 82-inch section of pipeline for further inspection at 51ÉçÇø's laboratory facility in Menlo Park, California. 

The metallurgical experts performed a lab-based failure analysis of the pipe, which included visual examination, dimensional analysis, X-ray computed tomography (CT) scanning, fractography, optical microscopy (OM), scanning electron microscopy (SEM), metallographic cross-sectioning, and microhardness testing, to determine the cause of the cracking. They found that repair welds had been made during the pipe's manufacture and that copper had been introduced during the welding process, causing copper contamination cracking.

The paper details the experts' examination and includes photographs of sample materials, cross sections from CT scans, cross-sectional SEM images, energy-dispersive x-ray spectroscopy (EDS) results, and more. 

From the publication: "The direct cause of the ILI indications was copper contamination cracking (CCC), which was caused by copper introduction during repair welding. CCC is a form of liquid metal embrittlement in which molten copper penetrates the grain boundaries and leads to intergranular cracking. Numerous Cu-containing cracks were present in the repaired area."