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Southern Seeks to Iron Out ‘Wrinkle Bend’ Hazards on Pipe System
Southern Natural Gas Co. LLC (SNG) has asked the Federal Energy Regulatory Commission for the green light to abandon nearly 20 miles of pipeline and associated facilities in Alabama to comply with a correction action order issued by the Pipeline and Hazardous Materials Safety Administration (PHMSA) to address the hazards associated with wrinkle bends, which led to a failure on SNG’s system in 2009.
Specifically SNG, which is owned by Houston-based El Paso Corp., is proposing to abandon in place 19.56 miles of its North Main Loop Line from the DeArmanville Compressor Station to the Rome-Calhoun Gate in Calhoun and Cleburne counties, AL, as well as install a 2.25-mile lateral off SNG’s 20-inch diameter North Mainline Line.
The application follows a rupture on the pipeline system in 2009, which SNG and PHMSA concluded was caused by a wrinkle bend in the North Main Loop Line. The loop line was originally installed in 1948, according to SNG. At the time, contractors commonly used a process of conforming steel pipe to the surrounding topography by forcefully compressing the pipe to create a bend in it. This technique created what have come to be known as “wrinkle bends” in the pipe.
“Removing the abandoned segment will not eliminate all of the wrinkle bends on Southern’s North Main Loop Line, but [it] will remove those wrinkle bends on the Southern system that both Southern and PHMSA believe create a higher risk of failure because of the underlying geological structure,” the pipeline said.
Southern said it is working with a third-party expert to identify and address factors that contribute to failures at wrinkle bends, such as bend orientation, geometry of the wrinkle, long-seam location and fabrication stresses, to “determine what factors have the greatest contribution to the potential for failure and to create a risk analysis process to better identify and mitigate those risks before failure occurs.”
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