NTSB Press Release

National Transportation Safety Board
Office of Public Affairs


NTSB DETERMINES FRACTURE ALONG SEAM CAUSED 2007 MISSISSIPPI PIPELINE EXPLOSION

October 14, 2009

Washington, DC - The National Transportation Safety Board determined today that the probable cause of the 2007 pipeline rupture near Carmichael, Mississippi was the failure of a weld that caused the pipe to fracture along the longitudinal seam weld, a portion of the upstream girth weld, and portions of the adjacent pipe joints.  

On November 1, 2007, a 12-inch diameter pipeline segment operated by Dixie Pipeline Company was transporting liquid propane at about 1,405 pounds per square inch gauge, when it ruptured, releasing about 431,000 gallons of propane, in a rural area near Carmichael, Mississippi. As a result, the propane began to vaporize and form a cloud that expanded over nearby homes.  Local emergency responders received calls informing them of the smell of gas and the sighting of white gas.  Approximately seven-and-a-half minutes after the rupture, the vapors ignited, creating a fireball.  There were two fatalities and several minor injuries.

The accident pipe was manufactured in 1961 using the low- frequency electric resistance welding (ERW) process for longitudinal seam welds. The majority of ruptures in ERW pipe involve the longitudinal seams.  At the time of the accident, no confirmed in-service pipeline ruptures in girth welds had been reported for the entire pipeline since it was installed.  Additionally, segments of the accident pipe had been inspected multiple times since 1998, using in-line inspection tools.   

As a result of the investigation, the Safety Board issued recommendations to the Pipeline and Hazardous Materials Safety Administration, the Clarke County Board of Supervisors, the American Petroleum Institute, and Dixie Pipeline Company on testing of pipeline, public awareness, and training and drills for 911 personnel.

A summary of the findings of the Board's report is available on the NTSB's website. 

NTSB Media Contact:
Terry N. Williams
202-314-6100
williat@ntsb.gov

 

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The National Transportation Safety Board (NTSB) is an independent federal agency charged with determining the probable cause
of transportation accidents, promoting transportation safety, and assisting victims of transportation accidents and their families.