Here’s the press release from the US National Transportation Safety Board:

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   NTSB PRESS RELEASE

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National Transportation Safety Board

Washington, DC 20594

FOR IMMEDIATE RELEASE: October 14, 2009

SB-09-58

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NTSB DETERMINES FRACTURE ALONG SEAM CAUSED 2007 MISSISSIPPI PIPELINE EXPLOSION

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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 at:

http://ntsb.gov/Publictn/2009/PAR0901.htm

Media Contact: Terry N. Williams

   (202) 314-6100

   terry.williams@ntsb.gov

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What do you think? Did they find the root cause? Comment at the link below.