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Information on corrosion control and prevention NTSB Member Robert Sumwalt views the site of pipe rupture. Photo courtesy of NTSB. pipeline was not odorized and is not required to be odorized when flowing through a transmission line. At the accident site, a 10-person NTSB investigation team, led by NTSB Member Robert Sumwalt, conducted feld surveys and examinations. The 20-ft section of the pipe that was ejected did not contain girth welds. It was fractured in the base metal along the entire longitudinal direction on the bottom of the pipe. The outside surface of the pipe was heavily corroded near the midpoint and along the longitudinal fracture. The thinned area was ~6 ft (1.8 m) in the longitudinal direction and 2 ft (0.6 m) in the circumferential direction. The lowest wall thickness measured was 0.078 in (1.98 mm), ~70% thinner than the nominal wall thickness. On the east and west sides of the rupture site, 10-ft (3-m) sections of the pipeline were excavated, cut out, and sent to the NTSB Materials Laboratory for a detailed evaluation. Additional preliminary fndings were also reported by the U.S. Department of NACE International, Vol. 52, No. 5 Transportation's Pipeline and Hazardous Materials Safety A dministration (PHMSA) Office of Pipeline Safety (OPS), which is a party in the investigation of the failure. The OPS observed general wall thinning on the underside of the affected pipeline at the failure location and preliminarily concluded that general wall thinning is a major factor in the cause of the failure. Line SM-80, a 26.2mile (42-km) long pipeline, was originally installed in 1951 from Lanham to Broad Run. In 1955, it was extended from Lanham to Leach. Since that time, various segments of the pipeline have been replaced, resulting in a line with various vintages of pipe, with the newest resulting from a 1992 project. In a press briefng on December 14, 2012, Sumwalt noted the NTSB's feld examination was just the beginning of this investigation and its investigators will continue to collect factual data, initiate an analysis phase of the investigation, and Continued on page 16 May 2013 MATERIALS PERFORMANCE 15