NTSB Safety Recommendation Letter P-76-002

Page 1Official PDFWASHINGTON, D.C. FOR RELEASE: 6:30 A,M,, E,D,T,, JANUARY 23, 1976 (202) 426-8787 ISSUED: January 23, 1976 Honorable William T. Coleman, Jr. Secretary Department of Transportation Washington, D. C. 20590 SAFETY RECOMMENOAT ION(S) P-76-2 - About 3:45 a.m. on March 15, 1974, the Southern Union Gas Company's 12--inch natural gas transmission pipeline ruptured in a desert near Farmington, New Mexico. Natural gas at almost 500 psig pressure escaped, ignited, and burned several hundred feet high. An 8-foot section of the 12-inch pipeline had blown out, digging a crater 40 feet long, 17 feet wide, and 10 feet deep. Three persons driving down a road adjacent to the pipeline died and the earth within a 300-foot diameter was charred. At 5 a.m., the valves on both sides of the break were closed, isolating the failed section within 8 . 9 miles. The longitudinal flash weld of the A. 0. Smith pipe, manufactured in 1948, showed severe crevice corrosion in the fusion line. Metal- lurgical examination showed that the brittle fracture initiated along the longitudinal seam on the bottom of the pipe and propagated in both directions from the origin area along the weld. The corrosion in the flash weld reduced the overall strength of the pipe by reducing the effective wall thickness; this resulted in higher-than-normal stresses in the weld line until the failure occurred. This uncoated pipeline had been under hot-spot protection since 1965 and, while experiencing many corrosion leaks, there had never been a rupture of this type in the past. The pressure at the time of failure was below the maximum allowable operating pressure of 565 psig. This is the only failure of this type ever experienced by Southern Union, but other operators may have had failures resulting from weakened flash welds. 1722 P Ad? - 75-3#

Page 2Therefore, the National Transportation Safety Board rec the Department of Transportation: Review all pertinent data such as leak and fail reports submitted by all pipeline operators to determine if lonaitudinal weld failures consti - a recurrent safety problem, and take appropriate regulatory action if they do. (Recommendation P-76-2) (Class 11, Priority Followup) REED, Acting Chairman, McALIAMS, THAYER, BURGESS, and HALEY, Members, --- John H. Reed Acting Chairman THIS DOCUMENT IS TO BE RELEASED TO THE PUBLIC ON THE DATE S NO PUBLIC DISSEMINATION OF THIS DOCUMENT SHOULD BE MADE BEFORE THAT DATE.#