Page:NTSB - Railroad Accident Report - Derailment on May 25, 1989.djvu/51

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The rupture was about 29 inches long and, with respect to the circumference, was located about 5 inches to the east of the top of the pipe as installed (about the 1:30 o’clock position looking north). The electric resistance welded seam was located about at the top of the pipe. Examination of the area indicated that there was plastic deformation (bulging of the pipe) associated with the rupture and that the rupture produced a "fish mouth" type opening of about 4.2 inches at its widest point (see figure 14). There was no apparent visual evidence of pipe material or manufacturing" deficiencies.

Plastic deformation (denting) was present in the area of the rupture. The primary "dent" extended approximately 27 inches longitudinally along the top portion of the pipe; the dent angled slightly from the longitudinal axis of the pipe. The primary dent began at a point 20 inches northwest of the rupture point and extended to a point 7 inches southwest of the rupture point. The primary dent was about 1⅜ inches wide at its widest point and the deepest depth of the dent was abou 0.07 inches.

The primary dent produced a protrusion (bulge) on the inside surface of the pipe and localized wall thinning. The minimum wall thickness, as measured in this area at the accident site, was 0.249 inches and was located about 4 inches from the point of rupture. Additional wall thinning was near the point of rupture ("Tests and Research," "Metallurgical Testing").

Nearly parallel to and below the primary dent was a mark/scratch on the pipe that extended from about the same downstream location as the primary dent to about the point of rupture.

A second pair of marks on the pipe was located upstream (south) about 36 inches south of the point of rupture. The pipe had been damaged (gouged) in an area about 5 inches below (east) the top of the pipe. The longer mark was about 36 inches long and located closer to the top of the pipe; a 2½-inch-wide section of the coating had been removed. revealing a 1½-inch-wide mark on the metal. The second mark began slightly north of the first; the maximum width of damage to the coating was about 2 inches and the length of damage was about one half that of the upper mark.

About 120 inches north of the point of rupture, some damage to the coating on the east side of the pipe was observed. Coating in widths varying from 4 to 7 inches had been removed from the pipe at the 3 o’clock position (looking north). No damage was apparent o the pipe metal.

At a location 188 feet north of the end of the Highland Road casing, two reas of damage to the pipe were found at the time the pipe was being removed for replacement. The section of pipe containing these two areas of damage were sent to the Southwest Research Institute for metallurgical examination. ("Tests and Research," "Metallurgical Testing").

Track and Signal Information

Track.—The train derailment occurred on the single mainline track in San Bernardino, California, near railroad MP 486.8. Approaching the