Pipeline Failure Investigation Report - PHMSA - U.S. Department of ...

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Executive Summary (continued)
A pipe sample for chemical analysis was removed from the joint that failed to determine the
composition. Transverse pipe samples for mechanical (duplicate tensiles and Charpy V-notch
impact) testing were removed from the base metal of the downstream joint.
The predicted burst pressure for the region of wall loss that contained the rupture was
calculated using the RSTRENG effective area method embodied in CorLAS TM . Two flaw
profiles were obtained. The first flaw profile (profile 1) was obtained by using a modified river
bottom method. A second flaw profile (profile 2) was constructed by measuring the wall
thicknesses at the edge of the counter-clockwise fracture surface. A flow strength of the
measured yield stress (MYS)+10 ksi was used for the calculation.
Below is a summary of our preliminary observations and conclusions:
• The failure occurred at a region of external wall loss from corrosion.
• The maximum depth of wall loss at the rupture surface was 0.210 inches (74.7% of wall
thickness).
• Bacteria did not likely play a role in the external corrosion based on the morphology of
the corrosion and the results of the bacteria culture testing.
• The morphology of the fracture surfaces suggests that the failure initiated in a ductile
manner.
• The morphology of the seam weld is consistent with an EFW seam.
• The microstructure and steel composition are consistent with line pipe steel.
• The results of the tensile and Charpy testing are consistent with this vintage of line pipe
steel.
• The estimated burst pressure ranged between 663 psig to 868 psig, compared to an
actual failure pressure of 790 psig.
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