EXPERIMENTAL

A failure analysis was performed. Internal inspection found 12 locations of pitting at or adjacent to welds in the Phase 1piping system. Radiography was performed to confirm the locations.

Water samples were taken from both Phase 1 and Phase 2 systems, following the failed hydrotesting. The city water contained very low chlorides, approximately 86 ppm nominal and 25 ppm from samples removed at the time of failure. The source of the city water is a combination of surface and well water. Microbiological analysis found corrosion-related microbes, including iron bacteria in the water.

Several areas were selected for metallurgical examination. Figures 1-3 show the results of this examination. The morphology of the pits found in the stainless steel were jagged, a characteristic of MIC but not of more conventional crevice corrosion in stainless steel.

Although the Phase 2 system was drained when the hydrotesting found leaks due to through?wall pitting, it was not drained dry, and some water remained stagnant. After approximately two months stagnant exposure to city water, this situation was discovered and additional inspection was performed. Inspection revealed shallow pitting had occurred in the Phase 2 system.

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