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Ghost Pearlite in External Corrosion of Buried Pipeline

Pipelines are subjected to Hydrostatic testing during construction and maintenance. The Hydrostatic test validates the pipeline integrity by ensuring that the pipeline can sustain the operating pressure. Hydrostatic tests can expose any anomalies present in the pipe that may result in failures at or a fraction above the operating pressure.

Product Number: 51323-19443-SG
Author: Sri Krishna Chimbli
Publication Date: 2023
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A failure analysis of buried API 5L Grade X42 pipeline that leaked exhibited ghost pearlite in the corrosion scale. Ghost pearlite refers to the preferential corrosion of the ferrite grains surrounding pearlite grains in carbon steel. The 12.75-inch OD, 0.25-inch wall pipeline was installed in 1949 and was in natural gas service. The work scope for the pipeline failure analysis included visual examination, metallography, energy dispersive X-Ray spectroscopy (EDS), X-Ray diffraction (XRD) analysis, Vickers hardness and tensile tests to determine the mechanism that led to the perforation. This paper provides the failure analysis results and the damage mechanism. Ghost pearlite is not typically observed in external corrosion products of buried pipelines and presents a unique case to share the findings.

A failure analysis of buried API 5L Grade X42 pipeline that leaked exhibited ghost pearlite in the corrosion scale. Ghost pearlite refers to the preferential corrosion of the ferrite grains surrounding pearlite grains in carbon steel. The 12.75-inch OD, 0.25-inch wall pipeline was installed in 1949 and was in natural gas service. The work scope for the pipeline failure analysis included visual examination, metallography, energy dispersive X-Ray spectroscopy (EDS), X-Ray diffraction (XRD) analysis, Vickers hardness and tensile tests to determine the mechanism that led to the perforation. This paper provides the failure analysis results and the damage mechanism. Ghost pearlite is not typically observed in external corrosion products of buried pipelines and presents a unique case to share the findings.