Hydrostatic testing of pipelines is critical during construction and maintenance. It is an important pre-commission test and destructive tool which validates the integrity of the pipeline prior to actual service with flammable fluids at high pressures. Hydrotesting provides the quality control needed to ensure that the required pipeline tensile strength is available to sustain the operating pressure, and that the welds and joints are defect free.

In this paper, we discuss a recent case study wherein metallurgical analysis was performed at our lab on a 20-inch API 5L X65 carbon steel pipeline. A leak was detected during the commissioning hydrotest of a newly constructed pipeline in the field at a client site. Dye penetrant testing, x-ray radiography and phased array UT inspection techniques revealed the presence of a defect at the electric resistance weld (ERW) seam. Based on the analyses, it was confirmed that the defect was due to incomplete fusion at the long seam weld during the ERW welding process.

Subject
Scanning electron microscopy, Test methods, Seams, Materials, Piping, Surface defects, Microstructure, Welding, Pipelines, Magnification, Mechanical failure, Defects, Hydrostatic testing
Keywords:
Metallurgical analysis, hydrostatic testing, pipeline welding defects, lack of fusion, ERW weld
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2021
Association for Materials Protection and Performance (AMPP)
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