Assessing changes in stress-corrosion damageability on the basis of repeated in-tube nondestructive testing

Advances in the development of in-tube nondestructive testing (INT) have allowed obtainment of comprehensive quantitative information that concerns the state of an operational gas pipeline at the moment of inspection and characterizes the quantity, location, and dimensions of flaws. By means of repeated testing, it is possible to assess changes in the state of an operational gas pipeline during the time period between inspections, thus showing the dynamics of corrosive damageability on the time scale and under conditions of commercial operations (within the limits of sensitivity and resolution of the flaw detectors used). In this study, the INT results for a segment of a multistrand pipeline from the Krasnotur’ insk compressor station to the Lyaly a compressor station collected in 2000–2004 with ДMT-1400 and ДMTII-1400 magnetic-pig flaw detectors are considered. On the basis of the analysis of the INT results characterizing the development of corrosion and stress-corrosion damageability at the moment of inspection, the possibilities and conditions for the use of the obtained data for comparative assessment of the changes in corrosion-related damageability of gas pipelines are considered. According to the collected information, there is no evidence that stress-corrosion damageability is enhanced during the period between two inspections and that corrosion and stress-corrosion damageability are superimposed (observation of etched longitudinal grooves during second inspection).