Coupling Inspection and Testing to Accurately Assess the Remaining Life of HIC Damaged Pressure Vessels

Abstract Hydrogen induced cracking (HIC) is a delayed failure mechanism that involves hydrogen diffusing towards stress concentrators within a susceptible material. Ultrasonic testing (UT) may provide a viable solution to successfully inspect components that have been affected by HIC. UT along with its advanced variants (specifically phased-array ultrasonic testing) can detect cracking in the range of millimeters with 90% probability of detection (POD) depending on the UT probe’s frequency. In addition to identifying HIC damage, an understanding of the material properties of a plate with that damage is necessary to determine if the vessel can continue to operate without intervention. This study utilized phased array UT (PAUT) technology that was oriented perpendicular to the pressure vessel plate’s surface to inspect HIC damage. The results of the inspection showed HIC damage throughout the plates’ thickness. The results of the phased array UT inspection were used to extract single-edge notched tension (SENT) and compact tension (CT) specimens from the pressure vessel plate. The extracted samples were tested to understand the fracture toughness (FT) properties of plates with in-service HIC damage and explore differences in FT properties measured using different notch orientations. Crack growth rate (CGR) data was collected as well. Testing was conducted in a mildly sour water environment consisting of approximately 250 ppm total sulfides at 40°C. The goal of the activity is to assess PAUT while assessing the possibility of removing unnecessary conservatism from current fitness-for-service approaches for evaluating HIC damage.