PSI - Issue 31

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Goran Vukelic et al. / Procedia Structural Integrity 31 (2021) 28–32 Goran Vukelic et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 3. Heavily corroded inner surface of the vessel. Microscopic examination of cut-out specimens containing cracks was performed using optical, Fig. 4, and scanning electron microscope (SEM), Fig. 5.

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Fig. 4. Optical microscope image at 20x magnification of pitting location on: a) outer surface; b) inner surface.

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Fig. 5. SEM image at 100x magnification of pitting location on: a) outer surface; b) inner surface. Fractographic analysis was employed as the major analytical method for the failure description and crack identification (Pantazopoulos et al. 2019). Heavily corroded inner surface can be noted in Fig. 4b), but in spite of the magnification, through-wall cracks couldn’t be detected on the locations of pitting corrosion. However, SEM inspection allows to analyze the condition of pressure equipment in detail (Muthanna et al. 2019) and images in Fig. 5 show the actual character of pits. SEM was also used for measuring the diameter of the opening of the crack to be used in subsequent numerical analysis. Non-destructive testing was performed, as a powerful tool in assessing the condition of the pressure equipment (Bertolin et al. 2020)(Porziani et al. 2020). Ultrasonic thickness measurement was performed before the specimens of the vessel were cut out in order to determine shell thickness variations. Locations of performed measurement are given in Fig. 6 and results in Table 1.