What is it about?

In this work, the rectangular parallelepiped-shaped corrosion defects with rounded corners without crack and with different relative defect depth to wall thickness ratios at the middle of the critical intrados section of a pipe elbow (API 5L X52 steel) were created to examine the effects of corrosion defects on the integrity assessment of pipe elbows. The limit pressure prediction for a pipe elbow containing corrosion defects at the intrados section is investigated using FEA. For limit pressure calculation in the pipe elbow with different defect depth ratios and to check the applicability of modified codes, the Goodall formula for calculation of the hoop stress (σθ) in pipe elbow was used in various codes.

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Why is it important?

The obtained results of the structural integrity assessment for pipe elbows with different relative corrosion defect depth ratios presented in this study are compared with our previously published results for a pipe elbow with different semi-elliptical relative crack depth ratios. The results were further compared with the numerical FEA results, and consequently, the applicability of different modified codes (adapted for the pipe elbow case) for the calculation of the limit pressure in the pipe elbow was also checked.


This study confirms that the pipe elbow is a critical part of piping systems. Moreover, the stresses at the intrados section of the pipe elbow are higher than at extrados or crown sections. Due to these facts, unmodified codes developed for the straight pipes are not applicable for pipe elbows. Further investigation of modified codes for the limit pressure calculation in the pipe elbow, taking into account the application of different contemporary formulas for the calculation of the hoop stress, is envisaged in our future research.

Professor Milos B. Djukic
University of Belgrade, Faculty of Mechanical Engineering

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This page is a summary of: Assessment of corroded API 5L X52 pipe elbow using a modified failure assessment diagram, International Journal of Pressure Vessels and Piping, December 2020, Elsevier, DOI: 10.1016/j.ijpvp.2020.104291.
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