Integrity assessment of a crack inside a pressure vessel wall in RHPP “Bajina Bašta”

Abstract

The goal of this research was to combine non-destructive test methods, specifically modern ultrasound testing techniques with numerical simulations via finite element method, to determine the risk of failure of a pressure vessel in the reversible hydropower plant “Bajina Bašta”. Using Phased Array Ultrasonic Technique and Time of Flight Diffraction technique, a crack with a length of 75 mm and depth of 20 mm was detected inside the pressure vessel wall, in the vertical welded joint. Based on the exact position and size of the crack, a numerical model was made in ABAQUS. Two models were made, with and without the crack, for comparison purposes. Since the obtained results did not show difference, it was decided to make another model, with different boundary conditions, providing a more realistic insight into the behaviour of the pressure vessel, which still remained in the safe zone.