Failure analysis of a ruptured compressor pressure vessel

Abstract This paper deals with failure analysis of a ruptured pressure vessel that served as a part of an air compressor. Pressure vessel failed during hydrostatic test when, at a pressure level lower than proof pressure, two cracks occurred on the shell and test fluid leakage was recorded. Experimental investigation methods were employed to determine possible causes of crack occurrence and vessel rupture. Liquid penetrate inspection was performed to check for other surface-breaking defects on the shell and locations of the cracks. Visual examination revealed the condition of the internal surface of the shell. Optical microscopy was used to inspect crack area while scanning electron microscopy examination at suitable magnification was employed to characterize fine microstructure of the fractured surface and to reveal flaws that served as rupture initiation points. Material’s chemical composition was determined using optical emission spectrometer with glow discharge source sample stimulation. Hardness test results were used to derive maximum tensile strength of the material. According to results obtained from performed investigations, it was concluded that excessive corrosion at the bottom part of the pressure vessel caused formation of pits that served as initiation points for leakage cracks. Recommendations for avoidance of such scenario with the rest of the user’s compressor pressure vessel were given. Also, ultrasonic testing of shell thickness was performed and results of the performed hydrostatic pressure test were recorded to be used in subsequent numerical failure analysis of the failed pressure vessel.