Failure analysis of a 300M steel pressure vessel

A failure analysis was made in a 300M steel pressure vessel which has failed during hydrotest. The rupture occurred suddenly at a pressure level lower than what has been expected for the proof pressure. According to the results of various examinations it was concluded that hydrogen assisted stress corrosion cracking was the mechanism responsible for the failure. The root causes of this failure have been identified, serving as base for the modification of testing procedures in similar components.