Significance of visual testing of welded joints on exploitation safety of pressure equipment

Abstract

More often than not, documentation about making and testing of welded structures does not include visual test reports, or includes such reports which are not in accordance with relevant standards. Welded structure failure is caused by cracks, which typically occur in welded joint defects. Some of these defects can only be detected using visual testing. In addition, visual testing is a reliable method for determining which parts of a welded joint have increased risk of crack initiation, i.e., repair locations during fabrication or exploitation, which also need to be subjected to other nondestructive test methods. In this way, probability of failure is decreased, i.e., welded structure safety is improved. This is of particular importance for pressure equipment. This paper shows the failure of a tank used for storage of liquid oxygen during exploitation. During tank fabrication, a number of defects were made in the welded joint. One of these defects, in the form of a notch, lead to the destruction of the tank after years of exploitation.