Common Root Causes of Pressure Vessel Failures: A Review

Abstract

Present rules in fabrication codes, such as BSI PD6493, are aimed to reduce the probability of failures in welded pressure vessels subjected to cyclic pressure or vibrations. Yet, several leaks and ruptures have recently occurred in pressure vessels and pipes. Common aspects of these failures are crack initiation in weld metal and heat affected zone of welds, all related to an insufficient design of the reinforcement and poor execution of the welding procedure. Weld inadequacy is in one case a result of an increase in thickness as an attempt to increase safety; which also increased cyclic stresses due to excessive weight of the vessel. In this article, a brief overview of various pressure vessel failure mechanisms has been presented w.r.t impact toughness of thermally aged specimen, effects of absorbed hydrogen and thermal aging on crack-tip plastic zone in welded steel, fatigue crack mechanism of welded austenitic steel and effects of fatigue crack growth of thermally aged welded steel. About 39 published studies (1976-2015) are reviewed in this paper. It is marked from the literature survey articles that pressure vessels remain unsafe unless carefully designed, operated and inspected at regular intervals.