Failure analysis of pipes used in a hydrodesulfuration system of a petrochemical plant

Some types of petroleum have high sulfur content, depending on the region of extraction. In order to make possible the industrial use of such oil, it is necessary to subject it to a hydrodesulfuration process. In this process, water is used to extract sulfur from the oil, and thus, generating acid water, which is carried away through a pipe system. In this work, failures in a pipe system were analyzed through optical microscopy and Vickers microhardness measurements. Just the most significant part of the several weld joints of this enormous hydrodesulfuration system is presented here. The failures were associated to the aggressive environment, weld defects, which acted as stress raisers, and an inadequate microstructure which increased cracks propagation.