Failure Analysis of API 5L Gr.B Steel Pipe Containing Low Pressure Condensate Steam in a Gas Refining Unit

The quality of low-pressure condensate steam, which is one of the important process fluids in the gas refining industry, in addition to its effect on the continuity and quality of refinery products, can be effective on the health and mechanical integrity of equipment and piping systems. The presence of destructive elements such as oxygen and carbon dioxide in the consumed steam and selected steam leads to severe corrosion in the piping system and equipment made of carbon steel. In this research, the causes of corrosion of the destroyed pipe with API 5L Gr.B material carrying low-pressure gas condensate steam related to one of the process units in one of Iran gas refineries have been evaluated. For this purpose, while reviewing technical documents and various characterization techniques such as stereography, spark emission spectrometry analysis, optical microscope, scanning electron microscope, analysis of corrosion products by X-ray fluorescence and measurement of dissolved oxygen in the fluid was carried out. The appearance of the created corrosion is similar to the corrosion caused by oxygen. Also, the results of the analysis of the remaining corrosion products on the inner surface of the pipe and inside the created holes showed the presence of iron oxide. Therefore, it was finally determined that the pipe in question suffered from corrosion caused by oxygen.