Abstract
Corrosion Under Insulation(CUI) of carbon steel and low alloy steel in oil refinery and petrochemical plants is the most important degradation phenomena of equipment materials. Since the characteristics of CUI have not been fully understood the accurate prediction and estimation of CUI is difficult actually. In this study, data collection of CUI was carried out in actual plants. This information is analyzed for clarifying the controlling factors of CUI. The modification of CUI Technical Module published by API is examined based on this analysis. From this study, it become obvious that the corrosion rates of CUI may follow Gumbel distribution, and CUI are controlled by types of equipments, temperature and structure design. In particular, corrosion rate of CUI is accelerated at impediment to drainage area such as stiffening ring of tower. Based on the present results, the modification of CUI technical module was established for the more accurate prediction and estimation of CUI.
