Keywords: corrosion, insulation, CUI, risk based inspection, RBI, degradation mechanisms, preventive maintenance.
This paper describes recent experiences in Yara with corrosion under insulation (CUI). CUI has been detected in some plants through existing inspection programs; other plants have had problems with production and economical losses as a consequence of corrosion under insulation issues.
A few years ago (2004) an ammonia leakage occurred in one of our ammonia plants. The investigation result clearly indicated CUI as the direct cause for this failure. A second incident occurred in 2005 (in another ammonia plant). In this case it was a gas fire in the synthesis loop of the ammonia plant. Also here, the investigation committee pinpointed CUI as the direct cause of the incident.
Based on these incidents several immediate and long term actions were taken all over Yara. Our conclusion is that corrosion under insulation can be avoided through a good cooperation between operations, inspection and maintenance departments.
Frank De Vogelaere, Yara Belgium S.A., Avenue Marcel Thiry 83, B-1200 Brussels, Belgium.
12 pages, 9 figures.