Corrosion under insulation mitigation by passive multivariate thermography

Corrosion under insulation (CUI) is one of the major concerns of oil and petrochemical installations as damage evolves invisibly under insulation layers and usually revealed on the occurrence of leaking or more catastrophic failure. Methods to early detect CUI and its causes is an urgent necessity to assure safety and performance of insulated process piping. Oil and petrochemical plants are often considered explosive environments in which thermal excitation devices are forbidden. The present work aims then on the consolidation of a passive thermographic methodology to reliably detect moisture trapped under insulation layers that will cause corrosion. The proposed methodology focuses on the thermal behaviour of the piping structure during process variations and interactions with the external ambient. The partial least-squares analysis showed promising performance on separating different physical phenomena, creating cleaner images for defect detection and extending the applicability of infrared thermography to the lower levels of surface emissivity that characterises clad insulation.