In the realm of corrosion management, corrosion under insulation (CUI) poses significant challenges, particularly for facilities operating in cryogenic service. A comprehensive approach to understanding and mitigating CUI risks is crucial for ensuring asset integrity, safety, and operational efficiency. This paper presents an in-depth case study of a natural gas liquids (NGL) fractionation facility, demonstrating the successful implementation of a holistic CUI management strategy applicable to a broader industry context. Notably, the facility has faced unique challenges, as some circuits have not been shut down or inspected for the past 40 years.
The paper details the extensive work carried out, encompassing risk mapping, mitigation strategies, inspection planning and prioritization, and repair planning. By adopting a systematic approach, the study effectively identifies and addresses CUI risks in the facility's cryogenic service operations.
The results of this research contribute to the existing body of knowledge on CUI management in cryogenic service, offering a recommended path forward for the industry to tackle CUI-related issues. By showcasing a comprehensive and adaptable approach, this paper holds great potential to foster increased safety, reliability, and efficiency in the corrosion industry, paving the way for future research and collaboration.
Corrosion Under Insulation (CUI) is a significant problem in the field of corrosion management, posing serious challenges to industry professionals. This insidious form of corrosion occurs when water, trapped between the insulation and the piping or equipment, facilitates a corrosion environment. This issue is especially acute within industrial facilities operating in cryogenic conditions, as the extreme low temperatures introduce additional complexities to the CUI. In cryogenic service, pipework and equipment often operate at extremely low temperatures, well below the freezing point of water. When insulation is removed for inspection or maintenance, the exposed surfaces can rapidly cool the surrounding moisture in the atmosphere, leading to the formation of ice. This ice can lead to component failure or system rupture. Furthermore, the expansion of water when it freezes can cause mechanical stresses on the piping material, which could contribute to the formation of cracks or other mechanical failures. As a result, pipe freezing necessitates a system shutdown to ensure safety and integrity, resulting in costly downtime. Therefore, the management of CUI in cryogenic conditions requires careful planning and execution to mitigate these risks. Several factors can further complicate the CUI challenge. Firstly, the intermittent operation of equipment, causing temperature variations, can exacerbate CUI, as per findings from the NACE SP0198-2017 standard practice. Secondly, the design of the equipment attachments or intrusions is a critical factor in CUI, with more attachments potentially leading to increased corrosion, due to moisture or rainwater bypassing the insulation and concentrating at the attachments point.
