CUI Assessment Near Insulation Support Rings Using Pulsed Eddy Currents

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Pulsed Eddy Currents (PEC) is an electromagnetic inspection method for detecting thickness variations in carbon steel and cast iron through various insulation and/or protective components. It is also resilient to liftoff variations, making it a valuable technique for Corrosion Under Insulation (CUI) assessment. The technology is widely used in the energy and petrochemical industries to detect and estimate the extent of corrosion in insulated or fire-proofed components like pipes and tanks without removing the covering.

Product Number: 51323-19031-SG

Author: Donald Picard, Olivier Bellavance, Charles Tremblay, Andréanne Potvin

Publication Date: 2023

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Pulsed Eddy Current (PEC) is a proven inspection technology used to detect and assess wall loss in ferromagnetic materials under any layer of insulation or coating that prevents direct access to the surface. One of its main applications is detecting Corrosion Under Insulation (CUI) in pressure vessels. Corrosion, caused by water or condensation ingress under the insulation, is generally found just above the Insulation Support Rings (ISR), interfering with the PEC signals. Hence, assessing this corrosion requires advanced data analysis tools combined with a clear understanding of the influence of the ISR on the signals. The objective of this paper is thus to establish a data analysis workflow for assessing this corrosion by evaluating the impact of the ISR on the PEC signals. The discrimination of the influence of the ISR on PEC data was best achieved by scanning perpendicular to the ISR and by analyzing signals taken on representative manufactured pressure vessel samples. Advanced analysis tools developed in recent years and the various PEC signals are presented and explained, demonstrating the capabilities of this technology to reveal the presence of true wall loss near interfering components. Such challenging applications require advanced data analysis tools and efficient workflow analyses to increase confidence.