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Microwave Detection of Metal Thinning on Steel Surfaces Covered by Sandy Oil Residues

Inspection of internal surfaces of processing vessels in oil and petrochemical facilities is a major challenge for their operators. These vessels are required to be inspected periodically to ensure continued safe operation. The current inspection practice is cumbersome, requiring the vessel to be shut down and removed from operation. Subsequently, the vessel goes through a thorough chemical cleaning followed by visual inspection. In addition to this inspection process being potentially harmful to the cleaning crew and inspectors, it also requires taking the vessel off-line and out of operation. Clearly, a more effective inspection method is desirous. High-resolution microwave imaging techniques, based on a synthetic aperture radar (SAR) approach, are suitable for this type of inspection. Signals at these frequencies penetrate through residues of materials stored in the vessels, eliminating the need for chemical pre-cleaning. Furthermore, these images are capable of indicating metal loss (for example, due to corrosion). In this paper, the efficacy and limitations of this imaging technique for detecting metal loss in three specially prepared steel panels while covered with up to ~20 mm of sandy oil residues with different sand concentrations is investigated. A discussion of the overall capabilities of this technique for in-field vessels is also provided.


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