Non-Destructive Evaluation Of Corrosion On Insulated Pipe Using Tangential Radiographic Technique
Alexander Boateng, Dr. K.A. Danso, Dr. C.P.K. Dagadu
Keywords: Tangential Radiographic Technique, Pitting Corrosion, Insulated Pipe, Ir-192, Attenuation Coefficient, Wall Thickness
Abstract: Tangential Radiographic Technique (TRT) principle was explored for evaluating deposits and corrosion attacks across the inner and outer walls of an insulated steel pipe using Iridium-192.The research was performed on a designed test piece to simulate corrosion attacks and deposits on industrial pipes. Pitting corrosion measurements based on TRT were more sophisticated, and therefore magnification factor and correction were used to establish the estimated pit depth on the film. From the relationship curve drawn between the radiographic film density and the thickness of the pipe, the attenuation coefficient of the insulating material was negligible compared to the concrete deposit. The TRT method overestimated the degree of penetrated corrosion attack in the tangential position in the neighbourhood of 9% and was within an accuracy of ± 0.37 mm. This tolerance limit is 5% less than the wall thickness of the pipe. From the results obtained, effective corrosion monitoring of insulated pipes can reliably be executed by the TRT without the costly removal of insulation material.
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