EVALUATION OF CORROSION UNDER INSULATION AND REMAINING LIFE OF CARBON STEEL PIPELINES

Abstract

Analysis of Corrosion Under Insulation (CUI) and calculation of the remaining life of corroded pipes of A-106-B material is carried out based on API 571, and ASME B31.3 standards which aim to determine the operational and environmental parameters for the formation of CUI on the pipeline. The tests used include chemical composition test using Positive Material Identification type portable OES and XRF, pipe thickness testing using Ultrasonic Thickness and microscope, corrosion deposit on the pipes was tested using SEM-EDX, hardness testing using Micro Vickers Hardness Test. The results of the analysis showed that the pipe had corrosion in the Outside Diameter (OD) which was categorized as CUI. The corrosion products on the outside of the pipe surface that are formed are Fe₂O₃ and Fe₃O₄. The result of the hardness value in the specimen is influenced by the surrounding environment which causes the specimen to become harder. The calculations of the remaining life of the pipes are 2.0, 5.4 and 9.2 years for NG, CG and CH pipes respectively.