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Picture for Techniques for Inspecting Wall Thickness Metal Loss of Pipelines under Nonmetallic Sleeves
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Techniques for Inspecting Wall Thickness Metal Loss of Pipelines under Nonmetallic Sleeves

Product Number: MPWT19-14377
Author: Hatim Alhamdan, Fadhel Al Asfoor, Aziz Rehman, Rashed Alhajri
Publication Date: 2019
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Composite repairs have been applied to pipelines and piping systems for structural reinforcement after external corrosion. Such repairs may consist of glass or carbon fibers embedded in a matrix of epoxy. Typically, these repairs are hand applied using either wet lay-up systems or prefabricated rolls of composite sleeve. In some applications, pipeline continued corrosion growth under composite repairs were reported using Inline Inspection (ILI) which raises a concern about the integrity of the metallic piping under composite repairs. When continued corrosion is detected by ILI, a difficulty is typically faced due to the inability to measure pipeline remaining thickness under such repairs. To resolve this challenge, this paper will discuss multiple inspection and corrosion monitoring techniques for metal loss under composite repairs. To measure the pipeline wall thickness due to internal corrosion, one or more of the three (3) Non-Destructive Testing (NDT) technologies namely; Dynamic Response Spectroscopy (DRS), Multi-skip Ultrasonic (MS-UT) and digital radiography were evaluated and found capable. To monitor for external corrosion, a scheduled visual inspection of the composite repair would be the first inspection step. If the composite repair appears to be intact then the visual inspection would suffice and the repair should be acceptable to its design life. If the original defect is external corrosion and a scheduled visual inspection of the composite repair shows damage to the composite repair then inspection to assess the integrity of the substrate must be used before permanently fixing the composite repair. For this scenario, digital radiography or MS-UT are recommended to assess the condition of the substrate