Methodology for Comparing Field Applied Liquid Epoxy and Hot Bituminous Tape Coating Repairs Using Inline Inspection Data

In this paper, pipelines with similar parameters (e.g., diameter, environment, temperature of the product, etc.) are used to compare the effectiveness of field repair coatings (i.e., liquid epoxy and tape coating systems) against external corrosion. Liquid epoxy and tape coating systems are compared based on number of corrosion features, severity, morphology and distribution of features over depth and length. Once corrosion defects are assessed in the field and a repair coating is applied, In-Line Inspection (ILI) tools can detect and size the corrosion features under these coatings. If the corrosion feature is growing, the growth can be detected and measured using ILI data assessment. In this paper, data from both field nondestructive examination (NDE) and ILI measurements collected from 1996 to 2013 are used to assess the corrosion growth rate (CGR) under both types of repair coatings. The CGR with respect to depth is compared for both liquid epoxy and tape coatings and then normalized by the number of corrosion features over the segment. In addition, the effectiveness of cathodic protection was evaluated at the locations of the assessed repair coating. Ultimately, this paper provides useful information to pipeline operators for decision making regarding the choice of repair coatings based on operational data collected over 14 years.