Developing Stress Intensification Factors for Composite Repair Systems Used to Repair Damaged Pipe

Abstract

For the better part of the past 15 years composite materials have been used to repair corrosion in high pressure gas and liquid transmission pipelines. This method of repair is widely accepted throughout the pipeline industry because of the extensive evaluation efforts performed by composite repair manufacturers, operators, and research organizations. Pipeline damage comes in different forms, one of which involves dents that include plain dents, dents in girth welds and seam welds. An extensive study has been performed over the past several years involving multiple composite manufacturers that installed their repair systems on the above mentioned dent types. The test samples were pressure cycled to failure to determine the level of life extension provided by the composite materials over a set of unrepaired test samples. Several of the repaired dents in the study did not fail even after 250,000 pressure cycles had been applied at a range of 72% SMYS. The primary purpose of this paper is to present details on how Stress Intensification Factors were derived using the empirically-generated data. The results of this study clearly demonstrate the significant potential that composite repair systems have, when properly designed and installed, to restore the integrity of damaged pipelines and piping systems to ensure long-term service.