Evaluation of Composite Sleeves for Reinforcement of Dented Pipelines

Composite sleeve repair systems, now of widespread use in the market, were originally developed for the reinforcement of corroded pipelines. Transpetro, the Brazilian pipeline operator, asked Petrobras/CENPES to address the behavior of those sleeves when applied to dented pipelines. A short verification experiment was envisaged, in which both the dent filling material and the sleeve material were varied. Artificial dents with depths of 19% OD were imposed to 22 in. OD, 0.5 in. thick, API 5L X60 tubular specimens. Concrete and polymeric materials were tested for dent filling, whereas glass and carbon fiber composites, in two different thicknesses, were tried as the sleeve structural material. The main purpose of the repair sleeve in this case is to provide a repair procedure installed at low temperature and capable of reducing the stress range at the hot spot in the dent. The goal is to improve the fatigue resistance of the repaired pipeline. Low cycle fatigue tests were performed, both using non-repaired specimens (to serve as the basis for comparison) and the specimens repaired using the different schemes proposed. The tests were fully instrumented to analyze deformations in each specimen. After the fatigue tests, each specimen was pressurized until collapse, in order to quantify their ultimate strength. This paper reports the main results of the tests and the deformation analysis of each repaired specimen, aimed to define parameters which will serve to the design of future cases.