Comparison of Composite Repair Performance on Drilled and Simulated Defects

Abstract

Erosion is a common failure mechanism in pipework. Particulate-laden flows are common in many industries and these particulate can quickly deteriorate piping at bends, transitions, and, if conditions are correct, straight line sections. Repair of damaged piping and pressure vessels has traditionally been accomplishing using welded repairs. During the past two decades, the use of composite materials to repair damaged pipelines has experienced a considerable increase as these repairs have become more cost effective and efficient. These repairs are frequently installed on erosion, or corrosion, damage that is on the interior of the pipe and can become through-wall. Design qualification of repairs for through-wall defects are performed using simulated flaws manufactured by drilling through the pipe wall. This creates straight-sided flaws with significant remaining stiffness, very different from the diffuse, tapered flaws produced by erosion or corrosion. In this study we investigate the performance of through-wall composite repairs installed on flaws generated by an erosion process. Hydrostatic pressure testing of these eroded flaws is performed and compared to failure pressures of repairs installed on drilled flaws. Digital image correlation is performed to understand the development of strains in the repair and to provide a quantitative comparison between the two flaw types. Recommendations are made regarding the influence of flaw shape on overall repair performance.