State-of-the-Art Assessment of Today’s Composite Repair Technologies

For almost 30 years composite repair technologies have been used to reinforce high pressure gas and liquid pipeline transmission systems around the world. The backbone of this research has been full-scale testing, aimed at evaluating the reinforcement of anomalies including, corrosion, dents, vintage girth welds, and wrinkle bends. Also included have been the assessment of reinforced pipe geometries including welded branch connections, elbows, and tees. Organizations sponsoring these research efforts have included the Pipeline Research Council International, regulatory agencies, pipeline operators, and composite repair manufacturers. Many of these efforts have involved Joint Industry Programs; to date more than 15 different industrysponsored programs and independent research efforts have been conducted involving more than 1,000 full-scale destructive tests. The aim of this paper is to provide for the pipeline industry an updated perspective on research associated with composite repair technologies. Because of the continuous advance in both composite technology and research programs to evaluate their effectiveness, it is essential that updated information be provided to industry to minimize the likelihood for conducting research efforts that have already been addressed. To provide readers with useful information, the authors will include multiple case studies that include the reinforcement of dents, wrinkle bends, welded branch connections, and planar defects. INTRODUCTION Composite repair technologies play a critical role in the integrity management programs of many of today’s gas and liquid pipelines. Much of the research associated with the development of composite repair systems has been funded by the gas transmission pipeline industry, with an emphasis on repairing high pressure pipelines. The primary use of composite materials has been to repair corrosion, although research dating back to the mid-1990s has also been conducted for repairing dents and other mechanical damage (the latter being accompanied by grinding to remove gouges or indications of cracked material) [4]. More recently, efforts have been undertaken to evaluate the ability of composite materials to reinforce plain dents [10], wrinkle bends [3], branch connections, elbows/bends [7, 13], girth welds, and even crack-like features [11]. This paper provides background documentation on repairing defects in pipelines, including external corrosion [9] and dents, using composite materials. The goal for making any repair is to restore strength to damaged sections of pipe to ensure performance levels are at least as sound as the original pipe. The effects of static and cyclic pressure should be considered in the design of any repair [8]. Additionally, if appropriate, accounting for the presence of external loads (e.g. axial and bending) should be considered, as well as elevated temperatures if they exist in service. It is imperative that the recommended installation techniques provided by each manufacturer be followed. The only composite repair systems that should be used are those manufactured by companies with certified training programs, where hands-on installation classes are required for certified installers. From a design standpoint, any composite repair system that is used to repair a pipeline must demonstrate that it can meet the requirements of the ASME PCC-2 [2] and ISO 24817 industry standards. Composite manufacturers must be able to produce documentation from a thirdparty organization demonstrating their compliance with these standards, including meeting the required material and performance properties. Additionally, when composite materials are used to repair and/or reinforce anomalies in addition to corrosion (i.e. dents, branch connections, wrinkles, etc.), testing should be conducted to demonstrate that adequate performance levels can be achieved. Examples are available in the open literature on how these types of qualification programs are accomplished and several case studies are included in this paper. The sections of this paper that follow include a brief background on the ASME PCC-2 composite repair industry standard, four case studies providing documentation on the reinforcement of dents, wrinkle bends, welded branch connections, and planar defects. INDUSTRY STANDARDS During the early periods during which composite materials were used to repair pipelines, industry was without a unified standard for evaluating the design of composite repair systems. Under the leadership of technical experts from around the world, several industry standards were developed that include ASME PCC-2 and ISO 24817 (hereafter referred to as the Composite Standards). Interested readers are encouraged to consult these standards for specific details; however, listed below are some of the more noteworthy contributions these standards are providing to the pipeline industry.  The Composite Standards provide a unifying set of design equations based on strength of materials principles. Using these equations, a manufacturer can design a repair system so that a minimum laminate thickness is applied for a given defect. The standards dictate that for more severe defects greater reinforcement from the composite material is required.