The history of composites dates back more than three millennia to 1500 B.C. when the Egyptians mixed mud and straw to fabricate large bricks for building. These proved superior in strength to other building materials of that era. It wasn’t until the 1930s, though, that fibers and plastics were combined to create strong, lightweight material.
The demand for lighter weight materials in World War II helped bring this new composite technology into production by using fiberglass as an alternative to heavier materials for military aircraft. Twenty years later, carbon fiber, specifically Rayon, was combined with better polymers, providing an even stronger composite system. Innovation and research continue to improve both the polymers, as well as the reinforcing fibers, to use in items as simple as a set of golf clubs to the F-117 stealth aircraft.
Many industries have adapted composites, specifically fiberglass and carbon fiber systems, to fit the needs of a specific application in the industry. Pipeline rehabilitation has greatly benefitted from composite repairs and continues to trust this technology to effectively repair pipelines and pipeline components. It wasn’t until 2006 that the ISO 24817 and ASME PCC2 Article 4.1 standards were created, dedicated to the use of composite materials to repair and rehabilitate pressure-containing equipment. Like various other repair methods, such as steel sleeves and clamps, composite repairs are forced to undergo a rigorous vetting process to prove their strength and verify industry compatibility.
The Beginning of Composite Pipeline Repair
The pipeline industry’s methods for repairing aging or damaged pipelines were bulky, expensive and difficult to install. The repairs needed to be faster, more reliable and easier to install. In the 1990s, companies began determining that composite materials could meet the need proposed by the pipeline owners and maintenance providers. They could provide solutions for aging pipelines and prepare the way for a new composites industry. Because of the increase in the number of composite repair companies in the market, each manufacturer is required to innovate different products and solutions to meet more of their customers’ needs at more competitive prices.
Installers of steel sleeves, clamps and injection systems currently use these methods because, according to many in the industry, they are the only alternative to full replacement of a section of pipeline. Oftentimes, these applications are large, heavy, take
more manpower to install and are more expensive. To the pipeline owners and maintenance providers, the ideal repair system would include the following benefits: Adding significant strength back to pipeline, minimal manpower to install, fast installation time, minimal downtime, no maintenance after installation and long-term repair.
Citadel Technologies designs repair kits with these concerns in mind, aiming to provide the best products and services possible to their customers. Although composites have proven to be an effective repair method in the industry for the past 20 years, there is still a strong reluctance to accept the technology as a viable and successful repair method.
The Battle for Industry Acceptance
Because of the substantial claims made by composite manufacturers, pipeline owners are reluctant to use this new repair method. This is likely due to the risk and liability assumed if a failure were to occur. This reluctance has worked to the pipeline owners’ advantage because it has required the composite repair manufacturers to provide increasing levels of testing to prove that the materials and designs are able to meet the needs of the industry. This process, in itself, has separated the pack of composite repair manufacturers, proving the long-term players and those willing to compromise material and design quality.
To prove the performance capabilities of a repair system, a pipeline owner may request that tests be preformed on site or under its supervision to precisely monitor every aspect of the repair. Citadel Technologies was asked to participate in a test for a gas company on a 24-in. line. In this case, the customer requested a full-scale rupture test on an area with mechanical damage that was approximately 80 percent of the remaining wall and 4 in. long. The repair system was designed to be stronger than the pristine base pipe, which would cause rupture outside of the repair area. The image on page 40 shows the pipe after pressurization to rupture, which was approximately 1,170 psi.
Choosing a Dedicated Composite Repair Manufacturer
Successful industry experience and/or third-party reviewed test programs are a requirement in proving the capabilities of any pipeline repair system. Citadel Technologies specializes in high temperature and odd configurations.
Many complex applications of the company’s products can be found throughout the world. For example, a 20-in. diameter high temperature petrochemical system, shown on page 42, suffering from a weld seam leak was repaired using their High Temperature Ambient product line. The system was running at approximately 200 F and 450 psi. The line was repaired quickly and easily, without shutting down operation.
It is crucial for a composites manufacturing company to comply with industry standards such as U.S. DOT regulations, ASME and ISO standards. These standards are written and reviewed by panels of experts in the field, specializing in practical application as well as scientific research.
Although the standards are in a constant state of review and improvement, it is a priority for each member of the review committee to keep the design criteria safe and conservative to ensure the greatest success.
Citadel Technologies has been involved with numerous third-party testing programs associated with Pipeline Research Council International, Stress Engineering and the University of Tulsa, Oklahoma.
A recent test program was performed on the repair of dents on welds, which is highly applicable to the pipeline industry. The study reviewed the viability of composite repairs to rehabilitate a line with a plain dent over straight pipe, a girth weld and an electrical resistance weld (ERW).
With the appropriate design and proper installation, a composite repair significantly lowers the strains on the base pipe, extending the life of the line significantly.
Citadel’s products have also been used in test programs researching the viability of using composites for underwater repairs, repairs in seismically active areas and as soft crack arrestors.
Because in some industries composites are currently not accepted as common repair methods, repair manufacturers should be willing to provide a substantial degree of education to their customers. They should be willing to explain the ASME and ISO standards to further prove the capabilities of composite repairs.
Armed with the knowledge of the industry standards and experimental data, confidence in composite repairs will expand the applications and overall market for all repair manufacturers. This will also allow manufacturers to employ the expertise of experienced engineers to expand research on non-standard applications.
Composites have proven successful in various industries and applications, but more opportunity still awaits. Working together as an industry will drive further innovation allowing new opportunities and applications to be explored.
Amanda Hawkins is manager of engineering services and Roger Walker is president and CEO of Citadel Technologies.