Updates of the code requirements along with the development of more robust Carbon Fiber Composite Repair Systems have allowed oil and gas refineries, chemical manufacturing plants and other industrial facilities to use these composite repairs on their critical piping systems. In the past, composites have only been used for circulating water lines and other low-risk piping. However, new advancements, such as Advanced FRP Systems’ work in high-pressure power transmission lines and other high-risk piping, have expanded the potential uses for these systems. Carbon Fiber composites combine excellent overall strength, superior resistance to corrosion, and are extremely light weight. They’re seen as a reliable and beneficial repair alternative compared to other pipe repair options. The creation and deployment of standards designed specifically for composite repairs of pressurized equipment has helped increase the range of usage of these materials. In 2006, ASME introduced articles 401 – 403 in the PCC-2 standard and ISO released their 24817 standard. These standards define material testing, design, and qualification requirements for composite repairs and provide a great deal of guidance and transparency helping facilities compare and evaluate these potential solutions. In this post, we’ll discuss the ins and outs of composite repairs specific to high-temperature environments and what you need to know about the current state and future of this approach. The Potential of Carbon Fiber Repairs for the Industry as a Whole At the start of 2020, the United States was home to 135 operable petroleum refineries. Given this and the number of other industries operating high-temperature piping throughout the US and around the globe, you can see that high-quality composite repairs could greatly benefit these industries. As materials, application techniques, and technologies continue to evolve, the range of use and application for composite repairs keeps expanding. Before these repairs are deployed in a high-temperature environment, it is crucial to test and understand these material’s performance at elevated temperatures. Many material properties are very different at 75°F than they are at 500°F. Further, a material that is cured at 75°F will not have the same properties as the same material cured at 250°F. It is crucial to run proper testing and field validation of the composite to ensure that the repair method will be successful and long-lasting. Repairs on a High-Temperature Flue Gas Piping System Critical Testing for High Temp Composites Though ASME PCC-2 and ISO 24817 standards provide excellent guidance on general composite repairs, neither standard provides sufficient testing requirements for high risk composite repairs at elevated temperatures. Specific material properties, such as the Tg (Glass Transition Temperature) and the HDT (Heat Deflection Temperature), are designed to look at elevated temperature performance of materials. Composite repairs should never be used in a structural capacity above their Tg or HDT and the cure temperatures of the lab tests must be mimicked in the field to truly reflect the material properties. There are various other critical tests that can help characterize the composite repair performance in a variety of high temperature environments and prevent failures. The testing of tensile strength and modulus of elasticity of the composites should be performed at elevated temperature to verify these critical engineering inputs. The adhesion properties of the composite must also be explored at operating temperatures using the ASME D4541 standard. Poorly adhering composites will not provide long-term reinforcement solutions. Thermal expansion and contraction must also be tested then compared to the substrate being reinforced. Carbon fiber composites designed for carbon steel will mimic the expansion and contraction of carbon steel, working well at elevated temperatures. However, when the same composite is used on aluminum, the increased thermal expansion will cause premature failure. Comprehensive lab testing must be performed to put a material “through its paces” at all possible operating conditions. Further, a deep understanding of the requirements of these tests must be employed to ensure they are used properly. Detailed Field Validation Process Once the material has been qualified and tested, application teams need to use it in an actual field repair setting. Curing of high-temperature composites is a real headache in the field where the repair cannot be put into a cure oven like lab samples. Because of the difficulty of curing high-temp composites in the field, Advanced FRP has pioneered an ambient cure, high-temperature system. That means you do not have to put in additional heat to get the system to cure prior to returning the asset to service. For services at elevated temperatures, most composites require additional heat to fully cure and maximize the high-temperature properties. This can be difficult to impossible in the field. We have tested and performed many projects using a “cure in service” technique where the pipe is brought back in service to slowly heat up to the operating temperature. Because our systems reach a majority of the cure at ambient and are flexible with the secondary cure temperatures, we can allow them to cure in service. Pre-impregnated composite solutions require a much more rigid heating cycle for an appropriate cure. Opportunities for the Future Today, refineries, chemical plants and other industries throughout the U.S. and across the globe are recognizing the potential for composite repairs for their elevated temperature piping systems. As new composite technologies and application techniques continue to come onto the market this will create additional opportunities for increasing the efficiency of repairs and decreasing the cost of repairs. Thorough testing, adherence with the appropriate standards as well as skilled application teams will ensure the reliability of these repairs. Coal Pipe Elbow, Operating at 300°F, After Carbon Fiber Composite Application Coal Pipe Elbow, Operating at 300°F, After Application of Heat-Resistant Topcoat With multiple carbon fiber based, composite pipe repair systems developed and tested for performance at elevated temperatures Advanced FRP Systems has a repair system for most service conditions. Further our ambient cure system avoids the need for additional heat in order for the pipe, tank or pressurized vessel to be returned to service. For more information on any of our high-temperature composite repair systems or composite repairs in general, please contact us.