Submarine pipelines are hailed as the lifeline of offshore oil and gas field development, serving as the most effective and safest means of transportation for marine oil and gas resources. However, due to the harsh operating environment of pipelines, inherent defects, long-term uninterrupted service, and the presence of many uncertainties, corrosion, defects, and damage to pipelines are inevitable. The existence of these defects seriously threatens the safe operation of pipelines. If not promptly addressed and repaired, significant losses and accidents may occur.
Currently, pipeline repair and reinforcement generally involve methods such as pipe replacement, welding, clamping, and composite materials. Carbon fiber composite reinforcement technology, a type of composite material repair technology, involves using carbon fiber bonded with resin to form a reinforcement layer on the pipeline, sharing the load borne by the pipeline, reducing the stress and strain on the pipeline wall, and thereby restoring or enhancing the pressure-bearing capacity of the pipeline. It is currently the most promising repair and reinforcement technology.
The carbon fiber composite sheet repair of steel pipeline structures is a structural repair and reinforcement technology that emerged in the 1990s, highly valued internationally. It has been widely used in chemical plants, civil buildings, bridges, and other special structures, becoming a trend in the development of steel pipeline structure repair and reinforcement. Compared to traditional metal repair methods, this repair technology has five distinct advantages: high tensile strength and modulus, excellent creep resistance; strong design capability, allowing for material layer design according to usage requirements and loading conditions; various molding processes for repairing and reinforcing large areas or complex structures such as bent pipes, tees, reducers, etc.; simple and quick construction, short repair and reinforcement time, low cost; and advantages such as no welding or hot work, pressure-bearing repair, and low risk.
In the past decade, carbon fiber composite material repair technology has been increasingly applied in the repair of severely corroded, mechanically damaged, cracked, and leaking pipes. Domestic scholars have conducted extensive research in this area. The carbon fiber composite material reinforcement and repair system consists of carbon fiber cloth, impregnation adhesive, primer, and special repair agent, all working together on the pipeline. When using the carbon fiber composite material repair system for defect repair, the defect is first filled with filling resin, and then carbon fiber wrapped with epoxy adhesive, forming a composite material repair layer on the outside of the pipeline. The filling resin cures to excellent compressive strength. After the carbon fiber composite material cures, it has very high tensile strength and elastic modulus. It restricts radial expansion deformation at the defect, reduces tensile stress and strain at the defect, limits stress concentration at the defect, achieving reinforcement and repair of the pipeline, restoring normal pressure-bearing capacity, and reducing pipeline risk.
The carbon fiber composite material repair system uses special repair agents to fill and repair defects, with the repair agent curing to an excellent compressive strength of over 100MPa. The special repair agent and epoxy primer act to transfer pressure along the radial direction of the pipe wall. By wrapping carbon fibers and epoxy resin on the outside of the pipeline, the resin cures to form carbon fiber composite material, which after curing, has high tensile strength. Through the special repair agent and the adhesion between itself and the pipeline, it can transfer pressure, share internal pressure of the pipeline, limit pipe expansion deformation, reduce tensile stress and strain at defects, and achieve reinforcement and repair of pipeline defects.
Carbon fiber composite material reinforcement and repair technology is a safe and reliable pipeline reinforcement and repair technology that can address common defects such as corrosion and mechanical damage in pipelines. With ongoing research into carbon fiber composite materials, the application scope of carbon fiber composite materials will continue to expand.