Feasibility of repairing urban gas pipeline weld defects by CFRP

Weld defects are common in long-distance pipelines, which severely reduce loading capacity of pipelines further affect safe operation ofthe pipelines. CFRP (carbon fiber composite) repair technology is a new welding-free pipeline repair technology, with simple construction method, hot work free, excellent repair effect and other characteristics. Feasibility of weld defects repairing for long-distance pipeline by carbon fiber composite is analyzed. In accordance with calculation results based on mechanical theory, unilateral laying length of weld carbon fiber composite shall not be less than 287 mm to axial shear force caused by the pipeline rupture when the weld is cracked completely.The results of full-scale burst testing, pressure fluctuation testing and simulated bending stress testing of pipeline under pressure show thant the repaired pipeline can completely restore loading capacity and have excellent resistance to pressure fluctuations and bending stress.However, due to the limitations of carbon fiber composite repair technology itself, defects of more than 80% and pipeline leakage defects can not be repaired.