An overview of composite repair techniques

At present, the total length of oil and gas pipelines in the world exceeds 1.7×106km, among which a large number of pipelines have been in service for more than 30 years and have a large number of defects such as external corrosion, resulting in the annual cost of pipeline repair between 6 billion and 8 billion dollars [1]. Generally, more serious external corrosion can be repaired directly by tube change or sleeve, which is expensive to repair.

In recent years, as a new repair technology for pipe defects, composite material has many advantages. The composite pipe body defect repair technology uses the high-strength filler coated on the defect site and the strong glue on the pipe body and between the fiber material layers to evenly transfer the stress acting on the defect site of the pipeline to the composite material repair layer. The composite material is closely combined with the defective pipe, co-deformation, reasonable distribution of the stress of the defective pipe, so as to achieve the purpose of strengthening.

Compared with traditional metal repair methods, composite repair technology has obvious advantages:

1) High specific strength and modulus of composites;

2) Strong designability of composite materials;

3) The composite material has a variety of forming processes, which is convenient for large area or complex structure reinforcement;

4) The repair process does not require outage, the repair time is short, the cost is low, and the equipment required for on-site repair is simple.

These advantages of composite materials basically meet the technical requirements of long distance oil and gas pipeline for pipe body repair materials, has become a development trend of pipe body defect repair technology. The commonly used composite materials for repairing tube defects include glass fiber composite (GRP) or carbon fiber composite (CFRP), etc. The commonly used resins include polyester, vinyl ester and epoxy resins. In the field of composite repair technology, the composite repair sleeve of America's ClockSpring company is the most representative. It is widely used in onshore and offshore oil and gas pipelines in North America, Europe and other countries. In recent years, some Asian countries have also begun to apply it.