Autofrettage and hydrostatic burst test of composite reinforced line pipe

As natural gas demand rises constantly, the pressure bearing capacity of long-distance pipelines shall meet higher requirements, but the improvement of pipe wall thickness and steel grade is limited. To solve this problem, a kind of composite reinforced line pipe was developed in this paper. The external surface of pipes is wound continuously with fiber composites to increase the pressure bearing capacity of pipelines. A sample of composite reinforced line pipe was prepared based on the line pipe with external diameter of 508 mm. Then, it was treated by means of autofrettage and hydrostatic burst test was performed on it. It is indicated that the pressure bearing capacity of composite reinforced line pipe is the loadbearing overlapping result of steel layer and composite layer. After pre-stress is applied, the stress of structural layers is redistributed, so the bearing ratio of composite layer is increased. In the case of pipeline failure, the composite layer will be firstly damaged. Based on the test results, the calculation method on design pressure of currently used composite reinforced line pipe was modified.