Collapse Resistance Analysis And Experimental Verification Of Unbonded Flexible Pipe

As the growth of the demand for energy and land exploration drawing to a close, exploring for marine oil and gas resources becomes the hot spot of international energy at present. Unbonded flexible pipe, an important carrying and stored equipment in energy exploitation, the study of its design and manufacture technology is significant. Unbonded flexible pipe is composed of mental armoured layers and functional layers of polymer material. The layers can be mutual sliding between each other. Due to installation, storage and transportation of unbounded flexible pipe, there may be radical compression failure and then collapse. Besides, deep water application results in collapse. Therefore, collapse resistance analysis of unbonded flexible pipe is necessary.In this paper, at first, the structural style and function of the unbonded flexible pipe and research status about collapse resistance analysis done by scholars both at home and abord have been investigated and summarized. A three dimensional finite element model is developed to simulate the radial compression behavior of the carcass under radial forces. At the same time, an analytic formula of the radial compression stiffness of a ring under radial force is deduced for the carcass. We also established a testing rig for the radial compression of the carcass. Through the radial compression test of carcass specimens, the correctness of the finite element model is verified. Numerical study also showed that the carcass radial compression stiffness increased with the increase of ration of its thickness over its diameter. The numerical model we established and the analysis technology provide efficient method and basis for design and analysis of radial compression property of the unbounded flexible pipe radial compression in industry. Next, a study of collapse resistance design of multilayered structure has been done. Using a simplified numerical model to simulate wet collapse and dry collapse. It is concluded that the pressure armor layer had a great influence on collapse resistance of the carcass layer. At the same time, the size of the gap between the pressure armor layer and the inner sheath layer also has effect on the collapse resistance property. It makes no sense by infinitely increasing the thickness of the pressure armor layer, on the other hand it increases the load and the cost burden. Aimed at pipes used in shallow water, we provide a simplified unbonded flexible pipe design, named economical flexible pipeline. In this way, not only can meet the functional requirements but also can save the cost. Using numerical and experimental method to analysis collapse resistance property of economical flexible pipeline, which concluded that it can meet the requirement of the depth of water. Meanwhile, it verifies the rationality of multilayer structure and the equivalent method of cross section.