Qingzhen Lu

Design of Cross-Sectional Layout of Steel Tube Umbilical

A design method is presented, which aims at the optimal cross-sectional layout of the multilayer steel tube umbilical. The merit of the method is to improve the tension stiffness and the fatigue life of umbilical. An optimization model is developed for arranging each component layer of the layout by considering the symmetry of mechanical performances of components. Finite element analysis (FEA) is carried out to check the contact force and the radial deformation of different layout types and to confirm the optimal layout design.

Reinforced Design of an Unbonded Flexible Flowline for Shallow Water

Flexible pipeline has been widely used in offshore engineering. Comparing to steel pipe, flexible subsea pipeline has some merits such as anti-corrosive, easy laying and recycling. So it is suitable to be used as flowline in shallow water. Especially there are lots of marginal oil fields in shallow water of China. Different from deepwater dynamic riser, flexible pipe for shallow water applications has a low requirement of resisting external pressure. On the other hand, Flexible pipe need to satisfy the requirement of tensile property during installation. Therefore, a kind of simple and economical flexible pipe can be developed to meet the requirement of shallow water application. This paper presents an economical unbonded flexible pipeline, which is helically wound by steel wires. In order to guarantee the safety of the economical flexible pipeline under the laying, installation and working loads, a reinforced design of tensile property is necessary. A helically wounded flat-steel layer is introduced to constrain the steel wire radial deformation and strengthen the axial tensile stiffness of the pipeline. A theoretical model is established to analyze the tension behavior of the flexible pipes and some suggestions are proposed to strengthen the flexible pipe design. Additionally, tensile experiments are carried out for the original and reinforced flexible pipes, which verify the theoretical model and the effectiveness of the reinforced design. The results show that the reinforced pipeline not only meets the tensile requirement during installation for shallow-water applications, but also meets requirements of the minimum bend radius as well as hydrostatic collapse (resistance of the external pressure) with low cost.Copyright

Multidisciplinary Optimization Design for Section Layout of Complex Umbilical Cables Based on Intelligent Algorithm

Umbilical which links the top floater and the subsea devices provides control functions through electrical cables and hydraulic remote transmission. They are treated as the “lifeline” of the subsea production system for offshore oil and gas exploitation. During operation, umbilical needs to undertake self-weight and periodical load due to the ocean environment. Meanwhile, the heat during power transmission in electric cable is released to the umbilical body, which influences the mechanical properties and optical transmission in the cable. However, there are a number of components and many kinds of sectional arrangement for the umbilical. So the sectional design with multiple components needs to be solved as a multidisciplinary optimization problem. From the mechanical point of view, the umbilical structure should be designed with more compacted and symmetric layout to obtain even probability of resistance to loads and reduce structural stress to improve its fatigue performance. Concerning thermal effect, these units should be arranged to dissipate the heat easily to avoid the influence on the functional and structural components. In this paper, compactedness, symmetry and temperature distribution are quantified through introducing corresponding indices. Then multidisciplinary optimization framework is established. Particle Swarm Optimization (PSO) intelligent algorithm is adopted to carry out the optimization to obtain the optimal solution, which is far superior to the initial design. The optimization design strategy is proved to be effective and efficient by some numerical examples, which provides reference for design of umbilical cables.© 2015 ASME

Cross-Sectional Layout Analysis of Steel Tube Umbilical

The paper presents four different layouts of a subsea steel tube umbilical which is composed of six steel tubes, three electrical cables and one optical fiber cable. When the umbilical is loaded, there will be a relatively large stress and deformation when the cross-sectional layout is unreasonable. So the principles of the cross-sectional layout of the umbilical are studied considering the stress and deformation of components. The contact stress between components, stress and deformation of components are analyzed and compared based on finite element method. The preferable design of cross-sectional layout for this umbilical is present.Copyright