The dynamic behavior of the flexible pipeline during deepwater Flex-lay directly determines the structures of laying facilities and the actual installation process. A coupled dynamic model considering the effects of different factors was established in this paper. Based on the model, the initial attitude of the flexible pipeline during the laying process was determined by using the natural catenary theory and Morison equation. The hydrodynamic analysis of the HYSY201 pipelaying vessel was carried out by using the finite element software AQWA. Under the specific sea condition, a flexible pipeline with outer-diameter of 352.42 mm being laid onto the 3000 m deep seabed was simulated by using the software OrcaFlex to study the pipeline dynamic behaviors including axial tension, bending moment and stress-strain in the laying process, and the factors affecting the dynamic behavior of the pipeline were analyzed. The results show a significant correlation between the marine loads, vessel motion and the dynamic response of the pipeline. Compared with the static state case, the maximum axial tension, bending moment and stress-strain of the pipeline under the interaction of the marine loads and the vessel motion increased by 42.7%, 220%, 52% and 18.7%, separately. Among the marine loads, the surface wave had the most significant effect on the dynamic performance of the pipeline. When the wave direction acts on the width of the ship, the wave height is greater than 2 m and the spectrum period is eight seconds, the wave has the greatest influence on the dynamic response of the pipeline.

During the reeling process of the reel-lay method, the pipe will be subjected to combined loading of tension and bending. Excessive ovalization of the pipe will affect the structural performance and even lead to structural instability of the pipe. In this paper, a numerical simulation model of the pipe-reeling process is established by finite element tools. The Ramberg–Osgood material model is used to study the ovalization and bending moment of the pipe cross-section during the pipe-reeling process based on the Von Mises plasticity and nonlinear kinematic hardening rules. The results show that the ovalization and bending moment of the pipe section will change significantly during the pipe-reeling process. Subsequently, one set of 6-inch pipe-reeling experimental setups was designed to conduct a full-scale experiment. Compared with the experimental results, the feasibility of the finite element model is verified. Finally, the effects of diameter-to-thickness ratio, the material parameters of the pipe, and the pipe axial tension on the ovalization and bending moment changes are studied. Research shows that each parameter has a certain influence on the pipe of the reeling process, and the diameter-to-thickness ratio of the pipe has the most obvious effect. When the diameter-to-thickness ratio decreases, the bearing capacity for bending moments and the ability to resist ovalization of pipe are enhanced. At the same time, each parameter has a significant impact on the reeling process of the pipeline.

This paper proposes a version of the deep-sea environment simulated test system for subsea control modules to solve the problem of incomplete testing systems for electro-hydraulic subsea control modules. Based on the subsea control module test requirements specified in APISTD17F, the test system in this paper is a highly integrated system, including a test hydraulic power unit, a control module test bench, a signal simulator, an electronic test unit, an umbilical simulator, a high-pressure chamber, and an incubator. Firstly, the design indicators of the test system were determined by analyzing the various functions of the subsea control module and its working environment. Secondly, the design scheme for the test system was proposed, and a detailed design was carried out. Finally, a hydro-electrical subsea control module for the Bohai Sea was fully tested with this system, with tests including the qualification test and the factory acceptance test. The test results show that all parts of the test system coordinated well and have achieved the design indicators, and the test system can simulate the working environment and complete a land test. The effectiveness and feasibility of the test system have been verified through the test. By adopting this system, the risk of subsea control module failure can be minimized, laying the foundations for future research and improvement of subsea control module testing equipment.

During the process of laying submarine pipelines using the R-lay (short for reel-lay) method, the interaction between the pipeline and the laying equipment undergoes continual fluctuations, leading to bending in the pipeline induced by the stochastic dynamics of various external loads. Considering the challenge in forecasting the dynamic behavior of pipeline bending moments and ovality throughout this procedure, we constructed a finite element-based shell element model for a 6-inch pipeline. In this paper, a multi-step simulation approach was used to replicate the pipeline laying process, and the dynamic response in pipeline bending moments and ovality during the winding, unwinding, and straightening processes was analyzed. Additionally, the effects of the pipeline’s diameter–thickness ratio and material properties on the dynamic response process were also studied. The results show that the dynamic response in bending moments and ovality is closely related to the curvature of the pipeline; a brief peak will appear at the critical point where the pipeline deforms, and the peak is related to the different bending stages of the pipeline, with the winding stage having a greater impact on the peak than the unwinding stage. During the unwinding process, a reverse bending moment will occur. The dynamic response of pipeline bending moments and ovality is influenced to some extent by the pipeline’s diameter–thickness ratio and material properties, with the diameter–thickness ratio demonstrating a more conspicuous impact.

A deep-water bolt flange automatic connection tool plays a very important role in the process of offshore oil exploitation and transportation. In the connection process, the alignment error of bolts and nuts is the key factor to ensure the connection process is successful. Using the kinematics modeling method, this paper created the alignment error model of the deep-water bolt flange automatic connection tool and analyzed the influence of manufacturing accuracy on the alignment error of bolts and nuts through computer simulation software. Based on the error matching design method, the manufacturing accuracy of parts were optimized with a part-size-based priority sequence to ensure the bolt–nut alignment error was within the allowable limits. The land tests, the pool tests and the sea test were carried out. The test results showed that the bolt and nut can be connected in the subsea environment reliably.