Stress Analysis of the Subsea Dynamic Riser BaseProcess Piping

Thesubsea dynamic riser base （SDRB） is an important piece of equipment for the floating production platform mooring system.One end is connected to the rigid pipeline, carrying a rigid pipeline thermal expansion load and the other end is connected to a flexible riser, carrying the dynamic load of the flexible riser, so its function is a transition connection between the flexible riser and the rigid pipeline which fixes the flexible riser on the seabed. On the other hand. as a typical subsea product, the design will satisfythe requirements of the standards for subsea products. By studying the stress analysisphilosophy of the topside piping and subsea pipeline, a physical model and procedure for piping stress analysis of the SDRB have been established.The conditions of the adverse design load have been considered, and a combination of the static load from the rigid pipeline and the dynamic load flexibility has also been optimized. And a comparative analysis between the AMSE, DNV and API standards for piping stress with the checking rules has been done.Because theSDRB belongs to the subsea pipeline terminal product, the use of DNV standards to check its process piping stress is recommended. Finally, the process piping stress of the SDRB has been calculated, and the results show that the jacket pipe and the carrier pipe stress of the SDRB process piping satisfy the DNV standards as a whole.The bulkhead cannot be accurately simulated by the AutoPIPE software which uses the FEA software ANSYS inthe detailed analysis, but the checking results will still meet the requirements of the DNV standards.

Stress Corrosion Cracking of High-strength Drill Pipe in Sour Gas Well

In high sour gas reservoir drilling process, it happens occasionally that high-strength drill pipe suffers brittle fracture failure due to stress corrosion cracking, and poses serious hazard to drilling safety. To solve this problem, this paper studied the stress corrosion cracking mechanism and infl uencing factors of highstrength drill pipe in sour environment with hydrogen permeation experiments and tensile tests. We simulated practical conditions in laboratory and evaluated the stress corrosion cracking performance of the high-strength drill pipe under conditions of high stress level. For the problems occurring in use of high-strength drill pipe on site, the paper proposed a technical measure for slower stress corrosion cracking.

Stress and Springback Analyses of API X70 Pipeline Steel Under 3-Roller Bending via Finite Element Method

3-Roller bending is a widely applied manufacturing process, particularly in structural steel pipe industry.However, due to the difficulty and high cost of measuring stress distribution inside sheet material via traditional method,internal stress/strain response during forming is largely unexplored. The focuses of this study are two：（1） to map the radii of curvature as well as the stress inside the work piece during forming by utilizing the meshing mechanism of finite element method, and（2） to further provide some numeric guidelines for the configuration of the rolling system in order to improve production efficiency and product quality. The results of this study indicate that：（1） it is crucial to properly choose forming parameter in order to produce product with desired radii;（2） much like a gradual springback process, the radii of curvature gradually increase from the top roller to the exit-side bottom roller;（3） under the assumptions made in this study, to produce pipes with a specified diameter with varying configurations of the 3-roller system will not significantly change the final residual stress; and（4） finally, shifting of the neutral axis up to 2.0% of the thickness toward the compressing side during the forming process is observed.

Quantitative Estimation of Pipeline Slope Disaster Risk in China

China’s economic development is closely related to oil and gas resources,and the country is investing heavily in pipeline construction.Slope geological hazards seriously affect the long-term safe operation of buried pipelines,usually causing pipeline leakage,property and environmental losses,and adverse social impacts.To ensure the safety of pipelines and reduce the probability of pipeline disasters,it is necessary to predict and quantitatively evaluate slope hazards.While there has been much research focus in recent years on the evaluation of pipeline slope disasters and the stress calculation of pipelines under hazards,existing methods only provide information on the occurrence probability of slope events,not whether a slope disaster will lead to pipeline damage.Taking the 2015 Xinzhan landslide in Guizhou Province,China,as an example,this study used discrete elements to simulate landslide events and determine the risk level and scope for pipeline damage,and then established a pipe-soil coupling model to quantitatively evaluate the impact of landslide hazards for pipelines in medium-and high-risk areas.The results provide a reference for future pipeline disaster prevention and control.