Erosion Analysis Of Carcass Layer Of Non-cohesive Flexible Pipe

Flexible bend pipe is widely used in offshore oil and gas transmission pipelines,the working condition of flexible bend pipe are bad,sand particle mixed in natural gas and oil will cause erosion on the inner wall of flexible bend pipe,erosion is the main reason that causes flexible bend pipe failure,it’s necessary to study the effect of erosion caused by subsea oil and gas to ensure the safety operation of subsea equipment.In order to comprehensively study the erosion characteristic of flexible bend pipe,provide safety guarantee for practical application of flexible bend pipe,a whole set of analysis method including modeling,simulation analysis,paramatric analysis,maximum erosion angle analysis and dangerous erosion position analysis is conducted for flexible bend pipe based on actual working condition.The main research contents in this paper are as follows:Firstly,a simplified flexible bend pipe model is established,flow field analysis is conducted based on control equation of continuous phase and discrete phase,mesh independence analysis and optimal length analysis of inlet and outlet straight pipe are carried out to determine the optimal finite element model,and the correction of the simplified model is validated after the comparison with related scholar’s research.Next,the best erosion prediction Oka model is selected for parameter analysis after applicability comparison of different erosion prediction models and comparison with limited experiment data.By changing particle velocity,particle mass flow rate,particle diameter parameter,pipe diameter,pipe curvature radius,the change rule of erosion rate under different particle and structure parameters are investigated.MATLAB is used for formular fitting to find the relationship between maximum erosion rate and particle and structure parameters.Then,the velocity distributions of flexible bend pipe at different angles of 0°～90° under different fluid and structural parameters are analyzed.The velocity distributions of flexible bending pipes at five positions of 15°,20°,25°,30°,45° are specially analyzed on the velocity distributions of flexible bending pipes at different angles along the curvature center of the bending section,and the variation of velocity law.Lastly,the effect of particle diameter,pipe diameter,pipe radius of curvature on the maximum erosion angle are investigated,a new formula of the maximum erosion angle of flexible bend pipe with respect to the bend ratio is established based on the Fluent simulation result.The result is compared with the existed maximum erosion angle prediction model.Stress analysis of flexible bend pipe with defects is carried out on the maximum erosion position.The research work of this paper has certain engineering guiding significance to reduce the erosion of flexible bend pipe caused by oil and gas carrying sand in subsea oil and gas production process,and improve the service life and economic benefits of flexible bend pipe.