Study On Evaluation Of Corrosion Degree Of Inner Wall Of Underwater Oil And Gas Pipeline Based On Ultrasonic Phased Array Technology

Underwater pipeline transportation is one of the important means of offshore oil and gas transportation.With the increase of pipeline operating time and laying length under water and the impact of harsh Marine environment,the pipeline will inevitably be corroded,resulting in various defects,resulting in thinner wall thickness and reduced bearing capacity of the pipeline.It is difficult to evaluate the corrosion degree and predict the life of pipeline because the corrosion of inner wall of pipeline is hidden and not easy to monitor.And once the underwater oil and gas pipeline breaks,it will cause oil and gas leakage,which will seriously affect the ecological environment and human life safety.Therefore,it is urgent to evaluate the inner wall corrosion of underwater oil and gas pipeline and predict its remaining life.This paper aims to use ultrasonic phased array technology to obtain data of underwater oil and gas transmission pipeline,establish a three-dimensional model of the pipeline,intuitively display the inner wall morphology of the pipeline,calculate the volume and distribution of inner wall defects,and evaluate the residual strength of the pipeline,and carry out the prediction of its remaining life,so as to provide data support for the management and maintenance personnel of underwater oil and gas transmission pipeline.The main research contents of this paper are as follows:(1)Study the imaging characteristics and rules of ultrasonic phased array sound field.The focusing and directivity of ultrasonic phased array are analyzed.By establishing a sound field model,the effects of sound field parameters,such as the number of array elements,center spacing of array elements,emission frequency and focusing depth,on the distribution characteristics of the focused sound field were numerically simulated,and the optimal parameter combination was obtained.Using 20 carbon steel as the experimental workpiece,the optimal phased array parameter combination was used to obtain the imaging effect of the inner wall defects,and verify the validity of the numerical simulation results.The results provide theoretical support for the probe selection of ultrasonic phased array.(2)Design the inner wall corrosion detection device of underwater oil and gas pipeline.According to the reality of underwater oil and gas pipeline,this paper designed the underwater oil and gas pipeline external detection device,the device is composed of pipeline straight mechanism and rotating trolley and other parts.The overall structure of the detection device is mainly designed.The dynamic analysis of the stress of the detection device under different underwater conditions is carried out with the help of ANSYS Fluent module,and the design and selection of its main components are carried out.(3)Study the data acquisition and imaging methods of the inner wall corrosion point cloud of underwater oil and gas pipelines.Based on ultrasonic phased array technology,the structure data of the inner wall of the pipeline were collected by an independently built experimental platform.Based on the data,the pipeline 3D model was reconstructed,and the feasibility and accuracy of the obtained point cloud data for the three-dimensional model reconstruction and defect characterization of the inner wall corroded pipeline were analyzed.The results show that the point cloud data obtained by this technique is feasible,and the built model has small size and shape errors with high accuracy,which is conducive to the three-dimensional model reconstruction of oil and gas pipeline and the accurate characterization of defects,and thus provides a basis for the evaluation of the inner wall corrosion degree of underwater oil and gas pipeline.(4)Study the evaluation method and software implementation of inner wall corrosion degree of underwater oil and gas pipelines.By comparing and analyzing the commonly used methods for evaluating the inner wall corrosion of underwater oil and gas pipelines,such as ASME B31 G standard,RSTRENG method,PCORRC method,DNV RP-F101 standard and grey system theory,the main parameters,application occasions and application steps of relevant methods are mastered.The residual corrosion strength evaluation and residual life prediction program of underwater oil and gas pipeline inner wall was designed based on Python language to realize the evaluation of corrosion degree and residual life prediction of oil and gas pipeline with different steel grades.It is verified and analyzed by engineering examples.The results show that the program has high accuracy in evaluating the inner wall corrosion degree of underwater oil and gas pipelines.