| In the pipeline, oil and natural gas need a certain pressure to transport, when the pipe wall corrosion defects, it will weaken the pressure of the pipeline. Correct and effective assessment of the ultimate bearing capacity of corroded pipes, which is of great significance to the pipeline in operation, we can make the decision to repair, replace or operate the pressure at the right time.In this paper, the residual strength evaluation method of corroded pipeline is studied in the following aspects:(1) The common corrosion pipeline residual strength evaluation methods are introduced in detail, such as ASME B31G, RSTRENG method, PCORRC method and DNV RP-F101 standards, the main parameters and application range of the commonly used evaluation methods are analyzed and compared;(2) First to analysis the PCORRC method, in the formula of PCORRC failure pressure prediction, the two parameters, nominal diameter D-t and pipe diameter D-2t, are introduced. The effects of three different parameters of D-2t, D-t and R on the calculation results of failure pressure of corroded pipeline are discussed, and the improved PCORRC method is proposed. The PCORRC method and the improved PCORRC method are used to calculate the failure pressure. The calculation results are compared with the experimental data. It is proved that the improved PCORRC method is more accurate. The failure pressure of corroded pipeline is calculated by the software of the residual strength of corroded pipeline, and the applicability of the residual evaluation method is compared with the calculation results.(3) By using the finite element software ANSYS and using the solidl86 three dimensional unit to establish with single point external corrosion defect model and pipeline with double points (axial and circumferential adjacent adjacent double point double point) external corrosion defects of pipeline model, selection of tetrahedral mesh, corrosion defect size was studied under internal pressure with single point external corrosion defects in pipes (long, deep and wide) influence on pipe failure pressure and corrosion defects with two point defects of pipeline external corrosion between non corroded areas (axial adjacent to the adjacent domain, corrosion ring region without corrosion) influence on pipe failure pressure, to analyze the influence law of corrosion defect size, axial and circumferential interaction between adjacent double point corrosion defects on the pipe failure pressure.(4) Based on the improved PCORRC method, this paper consider the axial and ring of no corrosion of pipeline for failure pressure effect, the axial and circumferential bidirectional projections of corrosion are carried out, and the combined length, width and effective depth of the corrosion area are calculated, a method for calculating the failure pressure of composite double point defects is put forward, and the calculation method of the failure pressure of the pipeline with complex multi spot corrosion defects is presented. Through the analysis and comparison of the calculated results with the experimental data from blasting, it is proved that the proposed composite double point defects of pipeline failure pressure calculating method and complex multi point corrosion of pipeline defect failure pressure calculation method is higher than the accuracy of DNV RP-F101 standard interaction defect evaluation method.(5) On the basis of the above study, this paper uses software development tools Visual C# to compile remaining strength of corroded pipeline assessment program, which contains the ASME B31G-1984, ASME B31-1991, RSTRENG0.85 area method and RSTREN effective area method, DNV RP F101 Xu with the force method of single point corrosion and mutual effect of corrosion and PCORRC method and the improved PCORRC method. The interface of the program is simple and easy to operate, and the relevant staff can choose the appropriate evaluation method to evaluate the residual strength of corroded pipeline according to the actual needs. |
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