The Research Of Corrosion Residual Life Prediction For Buried Gas Pipeline Based On Comprehensive Inspection

The medium transported in natural gas pipeline has the characteristics of inflammable, explosive, toxic, once corrosion leakage accident happens, not only can lead to serious casualties and great economic losses, but also can pollute the environment, result in very negative social impacts, if replacement the pipeline too early will cause unnecessary waste. Therefore, in order to find the balance point between the economy and safety, we need to conduct regular inspection for the buried gas pipeline, at the same time forecast it’s corrosion residual life, so as to extend the operating time of the pipe as much as possible, in condition of guaranteeing safety.This paper analyzed the advantages and disadvantages of commonly used buried gas pipeline inspection method in domestic and overseas at present, on the basis of which we designed an inspection scheme which combined a variety of inspection technology and overcome the limitations of single inspection method.Based on the theory of gray association degree, combining with buried experimental data of the pipeline test pieces, the grey correlation degree between soil corrosion factors and pipeline corrosion degree in the different buried time is calculated, we find out the main factors which influence the soil corrosivity. We also build the neural network model between the main soil corrosion factors and soil corrosion level by writing programs with MATLAB, then evaluate the soil corrosion level along the pipeline.In the following study, we built the corrosion depth model of the buried gas pipeline at different corrosion time and different environmental parameters through BP neural network and the buried test data come from test pieces. Then combining with excavation detection data, the corrosion development trend prediction model of buried gas pipeline is set up.We also analyzed the applicability of the various conventional residual pressure bearing capability evaluation method under different pipe parameters and corrosion defect parameters through the blasting experiment data of pipeline with defects. For thin wall pipeline, long corrosion defects pipeline and deep corrosion defects pipeline, we optimized the residual pressure bearing capability evaluation method through adopting different expansion coefficient and flow stress, and compared the results calculated by optimization method with the results calculated by conventional method, then analyzed the advantages and disadvantages of each method.Using the residual pressure bearing capability evaluation method selected above, the maximum corrosion depth calculation model is set up. In view of the model is implicit equation which cannot be directly solved, we write iterative calculation program with Java language for solving the maximum permit corrosion depth of pipe.Finally, according to the corrosion development trend prediction model and the maximum permit corrosion depth calculation model of buried gas pipeline, systematic corrosion residual life prediction method is established, and then applied in the practice.