The Numerical Simulation Of The Buried Pipeline Cathodic Protection Potential

This paper adopts the method of numerical simulation, the numerical model has been established, by taking Seninglan pipelines without stray current interference for example, the soil-pipe3d model has been established, the equivalent surface resistance between buried steel pipeline and soil has been deduced, which can be used as the cathode boundary condition of the numerical model, using ANSYS-CFX software to simulate the potential distribution of cahodic protection(CP) on pipelines, comparing the pipelines’potential of simulation values and detection values, the maximum bias between them is4.01%, the reliability of numerical model and method are verified.Analysis of the CP potential of Seninglan complex pipe, comparing the detected potential of single pipe with the crossed one or paralleled one, the result is that, the potential on the single pipe reached the most negative-0.899V at the anode bed, and monotonous reducing toward two ends, however, the crossed pipe reached minimum-0.872V at the crossed pot, and monotonous increasing toward two ends, the potential on the crossed one has been down. The potential on the pre-paralleled the pipeline reached the most negative-0.948V at the anode bed, and monotonous reducing toward two ends, however, the paralleled pipe reached two peaks-0.944V and-0.939V at two paralleled pipes’anode beds, and monotonous reducing toward two ends, the potential on the paralleled pipe has been down. Mechanism analysis of the potential changes on multi-channel pipelines, the reason which created the potential changes on pipelines is that the DC stray current interference between multi-channel pipeline’s CP systems has been exist.In order to further study of multi-channel buried pipes, the factors which decided to the CP system have been selected:the laying spacing of pipelines, the parameters of auxiliary anode(the value of CP current and anode bed position),the conductivity of buried pipe, the parameters of pipe’s coating(the surface resistance and coating damage rate),the conductivity of the soil. Studying the CP potential distribution of multi-channel buried pipes under the factors respectively. Getting the CP potential curves and the interference deep of the multi-channel buried pipes, the simulation results is that:Crossed pipe is more serious than paralleled pipe by interference, the performance is that, the potential on the crossed pot has been decreased obviously, even reached the under-protection. The greater the spacing of crossed or paralleled pipelines, the lower the degree of interference with the potential on the pipelines. More bigger the CP current is, more safer the multi-channel pipes. The farther vertical spacing between anode ground "bed and crossed pipelines, the lower the degree of interference between crossed pipelines. The farther spacing between anode ground bed and paralleled pipelines, the more uniform the po tential distribution on paralleled pipelines, the potential distribution will be best when the spacing more than equal to400m. The spacing between anode ground beds too small can cause the potential peaks superposition on one pipe. To the crossed pipes, more bigger the conductivity on pipes, more higher the potential is. To multiple pipes, improving the quality of coating and increasing the surface resistance can help to improve the CP potential on pipes. The smaller the damage rate of the coating, the higher the multiple buried pipeline CP potential, the damage rate of Seninglan’s multiple pipelines’ coating is best controlled at less than0.005. To improve the conductivity of the soil can help improve the potential of the crossed pipes,the conductivity of the soil should not be less than0.05S/m. To the multi-channel buried pipes, more bigger the conductivity of soil, more higher the CP potential on the pipes.