Numerical Simulation Research Of Cathodic Protection In Buried Metal Pipeline

Buried metal pipeline is not only widely used to transport oil and gas in petroleum, chemical and natural gas industry, but also a lot of use in the transmission of life and fire water. Due to the corrosion effect of soil on buried metal, cathodic protection technology is often used in the corrosion protection of pipeline to avoid corrosion and leakage, thus extending the service life of pipeline. The distribution of cathodic protection potential is an important factor to influence the protective effect, it has an important significance to understand the potential distribution of the cathodic protection about improving effect.Firstly, summarize the principle and type of electrochemical corrosion in soil and obtain corrosion protection measures of buried pipeline, then lead to the cathodic protection technology. Summarize the content and the research status of this technology, point out the shortage of the traditional method, and put forward using numerical simulation method to research the cathodic protection potential distribution in buried metal pipeline. Through theoretical derivation, on the basis of the Laplace equation and the combination of electrochemical polarization characteristics, obtain the mathematical model of cathodic protection potential distribution. Through electrochemical experiments get the 20# steel’s polarization characteristics in soil of different moisture content, which is also the boundary condition of the mathematical model. Through finite element method, solve a potential distribution of cathodic protection system, and analyze the simulation result logically, validate the feasibility of this method. Using this method to study the potential distributions of distributed anode ground bed, flexible anode ground bed, and deep well anode ground bed respectively, distributed anode ground bed can make potential distribution uniform by adjusting the number and location of distributed anode bed, pipe potential is lower near the anode. Flexible anode can generate the most uniform potential distribution, and the potential distribution of deep well anode is funneled. Through the numerical method, study the potential influence factors which include soil resistivity, number and location of anode in three different kinds of anode bed. The potential grows evenly when the soil resistance increases in distributed anode bed, and increasing the quantity of the anode can also achieve the same effect. Flexible anode is sensitive to the change of the influence factors, and cathodic protection system of this kind has poor stability. Deep well anode can obtain a better potential distribution in small resistivity soil layer, the influence of the middle soil layer is small to potential distribution, but the number of anode has a larger influence.Apply numerical simulation method in the design of cathodic protection, use the traditional method and numerical method to calculate a cathodic protection of water pipeline respectively. Obtain the conclusion that traditional method is indispensable to the numerical simulation by analyzing their characteristics. They complement and relate to each other closely. Through the combination of the two methods, it has important value and significance to improve the quality of cathode protection and reduce the risk of design mistake.