Output Parameters Of Buried Pipeline Cathodic Protection Station Adjustment

After more than 100 years' development, cathodic protection (CP) has become a principal technique to control corrosion effectively in soil and aqueous environment. Potential Criteria for adequate cathodic protection are recommended by many standards, so the potential distribution of CP is a key problem concerned in CP design. In this paper, the author has made researchs on the numerical methods of a cathodic protection system for a buried pipeline. Furthermore, considering to the cathodic variables will be vary in different season, the author has also made researchs on the adjustment of cathodic protection station. The result of the research work indicated that the approaches adopted are feasible in practice and scientific in theory.The main tasks of this research work are as follows:(1) Have gotten the conclusion that the environment factors which affect the cathodic station to run regularnormality can be separated to three main parts: coating quality,soil parameters and grounding resistance of the anode bed.By means of carbon steel's corrosion change as different season regularity. Which indicated that, soil's corrosion is vary with the season. The author made research on the potential distribution changes with season in condition that the pipeline is under cathodic protection. In conclusion, the water content in soil is the key factor that affects potential distribution of cathodic protection for buried pipeline.(2) According to the basic mathematics theory of boundary element method, deduced the boundary integral equation of cathodic protection, and introduced the problem about potential axisymmetry, made the boundary discretized into a series of pipe elements, deduced the mathematics model of cathodic protection system for buried pipeline. Meanwhile, the author has discussed about the factors that affect the accuracy of computation and the amounts of pipe elements' selection.(3) According to the theory of electrostatic field description, set Laplace equation as the represent equation about potential distribution, after analyzing and comparing the main numerical methods, the author determined to apply boundary element method (BEM) to solve the potential distribution model of a cathodic protection for buried pipeline.(4) A expression of the soil circuit's resistance is derived, indicates that, the assumption of neglect the soil circuit's resitance in the current industry standard—《SY/T 0036—2000》is needed to further research.(5) Applying analytical approach to calculate potential along pipeline. And take calculation results to the numerical model to calculate the current density of feeding point; then, we can get the whole pipeline's current requirement. According to the requirement of in every season, we can get the output voltage of cathodic protection station in every season. Which could get the value needed to be adjusted between the adjacent season.