Comprehensive Investigation Of Regional Cathodic Protection

The main problems of regional cathodic protection are to protect the bottom ofthe tank effectively, get rid of the electrical shielding and reduce the disturbance tothe outside cathodic protection system. In order to solve these problems, this research program is divided into four steps.Firstly, a tank bottom with diameter of 12m was built to simulate a 50000m3 tank.Various test methods were tried to measure the distribution of the potential of thetank bottom. The test result was analyzed and the conclusion was proved in theory.Secondly, a new regional cathodic protection system was built in LinYuan oiltransportation station of DaQing Oil Transportation Management Company. Thecomprehensive investigation of regional cathode protection was conducted such asthe site and depth of anode bed, the distribution of the electric potential of the tankbottom, the relationship of anodic field distribution, and the existence of unsafefactor of impress current cathode protection system. And then, the potential of thetank bottom was practically measured and the data was analyzed. Finally, in orderto find the way to get rid of electrical shielding and to reduce the disturbance to theoutside cathodic protection system, some practices were tested.The results show that where there are asphalt existed under the bottom, thedistribution of the potential of the tank bottom is uniform, and the site of the anodehas less effect on it. The cathodic potential of the tank bottom can be moreaccurately measured by burying test probe with coupons under the asphalt of thebottom or using emulated probe. Deep well anode is suitable for regional cathodicprotection system at tanks region if possible. The regional cathodic protectionsystem may disturb the outside pipeline cathodic protection system. In order toreduce the disturbance, some methods must be adopted. Using scattered anodegroups, combining far anode with near anode can get rid of electrical shieldingeffectively. Using mental with negative potential as earth-plates can get rid ofelectrical shielding in the region with numerous and jumbled earth-plates.