| Corrosion is one of the most serious problems that faces all metals exposed to soil and/or water. It becomes more serious in very large pipeline networks, where Failures can have severe consequences, both environmentally and economically. Therefore, it is very important to study corrosion prevention for buried pipelines. This work describes the fuzzy control of a pipeline corrosion by using impressed current cathodic protection. The purpose of this system is to maintain the distributed voltage of a steel pipeline at the set point (850mV with respect to copper/copper sulfate reference electrodes). The fuzzy controller is applied to the system to improve the performance of the cathodic protection, and to reduce power cost. The performance of the fuzzy control system depends on the control parameters, membership functions, control rules, and sealing factors. The fuzzy controller is constructed of linguistic control rules. In this study the control rules have been derived by modelling the cathodic protection of a buried pipeline. The simulated pipeline was divided of several points and by measuring the voltage at each point, the right current required to inhibit corrosion was determined. When controlling a single anode system with three measuring electrodes, a controller determining corrections to the current output was shown to work well in simulation. This controller was tuned by varying the choice of the output membership functions. The controller was extended to a two anode system by adding more rules. Again the controller performed well in simulation. The simulation was then verified by operating the controller on a physical system consisting of two anodes protecting a steel rod buried in damp sand. The performance after retuning was very similar to that of the simulation. Further tests where the anode size and location were changed gave expected results. |
