Research On Survey Technique For The Corrosion Protection Status Of Submarine Pipelines

The outer surface of subsea oil and gas pipelines is usually under the corrosion environment of sea mud or seawater, so the combined corrosion protection of coating protection and anode cathodic protection is generally used for submarine pipelines. Therefore it is very important to inspect the status of submarine pipeline protection. A theory based on the measurement of environment's potential difference was brought out by Xia Weijun to evaluate the corrosion protection status of submarine pipelines, and BP Neural Network Algorithm was used to establish the non-linear relationship between potential difference and those determined influence factors of the status of submarine pipeline cathodic system: the average coat defection of sacrificial anode, the current of sacrificial anode, remaining weight of sacrificial anode and etc. After Xia Weijun, a system about how to improve this technique was brought out and a corresponding scheme design of equipments was made by Luo Liping. The goal of this paper is to research the key survey technique for the corrosion protection status of submarine pipelines and bring out a system about type selection, integration and operation for corresponding equipments.Firstly, the neural network model is expanded for "infection factors database of electric field under cathodic protection system", which composed of eight calculation models corresponding to the known or unknown conditions of sea mud resistance rate, the pipeline radius and distance of sacrificed anode, then the nonlinear relationships between input and output parameters is gotten from the training of neural network. Based on the above works, the survey system of corrosion protection for any submarine pipeline influenced by condition factors is established.Secondly, appropriate equipments are selected and configured based on the requirement of survey system and the rationality for the install format of sensors is analyzed. The actual operation mode of GPS positioning system, workboat , USBL acoustic positioning system, environment potential measurement system and submarine pipeline magnetic survey system is determined. The surface and underwater positioning system are combined to obtain the absolute geographic coordinate of underwater vehicle.The visualization function of the software for the corrosion protection status survey of submarine pipelines is improved, including importing the design drawing into graphic visual digital sea map interface with a map format and making a real-time display for the actual location point of pipeline during the survey processing that can get the paving errors between design and actual pipeline. OpenGL visual system is used to image the corrosion protection status of submarine pipelines. All those make the software into actual application.Moreover, Simulation Experiment is performed in laboratory to verify the accuracy and reliability of corrosion protection evaluation.