M Gas Pipeline Cathodic Protection Adaptability Evaluation

With the increasing demand for natural gas,China has more than 70,000 kilometers of gas pipelines,so it is very important to ensure the safe operation of gas pipelines.Corrosion is one of the main factors for the safety of buried gas pipelines with high pressure and large diameter.The damage of corrosion to gas pipelines can be reduced effectively.Thus,the occurrence of pipeline accidents will decrease and the service life of pipelines will be longer,accompanied by the improvement of the safety and economy in pipeline operation.As cathodic protection is one of the most effective anti-corrosion methods for in-service natural gas pipelines,the adaptability of cathodic protection for M gas pipeline is studied in this paper based on the practical situation of the cathodic protection system.The specific contents are as follows:1.According to the principle of cathodic protection and relevant standards,combining the actual situation of M gas pipeline cathodic protection system,the main parameters of cathodic protection evaluation of the pipeline are identified,including polarization potential,grounding resistance of anode ground bed,potential difference between the protective end of insulated joint and the unprotected end,circuit resistance,etc.In addition,the evaluation process is also formulated.2.According to the actual situation of M gas pipeline,the output current and soil resistivity are considered to be the main factors influencing the polarization potential of M gas pipeline.With the cooperation of the staff of the cathodic protection station,field tests are carried out to analyze the influence of these two factors on cathodic protection potential of M gas pipeline.3.Different mathematical prediction methods are compared and analyzed,and an adaptive neural fuzzy system named ANFIS is selected for training simulation,and the polarization potential prediction model of M gas pipeline was established.At the same time,the prediction models were established by the least squares and the BP neural network.The values of the polarization potential predicted by the three methods were compared with the measured results to illustrate the accuracy of ANFIS prediction model.4.Based on the generality and the data of cathodic protection of gas pipelines in southwest China and the actual operation of cathodic protection system of M gas pipeline,the criteria for cathodic protection evaluation and fault detection of pipeline are proposed.Then,the criteria and polarization potential prediction model are combined to evaluate cathodic protection status of M gas pipeline.5.Summarizing the polarization potential prediction model,cathodic protection evaluation and fault detection criteria,the corresponding cathodic protection adaptability evaluation software is developed using VB language based on Microsoft Visual Studio platform.The evaluation software can automatically establish the polarization potential prediction model of M gas pipeline in different periods by using the historical cathodic protection data of M gas pipeline,and comprehensively evaluate the whole cathodic protection system of M gas pipeline.Thus,the costs of manpower,material resources and time in cathodic protection parameter testing can be reduced and the cathodic protection monitoring and management of pipeline is more convenient and feasible,while the evaluation results are more comprehensive and reliable.