Control of external corrosion impacts for gas pipeline technical condition evaluation
The peculiar feature of trunk gas pipeline corrosion prevention systems as subjects of research is their length, heterogeneity of protection target parameters, impact of hard-to-account external factors, and complex interaction of elements of the equipment set with each other. The system «trunk pipeline - ambient medium» is open and depends on a large number of external factors. This explains the complexity of modeling of such systems as a single interacting equipment and protective coating set. One of the key tasks of studies of corrosion protection systems is evaluation of the development of corrosion processes in time for further calculations on the basis of strength, fatigue endurance and fracture mechanics models. The paper is dedicated to the use of information on external corrosion impact parameters for evaluation of the gas pipeline technical condition. It is demonstrated that the development of corrosion defects depends significantly on the nature of damage of the protective coating and the type of the corrosion process. Therefore, evaluation of the possible level of limit corrosion impacts and the corrosion defect development rate shall be performed on the basis of models based on calculation of the corrosion rate, with account of the complex of data on the protective coating condition, parameters of electrochemical protection and external electromagnetic impacts. The possibility of calculation of geometric defect parameters on the basis of electrometric survey results, based on control of the limited sound number of control points, is confirmed by the example of the model of corrosion defect development under the impact of constant ground currents. Integration of calculation models of corrosion defect development based on the account of external impacts into the gas pipeline technical condition evaluation system will ensure improvement of longevity and accuracy of results of further calculations on the basis of strength, fatigue endurance and fracture mechanics models.