Feasibility study of using the magnetic flux leakage test method in detecting defects in the coating of supply and distribution gas lines

Today, the corrosion of oil and gas supply and distribution lines is a major challenge in these industries. In order to prevent the corrosion of underground pipes, various types of coatings, especially bituminous base coatings, are used to protect oil and gas pipelines. One of the widely used tests for detecting defects in metal pipes of gas transmission lines is the magnetic flux leakage test method. This test is performed only on the metal pipe itself and determines the defects of the pipe. In this paper, the possibility of using this test to detect pipeline coating defects has been investigated. If the coating defects are detected, they can be prevented from spreading and reaching the metal body of the pipe. For this purpose, the magnetic flux leakage test of a part of a gas pipe with a coal-based bitumen coating along with a defect and with different thicknesses in the pipe and coating was simulated in Comsol software. The magnetic properties of the coatings were also extracted with a magnetometer. The results of the simulations showed that the leakage of magnetic flux in the coating defects is insignificant and cannot be measured to reveal the defects.