Research on residual wall thickness inversion of oil and gas pipelinewith cladding based on support vector machine

The oil and gas pipelines in the oil field are usually equipped with a layer of cladding in certain thickness, and the pulsed eddy current testing technology can be adopted to measure the wall thickness without removing the cladding, which saves a lot of costs for the removal and assembly of the cladding. However, as a result of cladding, distance exists between the pulsed eddy current sensor and the pipeline, which leads to the variation of the equivalent resistance and inductance of the sensor, and further affects the voltage signal of the pulsed eddy current detection, reducing the accuracy of the residual wall thickness inversion. In order to solve this problem, a quantitative inversion model of lift-off, slope of late detection voltage signal and pipe wall thickness was established with a support vector machine(SVM), and inversion test of the residual wall thickness of the step specimen with the wall thickness of 5-21 mm was carried out with this model under the condition of 0-10 cm lift-off, with the error of the inversion result controlled within 7%. Thereby, the inversion model is verified to be valid with high practical value, and certain reference could be provided for the measurement of the residual wall thickness of the pipeline with cladding.