Study On Measurement Method Of Corrosion Degree Of Industrial Pipelines With Cladding Layer

In recent years,with the rapid development of domestic industry,the development of oil,natural gas and other energy resources and the increasing market demand,energy transport problems followed.As an important tool for energy transmission,ferromagnetic pipelines with coated layer have been widely used.When used for too long,the inner and outer walls of ferromagnetic pipelines will corrode.The pulsed eddy current testing technology can be used to quickly scan the coated ferromagnetic pipeline without removing the coating layer and effectively complete the in-service detection of the coated ferromagnetic pipeline.At present,the commonly used sensors include circular sensor,focusing(Y-shaped)sensor and U-shaped sensor.The U-shaped sensor has higher detection sensitivity and anti-interference ability than the other two kinds of sensors,which can better deal with the local corrosion frequently occurring in industrial pipelines and meet the requirements of actual industrial detection.Therefore,u-shaped probe is adopted in this thesis to carry out simulation research.In this paper,the simulation model of industrial pipeline with cladding layer and detection sensor is established by finite element simulation method,and the parameters of the sensor are determined and optimized.COMSOL software was used for simulation analysis to optimize coil structure parameters,select excitation signals and signal parameters to meet the requirements of data board acquisition,measurement range and measurement accuracy.The simulation research of quantitative detection on the change of different depth,length and position of defects is carried out.The simulation results show that when the defect depth changes,the voltage value in the detection coil decreases with the increase of the defect depth.When the defect length changes,the peak induced voltage of detection coil increases with the increase of the defect length.When the defect position moves to the foot of the pipe on one side of the Ushaped probe,the detection voltage decreases.Two detection coils can be used to detect the relative position of defects.The designed U-shaped probe can meet the requirements of detecting range and precision for pipeline corrosion defects.The method of u-shaped sensor to detect the pipe wall thickness and to overcome the influence of the removal of cladding layer is studied and the detection range of the pipe wall thickness of the sensor is determined.Often occurs in the industry by the wall outside enlarge and expand the two types of internally by wall defect detection has carried on the simulation research,the sensor on the outer wall of tube surface began to expand its corrosion depth small defect detection effect is not ideal,this is due to the defect length increases in the process of gradually more than the distance between the two detecting coil.However,for defects with small surface corrosion area and gradually expanding inside,the detection effect is good.This is because the continuous enlargement of the cavity inside the defect will cause enough obvious changes in the detection data.To sum up,the designed U-shaped sensor has good capability of qualitative detection and quantitative analysis of defects when the insulation layer thickness is below 350 mm,and also has sufficient capability of analysis and detection for defects in constant changes.