基于多频交流场指纹法的金属管道腐蚀监测研究

Field signature method (FSM) is a common monitoring technology for metal pipeline corrosion. However, there are a lot of shortcomings in FSM Technology such as the measurement results are easily disturbed by the drift and the temperature difference between the reference plate and the measured pipe will lead to a large measurement errors. Multi-frequency alternative current field signature method (MACFSM) is introduced to assess the wall thickness of metal pipeline based on finite element simulation. Multi-excitation current with a series of frequency from high to low is injected into the measured metal pipe, and penetration depth will increase with decreasing frequency while voltage between electrodes will decrease. When penetration depth reach to the inner wall of measured pipe, voltage between electrodes will remain the same. Therefore, all of the recorded voltages can be fitted into a function, then take the derivative of this function, while the penetration depth of the first zero of derivative is equal to the wall thickness of the measured pipe. Then, the experiment was applied to verify the simulation. 0.1 A multi frequency exciting current was injected into the metal pipeline with a defect depth of 3.5 mm, and the defect depth was solved accurately by the derivative extreme value. The simulation and experiment showed that multi-frequency alternative current Field signature method (MACFSM) does not need reference voltage, and the measured voltage also does not need to be compared with original voltage; especially this method can overcome the adverse effect caused by baseline drift of electric circuit system and change in temperature, therefore the reliability of long term on-line monitoring technology can be greatly improved.