Research On Several Key Problems Of High-speed Magnetic Flux Leakage Testing Of Steel Pipes

With the rapid development of energy industry,especially petroleum industry, the quantity demanded of steel pipe increased quickly and the client made more application for the quality of steel pipes. As an primary method to guarantee quality of steel pipes,Nondestructive testing(NDT) is being more important and the quantity demanded of equipment increases too. Magnetic flux leakage testing method (MFL) as an effective method is widely used in steel pipes inspection system. This paper researches several key problems to product and reconstruct the high-speed steel pipe inspection system. Firstly, the signal transmission system which includes clock circuit, coding circuit, decode circuit, magnify circuit and filter circuit is designed by time division multiplexing (TDM) and universal serial bus (USB) technology. Secondly, Time-frequency analysis method is used to identify inside and outside flaws. The 16 points short time Fourier transform (STFT) with Kaiser Window which can effectively distinguish the N10 inside flaw and the N5 outside flaw is chosen from many methods. Then the arithmetic of enactment benchmark and delicacy technology is used in the software by researching theory of benchmark technology. Lastly, the demagnetizable method to high-speed moving steel pipe is researched and the discrete time method is used to explain the demagnetizable processing of steel pipe. MFL signal process systems and online demagnetizable equipments used in foreign testing equipment are developed on the basis of these researches and applied widely.