关键词: 输油管道, 金属磁记忆检测, 漏磁信号, 小波阈值, 自适应阈值, 降噪方法

Abstract:

When the metal magnetic memory(MMM) inspection method is applied to make early diagnosis of oil pipeline, the magnetic memory signal is easy to be disturbed by various sources of noises, and the detectability of defect signals is greatly lowered. An improved method composed of wavelet threshold function and adaptive threshold was presented on the basis of the classic denoising method using soft and hard threshold algorithm and the characteristics of magnetic memory signals. The Daubechies wavelet was used as a wavelet function with four series, and the adaptive method was used to calculate the threshold. The magnetic flux leakage-magnetic memory detector was used to certify the algorithm. The testing results demonstrated that the new method could overcome the shortcomings of soft and hard threshold algorithm, and the signal-to-noise ratio of the rebuilt signal was improved, and the noises of signal were greatly eliminated. This denoising algorithm can provide the theoretical basis for estimation of stress concentration zone and early diagnosis of oil pipeline.

Key words: oil pipeline, metal magnetic memory inspection, magnetic flux leakage signal, wavelet threshold, adaptive threshold, denoising method