Hybrid Coded Excitation of the Torsional Guided Wave Mode T(0,1) for Oil and Gas Pipeline Inspection

Abstract

Ultrasonic guided wave testing is an essential technique in non-destructive testing for structural integrity of oil and gas pipelines. This technique, based on the pulse-echo method, is often used for the long-range detection of pipelines at any location. However, guided waves suffer from high attenuation when they propagate in attenuative material structures and multiple wave modes due to the excitation, which reduces the power of echo signals and induces corruption caused by coherent noise. In this paper, a developed hybrid coded excitation method that uses the convolution of a Barker code and Golay code pair is proposed and applied for an ultrasonic guided wave testing system to excite the torsional guided wave mode T(0,1) in a steel pipe. The proposed method combines the advantages of these two coding methods and increases the flexibility of code lengths. The performance is evaluated by signal to noise ratio and peak sidelobe level of the processed signal. Both theoretical simulations and experiments have investigated using the proposed codes composed of Barker codes and Golay code pairs of different lengths and combinations. The experimental results show the significant improvement of the signal to noise ratio and the peak sidelobe level due to the proposed hybrid code usage for the excitation of guided waves. The values are further improved to around 32 dB and around −24 dB, respectively. Overall, the proposed hybrid coded method for improving the echo SNR can benefit from guided wave testing to reduce coherent and random noise levels and many other potential applications.

Coded Excitation for Ultrasonic Testing: A Review

“…Therefore, the authors designed a multi-element encoding excitation method that significantly increased the amplitude of the echo signal under different damage conditions. Similar methods have also been proposed by Zeng Fan, who utilized a hybrid encoding approach to improve the SNR in the structural integrity testing of oil and gas pipelines [40], as depicted in Figure 19. Mehmet K. Yücel and colleagues proposed a novel signal processing technique using maximum length sequences and linear frequency-modulated excitation signals [96].…”

Split-Spectrum Processing with Raised Cosine Filters of Constant Frequency-to-Bandwidth Ratio for L(0,2) Ultrasonic Guided Wave Testing in a Pipeline

“…Mahal et al [10] studied the modulation effects of Chiript, Barker and Golay codes with a small main lobe width and found that the SNRs (Signal to Noise Ratios) after modulation by the above three methods were significantly higher than those using a Hanning window sinusoidal signal. Fan et al [11] proposed a hybrid coding excitation method using the convolution of the Barker and Golay code, and the results showed a significant improvement in SNR and peak sidelobe levels to approximately 32 dB and approximately −24 dB, respectively. However, PuC requires the design of excitation waveform, the performance of optimal excitation sequence depends on the detection conditions and the elimination of coherent noise is limited [12].…”