In-line inspection of unpiggable buried live gas pipes using circumferential EMAT guided waves

Abstract

Abstract. Unpiggable buried gas pipes need to be inspected to ensure their structural integrity and safe operation. The CIRRIS XI TM robot, developed and operated by ULC Robotics, conducts in-line nondestructive inspection of live gas pipes. With the no-blow launching system, the inspection operation has reduced disruption to the public and by eliminating the need to dig trenches, has minimized the site footprint. This provides a highly time and cost effective solution for gas pipe maintenance. However, the current sensor on the robot performs a point-by-point measurement of the pipe wall thickness which cannot cover the whole volume of the pipe in a reasonable timeframe. The study of ultrasonic guided wave technique is discussed to improve the volume coverage as well as the scanning speed. Circumferential guided wave is employed to perform axial scanning. Mode selection is discussed in terms of sensitivity to different defects and defect characterization capability. To assist with the mode selection, finite element analysis is performed to evaluate the wave-defect interaction and to identify potential defect features. Pulse-echo and throughtransmission mode are evaluated and compared for their pros and cons in axial scanning. Experiments are also conducted to verify the mode selection and detect and characterize artificial defects introduced into pipe samples.

Internal and External Pipe Defect Characterization via High-Frequency Lamb Waves Generated by Unidirectional EMAT

“…Wang studied the reflection and transmission coefficient curves of the circumferential SH0 wave (CSH0) and Circumferential SH1 wave (CSH1) modes with the depth of three types of axial slots through three-dimensional finite element simulation [4]. Liu used an EMAT laser for the quantitative identification of lamination defects in thin-walled metal pipes through beam analysis of lamination defects [5]. Lu analyzed the reflection of SH0-guided waves at the front and rear edges of circumferential cracks and the influence of circumferential crack geometric parameters on the two edge-reflected waves.…”

Numerical Investigation of Application of Unidirectional Generation to Improve Signal Interpretation of Circumferential Guided Waves in Pipes for Defect Detection

“…The latter has just one nonnull displacement component, perpendicular to the cross-section and to the wave propagation direction and present advantages such as no energy leakage to nonviscous fluid loading, and allow one to operate at a single-mode regime when the frequency is relatively low [4]. SH guided waves are widely used to detect defects in plates and pipes [9][10][11][12][13][14]. Circumferential guided waves (CGW) can also be divided into circumferential SH (CSH) [15] or circumferential Lamb-type waves [4], which present similar propagation characteristics to their flat-plate counterparts.…”

“…Therefore, careful signal interpretation should be carried out, considering this inherent propagation complexity. An adopted strategy consists of using separated transmitter and receiver transducers, positioned and such a way to define short and long propagation paths, due to the simultaneous generation in both clockwise and counterclockwise directions, and establishing expected baseline signal for a defect-free pipe [11,12].…”

Desenvolvimento De Solução Embarcada Baseada Em Fpga Do Tipo Zynq Para Sistema De Ultrassom Por Transdutores Emat

“…Focando no uso de transdutores do tipo EMAT, o sinal de excitação influencia a qualidade e o tipo de dados recuperados, possibilitando, a detecção de falhas especificas em tubulações. As referências [2] e [3] apresentam exemplos de trabalhos aplicados no estudo da influência da detecção de falhas usando transdutores do tipo EMAT.…”

“…Uma vez validado o funcionamento do circuito em FPGA, os testes passam para etapa com o circuito de amplificação e o transdutor, para tornar a solução aplicável. Um exemplo de uma situação teste que se aproxima do pretendido é encontrado em [2]. A implementação na Zybo Z7-20 teria, ainda, que passar por uma etapa de desenvolvimento da conexão entre PS-PL utilizando as interfaces citadas na subseção 2.a.4 e um software de controle para a solução.…”