A new acoustical method for inspection of industry piping

Abstract

A new acoustical method for inspection of the industry piping against development of corrosion and early stage cracks is presented. Impulse response of a defective pipe is obtained by launching an M-sequence at an end of the pipe, and cross-correlating it with the sequence received at the same end. The received sequence contains several replica of the M-sequence, reflected from various objects including the defects in the inner wall of the pipe. Therefore, the impulse response contains a peak corresponding to each reflection, the location of which determines the location of the reflecting object. Signal processing techniques are used to detect these very small peaks from heavy noise, and to distinguish the wanted peaks (due to defects) from unwanted peaks (due to other objects). A new technique is presented, which removes all kinds of unwanted peaks and other noise and significantly enhances the wanted peaks. This technique is proved much better than the classical noise removal techniques of moving average, subtraction and inverse filtering. A very simple experimental setup is presented and the results of successful detection of defects of different sizes in pipes of different dimensions are presented. [The presented research was financially supported by Japan Society for Promotion of Science.]