Ultrasonic Array Imaging Through Reverberating Layers for Industrial Process Analysis

In this paper, ultrasonic phased arrays are investigated as an imaging tool for industrial process analysis. Noninvasive process measurement, via transmission of information through a vessel wall, typically requires a window to create an optical path between the sensor and the process. Ultrasonic array imaging provides a means to overcome this barrier as it is specifically used to image into optically opaque structures. However, the large acoustic impedance mismatch between the steel process vessel and water load results in reverberations clouding the image scene containing reflections from within the process fluid. A methodology to identify and remove this reverberation interference from the image scene is proposed using subspace analysis coupled with phase coherence imaging. A 32 element, 5 MHz finite element array model mounted to the outside of a steel vessel wall is used to demonstrate the application of this methodology to a typical industrial process environment. The final image is free of reverberation artefacts, providing a means to accurately extract quantitative information about the process from these images.

I. Introduction

Industrial process analysis is the measurement of information used to control an industrial process. Correct control of an industrial process increases workplace safety, improves consistency of product quality and improves the environmental impact by reducing waste [1]. Under ideal conditions, the measurement sensor is positioned non-invasively without direct contact with the process. This reduces measurement uncertainty from disturbances to the flow and reduces the measurement cost as the hardware can be easily replaced without interruption to the process [2].