Assessment of Long-Range Guided-Wave Active Testing of Storage Tanks

Abstract

Guided Wave Testing (GWT) is now increasingly being used for the non-destructive testing of large structures. Petrochemical tank bottoms are particularly subject to corrosion. Today, the monitoring of corrosion in storage tanks is probably one of the most challenging applications of GWT because of the size and the complexity of such medium. This article deals with the main physical issues of this application, in particular, the prediction of the elastic field propagating in the tank wall and bottom, and the prediction of guided wave scattering by joints. Drawing on current research work, a representative numerical configuration is defined. The global diffusive effect and the local diffraction effect of the lap joints are studied. The methodology have led us to focus on the low ultrasound frequency range: from 10 to 50 kHz. A quantitative evaluation of the scattering by lap joint is carried out by means of simulations and experiments on elementary reduced scale joints. Dynamic range computations make it possible to get prior knowledge about the minimum signal-to-noise ratio (SNR) required to get information about the tank bottom, for a given configuration, leading to a SNR-resolution trade-off. The method can be extended to larger tanks. The results confirm that the use of GWT technology for long-range active testing and imaging of storage tanks is promising.