Tomographic and scattering based methods for damage detection on atmospheric storage tanks

Structural Health Monitoring (SHM) systems based on ultrasonic guided waves and sensors permanently installed on structures have the potential to decrease the maintenance costs and reduce the risk of failures of critical components in a chemical plant. Such systems, in fact, can check the health status of the structure, prompting maintenance interventions only when needed and not at prescribed intervals. Moreover, they can be used on a real time basis or activated in remote for extemporary checks. The monitoring process consists in two main steps: (i) detection of waves at specific positions via proper sensor-node networks and (ii) post processing the gathered signals with the aim of assessing the structural integrity. The aim of this paper is to compare two post processing techniques, namely (i) the tomography (TM) and (ii) the wave scattering method (WSM), commonly used for damage detection and localization. As a test case, guided waves propagating in small portion of a steel atmospheric tank mantle have been simulated via Finite Element and used to test the ability of both algorithms to detect and locate the position of the damage with respect to its severity and the adopted number of sensors.