Non-invasive structural health monitoring of storage tank floors

Abstract

Large above ground storage tanks filled with hydrocarbon and hazardous liquids such as oil, oil-derived products, chemicals and process plant liquids are in widespread use in the UK, Europe and throughout the world. Tank farms are normally located in coastal areas close to large centres of population. Leakage from corroded storage tanks, especially from their floors, is a major environmental and economic hazard and poses a significant threat to those living in the vicinity of tank farms, as well as to the rest of the UK and Europe. The current, and growing, risk of tank failure together with the potential risk for fire and explosion at nearby petrochemical plants is wholly unacceptable. This paper illustrates the work carried out in the UK Technology Strategy Board (TSB) Tank Integrity Monitoring (TIM) project, for the structural health monitoring of large above ground bulk liquid storage tank floors without the need to access the inside of the tank or to empty its contents, using ultrasonic guided waves (UGW) as a non-destructive testing technique. A structural health monitoring system for acquiring ultrasonic guided wave data over long periods of time was developed. The performance of the permanent attached transducers and the structural health monitoring system was also investigated to demonstrate their reliability. The propagation of the guided wave signals has been validated experimentally on a 4 m diameter tank floor, and tomography imaging has been developed for detection and location of defects.