By Jane Allwright and Ruth Sanderson
With hundreds of thousands of miles of pipelines being used throughout the oil and gas industry, as well as numerous other pipes and pipe-like structures in, for example, the power industry and many others, there is a strong need to ensure the integrity of large lengths of pipe. This requires the ability to inspect such structures in service, and to interpret the outcomes of such inspections in terms of any flaws or abnormalities that may have been detected. Long range ultrasonic testing procedures using guided waves are currently used to meet this inspection challenge, and provide a means of screening tens of metres of pipe from a single test location.
In recent years, improvements have been made to the guided wave inspection procedures for pipes. Using both finite element analysis and experimentation, methods have been developed to:
- Predict the size and shape of flaws.
- Focus the sound energy on particular regions of the pipe, giving increased sensitivity.
One of the main areas of interest in the field of guided waves is to derive quantitative information about flaws directly from the patterns of reflections and mode conversions in a standard guided wave inspection.
The purpose of this review was to understand and summarise this work, to collect together the various results, to establish links between them where possible, and so to identify the state-of-the-art.