Guided wave inspection of buried structures

This proposal seeks funding for a three year research programme into the inspection of buried structures using guided waves. The scientific basis for the use of guided waves to inspect structures such as pipelines, railway lines, plates and pipes has been developed successfully now for about 2 decades, led in particular by researchers in the UK. The new understanding has been taken up in industry, so far concentrating with great success on the inspection of pipelines. However, critically, the enabling scientific research was done for exposed structures, but guided waves in buried structures are radically different. The surrounding materials, which typically include sound-absorbing protective coatings, reduce the practical range of inspection and often give rise to unwanted components of signals which hinder interpretation. These limitations are becoming very apparent in industry where there is a huge attraction to apply the guided wave method to inspect buried parts of pipelines which are otherwise inaccessible. The proposed research will address these problems, aiming to provide the scientific basis for the reliable inspection of buried and coated pipes over maximum distances. The outcomes will have generic benefit also for the guided wave inspection of any other kinds of buried or coated structures.

The proposal is being submitted within the UK Research Centre in Non Destructive Evaluation (RCNDE) to the targeted research programme, the funding for which is earmarked by EPSRC for industrially driven research.

The inspection of pipelines using guided waves was first established for the oil and gas industry, where it is now used routinely. This success has led to its use also in the electricity power generation industry. The benefits of inspection using guided waves are very valuable: a significant reduction in cost, and a huge improvement in the probability of detection of defects. The latter, which improves the safe management of plant, is of course vital for both of these industrial sectors.

The guided wave testing of pipelines was developed for pipes which are exposed or are coated just with lightweight materials such as paint layers and insulation wraps. This was the easiest category to tackle at entry of the technology, and indeed it is useful for the majority of applications. However, the power of the method has generated increasing interest, and pressure on inspectors, to apply it to categories of pipelines which are not accessible, including pipes buried in the ground or in concrete. This is a natural direction for industry, enabling the inspection of lines which were impossible, or prohibitively expensive, to access. However the necessary science to underpin and optimise this category of guided wave inspection has not yet been done.

The proposed research aims to provide the scientific basis such that buried pipes can be inspected with confidence using guided waves. The obvious benefit will be the possibility to inspect a longer length of pipe from each inspection position. If the range can be doubled then the cost of digging pits for the full-length inspection of a line buried in the ground will be halved. Even more significantly, it will become possible to inspect pipes which are currently not inspectable at all, such as pipes embedded in concrete structures, passing under buildings, and so on. But at least as important as range is the increase in understanding of the measurements. In order to trust these measurements of reflections from remote features and defects, it is vital that the inspectors can interpret the complex signals which are received. The scientific knowledge which will be developed by this project will be the key to enabling that understanding, and thus providing the confidence to perform the inspections.

There is thus already a clearly identified industrial need to which the research will apply.

The primary route to communication of the results of the project to industry will be to the three collaborating companies. All three of these companies have a commitment to guided wave technology already, and are well set up to bring the findings into use. They will be engaged in the project programme throughout, including provision of information, provision of access to sites and plant, and participating in the review meetings, and so will take on the understanding during the project as well as the formal deliverables at the end. Additionally, the other industrial members of the UK Research Centre in NDE (RCNDE) will be informed of the principal steps of progress, via the RCNDE annual review, and so will be able to take early advantage of the new capabilities.

The NDE group at Imperial College has an outstanding record in technology transfer, via licensing, close working with partner industrial companies, and spinning out new companies, and are strongly focused on delivering the benefits of research to industry. They are thus well positioned to judge the appropriate transfer routes and maximise the the transfer of useful findings to industry.