The use of guided waves is now widespread in industrial NDT for locating metal loss in pipelines, that manifests as pitting, corrosion and general wall thinning. In this paper, a screening technique is assessed in terms of defect detection and defect sizing capability.Shear Horizontal (SH) guided waves propagate circumferentially around the pipe whilst the scanner is moved axially along the length. This type of tool is preferable to other methods, being applied to the exterior of the pipe, without requiring full circumferential access, and is able to operate through thin coatings (up to 1 mm thick). It is designed to provide a pipe screening tool for petrochemical pipelines both topside and subsea, particularly for detecting defects at pipe support areas. The system's efficacy in terms of detection and sizing of defects is considered via experimental measurements on artificially induced defects and in service corrosion patches, with results compared to finite element modelling of the interaction of the guided waves with artificial defects. Finite element modelling has 2 been used to better understand the behaviour of different wave modes when they interact with defects, focusing on the mode conversions and reflections that occur.

The detection of pipeline leaks is essential for pipeline operators. The quicker the leak can be identified and located, the less product is likely to be lost from the pipeline. Reducing the loss of product results in a reduction of monetary penalties both in the value of the product lost and the associated cleanup operation that is required to remove the product from the surrounding environment. As well as preventing the reputational damage that a leak can cause. Internally based leak detection systems struggle to find small leaks and externally based systems each have their own sensitivities and difficulties in affixing near to or on the pipeline. A demand therefore exists amongst the pipeline operators to investigate the future possibilities for leak detection using methods that can be incorporated in the pipeline coating. These methods could be introduced to a pipeline when repairs are carried out to provide extra instrumentation to find leaks at these positions that are vulnerable from previous damage or points at which a leak from the pipeline would cause significant damage to the surrounding environment. This document therefore provides a literature review of currently available leak detection sensors that are embedded in pipeline coatings for the detection of small leaks and continues to give a landscape view of the research into coating embedded leak detection sensors at this time that could be built on to bring these coating embedded leak detection systems to a commercially viable state. The report gives an indication of the state of the art of the sector and the possibilities for future development of systems and techniques. Many of these techniques are at early stages of development and would require significant time and investment to commercialize as a viable system.

Theory and numerical calculation of the acoustic field produced in metal by an electromagnetic ultrasonic transducer The Journal of the Acoustical Society of America 60, 1089 (1976) Abstract. Guided waves are now commonly used in industrial NDT for locating corrosion in pipelines in the form of wall thinning. Shear Horizontal waves generated by EMATs are used in a screening arrangement in this work to locate and size corrosion in terms of axial extent and circumferential positioning. This is facilitated by propagating SH waves circumferentially around the pipeline whilst moving a scanning rig axially, keeping transducer separation constant. This arrangement is preferential in that it can operate through thin(up to 1mm) coatings and does not require full access to the pipe's circumference and is useful for detecting corrosion in difficult to access regions, such as below pipe supports and in subsea applications. The performance of the system in terms of screening capability and the possibilities of extension into more quantitative measures are assessed. The behaviour of different wave modes as they interact with defects is investigated via experimental measurements on artificially induced corrosion patches and measurements on samples with in service corrosion. Measurement of the axial extent of corrosion patches, circumferential positioning and a range of possible remaining thickness is assessed. Finite element modelling of SH mode interaction with defects is used to understand what happens to different wave modes when they interact with defects in terms of reflection, diffraction and mode conversion.