WA Branch Technical Meeting - 13 July 2020

Source: Dr Paul Huggett CMP, Principal Scientist and Materials Manager

Based in Bibra Lake, Western Australia, Applus provides onsite non-destructive testing (NDT) services, focused the training of NDT operators including the use of rope-access techniques. The Materials Centre, which undertakes failure investigations, is a new and growing aspect of the services offered by Applus throughout Australia.

To conform with COVID-19 physical distancing rules, the visitors split into three groups and cycled through demonstrations of phased array eddy current inspection, virtual reality techniques for planning on-site inspections, and scanning electron microscopy (SEM). Visitors also passed through the ropeaccess training facility, where they were assured that using rope access techniques does not, as many had imagined, require great physical strength. However, it clearly demands a ‘good head’ for working at height! The eddy current technique is based on interpretation of impedance changes in a coil carrying an alternating current, caused by changes in conductivity and permeability of the adjacent material. This was demonstrated by showing how the use of a single coil can detect pitting corrosion, measure coating thickness, and sort different materials. The disadvantage of the single coil technique is that it is highly dependent on the skill of the operator, and the inspection rate per unit area is relatively slow. The eddy current array technique uses a set of coils arranged to target specific defects, such as corrosion pitting on pipes. This allows wider coverage, simpler interpretation and improved identification of location and size of defects. The associated reduction in workload, on rope access operators, is a notable benefit. Applus is known as a leader in the use of drone photography for visual inspection of operating process plants. Visitors were shown the most recent advancement in the use of photography, which involves the combination of tens of thousands of separate images, from drones and surface vehicles, to produce 3D models, viewable by the use of virtual reality headsets.

These models, sometimes supplemented by LIDAR scans, are used, in combination with CAD software, to plan operator entry for NDT inspections. Techniques demonstrated combined photogrammetry and computer games development. Applus Materials Manager, and current WA Branch President, Paul Huggett, gave a hands-on demonstration of SEM for investigation of failures and critical flaws detected by NDT. This included demonstrating the differences between back-scattered and secondary electron imaging modes. The demonstration showed that ‘what you see’ depends on imaging mode and sample orientation. Hence, it is essential to “engage with the microscopist” in planning and interpreting an SEM investigation. Dr Huggett then demonstrated elemental elemental X-ray mapping and the ‘environmental’ (low vacuum) mode of SEM operation, which is applicable to non-conductive samples. The three groups reconvened for general discussion and refreshments, with with Dr Huggett offering to go into more depth on his materials investigation work in a future presentation.