In-service degradation of piping systems

One of the major projects BINDT is working on is the in-service degradation of piping systems, specifically offshore. Recently, there have been two training weekends for trainers and examiners, one in Australia and the other in Aberdeen (which I attended). Available were actual pieces of pipe that had come out of service showing internal degradation, as in the photograph below, which shows the rounded pits evident in the pipe bore.

We were invited to ultrasonically test the samples from the external face, which was still covered in the original coatings, but were much more accessible than if they were in situ on an oil rig in the North Sea, which can be a very hostile environment.

From testing the samples it would be all too easy for an inspector to think that coupling has been lost when the probe is positioned over one of the rounded pits that do not reflect sound back to the probe to any great extent. One option would be to move the probe until a reasonable response is visible, which would probably be in a region of sound material. This would result in the loss of material being ignored and all the potential problems remaining unknown. Another challenge is coping with the paint/coating thickness, which can add 1-2 mm to the thickness reading. With industry’s input, new training and certification packages are being developed.

Other industry sectors, including power generation, are also looking at potential inspection problems that are associated with elderly plant and are running in-house specific courses to train staff on what to expect on their plant.

These are industry-led changes and are not being generated by BINDT to create even more certification; PCN is responding to industry’s requirements.

john.moody@bindt.org

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