Abstract

Detection of cracks in many engineering components is critically important as these often propagate to cause failures that can be catastrophic. Pipelines, particularly in establishments such as oil refineries, are an example of critical and extremely valuable infrastructure in which failures could be particularly catastrophic. Much of the pipework in such establishments is lagged, which makes inspection more difficult. This is especially the case with traditional inspection techniques in which pipelines are inspected through the section with equipment attached to the outside: this would require progressive removal of lagging, inspection then replacement of the lagging. The technology developed by Guided Ultrasonics Ltd is based on the simple principle of propagating waves longitudinally in components such as pipework. With this method, only a small amount of lagging has to be removed and replaced, and it is possible to inspect considerable lengths of pipework at a time. The “time of flight” of a wave between being broadcast and a response being received from a defect shows where a defect exists along a pipe. By varying the mode shape of the wave, it is possible to inspect particular areas of the pipe and to assess changes in dimensions such as the wall thickness, which could indicate that there are effects of corrosion. The same basic technology has been applied to inspection of rails, for which there is the possibility of inspecting areas such as the railhead and railfoot.