In the 19th century explosions of steam boilers on ships and locomotives were not uncommon. One of the factors that reduced these accidents was the introduction of X-ray testing of steam boilers, valves and tubes during the 1920s. This testing process is still used today. However, there are drawbacks such as the long time the component must be exposed to X-rays and the need to take the component apart to allow film to be placed in the right locations.
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Researchers under the European Union (EU)-funded HEDRad project have developed new techniques including digital X-ray imaging and image processing, helping significantly reduce the time used for the regular inspections of Europe's 110 refineries, 400 chemical plants and 10 million kilometers of pipelines.
HEDRad (High Energy Digital Radiography), supported by an EU grant of over €1.1 million and ran from October 2008 to February 2011, was coordinated by TWI Limited, a company specialised in the testing of components and materials, based in Cambridge, United Kingdom. The researchers involved in the project introduced two significant improvements in the existing processes: (1) the development of digital X-ray imaging systems to replace film and (2) a novel image processing software.
They also developed more powerful X-ray sources that allow the inspection of large, heavy-walled components without the need to take them apart. "Just like in a conventional X-ray machine used in medicine, the radiation source is placed on one side of the component. The X-ray beam passes through it and reaches the detector on the other side", explains Mathew Amos, a researcher at TWI Ltd.
In addition, the digital recording of the X-ray images shortens the inspection time. The image resolution of digital detectors helps achieve significant cost and time saving compared to traditional process. "As long as you can see the defects with your digital detector, then you can vastly reduce cost by speeding up inspection times and maintenance schedules," says Amos.
Amos reports the submission of a follow-up proposal for the development of an X-ray computer tomography system for on-site weld inspection. "Such a system would build? a full 3-D image of the component, similar to the computerized tomography X-ray scanners (CAT) used in medicine," says Amos. By rotating both the detector and the X-ray source around the weld, taking multiple recordings, one could? create a 3-D image.
The development of these projects is expected to help SMEs in Europe maintain a leading position, explains Amos. As an example, he mentions CIT Ltd, a SME based in Milton Keynes, United Kingdom, that actively promotes the HEDRad system internationally, making it available to customers who need an inspection system in the power plant on a permanent basis. The BAM Materials Institution in Berlin, who also collaborated with HEDRad, is now a world leader in the field, developing standards and procedures for digital radiographic inspection, says Amos.