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|NDT.net Issue - 2007-07 - NEWS |
A new automatic scanner to detect cracks in the blade root fixings of steam turbine discs has been developed for Alstom by Phoenix Inspection Systems.|
The scanner will allow Alstom to replace manual inspections with the latest phased array techniques, drastically reducing typical inspection times while at the same time providing a permanent record of the results. It will be deployed at power stations worldwide where Alstom power plants are installed.
The straddle root scanner will be used to test the root fixings of the disc where the turbine blades are attached. In place of four conventional probes, it uses one linear phased array probe, which is manipulated electronically to generate the same angles. The scanner is driven around the disc by a magnetic wheeled buggy, designed specially for the purpose by Alstom and fitted with guides to prevent it from drifting offline.
Karl Quirk, managing director of Phoenix Inspection Systems, said: Previously the inspection had been performed manually and required multiple scans from each side of the disc to cover each of the root steeples. Inspections can now be carried out with a single pass from each side of the disc and are further simplified by the fact that the radial scanning of the probe is performed electronically, eliminating mechanical movement in this direction.
The scanner reduces inspection times from six hours to 10 minutes per side. While we have incorporated the latest technology, we have also stuck closely to the design of the original scan, for example using the same angles. This makes it more user-friendly for operators and also allows Alstom to maintain its existing validation criteria.
The new system has been designed for rapid set-up and can be adapted to suit five different types of Alstom rotors simply by changing parts on the buggy.
Alstom is a global leader in the development of power generation infrastructure and its service arm provides testing and support services to ensure plant safety and efficiency. Dr Roland Moser, Alstom's research and development manager for inspection technologies, said: We were looking for a system that could help us to reduce inspection times and improve efficiency, one that would be easy to deploy and would not require us to totally change our existing procedures.
The system developed by Phoenix fits the bill perfectly and shows Alstom's commitment to maintaining our position at the forefront of NDT technology.