• Analytical Science and Technology
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• v.21 no.2
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• pp.148-157
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• 2008

To describe the lifetime prediction of gas turbine core parts serviced in some ten thousands rpms at over $1,000^{\circ}C$, the Larson-Miller Creep Curves, which are formed by creep rupture tests as the destructive experiment with parameters of stress and temperature, are used often, but not exact and reliable with errors of over some tens. On the other hand, this study shows a non-destructive method with increased accuracy and reliability. The SEM and TEM specimens were extracted by replica after polishing the local airfoil and root surfaces of the first stage scraped blade (bucket), serviced for 18,000 hours at $1,280^{\circ}C$ in Gas Turbines of Boryong. The observed TEM and SEM precipitates were digitalized for calculation of the average size. Here we could find the precipitate size grown from $0.45{\mu}m$ to $0.6{\mu}m$ during service and the grown precipitates to be still sound. From these results we could conclude that the scraped balde can be used for ten thous and hours additionally and for twenty thousand hours by additional heat treatments on the scraped blade.

• Journal of Power System Engineering
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• v.12 no.6
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• pp.70-77
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• 2008

The purpose of this study is to compare the quality of digital radiography image with that of classical film images for welded structure in power plants. The CMOS(Complementary Metal Oxide Semiconductor) flat panel detecter and Agfa D5 film are used to image flaw specimens respectively. In the test, CMOS flat panel detector has been determined to have a better image than that of film image. In the IQI(Image Quality Indicator) transmission test, one or two more line can be seen in digital image than in film image. Digital Radiography Test enabled to successfully detect all defects on the weld specimens fabricated with real reheat stem pipe and boiler tube as well. In the specific comparison test, Digital radiography test detected micro flaws in the size of 0.5 mm in length by 0.5 mm in depth. However, film test has limited it to 1.0 mm in length by 1.0 mm in depth. As a result of this study, digital radiography technology is estimated well enough to perform the inspection in the industry with far more cost effective way, compared to the classical film test.