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A total of 44 defects were found and marked and the areas with the most severe flaws were removed.
Minor defects were pad welded. The LFET scanners also were able to identify pitting as shallow as 20 percent wall loss or a wall remaining of 0.144? out of 0.180?. Some tubes had several pits over a 4´ area, while other tubes only showed a single pit. The repairs the plant made saved them from several forced outages.
The other two boilers were not experiencing failures in the horizontal reheater sections. The plant decided to go ahead and perform similar inspections on these units because they were the same design. The same areas were inspected and no defects were found in either boiler.
Through the use of NDT, both of these plants were able to reduce costly forced outages. The plants identified their issues and worked with a vendor to improve the boiler run time. The end results are less plant down time due to equipment failure, less unscheduled maintenance and fewer safety issues. The NDT inspections provided a more efficient
The keys to success in both of these cases were due to the plant accurately explaining the problem to the NDT company. Tube samples and drawings of the unit were provided and tubes were cut out during the inspection to verify results, improve accuracy and provide confidence. The plants made the proper repairs and collective actions were taken to prevent and or reduce future failures.
Editor's note: This paper, PWR2008-60056, was printed with permission from ASME and was edited from its original format. To purchase this paper in its original format or find more information, visit the ASME Digital Store at www.asme.org.
Shawn Gowatski received a BSME from the University of Pittsburgh in 1994 and he has been working for TesTex Inc. in Pittsburgh, Pa., since 1995.
Gowatski spent 3 years working as a Field Service engineer performing non-destructive testing inspections on boilers, heat exchangers, piping, above ground storage tanks, pressure vessels, etc. In 2008, Shawn became the manager, Solution Providers Group. You can contact him by e-mailing firstname.lastname@example.org.
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