This paper presents the outcomes of computational mechanics applied in the root-cause investigation on hot section failure of a 25 MW gas turbo generator in the domestic power plant after 2228 start-stops and 52,586 h operation. The failure includes the complete damage of the first and the second stage of nozzles, blades, seals, shroud segments, and also a peripheral damage on the disk of first stage. Several reported cases from the different power plants with similar events evidenced that the failure is a serious common type in the mentioned gas turbine engine. A previous study on complete metallurgical analysis of disk, moving blades, and lock-pins, was done by Poursaeidi and Mohammadi (2008, “Failure Analysis of Lock-Pin in a Gas Turbine Engine,” Eng. Fail. Anal., 15(7), pp. 847–855), which concluded that the mechanical specification of applied materials had been satisfied. Nevertheless, some problems were found in the fractographic results of lock-pins: the typical fatigue fracture surfaces in the neck of failed lock-pins and frankly localized pitting signs near the head of lock-pin. The lock-pins are kinds of small devices that lock the buckets after inserting them into disk grooves. In this work, a 3D finite element model (FEM) of a blade, a disk, and a lock-pin are made and analyzed by the ANSYS software. The results of the FEM showed a reasonable agreement between the analysis and position of fracture on lock-pins. Also, the results showed that the second vibrational mode of the bucket is a possible cause of failure because in this mode the peak stress occurs on the head of the lock-pin. However, inadequate design and long time service reduced the performance of lock-pins for sustaining a severe hot condition in the first stage of the turbine section.
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July 2009
Research Papers
Mechanical Investigation of a Failed Lock-Pin
E. Poursaeidi,
E. Poursaeidi
Department of Mechanical Engineering,
Zanjan University
, Zanjan, Iran; Research and Lab Division, Iran Power Plant Repair Co.
, P.O. Box 31585-381, Karaj, Iranepsaeidi@znu.ac.ir
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A. A. Pirmohammadi,
A. A. Pirmohammadi
Department of Mechanical Engineering,
Zanjan University
, Zanjan, Iran
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M. R. Mohammadi Arhani
M. R. Mohammadi Arhani
Research and Lab Division,
Iran Power Plant Repair Co.
, P.O. Box 31585-381, Karaj, Iran
Search for other works by this author on:
E. Poursaeidi
Department of Mechanical Engineering,
Zanjan University
, Zanjan, Iran; Research and Lab Division, Iran Power Plant Repair Co.
, P.O. Box 31585-381, Karaj, Iranepsaeidi@znu.ac.ir
A. A. Pirmohammadi
Department of Mechanical Engineering,
Zanjan University
, Zanjan, Iran
M. R. Mohammadi Arhani
Research and Lab Division,
Iran Power Plant Repair Co.
, P.O. Box 31585-381, Karaj, IranJ. Eng. Gas Turbines Power. Jul 2009, 131(4): 042501 (8 pages)
Published Online: April 9, 2009
Article history
Received:
December 14, 2007
Revised:
November 11, 2008
Published:
April 9, 2009
Citation
Poursaeidi, E., Pirmohammadi, A. A., and Arhani, M. R. M. (April 9, 2009). "Mechanical Investigation of a Failed Lock-Pin." ASME. J. Eng. Gas Turbines Power. July 2009; 131(4): 042501. https://doi.org/10.1115/1.3077660
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