Investigations of the Failure in Boilers Economizer Tubes Used in Power Plants |
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Authors: | Roozbeh Siavash Moakhar Mehrad Mehdipour Mohammad Ghorbani Milad Mohebali Behrad Koohbor |
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Affiliation: | 1. Department of Materials Science and Engineering, Sharif University of Technology, Azadi Avenue, P.O. BOX 11155-9466, Tehran, Iran 3. Metallurgy Department, Niroo Research Institute (NRI), Tehran, Iran 2. Department of Material and Engineering, K. N. Toosi University of Technology, Pardis St., Vanak Sq., Tehran, Iran
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Abstract: | In this study, failure of a high pressure economizer tube of a boiler used in gas-Mazut combined cycle power plants was studied. Failure analysis of the tube was accomplished by taking into account visual inspection, thickness measurement, and hardness testing as well as microstructural observations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Optical microscopy images indicate that there is no phase transformation during service, and ferrite-pearlite remained. The results of XRD also revealed Iron sulfate (FeSO4) and Iron hydroxide sulfate (FeOH(SO4)) phases formed on the steel surface. A considerable amount of Sulfur was also detected on the outer surface of the tube by EDS analysis. Dew-point corrosion was found to be the principal reason for the failure of the examined tube while it has been left out-of-service. |
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