Title: Oxide thickness measurements: a suitable tool for remaining life evaluation in power plants

Authors: Bruno R. Cardoso; Franco W. Comeli; Roberta Martins De Santana; Heloisa C. Furtado; Luiz Henrique De Almeida

Addresses: Electric Energy Research Center (CEPEL), Horácio Macedo 354, 21944-970, Rio de Janeiro, Brazil ' Tractebel Energia, Pascoal Apóstolo Pítsica nº 5064, 88025-255, Florianópolis, SC, Brazil ' Electric Energy Research Center (CEPEL), Horácio Macedo 354, 21944-970, Rio de Janeiro, Brazil ' Electric Energy Research Center (CEPEL), Horácio Macedo 354, 21944-970, Rio de Janeiro, Brazil ' Federal University of Rio de Janeiro (COPPE/UFRJ), Centro de Tecnologia, CT/UFRJ Bloco F, sala 204, CEP 21941-972, Rio de Janeiro, Brazil

Abstract: Boiler pipe failures are the most common cause of forced shutdown of power generation units. The oxide layer formed in the inner wall of those pipes is the main cause of overheating failures. From the measured value of the inner oxide layer, it is possible to estimate the remaining life of the component through correlation with parameters already established by the scientific community. The present paper compares the internal oxide layer thickness measurements of pipes performed by ultrasonic (non-destructive technique) and by metallography (destructive technique), in different ranges of thickness layers and an analysis of the effects of surface finishing in the reliability of the ultrasonic results. Finally, the paper analyses the remaining life calculation based on the measurement of the oxide layer thickness. The results obtained from the calculation were corroborated with a microstructural characterisation of the samples.

Keywords: ultrasonic testing; integrity evaluation; boilers; steel-oxide interface; power stations; power plants; oxide thickness; remaining life evaluation; boiler pipe failure; overheating; nondestructive testing; NDT; metallography; surface finishing; reliability; microstructure.

DOI: 10.1504/IJMMP.2014.066910

International Journal of Microstructure and Materials Properties, 2014 Vol.9 No.3/4/5, pp.274 - 291

Published online: 16 Jan 2015 *

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