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A creep life consumption study was conducted in a high-pressure turbine rotor belonging to a 363 MW thermal power plant. The component is manufactured with 30CrMoV412 steel, which is a typical 1CrMoV forged rotor steel, having operated for 112,000 h, under a pressure of 17.6 MPa and temperature of 520°C. The main objective of this paper is to evaluate the applicability of hardness tests as a tool for structural integrity analysis in the field. Two methods for estimating creep remaining life based on hardness measurements were used. Furthermore, metallographic replicas made during unit shutdown were observed by scanning electron microscopy, in order to detect creep voids and also to corroborate the results for accumulated creep damage obtained based on hardness measurements.

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Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the action of several damage mechanisms associated with the impact of hard particles from the residue of burnt coal, the ashes. The employment of coatings should be given into consideration particularly for critical components, which are subject to severe erosive conditions is one of the solutions. However, the choice of material will depend on several factors, including the properties of aggressive ashes. This paper aims to characterize ashes generated by a Brazilian coal-based power plant and a FeCrNbNi-based metallic coating obtained by the electric arc spraying process. No trace of sulfur content was found in fly ashes and it was defined that wear is mainly related to the impact and energy of hard particles are the leading causes of degradation in coal-fired boiler equipment. According to the assessment, applied coating showed (5 ± 2)% by volume of pores and cracks, with 1.6% of oxides after the spraying process and hardness 35% greater than ash particles. Preliminary results in field operation suggest that the material showed relatively low wear compared to the original substrate and showed great applicability in controlling material deterioration for this purpose.

The Brazilian thermoelectric plants that use coal as a thermal source use pulverized combustion technology. The aim of this work was to characterize some properties of a metallic coating obtained by arc electric thermal spray in order to protect boiler's surface against ash's aggressive action from coal burning. The evaluated parameters considerably influence the characteristics of the coating's lifes service. An iron chromium base alloy, reference herein as Alloy B, was used in this study. A chemical analysis of the coating, Alloy B, was performed in order to compare if there were any difference between the chemical composition of the wires used and what was incorporated into the coating by the thermal spray process. Therefore, Energy Dispersive Spectroscopy technique (EDS), Quantax software and PyMCA program were used. The chemical analisys results of the coating was quite similar to the given composition of the wires. To verify the coating hardness, Vickers (HV) microhardness measurements were performed on the coating region, on the substrate and on the boundary region of the coating between substrasts. Vickers microhardness measurements were obtained by PANTEC MV-1000A microdurometer. As substrate an 8 mm thick steel sheet with a chemical composition and thickness similar to the steels used in the water wall pipes of Brazilian boilers were used. The coating hardness (730 HV) was on the order of four times greater than the substrate's hardness (179 HV) to be protected. This property was homogeneous for the coated layer showing that hardness values indicates that good adhesion of coating's cast particles occurred, and the spray distance proved to be effective. The roughness was obtained through measurements made

The present paper describes the development of a monitoring, analysis and diagnosis system of power plant equipments based on strain measurements. The objective is to help companies increase availability and reduce maintenance costs. The aim is the integrity evaluation of a main steam and a hot reheat steam piping through inspection, strain monitoring and computational diagnosis. The benefits are, among others, reduction in the uncertainty of the remaining life prediction and reduction of work, through process automation and integration and real time monitoring (through the Internet) of the operational condition of the equipment. Thus, greater confidence and availability of the monitored generating unit is sought as well as cost reduction as a consequence of reduced frequency of unnecessary unit stops and greater speed in decision making due to more precise follow up of the operational condition of the target-equipment and of its remaining life.

RESUMOFalhas em tubos de caldeiras são as maiores causas de paradas forçadas de unidades de geração termelétrica, sendo que a espessura da camada de óxido, que se forma na parede interna destes tubos é a principal causadora de falhas por sobreaquecimento. A partir dos valores medidos da camada interna de óxidos é possível estimar a vida residual do componente através de correlações com parâmetros já estabelecidos na comunidade científica. O Cepel vem desenvolvendo metodologias para estimativa de vida residual de componentes de caldeiras de usinas termelétricas, seguindo as tendências mundiais e as necessidades de seus clientes no Brasil. Com a recente aquisição de equipamento para detecção de defeitos e medições de espessura via ultrassom, tornou-se possível realizar medidas de espessura tanto da parede das tubulações das caldeiras como da camada interna de óxidos presente nas mesmas. O presente artigo apresenta uma comparação entre os resultados de medições de espessura de camada de óxidos em tubos pela técnica não destrutiva de ultrassom e pela técnica destrutiva de metalografia associada à microscopia ótica, em diferentes faixas de espessura da camada e análise do efeito do acabamento superficial na confiabilidade destes resultados por ultrassom. Finalmente, o trabalho analisa de maneira crítica os resultados de vida remanescente, obtidos a partir da medição espessura de camada de óxido. Para esta análise tomou-se como base tubos de uma mesma unidade geradora com diferentes valores de camada de óxido e com o mesmo tempo de operação.Palavras chaves: Técnica ultrassônica, Camada de óxido, Vida remanescente. Expected life in tubes of boilers based on measurement of the thickness the oxide layer by ultrasonic ABSTRACTBoiler tube failures are the major causes of forced shut downs in thermoelectric units. The thickness of the oxide layer formed on the inner wall of these tubes is the main cause of failure due to overheating. From the measured values of the inner oxide layer, it is possible to estimate the residual life of the component via correlations with parameters established in the scientific community. Cepel has been developing methodologies for estimating the residual life of boiler components for power plants, following the world trends and the needs of its customers in Brazil. With the recent acquisition of ultrasonic equipment for detecting defects and to perform thickness measurements it has become possible to perform both operations at the same time. This article presents a comparison between the results of measurements of oxide layer thickness in tubes by the non-destructive ultrasonic technique and the destructive metallographic technique associated with optical microscopy. Oxide layers with different thicknesses were used to perform the analysis. Also, the effect of surface preparation was evaluated for the reliability of results by ultrasonic testing. Finally, the study examines, in a critical way, the remaining life results obtained from the measured oxide layer thickness. To perform this analysis,...