Abstract Mineral coal is a fuel that can be used by thermoelectric plants to generate electricity, however, the solid residues of its combustion, so-called ash, cause erosion and corrosion in the internal components of boilers that operate at high temperatures, causing failures in the system. This study proposes a metallic coating based on Fe-Cr-Si, obtained using the electric arc thermal spray technique as an alternative for protecting the most affected parts of boiler tubes by the ash impact. Optical microscopy (OM), scanning electron microscopy (SEM), semi-quantitative chemical analysis by Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD), roughness measurements, pull-off adhesion tests were used. Thermal diffusivity measurements and mathematical modelling were elaborated to evaluate the thermal exchange efficiency impact of the coating in thermoelectric plant boiler tubes. The results showed that the chemical components of the sprayed wire were well incorporated into a coating with a hardness of 730.54 ± 164.28 HV, approximately three times greater than the hardness of boiler pipes and only 11% less than the hardness of ash. XRD identified the presence of crystalline phases in the coating and adhesion tests showed that the failures were cohesive without substrate exposure. The presence of the coating reduced heat exchange of approximately 0.64% / tube length. These results showed that the proposed coating, which has a lower cost compared to others, be a promising solution to avoid unscheduled shutdowns in thermoelectric boilers.

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.

2.25Cr-1Mo steels are widely used in thermoelectric power plants. Under operational temperatures, their properties degrade due to microstructural changes related to carbide coalescence and stoichiometric transformations. The extent of such microstructural changes is controlled by stress, temperature and time. Therefore, these factors can be used to evaluate damage and as life assessment tools for the individual component. In the past, ferrite-pearlite was the predominate microstructure in commercial Cr-Mo steel products, owing to the well-known methodologies for remaining life assessment based degradation. Currently, the ferrite-bainite microstructure obtained through a more economical route is most commonly used for this steel grade. However, there is no consensus in the literature about microstructural changes that can be used as a degradation pattern for ferrite-bainite steels. This paper compares the aged microstructures and creep properties of ferrite-pearlite and ferrite-bainite 2.25Cr-1Mo steels. Aging was conducted at 500, 575 and 600ºC until 2,000 h, and creep tests were performed at 575ºC under a stress of 100 MPa. Microstructural changes were characterized by optical microscopy scanning electron microscopy. Metallographic observations of the ferrite-bainite steel show a more stable behavior at the ageing temperatures and time considered. However, creep tests revealed that the ferrite-pearlite microstructure possesses a better rupture time performance. Carbide size distribution and stoichiometric evolution of the carbides provided by transmission electron microscopy support the creep behavior. These results show that the current techniques for evaluating microstructural degradation of 2.25Cr-1Mo steels must be reconsidered.

Investigou-se a associação entre atividade física durante o segundo trimestre gestacional e os desfechos perinatais adversos: baixo peso ao nascer (BPN), nascimento pré-termo (NPT) e restrição de crescimento intrauterino (RCIU). Foi utilizada amostra da coorte BRISA, São Luís, Maranhão, Brasil, que incluiu mulheres com gravidez única, idade gestacional de 22 a 25 semanas confirmada por ultrassonografia obstétrica realizada com < 20 semanas, reentrevistadas nas primeiras 24 horas após o parto (n = 1.380). O nível de atividade física foi medido pelo Questionário Internacional de Atividade Física (IPAQ), versão curta, e categorizado em alto, moderado e baixo. Gráfico acíclico direcionado (DAG) foi utilizado para identificar ajuste mínimo para o controle de confundimento. Nível alto de atividade física não foi associado ao BPN (RR = 0.94; IC95%: 0,54-1,63), NPT (RR = 0,86; IC95%: 0,48-1,54) ou RCIU (RR = 0,80; IC95%: 0,55-1,15). Os resultados fortalecem a hipótese de que a prática de atividade física na gestação não parece resultar em desfechos adversos ao nascimento.

This study focused on the association between physical activity in the second trimester of pregnancy and adverse perinatal outcomes: low birth weight (LBW), preterm birth (PTB), and intrauterine growth restriction (IUGR). The study used a sample from the BRISA cohort, São Luís, Maranhão State, Brazil, which included women with singleton pregnancy, gestational age from 22 to 25 weeks confirmed by obstetric ultrasound performed at < 20 weeks, and re-interviewed in the first 24 hours postpartum (n = 1,380). Level of physical activity was measured by the International Physical Activity Questionnaire (IPAQ), short version, categorized as high, moderate, and low. A directed acyclic graph (DAG) was used to identify minimum adjustment to control confounding. High physical activity was not associated with LBW (RR = 0.94; 95%CI: 0.54-1.63), PTB (RR = 0.86; 95%CI: 0.48-1.54), or IUGR (RR = 0.80; 95%CI: 0.55-1.15). The results support the hypothesis that physical activity during pregnancy does not result in adverse perinatal outcomes.

Se investigó la asociación entre actividad física durante el segundo trimestre gestacional y los desenlaces perinatales adversos: bajo peso al nacer (BPN), nacimiento pretérmino (NPT) y restricción de crecimiento intrauterino (RCIU). Se utilizó una muestra de la cohorte BRISA, São Luís, Maranhão, Brasil, que incluyó mujeres con un embarazo único, edad gestacional de 22 a 25 semanas, confirmada por ultrasonografía obstétrica realizada con < 20 semanas, reentrevistadas en las primeras 24 horas tras el parto (n = 1.380). El nivel de actividad física fue medido por el Cuestionario Internacional de Actividad Física (IPAQ), versión corta, y categorizado en alto, moderado y bajo. El gráfo acíclico dirigido (DAG) se utilizó para identificar un ajuste mínimo para el control de confusores. Un nivel alto de actividad física no se asoció al BPN (RR = 0,94; IC95%: 0,54-1,63), NPT (RR = 0,86; IC95%: 0,48-1,54) o RCIU (RR = 0,80; IC95%: 0,55-1,15). Los resultados fortalecen la hipótesis de que la práctica de actividad física en la gestación no parece resultar en desenlaces adversos al nacimiento.

Investigou-se a associação entre atividade física durante o segundo trimestre gestacional e os desfechos perinatais adversos: baixo peso ao nascer (BPN), nascimento pré-termo (NPT) e restrição de crescimento intrauterino (RCIU). Foi utilizada amostra da coorte BRISA, São Luís, Maranhão, Brasil, que incluiu mulheres com gravidez única, idade gestacional de 22 a 25 semanas confirmada por ultrassonografia obstétrica realizada com < 20 semanas, reentrevistadas nas primeiras 24 horas após o parto (n = 1.380). O nível de atividade física foi medido pelo Questionário Internacional de Atividade Física (IPAQ), versão curta, e categorizado em alto, moderado e baixo. Gráfico acíclico direcionado (DAG) foi utilizado para identificar ajuste mínimo para o controle de confundimento. Nível alto de atividade física não foi associado ao BPN (RR = 0.94; IC95%: 0,54-1,63), NPT (RR = 0,86; IC95%: 0,48-1,54) ou RCIU (RR = 0,80; IC95%: 0,55-1,15). Os resultados fortalecem a hipótese de que a prática de atividade física na gestação não parece resultar em desfechos adversos ao nascimento.

This study focused on the association between physical activity in the second trimester of pregnancy and adverse perinatal outcomes: low birth weight (LBW), preterm birth (PTB), and intrauterine growth restriction (IUGR). The study used a sample from the BRISA cohort, São Luís, Maranhão State, Brazil, which included women with singleton pregnancy, gestational age from 22 to 25 weeks confirmed by obstetric ultrasound performed at < 20 weeks, and re-interviewed in the first 24 hours postpartum (n = 1,380). Level of physical activity was measured by the International Physical Activity Questionnaire (IPAQ), short version, categorized as high, moderate, and low. A directed acyclic graph (DAG) was used to identify minimum adjustment to control confounding. High physical activity was not associated with LBW (RR = 0.94; 95%CI: 0.54-1.63), PTB (RR = 0.86; 95%CI: 0.48-1.54), or IUGR (RR = 0.80; 95%CI: 0.55-1.15). The results support the hypothesis that physical activity during pregnancy does not result in adverse perinatal outcomes.

Se investigó la asociación entre actividad física durante el segundo trimestre gestacional y los desenlaces perinatales adversos: bajo peso al nacer (BPN), nacimiento pretérmino (NPT) y restricción de crecimiento intrauterino (RCIU). Se utilizó una muestra de la cohorte BRISA, São Luís, Maranhão, Brasil, que incluyó mujeres con un embarazo único, edad gestacional de 22 a 25 semanas, confirmada por ultrasonografía obstétrica realizada con < 20 semanas, reentrevistadas en las primeras 24 horas tras el parto (n = 1.380). El nivel de actividad física fue medido por el Cuestionario Internacional de Actividad Física (IPAQ), versión corta, y categorizado en alto, moderado y bajo. El gráfo acíclico dirigido (DAG) se utilizó para identificar un ajuste mínimo para el control de confusores. Un nivel alto de actividad física no se asoció al BPN (RR = 0,94; IC95%: 0,54-1,63), NPT (RR = 0,86; IC95%: 0,48-1,54) o RCIU (RR = 0,80; IC95%: 0,55-1,15). Los resultados fortalecen la hipótesis de que la práctica de actividad física en la gestación no parece resultar en desenlaces adversos al nacimiento.

O objetivo deste estudo foi analisar as mudanças na saúde perinatal em duas coortes de nascimento realizadas em 1997/1998 e 2010, em São Luís, Maranhão, Brasil. Um total de 2.493 nascidos vivos foi incluído em 1997/1998 e 5.166 em 2010. A taxa de baixo peso ao nascer (BPN) não se modificou (8,5% em 1997/1998 e 8,6% em 2010). A taxa de nascimento pré-termo (NPT) também permaneceu estável (13,2% em 1997/1998 e 13% em 2010). Nascimentos em adolescentes e em mulheres sem companheiro decresceram. A escolaridade materna e a cobertura do pré-natal aumentaram. A taxa de restrição de crescimento intrauterino (RCIU) diminuiu de 13,3% para 10,6% (p < 0,001). A taxa de mortalidade perinatal foi reduzida de 36,6 para 20,7 por mil (p < 0,001) e a taxa de mortalidade infantil diminuiu de 28,5 para 12,8 por mil (p < 0,001). A taxa de cesárea (TC) aumentou de 34,1% para 47,5% (p < 0,001). Apesar das mudanças favoráveis nas variáveis sociodemográficas, comportamentais e de serviços de saúde e da redução nas taxas de RCIU, mortalidade perinatal e infantil, as taxas de BPN e NPT permaneceram estáveis, enquanto a TC aumentou.

The objective of this study was to analyze changes in perinatal health in two birth cohorts started in 1997/1998 and 2010, respectively, in São Luís, Maranhão State, Brazil. A total of 2,493 live born infants were included in 1997/1998 and 5,166 in 2010. Low birth weight (LBW) rate did not change (8.5% in 1997/1998 and 8.6% in 2010). Preterm birth (PTB) rate also remained stable (13.2% in 1997/1998 and 13% in 2010). Teenage deliveries and births to single mothers decreased. Maternal schooling and prenatal care coverage increased. Intrauterine growth restriction (IUGR) decreased from 13.3% to 10.6% (p < 0.001). The perinatal mortality rate decreased from 36.6 to 20.7 per 1,000 (p < 0.001) and the infant mortality rate (IMR) dropped from 28.5 to 12.8 per 1,000 (p < 0.001). The cesarean rate increased from 34.1% to 47.5% (p < 0.001). In conclusion, despite favorable changes in socio-demographic, behavioral, and health service factors and decreasing rates of IUGR and perinatal and infant mortality, LBW and PTB remained stable, while the cesarean rate increased.

El objetivo de este estudio fue analizar los cambios de la salud perinatal en dos cohortes de nacimiento realizadas en 1997/1998 y 2010 en São Luís, Maranhão, Brasil. Un total de 2.493 niños nacidos vivos fueron incluidos en 1997/1998 y 5.166 en 2010. La tasa de bajo peso al nacer (BPN) no cambió (8,5% y 8,6%). La tasa del nacimiento prematuro (TNP) también se mantuvo estable (13,2% y 13%). Los nacimientos entre adolescentes y madres solteras disminuyeron. La escolaridad de la madre y la cobertura de atención prenatal aumentaron. La tasa de restricción del crecimiento intrauterino (RCIU) se redujo de un 13,3% a un 10,6% (p < 0,001). La tasa de mortalidad perinatal disminuyó de 36,6 a 20,7 por mil (p < 0,001), y la tasa de mortalidad infantil (TMI) se redujo de 28,5 a 12,8 por mil (p < 0,001). La tasa de cesárea (TC) aumentó de 34,1% a 47,5% (p < 0,001). A pesar de los cambios favorables en factores sociodemográficos, de conducta y de servicios de salud, y de la reducción de RCIU, mortalidad perinatal e infantil, las tasas de BPN y el PTB se mantuvieron estables, mientras que la TC aumentó.

O objetivo deste estudo foi analisar as mudanças na saúde perinatal em duas coortes de nascimento realizadas em 1997/1998 e 2010, em São Luís, Maranhão, Brasil. Um total de 2.493 nascidos vivos foi incluído em 1997/1998 e 5.166 em 2010. A taxa de baixo peso ao nascer (BPN) não se modificou (8,5% em 1997/1998 e 8,6% em 2010). A taxa de nascimento pré-termo (NPT) também permaneceu estável (13,2% em 1997/1998 e 13% em 2010). Nascimentos em adolescentes e em mulheres sem companheiro decresceram. A escolaridade materna e a cobertura do pré-natal aumentaram. A taxa de restrição de crescimento intrauterino (RCIU) diminuiu de 13,3% para 10,6% (p < 0,001). A taxa de mortalidade perinatal foi reduzida de 36,6 para 20,7 por mil (p < 0,001) e a taxa de mortalidade infantil diminuiu de 28,5 para 12,8 por mil (p < 0,001). A taxa de cesárea (TC) aumentou de 34,1% para 47,5% (p < 0,001). Apesar das mudanças favoráveis nas variáveis sociodemográficas, comportamentais e de serviços de saúde e da redução nas taxas de RCIU, mortalidade perinatal e infantil, as taxas de BPN e NPT permaneceram estáveis, enquanto a TC aumentou.

The objective of this study was to analyze changes in perinatal health in two birth cohorts started in 1997/1998 and 2010, respectively, in São Luís, Maranhão State, Brazil. A total of 2,493 live born infants were included in 1997/1998 and 5,166 in 2010. Low birth weight (LBW) rate did not change (8.5% in 1997/1998 and 8.6% in 2010). Preterm birth (PTB) rate also remained stable (13.2% in 1997/1998 and 13% in 2010). Teenage deliveries and births to single mothers decreased. Maternal schooling and prenatal care coverage increased. Intrauterine growth restriction (IUGR) decreased from 13.3% to 10.6% (p < 0.001). The perinatal mortality rate decreased from 36.6 to 20.7 per 1,000 (p < 0.001) and the infant mortality rate (IMR) dropped from 28.5 to 12.8 per 1,000 (p < 0.001). The cesarean rate increased from 34.1% to 47.5% (p < 0.001). In conclusion, despite favorable changes in socio-demographic, behavioral, and health service factors and decreasing rates of IUGR and perinatal and infant mortality, LBW and PTB remained stable, while the cesarean rate increased.

El objetivo de este estudio fue analizar los cambios de la salud perinatal en dos cohortes de nacimiento realizadas en 1997/1998 y 2010 en São Luís, Maranhão, Brasil. Un total de 2.493 niños nacidos vivos fueron incluidos en 1997/1998 y 5.166 en 2010. La tasa de bajo peso al nacer (BPN) no cambió (8,5% y 8,6%). La tasa del nacimiento prematuro (TNP) también se mantuvo estable (13,2% y 13%). Los nacimientos entre adolescentes y madres solteras disminuyeron. La escolaridad de la madre y la cobertura de atención prenatal aumentaron. La tasa de restricción del crecimiento intrauterino (RCIU) se redujo de un 13,3% a un 10,6% (p < 0,001). La tasa de mortalidad perinatal disminuyó de 36,6 a 20,7 por mil (p < 0,001), y la tasa de mortalidad infantil (TMI) se redujo de 28,5 a 12,8 por mil (p < 0,001). La tasa de cesárea (TC) aumentó de 34,1% a 47,5% (p < 0,001). A pesar de los cambios favorables en factores sociodemográficos, de conducta y de servicios de salud, y de la reducción de RCIU, mortalidad perinatal e infantil, las tasas de BPN y el PTB se mantuvieron estables, mientras que la TC aumentó.

Thermal power plants and refineries around the world share many of the same problems, namely aging equipment, high costs of replacement, and the need to produce more efficiently while being increasingly concerned with issues of safety and reliability. For equipment operating at high temperature, there are many different mechanisms of degradation, some of which interact, and the rate of accumulation of damage is not simple to predict. The paper discusses the mechanisms of degradation at high temperature and methods of assessment of such damage and of the remaining safe life for operation.