Monitoramento de corrosão sob tensão por meio dos métodos de ensaios não destrutivos de emissão acústica e ultrassom Phased Array
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Data
2021-12-17
Autores
Reis, Henrique dos
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Universidade Estadual Paulista (Unesp)
Resumo
Vasos de pressão são recipientes estanques para armazenar, sob pressão, vários tipos de fluidos (gasosos/líquidos). Estes equipamentos são fundamentais em muitos processos industriais e projetados para resistir a elevadas pressões. No entanto, representam alto risco se falhas ocorrerem em sua operação, sendo crucial um plano de inspeção por meio de técnicas de ensaio que garantam seu uso seguro. Devido as condições extremas e ação combinada de agentes agressores no ambiente, trincas oriundas de fenômenos de Corrosão sob Tensão (CsT) podem se formar. A CsT é uma das mais comuns e perigosas formas de corrosão, pois combina tensão estática e corrosão em meio fluido, acometendo estruturas/materiais. Caracteriza-se pela formação e propagação rápida de trincas que levam o material à súbita ruptura e falha catastrófica, gerando impactos sociais, econômicos e ambientais. Suas trincas são “rasas” e de difícil detecção via ultrassom convencional. Uma alternativa nova e pouco conhecida para contornar tal situação é a ultrassonografia mecanizada, que utiliza a técnica Total Focusing Method (TFM) para uma melhor aquisição de imagem (cada pixel é uma lei focal dedicada à região de interesse) através do pós-processamento de dados coletados pela tecnologia Full Matrix Capture (FMC), que captura elementos pulsantes e receptores. Já a Emissão Acústica (EA), detecta falhas através de sensores instalados na estrutura, captando informações de ondas mecânicas elásticas geradas quando uma irregularidade surge/propaga no material, indicando a localização das descontinuidades. Sendo assim, este trabalho surgiu da precariedade atual em dimensionar principalmente a altura de trincas “rasas” em vasos de pressão. A técnica de TFM é útil para dimensionar outros tipos de trincas (superficiais e subsuperficiais) resultantes de outros fenômenos, tais como Fadiga. Tendo o objetivo de empregar os dos dois NDTs supracitados para detectar, dimensionar e monitorar oito trincas de CsT em um vaso de pressão largamente utilizado na indústria química. Almeja-se assim preencher a lacuna atual no arcabouço acadêmico acerca das técnicas TFM e FMC. Os resultados encontrados evidenciam que o ultrassom mecanizado teve desempenho eficiente, determinando com precisão altura, profundidade e comprimento de oito descontinuidades na chapa do costado do vaso de pressão estudado. Com tal conclusão, etapas de cálculos de Mecânica da Fratura e inspeções em serviço terão maior assertividade na análise destas descontinuidades
Pressure vessels are watertight containers for storing various types of fluids (gaseous/liquids) under pressure. These equipments are fundamental in many industrial processes and designed to withstand high pressures. However, they represent a high risk if failures occur in their operation, being crucial an inspection plan through testing techniques that guarantee their safe use. Due to extreme conditions and the combined action of aggressive agents in the environment, cracks arising from Stress Corrosion (SC) phenomena can form. SC is one of the most common and dangerous forms of corrosion, as it combines static stress and corrosion in a fluid, affecting structures/materials. It is characterized by the formation and rapid propagation of cracks that lead the material to sudden rupture and catastrophic failure, causing social, economic and environmental impacts. Its cracks are “shallow” and difficult to detect via conventional ultrasound. A new and almost unknown alternative to overcome this situation is mechanized ultrasonography, which uses the Total Focusing Method (TFM) technique for better image acquisition (each pixel is a focal law dedicated to the region of interest) through the post-processing of data collected by Full Matrix Capture (FMC) technology, which captures pulsating elements and receivers. Acoustic Emission (AE) detects faults through sensors installed in the structure, capturing information from elastic mechanical waves generated when an irregularity arises/propagates in the material, indicating the location of discontinuities. Therefore, this work arose from the current precariousness in dimensioning mainly the height of "shallow" cracks in pressure vessels. The TFM technique is useful for dimensioning other types of cracks (surface and subsurface) resulting from other phenomena, such as Fatigue. With the objective of employing the two before mentioned NDTs to detect, size and monitor eight CsT cracks in a pressure vessel widely used in the chemical industry. Thus, the aim is to fill the current gap in the academic framework regarding the TFM and FMC techniques. The results found show that the mechanized ultrasound had an efficient performance, accurately determining height, depth and length of eight discontinuities in the side plate of the pressure vessel studied. With this conclusion, Fracture Mechanics calculation steps and in-service inspections will have greater assertiveness in the analysis of these discontinuities
Pressure vessels are watertight containers for storing various types of fluids (gaseous/liquids) under pressure. These equipments are fundamental in many industrial processes and designed to withstand high pressures. However, they represent a high risk if failures occur in their operation, being crucial an inspection plan through testing techniques that guarantee their safe use. Due to extreme conditions and the combined action of aggressive agents in the environment, cracks arising from Stress Corrosion (SC) phenomena can form. SC is one of the most common and dangerous forms of corrosion, as it combines static stress and corrosion in a fluid, affecting structures/materials. It is characterized by the formation and rapid propagation of cracks that lead the material to sudden rupture and catastrophic failure, causing social, economic and environmental impacts. Its cracks are “shallow” and difficult to detect via conventional ultrasound. A new and almost unknown alternative to overcome this situation is mechanized ultrasonography, which uses the Total Focusing Method (TFM) technique for better image acquisition (each pixel is a focal law dedicated to the region of interest) through the post-processing of data collected by Full Matrix Capture (FMC) technology, which captures pulsating elements and receivers. Acoustic Emission (AE) detects faults through sensors installed in the structure, capturing information from elastic mechanical waves generated when an irregularity arises/propagates in the material, indicating the location of discontinuities. Therefore, this work arose from the current precariousness in dimensioning mainly the height of "shallow" cracks in pressure vessels. The TFM technique is useful for dimensioning other types of cracks (surface and subsurface) resulting from other phenomena, such as Fatigue. With the objective of employing the two before mentioned NDTs to detect, size and monitor eight CsT cracks in a pressure vessel widely used in the chemical industry. Thus, the aim is to fill the current gap in the academic framework regarding the TFM and FMC techniques. The results found show that the mechanized ultrasound had an efficient performance, accurately determining height, depth and length of eight discontinuities in the side plate of the pressure vessel studied. With this conclusion, Fracture Mechanics calculation steps and in-service inspections will have greater assertiveness in the analysis of these discontinuities
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Vaso de pressão, Corrosão sob tensão, Trincas rasas, Ultrassom Mecanizado, TFM/FMC, Emissão acústica, Ensaio não destrutivo, Phased array, Pressure vessel, Stress crack corrosion, Shallow cracks, Mechanized ultrasound, Acoustic emission, Non-destructive testing, Vasos de pressão, Testes não destrutivos, Testes de emissão acústica