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Abstract(s)
As máquinas apresentam normalmente avarias ao longo da sua vida útil, que são decorrentes do seu próprio funcionamento ou de causas acidentais. O objetivo principal da manutenção é assegurar que os equipamentos desempenhem a sua função corretamente durante o maior período de tempo possível. A monitorização da condição constitui um tipo de manutenção baseada num acompanhamento contínuo das condições de operabilidade da máquina. A análise de vibrações é um conjunto de metodologias de monitorização com base na análise do sinal e do espetro de vibração, e na sua evolução ao longo do tempo, permitindo diagnosticar diversas avarias em máquinas. O desequilíbrio é uma das causas mais frequentes de vibração em máquinas, presente em diferentes graus de severidade em quase todas as máquinas rotativas. O trabalho desenvolvido teve como principal objetivo identificar e analisar os três tipos de desequilíbrios que podem ocorrer em veios: estático, de binário e dinâmico. Para tal, recorrendo a um equipamento de simulação de avarias, simularam-se os três tipos de desequilíbrios, acrescentando massas de desequilíbrio aos planos do veio. Posteriormente, recorrendo a um programa desenvolvido para o efeito, foram recolhidos os sinais de vibração nos apoios do veio, captados por um acelerómetro triaxial. Através da análise do espetro, verificou-se, para os três tipos de desequilíbrios, uma elevada magnitude de vibração correspondente à frequência de rotação do veio. A análise da fase permitiu identificar e distinguir os tipos de desequilíbrios simulados. Efetuou-se, ainda, a correção de desequilíbrio estático pelo método vetorial, a partir de um programa desenvolvido para o efeito. O procedimento passou pela introdução de uma massa de desequilíbrio num plano do veio e obtenção do vetor polar do desequilíbrio. Em seguida, introduziu-se uma massa de teste e determinou-se novamente o vetor polar. Por fim, introduziu-se a massa de correção e realizou-se uma nova aquisição do sinal de vibração, tendo-se verificado uma redução substancial da magnitude de vibração.
Machines usually have malfunctions throughout their useful life, which are due to their own operating conditions or to accidental causes. The main purpose of maintenance is to ensure that equipments perform their functions correctly for the longest possible time period. Condition monitoring is a type of maintenance based on continuous monitoring of a machine's operating conditions. Vibration analysis is a set of monitoring methodologies based on the analysis of the signal and the vibration spectrum, and on its evolution over time, allowing the diagnosis of various machine’s failure modes. Unbalance has been found to be one of the most common causes of machinery vibration, present in various degrees on nearly all rotating machines. The main goal of the experimental work was to identify and analyze the three types of unbalance that can occur on a machine’s shaft: static, coupled and dynamic. In order to do so, a rotor simulator was used and the three types of unbalance were induced by adding unbalancing masses to the shaft’s planes. After that, the vibraton signals at the shaft’s support bearings were picked up by a triaxial accelerometer, using software specifically developed for this purpose. Through spectral analysis, all the samples’ spectrum showed a high vibration magnitude at 1X the shaft’s rotational speed. Phase analysis allowed to identify and distinguish the types of unbalance that were being induced. In addition, single plane balancing was performed in a statically unbalanced shaft, through the vector method, by means of a computer program designed for that purpose. The procedure went as follows: an unbalancing mass was introduced in one of the shaft’s planes and the polar vector of the unbalance was obtained. Next, a trial mass was added and the new polar vector of the unbalance was obtained. Finally, the correction mass and angular position were calculated and applied, followed by the acquisition of the vibration signal. After applying this procedure, the magnitude of initial unbalance showed a substantial reduction.
Machines usually have malfunctions throughout their useful life, which are due to their own operating conditions or to accidental causes. The main purpose of maintenance is to ensure that equipments perform their functions correctly for the longest possible time period. Condition monitoring is a type of maintenance based on continuous monitoring of a machine's operating conditions. Vibration analysis is a set of monitoring methodologies based on the analysis of the signal and the vibration spectrum, and on its evolution over time, allowing the diagnosis of various machine’s failure modes. Unbalance has been found to be one of the most common causes of machinery vibration, present in various degrees on nearly all rotating machines. The main goal of the experimental work was to identify and analyze the three types of unbalance that can occur on a machine’s shaft: static, coupled and dynamic. In order to do so, a rotor simulator was used and the three types of unbalance were induced by adding unbalancing masses to the shaft’s planes. After that, the vibraton signals at the shaft’s support bearings were picked up by a triaxial accelerometer, using software specifically developed for this purpose. Through spectral analysis, all the samples’ spectrum showed a high vibration magnitude at 1X the shaft’s rotational speed. Phase analysis allowed to identify and distinguish the types of unbalance that were being induced. In addition, single plane balancing was performed in a statically unbalanced shaft, through the vector method, by means of a computer program designed for that purpose. The procedure went as follows: an unbalancing mass was introduced in one of the shaft’s planes and the polar vector of the unbalance was obtained. Next, a trial mass was added and the new polar vector of the unbalance was obtained. Finally, the correction mass and angular position were calculated and applied, followed by the acquisition of the vibration signal. After applying this procedure, the magnitude of initial unbalance showed a substantial reduction.
Description
Keywords
Diagnóstico de avarias Monitorização da condição Análise de vibrações Desequilíbrios Espetro de frequência Breakdown diagnosis Condition monitoring Frequency spectrum Unbalances Vibration analysis