Introduction

Vibration analysis in industrial assets is highly relevant to ensure the safe and efficient operation of equipment and structures, and is also extremely important to safeguard the health of workers and provide a quality end product. This analysis aims to promote availability and safety for the operation, since an asset in operation generates vibrations which, if not treated properly, can drastically reduce the useful life of the structure or even cause it to collapse due to frequency coupling.

Esses dados vibracionais são comumente utilizados em conjunto com a análise estrutural pelo método dos elementos finitos (MEF), que simula o comportamento de equipamentos e estruturas quando submetidos a acelerações e vibrações. As medições de vibração são utilizadas para calibração do modelo computacional, estabelecendo um comparativo entre os dados teóricos e experimentais com o objetivo de validar o modelo elaborado.

This article will present two successful cases, each using a different methodology for collecting and analyzing vibrations: accelerometry and the motion amplification camera.

Accelerometry

Methodology

Accelerometer instrumentation is widely used in industrial assets to measure and monitor vibrations. As the name implies, the method uses an accelerometer, which is an acceleration-sensitive device that converts mechanical vibration into an electrical signal, which is proportional to the acceleration. Figure 1 shows one of these sensors.

Figure 1: Accelerometer model - SOURCE: Kot Collection.

These sensors are fixed to the surfaces of the assets to be monitored, and their positioning is extremely important if the vibrations of interest are to be captured. Once installed, the vibrations are recorded over time, so that this data can be collected both punctually, at specific intervals, and continuously.

After collection, the electrical signals generated by the accelerometers are processed by specific software, making it possible to extract relevant vibration data such as frequency, amplitude and waveform. This data is then interpreted, at which point possible vibration patterns and non-conformities with the applicable standards are assessed, which may be indications of problems such as misalignment, unbalance or even looseness in components and structures.

Succes story

Em um de seus serviços recentes, a Kot Engenharia realizou medições de vibração em um prédio de estruturas metálicas integrante de uma planta de mineração. Esse tipo de ativo costuma ser integrado por diversos equipamentos cujo funcionamento resultam em cargas dinâmicas, nas quais a magnitude, direção e posição podem sofrer variações ao longo do tempo. Com isso, as respostas do ativo em relação ao deslocamento, velocidade e aceleração também podem variar, sendo de extrema relevância a medição e coleta de dados vibracionais para avaliação da condição estrutural do prédio.

In this study, the client had reported excessive vibrations in the building's structure. This prompted a request to carry out vibration measurements on the building, followed by a structural analysis and, if necessary, proposed changes to remedy the excessive vibrations in the structure.

Initially, accelerometer measurements were taken at a few points of interest in the structure, with the aim of assessing vibration levels in beams, columns and equipment bases. Figure 2 shows one of these sensors after it has been installed.

Figure 2: Accelerometer installed - SOURCE: Kot Collection.

The measurements collected cross-sectional, vertical and longitudinal data, in which speeds higher than those permitted by the standard for long-term vibrations in industrial buildings were identified. This data was used to calibrate the computer model, which was then used to analyze the structure of the asset and propose improvements to adjust vibration levels. Gif 1 shows one of the natural vibration modes investigated in the modal analysis and Gif 2 shows the variation in speed over time in one of the axes.

Gif 1: Natural vibration modes - SOURCE: Kot Collection.

Gif 2: Speed variation over time - SOURCE: Kot Collection.

As a result, it was possible to identify that the main vibrations in the structure were coming from a specific piece of equipment. Reinforcements were then proposed which, after a new structural analysis, indicated a significant improvement in the structure's vibration levels.

Motion amplification camera

Methodology

One of the methodologies recently developed for collecting and processing vibration data is image processing, a method associated with the use of a high-speed camera responsible for generating video recordings that measure the actual displacement of the structure. These recordings are processed in specific software, resulting in waveforms and vibration spectra from the amplified videos.

One of the main benefits of this methodology is that several points can be measured simultaneously, with the only requirement being that these points be framed in the same image to be captured. The camera also eliminates the need to stop equipment to install sensors, so that measurements can be taken at a safe distance from the asset being assessed.

This method is capable of taking high-precision measurements, using a system made up of high-resolution, high-speed cameras, lighting systems, lenses and computers with specific software. The software in question transforms the pixels of the image into "sensors", and these points are then analyzed to obtain the vibration spectrum and waveform. Figure 3 shows a Kot professional using the equipment in question to collect vibrational data.

Figure 3: Vibration measurement with a motion amplification camera - SOURCE: Kot Collection.

Success of success

In one of the applications of this methodology, one of our clients requested the collection of vibrations in an industrial building that had undergone some modifications. After the installation of these new structures, the building began to show excessive vibrations, which is why an assessment of the structural condition of the asset under these conditions was requested, with the proposal of improvements to bring the vibration levels into line with those permitted by the standard, if necessary.

As a result, the use of a motion amplification camera was proposed to meet the client's needs. Gif 3 shows one of the recordings taken during field measurements.

Gif 3: Images collected by the camera - SOURCE: Kot Collection.

After the vibration measurements, the data collected was used to calibrate the computer model, which was then used to carry out the structural analysis using the finite element method (FEM). This evaluation showed that the building's excitation loads were below the maximum dynamic loads specified in the design. A comparison was then made between the displacements in the axes for the real condition, measured in the field with the camera, and for the theoretical condition, and the model was validated based on the proximity of these values, as can be seen below in Figure 4.

Figure 4: Displacement on one of the axes - SOURCE: Kot Collection.

After calibration, it was found that the vibration frequency of the structure was very close to the operating frequency of a specific piece of equipment located in the building. This was due to the proximity of the equipment's frequency to the building's first natural frequencies. After the study, structural non-conformities were identified at certain points in the structure, and reinforcements were proposed to bring the vibrations into line with the admissible levels recommended by the applicable standards.

Conclusion

Following the two cases presented, it is clear that the methodologies for carrying out vibration measurements and analysis are increasingly present in day-to-day industry, and are very relevant for assessing the levels of vibration acting on equipment, components and structures, and their possible implications.

In addition, prior knowledge of these methodologies is essential in order to define the best course of action for each situation. With the assessment of technical experts, this information is used to make decisions, defining improvements and modifications to be implemented for greater reliability, safety and operational efficiency.

A Kot conta com um amplo time de profissionais qualificados para avaliação, seleção e aplicação das metodologias e soluções melhor aplicáveis ao seu negócio e aos seus ativos. Consulte nossa equipe para mais informações!

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