Static mixers are widely used in the chemical, oil and gas, and food industries. They are used to mix liquids and gases without the use of moving parts. Thanks to their simple design, high reliability, and low maintenance costs, they have become an integral part of production lines.
Like any other industrial equipment, static mixers are subject to dynamic forces and vibrations from their surroundings. Vibrations can be caused by uneven flow, pressure fluctuations, or environmental factors such as vibrations from neighboring equipment. If these vibrations are not detected and corrected, they can lead to equipment failure, reduced mixing performance, and even safety hazards.
This article discusses static vibration analysis of mixers , its importance, its implementation, and solutions for vibration reduction.
What is vibration and why is it important?
Vibration is the oscillating motion of an object around a point of equilibrium. In industrial systems, such as stationary mixers, vibration can occur in various forms:
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Vibrations caused by fluid flow : Disturbances or changes in the flow velocity can lead to constant vibrations in the engine.
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Mechanical vibrations : Vibrations from pumps, compressors and other auxiliary equipment can be transmitted to the stationary engine.
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Environmental vibrations : Earthquakes, structural vibrations, or pressure changes in pipelines can also cause vibrations.
Uncontrolled vibrations can lead to the following consequences:
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Material stress and mechanical damage : Constant vibration can cause metal stress and microcracks, which can lead to equipment failure over time.
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Poor mixing quality : Uneven vibrations disrupt the liquid flow and lead to incomplete mixing.
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Contamination and safety risks : If parts break or fall, there is a risk of chemical leakage, which can be dangerous.
Static analysis of mixer vibration
Definition of vibration analysis
Vibration analysis examines the dynamic behavior of equipment under the influence of vibration forces. The goal of this analysis is to determine natural frequencies, vibration modes, and structural defects.
Steps to perform a vibration analysis
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Data collection : In this phase, the mixer specifications, material type, layer thickness, operating conditions and fluid type are checked.
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Dynamic simulation : Use engineering software such as ANSYS, Abaqus, or COMSOL to create a 3D model of the mixer and determine the material properties.
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Mode analysis : Determination of natural frequencies and vibration patterns. This step helps ensure that the system ‘s excitation frequencies do not match its natural frequencies, as this deviation can lead to increased vibration and damage.
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Harmonic Analysis : Examines the response of a motor to sinusoidal or harmonic excitation, typically caused by variations in pump pressure or current.
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Vibration transmission analysis : Examines how vibrations from neighboring equipment are transmitted to the engine and what effect they have on the entire system.
Advantages of vibration analysis
Conducting a static vibration analysis of a mixer offers several benefits, including:
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Extend the lifespan of your devices : By identifying weak points in the design , you can take measures to improve them.
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Lower maintenance costs : Predicting failures reduces the need for emergency repairs and production downtime.
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Improve mixing quality : By reducing unwanted vibrations, the liquid flow becomes more uniform and the mixing more complete.
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Improved safety : Reduced risk of equipment failure and release of hazardous substances.
Stationary mixer from Cemplant
Factors influencing the vibration of static mixers
Motor material and thickness
The material and thickness of the metal wall directly affect the natural frequency and the extent of absorbed vibration. For example, high-strength steel absorbs low-frequency vibrations less effectively, while aluminum or composite materials are more flexible and may require reinforcement.
Length and geometry
The internal shape of the engine and the length of the tubes influence the type of vibration. The longer the tube and the more complex its internal structure, the greater the likelihood that the natural frequencies will approach the excitation frequencies.
Flow conditions
The type of fluid (viscosity, density), flow rate , and inlet pattern can cause turbulent vibrations. Uneven flow is often the main cause of mixer vibrations.
Devices nearby
Pumps, compressors, and other piping can transmit vibrations to the motor. These external vibration sources should also be considered in the vibration analysis.
Depreciation method
Once the sources and patterns of vibrations have been identified, there are several ways to reduce them:
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Strengthening the structure : Increasing the wall thickness or using reinforced ribs and beams.
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Natural frequency shift : By changing the material or geometry, the natural frequency can be shifted outside the excitation frequency range .
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Use shock absorbers and dampers : Install mechanical shock absorbers or flexible materials between the motor and the support base.
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Optimize fluid flow : Design inlets and flow paths to ensure smooth flow and minimize turbulence.
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Control of peripheral equipment: Install shock absorbers on pumps and compressors to reduce vibration transmission.
Software and analysis tools
Various tools and software are available for carrying out static vibration analyses of vibration machines:
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ANSYS : modular analysis, harmonic analysis and transient analysis.
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Abaqus: can model complex materials and perform dynamic vibration analyses.
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COMSOL Multiphysics : Integrated flow and vibration simulation.
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MATLAB/Simulink : Vibration data analysis and system response modeling.
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Vibrometers and accelerometers : used to measure actual vibrations on site.
Practical research and experience
In the chemical and petroleum industries, static vibration analysis of engines is part of a preventive maintenance program. Examples:
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Unusual vibrations from the engine of a petrochemical plant caused microcracks on the rim.
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In water treatment plants, changing the internal geometry of the motor and optimizing the flow paths can reduce turbulent vibrations and improve the quality of the chemical mixture.
Finally
Vibration analysis of stationary mixers is an important tool for process engineers and maintenance specialists. Determining the type and natural frequency of vibrations enables:
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Prevent premature equipment failure,
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Improve the quality of the mix,
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Reduced maintenance costs and
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Improved production line safety.
Thanks to technological developments and the use of modern software, vibration analysis is no longer an option but a necessity for sustainable and safe production in industry.