In the primary fan system of a thermal power plant, the integrated vibration transmitter VMS11120, as a core monitoring device, needs to operate stably for a long time in a complex vibration environment. However, the coincidence of the natural frequency of the mounting bracket and the vibration frequency of the equipment may cause a resonance effect, resulting in sensor measurement distortion, structural fatigue, and even failure. To avoid this risk, comprehensive measures should be taken from multiple dimensions such as design, installation, materials, and dynamic monitoring to ensure the accurate capture of vibration signals and the long-term reliability of the equipment.

1. Resonance risk and equipment operation characteristics

As a rotating machine, the vibration frequency of the primary fan is mainly determined by the rotor speed, impeller structure, and bearing characteristics. Usually, the vibration frequency range of the fan is concentrated in the low frequency band, while its high-frequency vibration may be caused by airflow pulsation or blade impact. The frequency response range of the VMS1120 integrated vibration transmitter is 10-1000Hz, and its self-oscillation frequency is 10Hz. Special attention should be paid to whether the natural frequency of the bracket is close to the main vibration frequency of the equipment or its multiples. If the natural frequency of the bracket coincides with the vibration frequency of the equipment, the amplitude will be amplified sharply, forming resonance, which will not only accelerate the fatigue fracture of the bracket, but also interfere with the signal acquisition accuracy of the sensor, and even cause false alarms or data distortion.

2. Optimization of the dynamic characteristics of the mounting bracket

The natural frequency of the mounting bracket of the vibration transmitter VMS1120 is determined by its stiffness and mass. To avoid resonance, it is necessary to adjust the geometry, material properties or additional mass of the bracket to make its natural frequency deviate from the vibration frequency range of the equipment. For example, increasing the stiffness of the bracket can increase the natural frequency; while adding a counterweight or damping material to the bracket can reduce the natural frequency. In actual engineering, finite element analysis is often used to simulate the modal characteristics of the bracket, combined with the actual vibration spectrum of the fan, to verify the rationality of the design parameters. If it is found that the natural frequency of the bracket is close to the vibration frequency of the equipment, it is necessary to adjust the structural parameters through iterative optimization until the difference between the two reaches the safety threshold.

In the installation process, the layout position and connection method of the VMS1120 vibration transmitter have a direct impact on the vibration transmission path. First, avoid the areas where the fan vibrates most violently (such as the bearing seat or blade outlet), and give priority to stable areas close to the casing or support frame. Secondly, the connection between the bracket and the equipment needs to introduce vibration reduction elements, such as rubber gaskets, elastic bolts or hydraulic dampers, to absorb high-frequency vibration energy and isolate low-frequency resonance. For example, the use of multi-layer rubber buffer pads can reduce the vibration transmission rate between the bracket and the equipment by more than 50%, while dispersing stress concentration. In addition, the fixing bolts of the bracket should adopt preload control technology to ensure uniform contact stiffness of the connection interface and avoid local vibration amplification caused by looseness or gaps.

3. Dynamic monitoring and preventive maintenance

Even if the risk of resonance has been avoided in the design stage, the stability of the bracket still needs to be verified by dynamic monitoring during long-term operation. The 4-20mA output signal of the VMS1120 integrated vibration transmitter can be directly connected to the DCS system to record the vibration spectrum data of the fan in real time. Through Fourier transform analysis, the abnormal vibration frequency of the bracket can be identified and compared with the theoretical mode. If the natural frequency of the bracket is found to be offset, the installation parameters must be adjusted immediately or the bracket must be replaced. In addition, regular knock tests or laser vibrometer scans can quantify the modal characteristics of the bracket to ensure that it is always within the safe range.

In practical applications, resonance control needs to be combined with dynamic adjustment strategies for specific working conditions. For example, when seasonal loads fluctuate, the vibration frequency of the fan may shift due to changes in speed, and the natural frequency matching of the bracket needs to be re-evaluated. For old equipment, fatigue damage to the bracket may lead to a decrease in stiffness, which needs to be compensated by adding additional mass or damping elements.

The overlap of the natural frequency of the mounting bracket of the VMS1120 integrated vibration transmitter and the vibration frequency of the equipment is essentially a comprehensive challenge of mechanical dynamics and engineering design. By optimizing the stiffness and mass distribution of the bracket, using vibration reduction elements, selecting high damping materials, and implementing dynamic monitoring, the risk of resonance can be effectively avoided and the long-term stable operation of the sensor can be ensured.

When looking for high-quality, reliable vibration sensors, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:
E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

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