Cooling Tower Resonance Problem

Paylaşıldı

During the commissioning phase of a biomass power plant, an urgent request for support was made to the Resonance Institute technical team due to high-amplitude vibrations occurring in the cooling towers.
During field observations, the presence of a ‘structural vibration’ problem affecting the cooling tower base was identified.

Problem Identification:

In the structural vibration measurement package, vibration measurements taken simultaneously with the Motion Amplification camera and 16-channel analyser revealed that the vibration amplitudes on the cooling tower reducer and motor were around 32 mm/s RMS. According to the table in the ‘CTI STD 163’ reference standard, these vibration levels fall within the ‘D zone: Vibration is damaging the machine’ range.

Analysis of data collected simultaneously from a 16-channel analyser revealed that high-amplitude vibrations occur at the blade passing frequency of the tower fan.
The bulge below the blade passing frequency indicates that the situation has developed into a resonance problem.
The blade passing vibrations examined in the flow-induced vibration group occur at multiples of the blade number. The fact that the resulting flow forces are so high stems from this frequency exciting a natural frequency, thereby creating the resonance problem.

Simultaneously with the measurements taken with the analyser, footage was also captured from outside and inside the tower using a Motion Amplification camera.
To prevent the footage from being affected by high-amplitude vibrations on the ground, the camera was placed on a basket attached to the crane.
The footage clearly shows the vibration pattern of the base at a blade passing frequency of 16.5Hz.

As seen in the videos, in order to eliminate the structural vibration problem in the base, the effective natural frequency at 16.5Hz must be removed from the operating range.
To this end, it is recommended that the support profiles shown in the image below be removed.
Following the implementation of the recommended support work, it was observed that the vibration values decreased to acceptable levels according to the CTI STD 163 standard.