On my daily routine inspection in Steel Plant, a Gas Recycle Fan where a 4 pole Squirrel cage Induction motor is directly coupled to fan,We could hear a strange noise.
Need your help in finding the root cause.
Request for Vibration Data:
To accurately diagnose the issue with the Gas Recycle Fan, we need specific vibration data. Please provide the following details:
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Frequency Analysis Data:
- Observed Frequencies
- Amplitude of Frequencies
- Sensor Position and Direction
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Phase Analysis Data:
- Sensor Positions
- Phase Angles
This data will enable us to classify frequencies, assess directional responses, and conduct a detailed phase analysis for an accurate diagnosis.
Vibration measurements was taken from the Motor NDE Side in Horizontal Direction as the sound is coming from the motor.
Machine Details:
Supply Frequency: 50 Hz
Motor Speed: 24.333 Hz
Below are the observations:
Spectrum shows harmonics from 1X RPM up to 8X RPM.
Clear sidebands Surrounding the 1X to 8X Rpm harmonics with spacing of sidebands measured at 2.666 Hz.
extended time waveform vibration analysis clearly shows a regular humming which is inline with the noise we noticed earlier.
No phase analysis done.
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Main Finding: The observations indicate harmonics from 1X to 8X RPM with modulation sidebands spaced at 2.666 Hz, suggesting a
Synchronous Harmonic and Modulation [F_G_8]frequency group. The measurements taken in the horizontal direction point to a radial response. -
Recommended Action: Considering the identified frequency group and directional response, the most probable fault is a
Rotor Bar Fault (Rb). Further validation through natural frequency testing is advised to confirm this fault. -
Priority Level: High
Mathematical Validation:
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Slip Calculation:
- Synchronous Speed (Ns) = 1500 RPM
- Slip = 40 RPM
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Pole Passing Frequency (PPF) Calculation:
- PPF = 2.666 Hz
The calculated PPF aligns with the modulation sidebands observed, supporting the hypothesis of a rotor bar fault.
Ok, Thanks for the analysis.
You're welcome! I'm glad I could assist you with the analysis. If you have any more questions in the future or need further assistance with any other machinery diagnostics or maintenance issues, feel free to reach out. Have a great day and good luck with the maintenance work on your gas recycle fan!
Stay safe and take care!