Propane Screw Compressor Journal Bearing Failure
A propane screw compressor at Jam Polypropylene experienced a significant vibration increase, prompting a shutdown and inspection. Vibration analysis revealed a journal bearing failure, which was repaired, restoring normal operation.
Technical Case Study: Vibration Increase in Propylene Compressor (Jam Polypropylene Plant)
In the polymer unit of Jam Petrochemical Company (Jam Polypropylene), a propane screw compressor (Oil Injection type) plays a vital role in the production process. This oil-immersed compressor is supported by:
On one side: Journal Bearings
On the other side: Angular Contact Bearings
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🔍 Observation: Abnormal Vibration Increase
During routine condition monitoring, a significant increase in vibration levels was observed. Vibration velocity (RMS) values rose from approximately 3 mm/s to over 7 mm/s — a clear indication of emerging mechanical issues.
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🎯 Detailed Frequency Analysis Using SPM Portable Device
Using a portable vibration analysis device from SPM Instrument, waveform and FFT spectra were analyzed. Notably, dominant frequency peaks were observed around the screw characteristic frequency.
Given the screw ratio of 4:6 and an operating speed of 2996 RPM, the calculated screw frequency was approximately 198 Hz — exactly matching the dominant peak in the spectrum.
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⚠️ Root Cause & Immediate Action
The vibration data indicated a likely failure in the journal bearings. Based on this insight, the compressor was promptly shut down and dismantled for inspection.
Upon opening the unit, severe damage to the journal bearings was confirmed. Continued operation under these conditions could have led to major damage and costly downtime.
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🛠️ Post-Maintenance Condition
After performing necessary maintenance and replacing the damaged bearings, vibration levels dropped back to a stable 2 mm/s RMS, indicating a successful repair and healthy machine status.
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🧠 Takeaway
This case highlights the critical value of precision vibration analysis and condition monitoring — especially using portable tools like SPM Instrument — in preventing unexpected failures and ensuring reliable plant operation.
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📸 Attached images show the vibration trends before and after corrective actions.
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