VACUUM PUMP-3A. Running Hour: 8646 Ref Speed: 660 RPM OBSERVATION. Peakvue reading was 0.3 at Vacuum Pump NDE bearing.

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1 VACUUM PUMP-3A Machine Component Vacuum Pump NDE Bearing Spectrum, Vol-1, Oct-2013 ISO Severity level for class III Machine Vibration Level NORMAL MARGINAL CRITICAL Up to 4.5 mm/sec 4.5 to 11.2 mm/sec Above 11.2 mm/sec Condition Running Hour: 8646 Ref Speed: 660 RPM TIME LINE OBSERVATION Vacuum Pump was running normal with vibration 1.5 mm/sec at NDE bearing. Peakvue reading was 0.3 at Vacuum Pump NDE bearing. Flow induced vibration/cavitations was observed in spectrum Vibration increased to 10.4 mm/sec in Vertical direction at Vacuum pump NDE Bearing. Peakvue increased to 1.7 Gs BSF & BPFI were observed in peakvue spectrum. BPFI started appearing in all direction (Horizontal, Vertical & Axial) Bearing temperature was found to be 73 deg C. whereas it was 55 deg C in other healthy vacuum pump. ANALYSIS & RECOMMENDATION: Initial stage bearing defect is suspected in vacuum pump NDE bearing High acceleration is observed in vacuum pump NDE bearing. Check the lubricant condition & ensure proper lubrication of bearing Bearing lubricant was checked and lubricant was replaced after proper purging. (Bearing could not be inspected) Trial was taken Vibration reduced to 4 mm/sec, acceleration reduced to 1 Gs.

2 While vibration was constant at 4 mm/sec peakvue acceleration started increasing and went up to 2.7 Gs Bearing temperature was continuously maintaining at 70 deg C. Abnormal sound started coming from NDE side bearing BPFI level increased as compared to previous reading. ANALYSIS & RECOMMENDATION: - Please inspect the bearing for any defect. It was decided to dismantle the bearing for inspection following were observed:- Pump NDE bearing was found in damaged condition. Lower bottom of outside portion of Outer race periphery (Please Refer Fig) was in damaged condition while other parts were in good condition. Few rolling elements of outside portion (See Fig) were also found in damaged condition. Inner race was found damaged throughout its periphery Bearing replaced and trial taken Vibration reduced to 1.8 mm/sec while acceleration reduced to 0.3 Gs.

3 Vibration Measurement Results: Date: Location RMS VELOCITY (mm/sec) H V A PEAKVUE (Gs) MOTOR NDE MOTOR DE PUMP DE PUMP NDE

4 Vibration Measurement Results: Date: Location RMS VELOCITY (mm/sec) H V A PEAKVUE (Gs) MOTOR NDE MOTOR DE PUMP DE PUMP NDE

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10 Load due to gravity/weight Thrust load Damaged Lower bottom of outer race (outside portion) Smooth Top portion of Outer race Smooth (inside) outer race and inner race Discharge Side (+Ve) Pressure Suction Side (-Ve) Vacuum Damaged Lower bottom of outer race (outside portion)

11 Conclusion Mode of Failure: - Spalling due to Excessive/high thrust load Possible Explanation & Supporting facts: - From the above type of damage following three things can be concluded:- 1. Possible misalignment. 2. Tolerances & Mounting dimensions/misfit or inappropriate mounting resulting in unequal load sharing between DE & NDE bearing. 3. Excessive axial thrust load due to cavitations. As misalignment was checked and was not present, and there was no presence of 1X or 2X peaks in the spectrum (in any direction), neither there were any harmonics of running speed frequency: the above two cases (case no 1 & 2) are ruled out. As the failure pattern was same in all the three vacuum pumps-3a, 3B & 4A and also suspected in Vacuum pump-4b & 2B (though the severity in 4B & 2B is lesser) so the most probable cause can be cavitations or excessive thrust due to inherent design of the Pump( Which can be confirmed from OEM)