1. Vibration analysis of machine 2GB-401A found increasing vibration trends over time, peaking at 4.25 mm/s RMS on June 20, 2005. 2. Analysis revealed a looseness in bearing #8, shown by pump rotor speed harmonics up to 9x in the spectrum and increasing noise floor. The bearing condition started deteriorating in mid-May 2005. 3. After overhaul and replacement of bearing #8, vibration levels decreased significantly from 6.37 to 0.39 BCU pp, indicating the root cause was failure of that bearing due to lack of proper clearance allowing water intrusion.

1. Puji Harjono
(Electrical Spv/Vibration Analyst)
23 September 2005

3. Spesifikasi Mesin:
• Machine Name : 2GB-401A
• Power Drive : ACMotor Driven : Vacuum Pump
• Manufacture : Reliance Electric Manufacture : NASH US
• Mode/Type : CHEM-Duty Master No.of Impeller : 16
• Rotation/Minute : 1500 RPM Speed : 500 RPM
• Volt/Phase/Freq : 380V/3/50Hz DE Bearing : TIMKEN 71000
• IP Code : IP55 NDE Bearing : TIMKEN 71000
• No. of Pole : 4 HS Shaft : 1470 RPM
• Power Output : 125 kW LS Shaft : 500 RPM
• Insulation Class : F Coupling : Gear Box
• Ampere : 127 Amp Manufacture : The FALK Corp.
• NDE Bearing : SKF 90BC03J No.of Teeth : 17/50
• DE Bearing : SKF 90BC03J SF : 2.93

4. MACHINE CONFIGURATION:

5. 1. OVERALL RESULT OF VIBRATION MEASUREMENT ON 2GB-401A IS
SHOWING THE INCREASE OF TEND. (PICTURE-1 AS BELOW:
Gambar-1, Tending overall vibrasi 2GB-401A

6. DATE OF MEASUREMENT :
18 MARCH 2005 AT 10:29:14 AM AMPLITUDE 0.9836 MM/S RMS
6 APRIL 2005 AT 09:40:01 AM AMPLITUDE 0.9690 MM/S RMS
16 MAY 2005 AT 09:46:25 AM AMPLITUDE 2.8764 MM/S RMS
15 JUNE 2005 AT 09:26:54 AM AMPLITUDE 3.9735 MM/S RMS
20 JUNE 2005 AT 01:55:50 PM AMPLITUDE 4.2563 MM/S RMS
2. Vibration increase at point measurement no.8 (see MACHINE CONFIGURATION)
3. Look like a “looseness” in spectrum on pump bearing no.8. See Picture-2
(BCS/Bearing Condition Signature) and Picture-3 (spectrum) appear pump rotor
speed harmonics up to 9x.
4. Also 0.5x, 1.5x- speed. Increasing of “noise floor” on that spectrum. This is
showing a looseness. Amplitude still in tolerance (1 mm/s RMS)

7. Picture-2, BCS of bearing no.8 2GB-401A (looseness and harmonics)

8. Picture-3, Spectrum at NDE Bearing of 2GB-401A ( harmonic up to 9x)

9. Picture-4, Trending BCU Bearing no.8 2GB-401A
5. Next, about trending of BCU (Bearing Condition Unit) on Picture-4 above , BCU start
increase 16 May 2005 then 15 June 2005 and 20 June 2005. On 23 June 2005, BCU
value going down because No. 8 bearing severity is saturated

10. 6. In BCS (Bearing Condition Signature) spectrum analyze on Picture-5 also spectrum in
SED (Selective Enveloping Detection) on Picture-6 at point measurement No.8 , the
frequency natural of BPFO (Ball Pass Frequency Outer) bearing and harmonic’s is very
clear upto 5x and followed by sidebands of BPFO . Especially in BCS Spectrum (Picture-
5). The severity of bearing in Stage-3.
Gambar-5, BCS spectrum di bearing no.8 2GB-401A

11. Picture-6, SED (Selective Envelopping Detection) Spectrum no.8 bearing of 2GB-401A

12. 7. On June, 23rd 2005, BCU severity going down till saturated. It followed
with FTF (Fundamental Train Frequency) of bearing and harmonic’s.
8. Also BPFO is disappear slowly. (Picture-7)
Picture-7, Spectrum BCS (Bearing Condition Signature) with FTF

13. 8. After overhaul had been done, 2GB-401A Vacuum pump test run and measuring of vibration on
August 22nd , 2005 , BCU value is decrease from 6.357 BCUp-p to 0.389 BCU p-p. (Picture-8 and
Picture-9
9. On Picture-8 (Vibration Spectrum) dan Picture-9 ( BCS Bearing Spectrum) :
• Spectrum with blue color is new bearing
• Spectrum with red color is defect bearing
Picture-8, Vibration Spectrum Vibrasi at point No.8

14. Picture-9, BCS Spectrum new bearing dan defect bearing

15. 10. Picture-10 NDE Outer Race defect bearing of 2GB-401A Vacuum Pump.

16. Conclusion
1. Bearing Damage on stage is showing the natural frequency of :
– BPFO (Ball Pass Frequency Outer),
– BPFI (Ball Pass Frequency Inner), BSF (Ball Spin Frequency)
– FTF (Fundamental Train Frequency)
– Followed of their sidebands
2. “Flaking” of bearing because more axial force also water enter to
lubrication system
3. Based on mechanical team when they overhaul the pump, they found lock
nut of bearing not tight properly. It should be have clearance around 0.05
for accommodate thrust axial force