Puji Harjono (Electrical Spv/Vibration Analyst)

23 September 2005

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

MACHINE CONFIGURATION:

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

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)

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

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

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

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

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

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

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

Picture-9, BCS Spectrum new bearing dan defect bearing

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

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