Anti-friction Bearings & Electrical Discharging Here is an acceleration spectrum recorded on the drive motor of the Penthouse 7 Supply Fan

Anti-friction Bearings & Electrical Anti-friction Bearings & Electrical DischargingDischarging

Here is an acceleration spectrum recorded on the drive motor Here is an acceleration spectrum recorded on the drive motor of the Penthouse 7 Supply Fan.of the Penthouse 7 Supply Fan.

TEST - PENTHOUSE 7, MOTOR ONLY, VFDTEST ACPH7-MOV MOTOR OUTBOARD BRG VERT

Label: Mtr run only, VFD by-passedPriority: 2

Analyze Spectrum 11-JUN-98 11:10:33

RMS = 4.89 LOAD = 100.0 RPM = 1801. RPS = 30.01

0 20 40 60 80 100 120 140

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Frequency in Order

RM

S A

ccele

rati

on

in

G-s


High frequency, non-synchronous peaks appear in the upper region High frequency, non-synchronous peaks appear in the upper region of the spectrum. These peaks contain “sideband” peaks that of the spectrum. These peaks contain “sideband” peaks that

coincide with the fault frequency of the outer race (BPFO) for the coincide with the fault frequency of the outer race (BPFO) for the outboard bearing.outboard bearing.



Analyze Spectrum 11-JUN-98 11:10:33

RMS = 4.89 LOAD = 100.0 RPM = 1801. RPS = 30.01

0 20 40 60 80 100 120 140

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Frequency in Order

RM

S A

ccele

rati

on

in

G-s

Ordr: Freq: Spec: Dord:

68.94 124139. 3.329 3.628

Sideband peaks occurring at the

BPFO defect frequency


LOOKUP In Bearing File: MVWBRG.DAT **************************************************

ID# BEARING TYPE #B/R FTF BSF BPFO BPFI ------- ----------------------- ------ ------ ------- --------- -------- 8303 NSK 6208z 9 .401 2.421 3.607 5.393 8608 NSK 6208 (MVW) 9 .401 2.421 3.607 5.393

Actual fault frequency is occurring at

3.628xRPM

The outer race defect (BPFO) lists a defect frequency at 3.607 The outer race defect (BPFO) lists a defect frequency at 3.607 orders. The actual faults are occurring at sidebands 3.628 orders. The actual faults are occurring at sidebands 3.628 orders. The frequency is higher because of geometrical orders. The frequency is higher because of geometrical

changes that have occurred as a result of degradation. changes that have occurred as a result of degradation.


Waveform data indicates signs of severe impacting. Peak to Waveform data indicates signs of severe impacting. Peak to peak energy exceeds 28.0 G’s of acceleration. The waveform peak energy exceeds 28.0 G’s of acceleration. The waveform

data helps determine a sense of severity of the bearing data helps determine a sense of severity of the bearing defect.defect.



Analyze Waveform 11-JUN-98 11:10:33

RMS = 5.01 LOAD = 100.0 RPM = 1801. RPS = 30.01

PK(+) = 14.27 PK(-) = 13.93 CRESTF= 2.85

0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0

-18

-15

-12

-9

-6

-3

0

3

6

9

12

15

18

Revolution Number

Accele

rati

on

in

G-s

Over 28 G’s pk to Over 28 G’s pk to pk accelerationpk acceleration

Impacting with high

peak to peak energy


A comparison spectrum shows the drive motor condition both A comparison spectrum shows the drive motor condition both before and after bearing replacement. Note the amplitude before and after bearing replacement. Note the amplitude reduction in the non-synchronous harmonic peaks.reduction in the non-synchronous harmonic peaks.



0

0.5

1.0

1.5

2.0

2.5

3.0

3.54.0

Comparison Spectrum TEST ACPH7-MOV 11-JUN-98 11:10

0 20 40 60 80 100 120 140

0

0.5

1.0

1.5

2.0

2.5

3.0

3.54.0

Reference Spectrum TEST ACPH7-MOV 25-JUN-98 14:06

Frequency in Order

RM

S A

ccele

rati

on

in

G-s

Before bearing

replacement

After bearing

replacement


Outer Outer bearing race bearing race

has has indications indications of “fluting” of “fluting” as a result as a result

of electrical of electrical discharging. discharging. A shaft A shaft

grounding grounding brush was brush was

installed on installed on this drive this drive motor!motor!

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Anti-friction Bearings & Electrical Discharging Here is an acceleration spectrum recorded on the drive motor of the Penthouse 7 Supply Fan