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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
Anti-friction Bearings & Electrical Anti-friction Bearings & Electrical DischargingDischarging
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.
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
Ordr: Freq: Spec: Dord:
68.94 124139. 3.329 3.628
Sideband peaks occurring at the
BPFO defect frequency
Anti-friction Bearings & Electrical Anti-friction Bearings & Electrical DischargingDischarging
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.
Anti-friction Bearings & Electrical Anti-friction Bearings & Electrical DischargingDischarging
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.
TEST - PENTHOUSE 7, MOTOR ONLY, VFDTEST ACPH7-MOV MOTOR OUTBOARD BRG VERT
Label: Mtr run only, VFD by-passedPriority: 2
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
Anti-friction Bearings & Electrical Anti-friction Bearings & Electrical DischargingDischarging
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.
TEST - PENTHOUSE 7, MOTOR ONLY, VFDTEST ACPH7-MOV MOTOR OUTBOARD BRG VERT
Label: Mtr run only, VFD by-passedPriority: 2
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
Anti-friction Bearings & Electrical Anti-friction Bearings & Electrical DischargingDischarging
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!