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05 October 2011 SKF Group Slide 0
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Main Bearing PreventiveMaintenance & Condition
Monitoring Techniques
NREL CBM Workshop 2011
Korey Greiner and Mark Dunn
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05 October 2011 SKF Group Slide 2
Typical maintenance techniques today
Maintenance strategies to improve reliability
Preventive
Manual inspection of bearing
Re lubrication of bearing
Predictive
Continuous condition monitoring
Typical maintenance techniques today
Manual re lubrication - 6 & 12 months scheduled maintenance Automated lubrication
Some utilizing condition based monitoring
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05 October 2011 SKF Group Slide 3
1Main Bearing Inspection andMaintenance
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05 October 2011 SKF Group Slide 4
Example 3 point bearing system
Increasing number of main bearing failures in the market
Root cause still under investigation
Lubrication is one possible cause
Heavy loads on Down wind side of bearing
Light load on upwind side of bearing
Upwind Side Load Zone
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05 October 2011 SKF Group Slide 5
Grease separation - a growing concern
Grease separation
Oil separating from thickener Thickener hardening
No mixing
Hardened grease preventing properlubrication
Blocking the bearing grease path(W33groove)
Corrective measures Manual inspection of bearings every two
years (once if auto lubrication system isused)
Increase grease quantity to 100% fill
Increase schedule manual relubrication Good experience with NLGI 1 grease
due to easier pumpablity, shearcharacteristics and ability to operate allweather conditions
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05 October 2011 SKF Group Slide 6
Manual Inspection of Bearing
On Models that the front cover can be
removedGrease
Condition and amount
Grease path
Grease Samples
Remove old grease
Bearing
Measure internal clearance
Inspect inner and outer of bearing fordamage (spalling, fragment denting, etc)
Inspect rollers (Smearing on face, fragmentdenting, etc)
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05 October 2011 SKF Group Slide 7
Re lubrication
Manually grease bearing using the
inlet port at the top of the bearing
Grease should emerge from center ofbearing
Remove any old grease pushed from
inside bearing. Grease can now be hand packed
Reassemble Bearing
Continue to add grease until new greasecomes out of portal at the bottom of
housing
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05 October 2011 SKF Group Slide 8
Bearings that can not be disassembled
Contact bearing manufacture for
calculation of 100% Free space fill
Open the grease outlet at the bottom
of housing
Pump calculated amount of grease
into housing inlet
If possible rotate Shaft several times
When new grease begins to come
out of outlet.
Rotate shaft for several minutes and
replace plug in outlet
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05 October 2011 SKF Group Slide 9
Auto Lubrication Systems
Benefits of Auto Lubrications
Small amount of grease addedoften (1 minute every 6 hours)
Reduced heat
Reservoir will hold enough greasefor a year or more
Using the IFM module grease willbe added only while turbine is
operating
Reduced cost
Less waste, buy in bulk, reduced manhours
S M i B i I ti d
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05 October 2011 SKF Group Slide 10
Summary - Main Bearing Inspection andMaintenance
Root cause failure still under investigation, Lubrication is one possiblecause
Recommend manual inspection every 2 years if continuing with manualre lubrication
Recommend manual inspection before installing auto lubrication system
Small amount of grease added daily reduces heating, oil separation(hardening), Improves oil film.
Proper lubricating procedures will increase bearing life
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05 October 2011 SKF Group Slide 11
2Main Bearing
Condition Monitoring
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05 October 2011 SKF Group Slide 12
Condition monitoring at the main bearing
Challenges,
Slow rotating bearing
Variable speed and load conditions
Relatively low shaft rotational speed typically < 20rpm
Transmitted vibration (tower resonance, gearbox, etc.)
Changing ambient temperature
All points influence the vibration values
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05 October 2011 SKF Group Slide 13
Methods for predictive maintenance
Different methods/techniques used to measure the
condition,
Temperature
Lubrication (grease) analysis
Overall Vibration values
Spectral analysis
Main bearing and rotor
Main bearing
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05 October 2011 SKF Group Slide 14
On-site preparation/sensor location
2 Sensors recommended > axial and radial directions
Low frequency sensors required to detect running speed frequency
Sensors should have a high sensitivity to detect bearing failures (low energy)
Sensor locations at the main bearing
R i t f th diti it i
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05 October 2011 SKF Group Slide 15
Requirements of the condition monitoringsystem
Minimum 16 bit dynamic resolution, better 24 bit
New CMS should have order tracking
Spectra and trend data should recorded at similar
conditions
Benefit of active ranges:
-Saved spectra without smearing if used with allowed delta
-Better stable trend values no up and down
-No grab spectra
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05 October 2011 SKF Group Slide 16
Measurement setup slow speed
-Due to the slow speed, a long measurement time is needed
-Min. 12 main shaft revolutions should be taken inside the meas.time
-Fmax should include the 4. harmonic defect frequency
Order tracking setup
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05 October 2011 SKF Group Slide 17
Example of a main bearing defect
Turbine data:
-1.5 MW turbine
-Life time 9 years
-Onshore
-Three point bearing design (1 main bearing / gearbox)-Spherical Roller Bearing
-Similar to several main bearing defects
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05 October 2011 SKF Group Slide 18
Comparison of different trend data
velocity trend
acceleration trend
Overall trends are not reliable to track main bearing issues.
Good for rotor/blades and tower vibration
Gearbox and main bearing changed12.03.09
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05 October 2011 SKF Group Slide 19
Envelope Trend (envelope filter -200Hz)
Gearbox and main bearing changed
Trend values decrease after change
The envelope trend value is more appropriate to detect bearing failures
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05 October 2011 SKF Group Slide 20
Main bearing defect acceleration spectra
Outer ring defect
Outer ring defect with harmonics
Inner ring defect frequency
with rotor speed spaced sidebands
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05 October 2011 SKF Group Slide 21
Diagnostic techniques in SKF software
First overrun frequencies detected
One year before bearing
replacement report to customer
Trend values increased, until maintenance
Main bearing replacement was merged together
with the planned gearbox exchange
Values drops down after maintenance
Benefit: Gearbox replace could be merged together with the main bearing replacement
Diagnosis trend:
Software generated band values around the bearing defect values
It is possible to track the defect development
Analysis is performed automatically by the software reduces the needed analysis time
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05 October 2011 SKF Group Slide 22
Pictures of the damaged bearing
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05 October 2011 SKF Group Slide 23
Condition Monitoring Summary
Main Bearing defect analysis/identification is achievable
Accurate & reliable main bearing defect analysis is not easy
SKF have proven reliable techniques, along with specific
application experience to analyze and detect main bearing defects
Most main bearing defects visible in axial and radial directionsBest to measure in acceleration spectrum
Most main bearing defects exhibit low fundamental bearing defect
frequency amplitudes, compared to the harmonics
At low wind classes (low load), the defect is often more
visible/easier to diagnose (less transmitted frequencies)
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05 October 2011 SKF Group Slide 24
Next Steps.
Connecting Technologies..
Connecting Condition Monitoring & Auto
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05 October 2011 SKF Group Slide 25
Connecting Condition Monitoring & AutoLubrication
+ +
WindCon WindLubObserver software
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05 October 2011 SKF Group Slide 26
Working principle
Enveloped
acceleration
IMx-W relay driver
Time (t)
Lubrication cycles
Alarm/warning threshold value
Normal lubrication period
Relay / timer
modules
Additional lubrication cycle
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05 October2011 SKF Group Slide 27
Thank you any questions please
?