Date post: | 19-Aug-2014 |
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Wind Drivetrain Bearing Reliability
Before We Start This webinar will be available at
www.windpowerengineering.com & email
Q&A at the end of the presentation
Hashtag for this webinar: #WindWebinar
Moderator Presenter
Paul DvorakWindpower
Engineering & Development
Rick BrooksThe Timken Company
Wind Drivetrain Bearing Reliability
Presented by The Timken Co.Richard Brooks, Mgr. Wind North America
WIND TURBINE DRIVETRAIN - COMMON BEARING DAMAGE
Generator Bearings
Gearbox High Speed Bearings
Gearbox Planet Bearings
Main Shaft Bearings
FINANCIAL IMPACT - WIND DRIVETRAIN BEARING DAMAGE
Low High$0
$500,000TOTAL REPAIR
COST
Frequency of Occurrence
Generator BearingsGearbox High Speed Bearings
Gearbox Planet Bearings
Main Shaft Bearings
$$$
$
UP TOWER VS. DOWN TOWER REPAIRSUp Tower Down Tower
Crane Costs +++ ---Self Perform ++ -Clean Environment - ++Load Test --- ++Per Event Cost ~$10-$20k ~$250k-$500k
Two TS
TDI and CRB Ultrawind
Two SRBs
Single SRB
WIND TURBINE MAIN SHAFT MOUNTS
Hub Weight
Wind Thrust
Torque
Overturning Moments
Spherical Roller (SRB)
Main Bearing
MAIN SHAFT APPLICATION REVIEW-3 POINT MOUNT SRB
MAIN SHAFT SRB – OBSERVED DAMAGE MODES:LOW SPEED AND HIGH THRUST COMBINED=• Micropitting
x
MAIN SHAFT SRB – OBSERVED DAMAGE MODES:LOW SPEED AND HIGH THRUST COMBINED=• Edge Loading
MAIN SHAFT SRB – OBSERVED DAMAGE MODES:LOW SPEED AND HIGH THRUST COMBINED=• Single Piece Cage Damage
MAIN SHAFT SRB – OBSERVED DAMAGE MODES:LOW SPEED AND HIGH THRUST COMBINED=• Debris Damage
MAIN SHAFT SRB ENHANCEMENTSEnhanced Geometry • Reduce edge loading• Improves roller/race contact• Decreases roller stresses
x
MAIN SHAFT SRB ENHANCEMENTSSurface Finish• Reduced asperity contact and stress• Higher surface film, lower torque• Reduce friction and wear
MAIN SHAFT SRB ENHANCEMENTSTwo Piece Cage:• Lower operating forces/stress
MAIN SHAFT SRB ENHANCEMENTSWear Resistant “DLC” Coatings• Mitigate surface wear damaged• Increase fatigue life• Increase debris resistance
TECHNOLOGY DESCRIPTION BENEFITS
Roller Finishing Low Roughness,Isotropic Finish
Reduced Asperity Contact & Stress
Roller Coating WC/aC:H Coating1 µm thick
Increased Wear Resistance,Increased Fatigue Life,Increased Debris Resistance.
Internal Geometry Roller/IR Conformity Decreases Roller Stress,Reduces Potential Roller SkewCreates Favorable Traction
Split Cage Two-Piece Machined Brass Cage
Lowers Possible Operating Forces
TIMKEN WEAR-RESISTANT SRBWear Resistant SRB
Grease / Debris
Race condition
RESULTS OF TIMKEN WEAR RESISTANT SRBS AFTER 4 YEARS OPERATION
MAIN SHAFT BEARING HEALTH- OTHER FACTORS• Condition Monitoring
• Statistical analysis and trending of bearing temperatures• Vibration or Shock Pulse analysis
• Lubrication Practices• Variation in manual greasing practices (amount & frequency)• Value of Auto-Lubrication systems
• Grease Selection• Investigate characteristics of current grease and alternatives
• Grease Flush• Designed to extend the life of bearings in early stages of wear
20
High Speed & Intermediate shafts:• High occurrence Rate •Axial cracks on Inners
Planetary positions:• Medium occurrence Rate• Debris & load damage
WIND GEARBOX BEARINGSPlanet Carrier & Low Speed Positions:•Low occurrence Rate•Thrust damage
SRB CRB TRB
Integrated CRB Integrated TRB
PLANET BEARING ARRANGEMENTS - DEVELOPMENT
PLANET BEARING - OBSERVED DAMAGE MODES
23
Non-Integrated Integrated
TRB • Debris damage• Creeping Outer
• Debris damage
CRB • Debris damage• Thrust load • Heavy / Uneven loading• Smearing• Creeping outer
• Debris damage• Thrust Loading• Smearing
PLANET BEARING ENHANCEMENTS• SRB:
• Replace with new design• CRB:
• Case carburized• DLC coating• Modified controlled clearances• Redesign as TRB or integrated
• TRB:• Case carburized• Redesign as integrated
CRBCRB + ball bearing
HIGH SPEED AND INTERMEDIATE COMMON GEARBOX BEARING ARRANGEMENTS
Non-locating Position Locating Position Options
Double TRB
Single TRB
HIGH SPEED & INTERMEDIATE BEARINGS – OBSERVED DAMAGE MODES
I
R
r
Rr
F
1. Smearing 3. White Etch AreaAxial Cracking / Flaking
2. Inclusion Related:Axial Cracking / Spalling
ROLLER SLIDING / SMEARING IN CRB
IR
r
RIRR
r
Outer Race
Inner Race
Cage
Roller
D - roller sliding increases outside the load zone
C – load zone exit – most of the traction forces are lost beyond this point
F
B - traction forces restore roller velocity to pure rolling motion in load zone
A– smearing as roller accelerates entering the load zone
Load distribution in load zone
INCLUSION RELATED AXIAL CRACKING• Caused by non-ferrous contaminants in the steel• Commonly manifests as White Etch Butterflies• Material transforms in the area of the inclusion• Crack forms and prorogates to the surface or spalls
WHITE ETCH AREAS CRACKS1. Hoop Stress from original Press Fit on shaft2. Tensile stresses from roller sliding & skewing3. Dynamic conditions begin the subsurface
transformation4. Crack forms in the hard & brittle transformed area5. Crack propagates to the surface
WHITE ETCH AREAS CRACKS2. Tensile stresses from roller sliding & skewing
IR
r
Rr
F
WHITE ETCH AREAS CRACKS
3.
3. Dynamic conditions begin the subsurface transformation
WHITE ETCH AREAS CRACKS
Dynamic Event
Dynamic Event
NormalLoad
NormalLoad
Plastic Deformation Transformation
Plastic Deformation Transformation
4.
4. Crack forms in the hard & brittle transformed area
WHITE ETCH AREAS CRACKS
5.
5. Crack propagates to the surface
BEARING ENHANCEMENTS - HIGH SPEED & INTERMEDIATEEnhancement White Etch Inclusions Smearing
Steel Cleanliness + +++
Black Oxide +(early stages)
++(early stages)
‘DLC’ Coatings + +++
Case Carburized +++ ++
0
1
2
3
4
Com
plet
ed Sm
earin
g Tes
t Cyc
les
Smeared during first cycle
ENGINEERED SURFACE: PERFORMANCE COMPARISON
Ground Honed/ES20 Honed/ES20/Black Oxide Wear-Resistant
ENGINEERED SURFACES (COATINGS & TREATMENTS) Black Oxide Surfaces• Black oxide is a conversion treatment:
• Metallic parts are put into a hot bath containing oxidizing salts• Steel reacts with the oxidizing salts to form a
thin layer of magnetite on the surface (Fe3O4).
• Black oxide is a sacrificial surface• Benefits:
• Aesthetics• Corrosion prevention• Run-in and/or performance improvement• Prevents mild adhesive wear damage• Improve rolling contact fatigue life
DLC Coated Surfaces• DLC is a hard coating:
• Tungsten carbide incorporating an amorphous hydrocarbon composite. • Applied with a Physical Vapor Deposition
process in a vacuum chamber.
• Benefits:• Improve rolling contact fatigue life.• Mitigate life limiting wear damaged caused by
metal adhesion.• Increased fatigue Life• Increased debris resistance• Prevent scuffing or smearing damage
(Timken Wear Resistant coating)
Inner Race Subsurface Condition
Roller coating intact
RESULTS OF TIMKEN CRB (CASE CARBURIZED AND WEAR RESISTANT) AFTER 18 MONTHS
GEARBOX BEARING HEALTH – OTHER FACTORS• Condition Monitoring• Oil analysis programs and Online oil monitoring systems• Vibration or Shock Pulse analysis
• Oil Selection • Anti-Foaming• Additives / Properties
• Oil System Accessories• Moisture removal systems• Oil filtration systems
• Quality Oil Changes• Frequency based on oil monitoring condition• Vendor oil change features
38
GENERATOR BEARING OBSERVED DAMAGE MODES•Electrical Fluting •Inadequate Lubrication
GENERATOR BEARING ENHANCEMENTS• Add on shaft grounding ring • Upgrade the ground brushes from carbon to metal fiber• Upgrade bearings from metal/ceramic coated to ceramic balls
Generator Bearings
Gearbox High Speed Bearings
Gearbox Planet Bearings
Main Shaft Bearings
WIND TURBINE DRIVETRAIN - SUMMARY BEARING DAMAGE AND UPGRADES•Wear Resistant coating
•Case Carburized•Controlled clearance
•Grounding improvements•Ceramic balls
•Case Carburized•Wear Resistant coating
•Wear Resistant coating•Two piece cage•Geometry enhancements
Questions?Paul Dvorak Windpower Engineering & [email protected]: @Windpower_Eng
Rick BrooksThe Timken [email protected] Phone: 330-471-7812
Thank You This webinar will be available at
www.windpowerengineering.com & email Tweet with hashtag #WindWebinar Connect with Windpower Engineering &
Development
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