wind drivetrain bearing reliability

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 & Developmentpdvorak@wtwhmedia.comTwitter: @Windpower_Eng

Rick BrooksThe Timken CompanyRick.brooks@timken.com 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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