Contamination ControlFor Wind Turbines

ASMEGraduate Student Workshop

October 2009

Bill NeedelmanChief Science AdvisorDonaldson Company, Inc

Study by Professor E. Rabinowicz, MIT

Loss of Usefulness

Obsolescence

(15%)

Surface Degradation

(70%)

Accidents

(15%)

Corrosion

(20%)

Mechanical Wear

(50%)

Abrasion AdhesionFatigue

“Six to seven percent of the Gross National Product is required

just to repair the damage caused by mechanical wear.”

Note: Currently ~$1 trillion

Wind TurbineReliability & Performance

• 25 % of Cost of Ownership of Wind Turbines is Maintenance

• Reliability Problems

Gearbox > Blades > Generators

• 80% Of Operating Problems Due to GBX

Mostly Gearbox Repair & Replacement

• Bearings are #1 Cause of Gearbox Failures

• Most Gearbox Warrantees ~2 Years,

Costly Repairs Start ~4th Year

• 90% Anticipated Energy Production

5% GBX, 3% Wind, 2% All Others

Hard Particle DamageBearing Fatigue

0.001

0.01

0.1

1

40 50 60 70 80 90 100 110 120 130

Debris Particle Size

Life Relative to Non-Dented Bearings

Hard Ductile (e.g. T15 & 52100 Steel) Hard Rigid (e.g. Al2O3 & SiC) Hard Friable (e.g. TiC)

Ref: Kotzalas & Needelman, AWEA Wind Power Conf, 2008

Outline

• Problems Caused by Oil Contamination

• Particle Filters

• Water Contamination Control

• Best Practices

• Benefits & Conclusions

Types of Contaminants

Particles - Hard & Soft

Water

Air/Gases

Fuels, Acids, Glycols

What is a MICRON ?What is a MICRON ?

40µµµµ

100 µµµµ

10

µµµµ

1µµµµ

PARTICLE SIZE

100µ=Grain of table salt

40µ=Lower limit of visibility

10µ=Talcum powder

2µ=Bacteria

Unit of Measurement

1 Millionth of a Meter (micrometer)

Or .000039"

µ = Micron Symbol

MICRON

70µ=Typical human hair diameter

The Particle Zoo

21/20/18

TOO DIRTY TO

EVALUATE

23/22/20

19/17/1518/16/14

26/24/22

20/19/17 16/15/13

15/14/1221/20/1821/20/18

Major Types & Sources of Hard Particle Contaminants in Wind Turbines

• Hard Particles

– Manufacturing Swarf

• Machine Chips, Casting Sand, Grinding Debris, Abrasives

– Internal Wear Debris

• Gear Tooth Wear

– Internal Corrosion Products

• Rust, Aluminum Oxide

– Environmental Grit

• Airborne Mineral Dust, Sand

Bath Tub Model

Hard Particle Problems

• Rolling Contact Fatigue

• Abrasive Wear & Erosion

• Lubricant Oxidation

Abrasive Wear

Adhesive Wear

Rolling Contact Fatigue

Mechanical Wear By Hard Particles

All Three Forms of Wear

Result in Loss of Clearance,

Rough Surfaces, and

Greater Friction

Gear Tooth ContactsSliding

Contacts

Rolling

Contact

Gear Friction Increases As Gear Tooth Surface Roughens

16

Rolling Contact Fatigue: Surface Origin Spalls

Initiation point

Roller Path

Spalled

Area

Load

Dynamic Fluid Film

Thickness (µm)

Older Bearings Failed BySub-surface Initiated Fatigue Spalling

Slag Inclusion

In Steel

Particles & Surface Initiated Fatigue

Particle CaughtParticle Caught

LoadLoad

Particles & Surface Initiated Fatigue

LoadLoad

Surface Dented,

Crack Initiation

Surface Dented,

Crack Initiation

Particles & Surface Initiated Fatigue

LoadLoad

Crack Propagation

Cracks Spread

With Repeated Cycles

Crack Propagation

Cracks Spread

With Repeated Cycles

Particles & Surface Initiated Fatigue

Fatigue Spall Crater Forms

Hard Particles Released

Fatigue Spall Crater Forms

Hard Particles Released

LoadLoad

SpallSpallSpall

The ChallengeCleaner Gear OilDrier Gear Oil

Same For Hydraulic Fluids

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Element Design����

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DT Steel Std

Collapse High Collapse

DT Steel

Coreless

1 Outer Wrap n/a n/a n/a

2 Support Mesh (2)

epoxy coated

steel for

support and

spacing

stainless steel

for support and

spacing

epoxy coated

steel for

support and

spacing

3 Flow Control Layers (2)

synthetic layers

to strengthen

media

synthetic layers

to strengthen

media

synthetic layers

to strengthen

media

4 Synteq® Media

thin glass-fiber

media for

performance

thin glass-fiber

media for

performance

thin glass-fiber

media for

performance

Filter Media Types

- Cellulose

- Synthetic (Glass Fiber)

- Wire Mesh

Pressure Loss Across A Filter Element(∆∆∆∆P)

Pressure Loss ∝∝∝∝ Flow Rate

X Viscosity

X Tortuosity

Gear Oil Oils: High Viscosity

Gear Boxes: Moderate Flow Rates

Fine Filters: High Tortuosity

Pore StructureGraded Pore Filter Media

State-Of-The Art Filter Media

Conventional Media

Resin Bonded

New Media

Bi-Component

Thermoplastic B

Sheath

Bicomponent Binder Fiber

Thermoplastic A

Core

Glass

microfibers

Bi-Component Filter Medium

Bi-Component Filter MediumGlass

microfibers

Thermoplastic

binder

fiber

Field Data: GE 1.5 MW

Turbine #5

0

1000

2000

3000

4000

5000

6000

7000

12/1/08 1/1/09 2/1/09 3/4/09 4/4/09 5/5/09 6/5/09 7/6/09 8/6/09

Dates

Particles/ml

>4um

>6um

>14um

Hydac 10um

DT 5um XPNew 5 um

Current 10 um

Dissolved & Free Water

Free Water

Emulsified

Dissolved Water

Below

Saturation

Free Water

Bulk

Separation

Major Sources of Water Contaminationin Wind Turbines

• Water Vapor - Humidity

• Rain (Through Vents & Seals)

• New Oil

Oil Has A Relative Humidity (RH)

50% RH Oil

At Equilibrium

RH of Air

Equals

RH of Oil

(RH Oil = %Saturation)

Water

Molecules

50% RH Air

Humidification

Water moves from high relative humidity

to low relative humidity

0

10

20

30

40

50

60

70

80

0 8 16 24

T im e (H ou rs )

Moisture Content (% Saturation)

Mobil DTE PM 220

in contact with air

controlled at 90oF

& 80% RH

Problems Caused by Water Contaminationin Wind Turbines

• Rolling Contact Fatigue

• Adhesive Wear

• Additive Dumping

• Oil Oxidation

Water DamageBearing Fatigue

0.1

1

10

10 100 1000

Water Concentration in Lubricant (PPM)

Relative Fatigue Life

SAE 20 + R&O SAE 5 + EP (100/X)^0.6 Navy Data

Ref: Kotzalas & Needelman, AWEA Wind Power Conf, 2008

Water & Rolling Contact Fatigue

Oil + Dissolve Water Forced Into Cracks in the Contact Zone

LoadLoad

Water & Fatigue Crack Propagation

Hydrogen

Embrittlement

Loss of Fluid Film Lubrication& Adhesive Wear

Load

Low Viscosity

Water Not Able

To Support Load

Film Collapses

Dynamic Fluid

Film Thickness (um)

Water DamageAdditive Drop-Out

Fouled & Disabled Oil-Level Sensor

Water DamageAdditive Drop-Out

Courtesy COT-Puritech, Inc.

Fouled & Disabled Thermostat

Keeping Gear Oils & Hydraulic Fluids Dry in Wind Turbines

• Prevention

– Minimize Ingression

• Removal

– Rapid

Regenerable Breather Dryer

Inhalation ExhalationCaptures H2O Regenerates By

Releasing H2O

Ultrapac

ARV-3: P568790

ARV-10: P568791

Customer Supplied

Pressure Regulator

with Guage

(set to 100 psi)

Incoming

Compressed Air

Customer Supplied

Shut-off Valve

(Required for

maintenance of unit)

Customer Supplied

Shut-off Valve

Reservoir

Customer Supplied

Flow Meter

(Optional to adjust

compressed air

usage as required)

TRAP Breather with

Tee and Relief Valve

Orifice

ARV-3: P568606

ARV-10: P568799

(Must be installed for proper

operation of ARV)

Inlet

Port

Outlet

Port

Inlet & Outlet Installed On

Opposite Corners Ideal

Dry Air Blanket System

Dry Air Blanket System

Time

• Dry Air

• Dry Oil

• Humid Air

• Saturated Oil

• Purging

Humid Air

• Saturated Oil

• Dry Air

• Moisture

Desorbing

from Oil

Na12 [(AlO2)12(SiO2)12] x H2O - 10 Angstrom Molecular Sieve

Pressure Swing Adsorption Dryer

Dry Air Blanket Keeping Oil in Contact With Very Dry Air

0

10

20

30

40

50

60

70

80

0 8 16 24

Time (Hours)

Head Space Air Relative Humidity (%)

2

Reservoir Head Space Air

6

20

200

0

10

20

30

40

50

60

70

80

0.0 8.0 16.0 24.0

Time (Hours)

Oil Percent Saturation (%)

20

2

Reservoir Oil

200

6

Exchanges/hour

Best PracticesTotal Contamination Control Plan

1) Design

2) Roll-Off Cleanliness

3) Transportation

4) On-Site Storage

5) Clean Maintenance Practices

6) Ingression Prevention

7) Rapid Removal

Best Practices ForIngression Prevention & Rapid Removal

Inline Filter

ββββ5(c)=1000

Gearbox

Offline Filter

ββββ3(c)=1000

Offline Water

Absorption

Filter

Regenerable Breather

Dryer with 3 Micron Filter

Objectives: ISO 14/12/10

. 125 ppm max

Cooler

Dry Air

System

NASA/STLE Roller Bearing

Life Factors for Wind Turbines

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

0 5 10 15 20 25 30 35 40

Filter Rating Where ¬¬¬¬(C) = 1000

(Microns)

Bearing Life Factors

Adapted from Needelman & Zaretsky, STLE Annual Mtg. Proc. May 09

12 um10 um

8 um

5 um

2um

NASA/STLE ModelWater Contamination & Bearing Life

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

0 100 200 300 400 500 600

Water (ppm)

Relative Bearing Life

Maintaining Dry Oil

Estimated To Increase

Bearing Life ~200%

Current

Target

Conclusions

• Benefits Of Excellent Contam Control

– Greater Gearbox Reliability

–More Uptime, More Production

– Extended Warrantees

– Up To 5 Year Gear Oil Life

• Needed

– Coherent Contamination Control Plan

– Use Best Technologies & Practices

Thank You For Your Interest

__________________

Questions?

Comments?