Wind Turbine Grease Sampling and Analysis

Richard N. WurzbachASNT Level III PdM

Machinery Lubricant Analyst, Level II

MRG Labs

York, Pennsylvania

Lubricant Sampling

• Oil analysis using valves and gravity

• Drop tube sampling

• Retrofit sampling mini-mess

• Importance of sample location

• Drop tube point of sample uncertain

Image from Noria Corporation

Grease Sampling

• Historically during disassembly following failure

• Using “popsicle stick”, screwdriver, cable ties

• Samples only available near access points, ports

• “Grab Sample” has similar limitations to “Drop Tube Sampling”

• ASTM Grease subcommittee initiates working group to develop sampling standard, 2009

• Projects initiated in USA and Denmark to test effectiveness of grease sampling in 2010, 2012

Motor Operated Valves (MOV)

• EPRI method using plastic tubing at gears

• Grease removed and visually inspected

• Kits made utilizing known consistency greases for comparison to obtained sample

• Questionable samples; very subjective analysis

Photos: Bolt, et. al. Machinery Lubrication Magazine. May 2003

Grease sampling devices

• Maintain purge function with little/no backpressure when threaded into machine

• Can be attached to T-handle for precise sample location adjacent to internal gears

• Design to optimize the analysis process

Sampling Techniques

• MOV Gearbox

1 2 3 4 5

• Electric Motor Bearing

1 2 3 4 5

• Pillow Block Bearing

1 2 3 4

MOV Test Stand-EPRI Project

•Actuators filled with in-service grease

•Cycled forward and backward

•Produced video of grease flow

•Data on consistency of wear levels

Wear monitoring

• Hall effect sensor counts total ferrous debris level of sample, not the variable amount through the body of grease

Method AverageStandard

Deviation

Relative Standard

Deviation

fdM+ 277 ppm 7 2.53

DR- 205 46 22.44

RDE 57 ppm 16 28.07

Method AverageStandard

Deviation

Relative Standard

Deviation

fdM+ 277 ppm 7 2.53

DR- 205 46 22.44

RDE 57 ppm 16 28.07

Wear Evaluation

Wind Turbine Lubricant Monitoring

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Wind Turbine grease sampling and analysis

• 2-year project conducted with DONG Energy and Vattenfall, two largest offshore wind operators in the world

• Dr. Kim Esbensen, internationally recognized expert in Theory of Sampling (TOS), Denmark

• Rich Wurzbach, MRG Labs, inventor of Grease Thief

• Systematic evaluation of grease heterogeneity, sampling methodology, and analysis validity and repeatability for wind turbine main bearings in on-shore and off-shore applications

• Results published at OilDoc, LUBMAT, and AWEA

Wind Main Bearing Sampling

• Grease flow dependent on temperature, bearing movement

• Grease Thief & T-handle used to capture flowing grease

• Revised T-handle developed for Denmark Off-shore Wind Research Project

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ASTM Standard Development

• Incorporation of grease sampling research

• Inclusion of historical methods for sampling with considerations and limitations

• Failed component sampling, care in obtaining sample or multiple samples

• Use of tubing, adequacy of suction alone, possibility of peripheral grease sampling

• Inclusion of new technologies for active and passive sampling

Active Sampling

• T-handle Coring with active or passive sampler

• Spatula and syringe on pillow block

• Syringe and tubine on slewing bearing

“Taking a sample” from Rothe Erde “Grease Sampling Set” instructions

Cautions and Concerns

• Use of plastic tubing may not properly suction all representative grease, point of sampling may vary, as in oil “drop-tube” sampling

• Samples must be taken from “live-zone” in the machine, understanding of flow dynamics important

• Sample must be properly labeled and protected during shipment

• Quantity must be sufficient for required tests

Acceptance and Use

• D7718 is basis for AWEA Recommended Practices for wind turbine sampling– 812 Grease Sampling - Main Bearing– 813 Grease Sampling - Generator Bearing– 814 Grease Sampling - Pitch Bearing– 815 Grease Analysis

• Used by largest operators in Danish Offshore Wind industry• Published by US Nuclear Industry in “Effective Grease Practices” NMAC Guideline• Analysis utilized by labs in Europe, Asia, North America

• Sampling kits used on six continents around the globe

Analysis Techniques

Sample is received. fdM+ is runDie extrusion is performed and substrate is made

Two strips are used to make

a dilution to run RDE/ICP.

One Strip is used

for FT-IR.

One Strip is Dissolved in Green

RULER solution to run RULER.

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Die Extrusion Analyzer

Grease Consistency – Back Bearings in a USA Wind Farm: Outliers in Yellow

Optical Spectroscopy

•Optical spectroscopy quantifies the appearance of grease

•Grease aging, contaminants, mixtures, chemometrics

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FdM Wear Levels across Wind Farm

21

3-D Sampling, OEM repair shop

3-D sampling

Trends of moisture in bearings

0

100

200

300

400

500

600

700

800

900

Mo

istu

re, p

pm

314 Front

314 Rear

319 Front

319 Rear

Grease type: SKF LGWM1

• Thickener: Li

• Base oil: Mineral oil

• Viscosity @ 40C: 200 cSt

• NLGI-class: 1

Next Steps• Development of ASTM Standard for Grease Analysis

– Integrated Tester section of ASTM with a balloted Work Item

–Currently in Interlaboratory Study (ILS) in US labs for precision statement

– Laboratories in Asia, Europe and North America to participate in development of methods

• Development of “Slim” version of sampler to access rail locomotive wheel bearings, certain wind bearings

• Mini-lab development for “In-Sampler” Analysis, including ferrous debris, colorimetry

• Real-time particle counting in grease as it is being extruded

• Major lubricant manufacturers worldwide utilizing for support of customer base