Presentation by Rich Wurzbach, MRG Labs, at the NREL Gearbox Reliability Collaborative meeting in Golden, CO, February 18, 0215. Gives background development of grease sampling tools for wind turbines, standards development, and recommended practices by AWEA.

1. Wind Turbine Grease Sampling and
Analysis
Richard N. Wurzbach
ASNT Level III PdM
Machinery Lubricant Analyst, Level II
MRG Labs
York, Pennsylvania

2. 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

3. 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

4. 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

5. 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

6. Sampling Techniques
• MOV Gearbox
1 2 3 4 5
• Electric Motor Bearing
1 2 3 4 5
• Pillow Block Bearing
1 2 3 4

7. 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

8. Wear monitoring
• Hall effect sensor counts total ferrous debris
level of sample, not the variable amount
through the body of grease
Method Average
Standard
Deviation
Relative Standard
Deviation
fdM+ 277 ppm 7 2.53
DR- 205 46 22.44
RDE 57 ppm 16 28.07
Method Average
Standard
Deviation
Relative Standard
Deviation
fdM+ 277 ppm 7 2.53
DR- 205 46 22.44
RDE 57 ppm 16 28.07

9. Wear Evaluation

10. Wind Turbine Lubricant Monitoring
10

11. 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

12. 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
12

13. 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

14. 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

15. 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

16. 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

17. Analysis Techniques
Sample is received. fdM+ is run Die 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.
17

18. Die Extrusion Analyzer

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

20. Optical Spectroscopy
•Optical spectroscopy quantifies the appearance of grease
•Grease aging, contaminants, mixtures, chemometrics
20

21. FdM Wear Levels across Wind Farm
21

22. 3-D Sampling, OEM repair shop

23. 3-D sampling

24. Trends of moisture in bearings
0
100
200
300
400
500
600
700
800
900
Moisture,ppm
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

25. 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